CYP3A4

Gene Summary

Gene:CYP3A4; cytochrome P450, family 3, subfamily A, polypeptide 4
Aliases: HLP, CP33, CP34, CYP3A, NF-25, CYP3A3, P450C3, CYPIIIA3, CYPIIIA4, P450PCN1
Location:7q21.1
Summary:This gene encodes a member of the cytochrome P450 superfamily of enzymes. The cytochrome P450 proteins are monooxygenases that catalyze many reactions involved in drug metabolism and synthesis of cholesterol, steroids and other lipids. This protein localizes to the endoplasmic reticulum and its expression is induced by glucocorticoids and some pharmacological agents. This enzyme is involved in the metabolism of approximately half the drugs in use today, including acetaminophen, codeine, cyclosporin A, diazepam and erythromycin. The enzyme also metabolizes some steroids and carcinogens. This gene is part of a cluster of cytochrome P450 genes on chromosome 7q21.1. Previously another CYP3A gene, CYP3A3, was thought to exist; however, it is now thought that this sequence represents a transcript variant of CYP3A4. Alternatively spliced transcript variants encoding different isoforms have been identified. [provided by RefSeq, Feb 2011]
Databases:OMIM, HGNC, GeneCard, Gene
Protein:cytochrome P450 3A4
HPRD
Source:NCBIAccessed: 27 February, 2015

Ontology:

What does this gene/protein do?
Show (38)
Pathways:What pathways are this gene/protein implicaed in?
Show (4)

Cancer Overview

Research Indicators

Publications Per Year (1990-2015)
Graph generated 28 February 2015 using data from PubMed using criteria.

Literature Analysis

Mouse over the terms for more detail; many indicate links which you can click for dedicated pages about the topic.

  • p53 Protein
  • Testicular Cancer
  • Prostate Cancer
  • Antineoplastic Agents
  • Cytochrome P-450 CYP3A
  • Rifampin
  • Smoking
  • Transcription
  • Polymorphism
  • Messenger RNA
  • Restriction Fragment Length Polymorphism
  • Receptors, Steroid
  • Regression Analysis
  • Cancer Gene Expression Regulation
  • Genotype
  • Urban Population
  • Siblings
  • Scotland
  • Aryl Hydrocarbon Hydroxylases
  • Steroids
  • RTPCR
  • Xenograft Models
  • Receptor, erbB-2
  • Statistics as Topic
  • Washington
  • Survival Rate
  • Receptors, Opioid, mu
  • Lung Cancer
  • Breast Cancer
  • Oligonucleotide Array Sequence Analysis
  • Severity of Illness Index
  • Genetic Predisposition
  • Taxoids
  • Case-Control Studies
  • Chromosome 7
  • South Africa
  • Cytochrome P-450 Enzyme System
  • Soft Tissue Sarcoma
  • Women's Health
  • Tamoxifen
Tag cloud generated 27 February, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (5)

Data table showing topics related to specific cancers and associated disorders. Scope includes mutations and abnormal protein expression.

Note: list is not exhaustive. Number of papers are based on searches of PubMed (click on topic title for arbitrary criteria used).

Latest Publications: CYP3A4 (cancer-related)

Lin TY, Ki CS, Lin CC
Manipulating hepatocellular carcinoma cell fate in orthogonally cross-linked hydrogels.
Biomaterials. 2014; 35(25):6898-906 [PubMed] Related Publications
De-differentiation and loss of function in hepatocytes during two-dimensional (2D) tissue culture significantly hinders the progress of liver research. An ideal three-dimensional (3D) in vitro liver parenchymal cell culture platform should restore cell-cell and cell-matrix interactions, as well as normal hepatocyte polarity. Here, we report an orthogonal thiol-ene hydrogel system for culturing liver cell lines (e.g. Huh7 and HepG2). The hydrogels were prepared by a radical-mediated orthogonal thiol-norbornene photo-click chemistry using poly(ethylene glycol)-tetra-norbornene (PEG4NB) macromer and di-thiol containing linker (e.g., dithiothreitol (DTT) or bis-cysteine matrix metalloproteinase (MMP)-sensitive peptide). This system also allows facile incorporation of bioactive peptides (e.g., fibronectin-derived RGDS) to improve cell-matrix interactions. Encapsulated Huh7 and HepG2 cells showed elevated urea secretion and CYP3A4 enzymatic activities, as well as up-regulated mRNA levels of multiple hepatocyte genes (e.g., CYP3A4, BESP, and NTCP). Importantly, this is the first 3D hydrogel system that up-regulates the expression of NCTP in encapsulated Huh7 and HepG2 cell lines without any genetic modification or the addition of growth factors and chemical additives. Furthermore, the encapsulated cells displayed hepatocyte-like polarity distinctively different from the polarity displayed in 2D culture. These characteristics not only allow the study of hepatology in 3D using inexpensive cell lines, but also permit large-scale small-molecule screening. The up-regulation of NTCP expression and restoration of hepatocyte-like polarity in our hydrogels also shed light on future study of hepatitis B virus infection in vitro.

Ye L, Yang X, Guo E, et al.
Sorafenib metabolism is significantly altered in the liver tumor tissue of hepatocellular carcinoma patient.
PLoS One. 2014; 9(5):e96664 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Sorafenib, the drug used as first line treatment for hepatocellular carcinoma (HCC), is metabolized by cytochrome P450 (CYP) 3A4-mediated oxidation and uridine diphosphate glucuronosyl transferase (UGT) 1A9-mediated glucuronidation. Liver diseases are associated with reduced CYP and UGT activities, which can considerably affect drug metabolism, leading to drug toxicity. Thus, understanding the metabolism of therapeutic compounds in patients with liver diseases is necessary. However, the metabolism characteristic of sorafenib has not been systematically determined in HCC patients.
METHODS: Sorafenib metabolism was tested in the pooled and individual tumor hepatic microsomes (THLMs) and adjacent normal hepatic microsomes (NHLMs) of HCC patients (n = 18). Commercial hepatic microsomes (CHLMs) were used as a control. In addition, CYP3A4 and UGT1A9 protein expression in different tissues were measured by Western blotting.
RESULTS: The mean rates of oxidation and glucuronidation of sorafenib were significantly decreased in the pooled THLMs compared with those in NHLMs and CHLMs. The maximal velocity (Vmax) of sorafenib oxidation and glucuronidation were approximately 25-fold and 2-fold decreased in the pooled THLMs, respectively, with unchanged Km values. The oxidation of sorafenib in individual THLMs sample was significantly decreased (ranging from 7 to 67-fold) than that in corresponding NHLMs sample. The reduction of glucuronidation in THLMs was observed in 15 out of 18 patients' samples. Additionally, the level of CYP3A4 and UGT1A9 expression were both notably decreased in the pooled THLMs.
CONCLUSIONS: Sorafenib metabolism was remarkably decreased in THLMs. This result was associated with the down regulation of the protein expression of CYP3A4 and UGT1A9.

Vilanova-Costa CA, Porto HK, Pereira Fde C, et al.
The ruthenium complexes cis-(dichloro)tetramineruthenium(III) chloride and cis-tetraammine(oxalato)ruthenium(III) dithionate overcome resistance inducing apoptosis on human lung carcinoma cells (A549).
Biometals. 2014; 27(3):459-69 [PubMed] Related Publications
Lung cancer is one of the leading causes of death in the world, and non-small cell lung carcinoma accounts for approximately 75-85 % of all lung cancers. In the present work, we studied the antitumor activity of the compound cis-(dichloro)tetramineruthenium(III) chloride {cis-[RuCl2(NH3)4]Cl} against human lung carcinoma tumor cell line A549. The present study aimed to investigate the relationship between the expression of MDR1 and CYP450 genes in human lung carcinoma cell lines A549 treated with cisCarboPt, cisCRu(III) and cisDRu(III). The ruthenium-based coordinated complexes presented low cytotoxic and antiproliferative activities, with high IC50 values, 196 (±15.49), 472 (±20.29) and 175 (±1.41) for cisCarboPt, cisCRu(III) and cisDRu(III), respectively. The tested compounds induced apoptosis in A549 tumor cells as evidenced by caspase 3 activation, but only at high concentrations. Results also revealed that the amplification of P-gp gene is greater in A549 cells exposed to cisCarboPt and cisCRu(III) than cisDRu(III). Taken together all these results strongly demonstrate that MDR-1 over-expression in A549 cells could be associated to a MDR phenotype of these cells and moreover, it is also contributing to the platinum, and structurally-related compound, resistance in these cells. The identification and characterization of novel mechanisms of drug resistance will enable the development of a new generation of anti-cancer drugs that increase cancer sensitivity and/or represent more effective chemotherapeutic agents.

Tulsyan S, Agarwal G, Lal P, Mittal B
Significant role of CYP450 genetic variants in cyclophosphamide based breast cancer treatment outcomes: a multi-analytical strategy.
Clin Chim Acta. 2014; 434:21-8 [PubMed] Related Publications
BACKGROUND: Cyclophosphamide (CP), an alkylating chemotherapeutic drug, is catalyzed by the Phase I cytochrome P450 (CYPs) isozymes - CYP3A4, CYP3A5, CYP2B6, CYP2C8, CYP2C9 and CYP2C19. Hence this study aimed to elucidate the influence of genetic variants in CYP450 metabolizing enzymes on breast cancer treatment outcomes, using multi-analytical approaches.
METHODS: Treatment response was noticed in 111 patients whereas 234 patients were followed for myelo-toxicity. Eight known functional single nucleotide polymorphisms (SNPs) in six CYP450 genes were selected for the study on the basis of CP metabolizing enzyme polymorphisms. The possible functional effects of CYP450 polymorphisms were determined by online Web servers F-SNP. Multifactor dimensionality reductions (MDR), haplotype analysis were combined with logistic regression to characterize gene-gene interaction model with treatment outcomes.
RESULTS: Haplotype analysis revealed significant association of G(rs10509681)-*1(rs1799853)-*3(rs1057910)-G(rs4244285) on chromosome 10 with overall toxicity (P=0.024) and grade 2-4 leucopenia (P=0.03). On MDR analysis, CYP3A5*3, CYP2C19*2, CYP2B6*5 yielded the highest testing accuracy for treatment response (0.60) and CYP2C8*3, CYP2C9*2 for overall toxicity (0.50).
CONCLUSION: Multi-analytical approaches may provide a better clinical prediction of pharmacogenetic based treatment outcomes in breast cancer patients.

Terzolo M, Zaggia B, Allasino B, De Francia S
Practical treatment using mitotane for adrenocortical carcinoma.
Curr Opin Endocrinol Diabetes Obes. 2014; 21(3):159-65 [PubMed] Related Publications
PURPOSE OF REVIEW: Description of novel findings about the mechanism of action of mitotane and its activity as an adjunctive postoperative measure, or for treatment of advanced adrenocortical carcinoma.
RECENT FINDINGS: Several in-vitro studies have shown that mitotane suppresses gene transcription of different enzymatic steps of the steroidogenetic pathway. Moreover, mitotane induces CYP3A4 expression, thus accelerating the metabolic clearance of a variety of drugs including steroids. Retrospective studies provided evidence that adjunctive mitotane can prolong recurrence-free survival of treated patients. The concept of a therapeutic window of mitotane plasma concentrations was confirmed also for adjunctive treatment, but the relationship between mitotane concentration and given dose is loose. Genetic variability of the P450-dependent enzymes metabolizing mitotane may explain individual differences.
SUMMARY: Mitotane concentration of 14-20  mg/l should be reached and maintained during treatment also in an adjunctive setting. In advanced adrenocortical carcinoma, a high-dose starting regimen should be employed when mitotane is used as monotherapy. The combination of mitotane with other drugs should consider the possibility of pharmacologic interactions due to mitotane-induced activation of drug metabolism. This concept applies also to steroid replacement in mitotane-treated patients, who need higher doses to adjust for increased steroid metabolism.

Tulsyan S, Chaturvedi P, Singh AK, et al.
Assessment of clinical outcomes in breast cancer patients treated with taxanes: multi-analytical approach.
Gene. 2014; 543(1):69-75 [PubMed] Related Publications
Polymorphisms in genes encoding CYPs (Phase I) and ABCB1 (Phase III) enzymes may attribute to variability of efficacy of taxanes. The present study aims to find the influence of CYP and ABCB1 gene polymorphisms on taxanes based clinical outcomes. 132 breast cancer patients treated with taxanes based chemotherapy were genotyped for CYP3A4*1B, CYP3A5*3, CYP1B1*3, CYP2C8*3, ABCB1 1236C>T, 2677G>T/A and 3435C>T polymorphisms using PCR-RFLP. Associations of genetic variants with clinical outcomes in terms of response in 58 patients receiving neo-adjuvant chemotherapy (NACT), and chemo-toxicity in 132 patients were studied. Multifactor dimensionality reduction (MDR) analysis was performed to evaluate higher order gene-gene interactions with clinical outcomes. Pathological response to taxane based NACT was associated with GA genotype as well as A allele of CYP3A5*3 polymorphism (Pcorr=0.0465, Pcorr=0.0465). Similarly, association was found in dominant model of CYP3A5*3 polymorphism with responders (Pcorr=0.0465). Haplotype analysis further revealed ACYP3A4-ACYP3A5 haplotype to be significantly associated with responders (Pcorr=0.048). In assessing toxicity, significant association of variant (TT) genotype and T allele of ABCB1 2677G>T/A polymorphism, was found with 'grade 1 or no leucopenia' (Pcorr=0.0465, Pcorr=0.048). On evaluating higher order gene-gene interaction models by MDR analysis, CYP3A5*3; ABCB11236C>T and ABCB1 2677G>T/A; ABCB1 3435C>T and CYP1B1*3 showed significant association with treatment response, grade 2-4 anemia and dose delay/reduction due to neutropenia (P=0.024, P=0.004, P=0.026), respectively. Multi-analytical approaches may provide a better assessment of pharmacogenetic based treatment outcomes in breast cancer patients treated with taxanes.

Molina-Ortiz D, Camacho-Carranza R, González-Zamora JF, et al.
Differential expression of cytochrome P450 enzymes in normal and tumor tissues from childhood rhabdomyosarcoma.
PLoS One. 2014; 9(4):e93261 [PubMed] Free Access to Full Article Related Publications
Intratumoral expression of genes encoding Cytochrome P450 enzymes (CYP) might play a critical role not only in cancer development but also in the metabolism of anticancer drugs. The purpose of this study was to compare the mRNA expression patterns of seven representative CYPs in paired tumor and normal tissue of child patients with rabdomyosarcoma (RMS). Using real time quantitative RT-PCR, the gene expression pattern of CYP1A1, CYP1A2, CYP1B1, CYP2E1, CYP2W1, CYP3A4, and CYP3A5 were analyzed in tumor and adjacent non-tumor tissues from 13 child RMS patients. Protein concentration of CYPs was determined using Western blot. The expression levels were tested for correlation with the clinical and pathological data of the patients. Our data showed that the expression levels of CYP1A1 and CYP1A2 were negligible. Elevated expression of CYP1B1 mRNA and protein was detected in most RMS tumors and adjacent normal tissues. Most cancerous samples exhibit higher levels of both CYP3A4 and CYP3A5 compared with normal tissue samples. Expression of CYP2E1 mRNA was found to be significantly higher in tumor tissue, however no relation was found with protein levels. CYP2W1 mRNA and/or protein are mainly expressed in tumors. In conclusion, we defined the CYP gene expression profile in tumor and paired normal tissue of child patients with RMS. The overexpression of CYP2W1, CYP3A4 and CYP3A5 in tumor tissues suggests that they may be involved in RMS chemoresistance; furthermore, they may be exploited for the localized activation of anticancer prodrugs.

Xu J, Wang J, Hu Y, et al.
Unequal prognostic potentials of p53 gain-of-function mutations in human cancers associate with drug-metabolizing activity.
Cell Death Dis. 2014; 5:e1108 [PubMed] Free Access to Full Article Related Publications
Mutation of p53 is the most common genetic change in human cancer, causing complex effects including not only loss of wild-type function but also gain of novel oncogenic functions (GOF). It is increasingly likely that p53-hotspot mutations may confer different types and magnitudes of GOF, but the evidences are mainly supported by cellular and transgenic animal models. Here we combine large-scale cancer genomic data to characterize the prognostic significance of different p53 mutations in human cancers. Unexpectedly, only mutations on the Arg248 and Arg282 positions displayed significant association with shorter patient survival, but such association was not evident for other hotspot GOF mutations. Gene set enrichment analysis on these mutations revealed higher activity of drug-metabolizing enzymes, including the CYP3A4 cytochrome P450. Ectopic expression of p53 mutant R282W in H1299 and SaOS2 cells significantly upregulated CYP3A4 mRNA and protein levels, and cancer cell lines bearing mortality-associated p53 mutations display higher CYP3A4 expression and resistance to several CYP3A4-metabolized chemotherapeutic drugs. Our results suggest that p53 mutations have unequal GOF activities in human cancers, and future evaluation of p53 as a cancer biomarker should consider which mutation is present in the tumor, rather than having comparison between wild-type and mutant genotypes.

Pibiri F, Kittles RA, Sandler RS, et al.
Genetic variation in vitamin D-related genes and risk of colorectal cancer in African Americans.
Cancer Causes Control. 2014; 25(5):561-70 [PubMed] Free Access to Full Article Related Publications
PURPOSE: Disparities in both colorectal cancer (CRC) incidence and survival impact African Americans (AAs) more than other US ethnic groups. Because vitamin D is thought to protect against CRC and AAs have lower serum vitamin D levels, genetic variants that modulate the levels of active hormone in the tissues could explain some of the cancer health disparity. Consequently, we hypothesized that genetic variants in vitamin D-related genes are associated with CRC risk.
METHODS: To test this hypothesis, we studied 39 potentially functional single-nucleotide polymorphisms (SNPs) in eight genes (CYP2R1, CYP3A4, CYP24A1, CYP27A1, CYP27B1, GC, DHCR7, and VDR) in 961 AA CRC cases and 838 healthy AA controls from Chicago and North Carolina. We tested whether SNPs are associated with CRC incidence using logistic regression models to calculate p values, odds ratios, and 95 % confidence intervals. In the logistic regression, we used a log-additive genetic model and used age, gender, and percent West African ancestry, which we estimated with the program STRUCTURE, as covariates in the models.
RESULTS: A nominally significant association was detected between CRC and the SNP rs12794714 in the vitamin D 25-hydroxylase gene CYP2R1 (p = 0.019), a SNP that has previously been associated with serum vitamin D levels. Two SNPs, rs16847024 in the GC gene and rs6022990 in the CYP24A1 gene, were nominally associated with left-sided CRC (p = 0.015 and p = 0.018, respectively).
CONCLUSIONS: Our results strongly suggest that genetic variation in vitamin D-related genes could affect CRC susceptibility in AAs.

Doherty D, Dvorkin SA, Rodriguez EP, Thompson PD
Vitamin D receptor agonist EB1089 is a potent regulator of prostatic "intracrine" metabolism.
Prostate. 2014; 74(3):273-85 [PubMed] Related Publications
BACKGROUND: A contributing factor to the emergence of castrate resistant prostate cancer (CRPC) is the ability of the tumor to circumvent low circulating levels of testosterone during androgen deprivation therapy (ADT), through the production of "intracrine" tumoral androgens from precursors including cholesterol and dehydroepiandrosterone (DHEA). As these processes promote AR signaling and prostate cancer progression their modulation is required for disease prevention and treatment.
METHODS: We evaluated the involvement of the vitamin D receptor ligand EB1089 in the regulation of genes with a role in androgen metabolism using the androgen dependent cell lines LNCaP and LAPC-4. EB1089 regulation of androgen metabolism was assessed using QRT-PCR, luciferase promoter assays, western blotting, enzyme activity assays, and LC-MS analyses.
RESULTS: EB1089 induced significant expression of genes involved in androgen metabolism in prostate cancer cells. Real-Time PCR analysis revealed that VDR mediated significant regulation of CYP3A4, CYP3A5, CYP3A43, AKR1C1-3, UGT2B15/17, and HSD17B2. Data revealed potent regulation of CYP3A4 at the level of mRNA, protein expression and enzymatic activity, with VDR identified as the predominant regulator. Inhibition of CYP3A activity using the specific inhibitor ritonavir resulted in alleviation of the anti-proliferative response of VDR ligands in prostate cancer cells. Mass spectrometry revealed that overexpression of CYP3A protein in prostate cancer cells resulted in a significant increase in the oxidative inactivation of testosterone and DHEA to their 6-β-hydroxy-testosterone and 16-α-hydroxy-DHEA metabolites, respectively.
CONCLUSIONS: These data highlight a potential application of VDR-based therapies for the reduction of growth-promoting androgens within the tumor micro-environment.

Alcazar-González GA, Calderón-Garcidueñas AL, Garza-Rodríguez ML, et al.
Comparative study of polymorphism frequencies of the CYP2D6, CYP3A5, CYP2C8 and IL-10 genes in Mexican and Spanish women with breast cancer.
Pharmacogenomics. 2013; 14(13):1583-92 [PubMed] Related Publications
AIM: Pharmacogenetic studies in breast cancer (BC) may predict the efficacy of tamoxifen and the toxicity of paclitaxel and capecitabine. We determined the frequency of polymorphisms in the CYP2D6 gene associated with activation of tamoxifen, and those of the genes CYP2C8, CYP3A5 and DPYD associated with toxicity of paclitaxel and capecitabine. We also included a IL-10 gene polymorphism associated with advanced tumor stage at diagnosis.
PATIENTS & METHODS: Genomic DNAs from 241 BC patients from northeast Mexico were genotyped using DNA microarray technology.
RESULTS: For tamoxifen processing, CYP2D6 genotyping predicted that 90.8% of patients were normal metabolizers, 4.2% ultrarapid, 2.1% intermediate and 2.9% poor metabolizers. For paclitaxel and the CYP2C8 gene, 75.3% were normal, 23.4% intermediate and 1.3% poor metabolizers. Regarding the DPYD gene, only one patient was a poor metabolizer. For the IL-10 gene, 47.1% were poor metabolizers.
CONCLUSION: These results contribute valuable information towards personalizing BC chemotherapy in Mexican women.

Islam MS, Mostofa AG, Ahmed MU, et al.
Association of CYP3A4, CYP3A5 polymorphisms with lung cancer risk in Bangladeshi population.
Tumour Biol. 2014; 35(2):1671-8 [PubMed] Related Publications
The rate of direct smoking, second hand smoking, and smokeless tobacco users as well as the amount of environmental pollutant like polycyclic aromatic hydrocarons is increasing in Bangladesh. Therefore, the prevalence of lung cancer is increasing day by day. To the best of our knowledge, no pharmacogentic study of CYP3A4, CYP3A5 genes has been reported on Bangladeshi population relating those with lung cancer. The present study was conducted to determine the association of CYP3A4, CYP3A5 gene polymorphisms and tobacco smoking in the development of lung cancer in Bangladeshi population. A case-control study was carried out on 106 lung cancer patients and 116 controls to investigate three allelic variants-CYP3A4*1B, CYP3A5*3, and CYP3A5*6 using Polymerase Chain Reaction Restriction Fragment Length Polymorphism. Risk of lung cancer was estimated as odds ratio (OR) and 95 % confidence interval (CI) using unconditional logistic regression models. The variant allele frequencies for CYP3A4*1B (*1A/*1B + *1B/*1B) were 2.83 % and 0.86 % and that of CYP3A5*3 (*1A/*3 + *3/*3) were 88.68 % and 85.34 % in cases and controls, respectively. Individual carrying at least one variant allele of CYP3A4*1B (CYP3A4*1A/1B + *1B/1B) has a 3.35 times more risk (OR = 3.35, 95 % Cl = 0.34-32.71, p = 0.271) for developing lung cancer whereas individual carrying at least one variant allele of CYP3A5 (CYP3A5*1A/3 + *3/3) has a 1.26 times more risk (OR = 1.35, 95 % Cl = 0.61-2.97) and both are statistically non-significant (p > 0.05). CYP3A5*6 was absent in the study population. No association of lung cancer with the mentioned polymorphisms was found both in heavy and light smokers. In the cases of all three major types of lung cancer-squamous cell carcinoma, adenocarcinoma, and small cell carcinoma-significantly strong relationships (p ˂ 0.05) have been found. To confirm the association of lung cancer with the mentioned polymorphisms, large number volunteers (patients and controls) will be required.

Li WJ, Zhong SL, Wu YJ, et al.
Systematic expression analysis of genes related to multidrug-resistance in isogenic docetaxel- and adriamycin-resistant breast cancer cell lines.
Mol Biol Rep. 2013; 40(11):6143-50 [PubMed] Related Publications
Docetaxel (Doc) and adriamycin (Adr) are two of the most effective chemotherapeutic agents in the treatment of breast cancer. However, their efficacy is often limited by the emergence of multidrug resistance (MDR). The purpose of this study was to investigate MDR mechanisms through analyzing systematically the expression changes of genes related to MDR in the induction process of isogenic drug resistant MCF-7 cell lines. Isogenic resistant sublines selected at 100 and 200 nM Doc (MCF-7/100 nM Doc and MCF-7/200 nM Doc) or at 500 and 1,500 nM Adr (MCF-7/500 nM Adr and MCF-7/1,500 nM) were developed from human breast cancer parental cell line MCF-7, by exposing MCF-7 to gradually increasing concentrations of Doc or Adr in vitro. Cell growth curve, flow cytometry and MTT cytotoxicity assay were preformed to evaluate the MDR characteristics developed in the sublines. Some key genes on the pathways related to drug resistance (including drug-transporters: MDR1, MRP1 and BCRP; drug metabolizing-enzymes: CYP3A4 and glutathione S-transferases (GST) pi; target genes: topoisomerase II (TopoIIα) and Tubb3; apoptosis genes: Bcl-2 and Bax) were analyzed at RNA and protein expression levels by real time RT-qPCR and western blot, respectively. Compared to MCF-7/S (30.6 h), cell doubling time of MCF-7/Doc (41.6 h) and MCF-7/Adr (33.8 h) were both prolonged, and the cell proportion of resistant sublines in G1/G2 phase increased while that in S-phase decreased. MCF-7/100 nM Doc and MCF-7/200 nM Doc was 22- and 37-fold resistant to Doc, 18- and 32-fold to Adr, respectively. MCF-7/500 nM Adr and MCF-7/1,500 nM Adr was 61- and 274-fold resistant to Adr, three and 12-fold to Doc, respectively. Meantime, they also showed cross-resistance to the other anticancer drugs in different degrees. Compared to MCF-7/S, RT-qPCR and Western blot results revealed that the expression of MDR1, MRP1, BCRP, Tubb3 and Bcl-2 were elevated in both MCF-7/Doc and MCF-7/Adr, and TopoIIα, Bax were down-regulated in both the sublines, while CYP3A4, GST pi were increased only in MCF-7/Doc and MCF-7/Adr respectively. Furthermore, the changes above were dose-dependent. The established MCF-7/Doc or MCF-7/Adr has the typical MDR characteristics, which can be used as the models for resistance mechanism study. The acquired process of MCF-7/S resistance to Doc or Adr is gradual, and is complicated with the various pathways involved in. There are some common resistant mechanisms as well as own drug-specific changes between both the sublines.

Wolf RJ, Hilger RA, Hoheisel JD, et al.
In vivo activity and pharmacokinetics of nemorosone on pancreatic cancer xenografts.
PLoS One. 2013; 8(9):e74555 [PubMed] Free Access to Full Article Related Publications
Pancreatic cancer is one of the leading cancer-related causes of death in the western world with an urgent need for new treatment strategies. Recently, hyperforin and nemorosone have been described as promising anti-cancer lead compounds. While hyperforin has been thoroughly investigated in vitro and in vivo, in vivo data for nemorosone are still missing. Thus, we investigated the growth-inhibitory potential of nemorosone on pancreatic cancer xenografts in NMRI nu/nu mice and determined basic pharmacokinetic parameters. Xenograft tumors were treated with nemorosone and gemcitabine, the current standard of care. Tumor sections were subjected to H&E as well as caspase 3 and Ki-67 staining. Nemorosone plasma kinetics were determined by HPLC and mass spectrometry. Induction of CYP3A4 and other metabolizing enzymes by nemorosone and hyperforin was tested on primary hepatocytes using qRT-PCR. At a dose of 50 mg/kg nemorosone per day, a significant growth-inhibitory effect was observed in pancreatic cancer xenografts. The compound was well tolerated and rapidly absorbed into the bloodstream with a half-life of approximately 30 min. Different metabolites were detected, possibly resembling CYP3A4-independent oxidation products. It is concluded that nemorosone is a potential anti-cancer lead compound with good bioavailability, little side-effects and promising growth-inhibitory effects, thus representing a valuable compound for a combination therapy approach.

Fernández-Santander A, Gaibar M, Novillo A, et al.
Relationship between genotypes Sult1a2 and Cyp2d6 and tamoxifen metabolism in breast cancer patients.
PLoS One. 2013; 8(7):e70183 [PubMed] Free Access to Full Article Related Publications
Tamoxifen is a pro-drug widely used in breast cancer patients to prevent tumor recurrence. Prior work has revealed a role of cytochrome and sulfotransferase enzymes in tamoxifen metabolism. In this descriptive study, correlations were examined between concentrations of tamoxifen metabolites and genotypes for CYP2D6, CYP3A4, CYP3A5, SULT1A1, SULT1A2 and SULT1E1 in 135 patients with estrogen receptor-positive breast cancer. Patients were genotyped using the Roche-AmpliChip® CYP450 Test, and Real-Time and conventional PCR-RFLP. Plasma tamoxifen, 4-hydroxy-tamoxifen, N-desmethyl-tamoxifen, endoxifen and tamoxifen-N-oxide were isolated and quantified using a high-pressure liquid chromatography-tandem mass spectrometry system. Significantly higher endoxifen levels were detected in patients with the wt/wt CYP2D6 compared to the v/v CYP2D6 genotype (p<0.001). No differences were detected in the remaining tamoxifen metabolites among CYP2D6 genotypes. Patients featuring the SULT1A2*2 and SULT1A2*3 alleles showed significantly higher plasma levels of 4-hydroxy-tamoxifen and endoxifen (p = 0.025 and p = 0.006, respectively), as likely substrates of the SULT1A2 enzyme. Our observations indicate that besides the CYP2D6 genotype leading to tamoxifen conversion to potent hydroxylated metabolites in a manner consistent with a gene-dose effect, SULT1A2 also seems to play a role in maintaining optimal levels of both 4-hydroxy-tamoxifen and endoxifen.

Niu Y, Wu Z, Shen Q, et al.
Hepatitis B virus X protein co-activates pregnane X receptor to induce the cytochrome P450 3A4 enzyme, a potential implication in hepatocarcinogenesis.
Dig Liver Dis. 2013; 45(12):1041-8 [PubMed] Related Publications
BACKGROUND: Hepatitis B virus X protein is a key regulator of hepatocarcinogenesis. The pregnane X receptor is a xenobiotic nuclear receptor that plays a role in the regulation of drug-metabolizing enzymes including the cytochrome P450 3A4, an enzyme important for the bioactivation of the liver carcinogen aflatoxin B1.
AIMS: To identify novel host factor that interacts with hepatitis B virus X protein and the functional interaction between hepatitis B virus X protein and pregnane X receptor in hepatocarcinogenesis.
METHODS: Co-immunoprecipitation, glutathione S-transferase pull-down, and chromatin immunoprecipitation were utilized to assess the interaction between hepatitis B virus X protein and pregnane X receptor. The functional relevance of hepatitis B virus X protein-pregnane X receptor interaction was investigated in cell cultures and hepatocellular carcinoma samples.
RESULTS: We observed that hepatitis B virus X protein and pregnane X receptor co-localize in hepatic cells. Pregnane X receptor interacted with hepatitis B virus X protein via the ligand-binding domain of pregnane X receptor. Functionally, hepatitis B virus X protein increased the transcriptional activity of pregnane X receptor. Pregnane X receptor was able to recruit hepatitis B virus X protein to the CYP3A4 gene promoter. In clinic samples, the expression of pregnane X receptor was high in hepatitis B virus-associated liver cirrhosis and stage I hepatocellular carcinoma, but low in state II and stage III hepatocellular carcinoma.
CONCLUSION: We revealed a novel function of hepatitis B virus X protein in co-activating pregnane X receptor. The increased expression of pregnane X receptor and its target gene CYP3A4 are potential biomarkers for the early stage of hepatitis B virus-associated hepatocarcinogenesis.

Timm A, Kolesar JM
Crizotinib for the treatment of non-small-cell lung cancer.
Am J Health Syst Pharm. 2013; 70(11):943-7 [PubMed] Related Publications
PURPOSE: The pharmacology, pharmacokinetics, clinical efficacy, safety, adverse effects, and dosage and administration of crizotinib in the management of non-small-cell lung cancer (NSCLC) are reviewed.
SUMMARY: Crizotinib (Xalkori, Pfizer Inc.) is a novel tyrosine kinase inhibitor approved for the treatment of patients with locally advanced or metastatic NSCLC who exhibit assay-confirmed mutations of the gene coding for anaplastic lymphoma kinase (ALK). The primary biochemical mechanism of crizotinib is to inhibit ALK expression, leading to increased cell proliferation and decreased apoptosis. Crizotinib is metabolized and excreted after O-dealkylation by cytochrome P-450 (CYP) isoenzyme 3A4/5; as crizotinib is also an inhibitor of CYP3A4/5, its use entails a high potential for drug interactions, including confirmed interactions with ketoconazole and rifampin that can alter crizotinib pharmacokinetics. A Phase I trial involving patients with ALK gene mutation-positive NSCLC demonstrated significant disease control with oral crizotinib use, including an overall eight-week response rate of 87% and an estimated six-month survival of 72%. At the standard dosage of 250 mg twice daily, crizotinib is well tolerated. In clinical trials to date, the most common grade 1 or 2 adverse events were nausea, diarrhea, vomiting, and visual disturbances; more severe toxicities included transaminase elevations (less than 7% of patients) and pneumonitis (less than 2% of patients). Hypogonadism leading to low testosterone levels appears to be universal among male patients treated with crizotinib.
CONCLUSION: Crizotinib appears to be efficacious and well tolerated in patients with NSCLC and may have future potential applications in treating lymphomas and other cancers driven by ALK or c-MET gene mutations.

Takimoto T, Kijima T, Otani Y, et al.
Polymorphisms of CYP2D6 gene and gefitinib-induced hepatotoxicity.
Clin Lung Cancer. 2013; 14(5):502-7 [PubMed] Related Publications
INTRODUCTION: Gefitinib induces severe hepatotoxicity in approximately a quarter of Japanese patients with epidermal growth factor receptor (EGFR) mutation-positive non-small-cell lung cancer (NSCLC). Gefitinib is metabolized by cytochrome P450 (CYP) enzymes--including CYP3A4/5, CYP1A1, and CYP2D6--in the liver. We hypothesized that polymorphisms of the CYP2D6 gene may account for gefitinib-induced hepatotoxicity.
PATIENTS AND METHODS: Polymorphisms of the CYP2D6 gene were analyzed in 55 patients with NSCLC who experienced grade ≥ 2 transaminase elevation from gefitinib. The distribution of the CYP2D6 genotype was compared with that of the healthy Japanese population. The correlations between the nonfunctional allele *5 or the reduced-function allele *10 and hepatotoxicity-related clinical factors were also examined.
RESULTS: The distribution of the CYP2D6 genotype in the study participants was not different from that of the general Japanese population, reported previously. Existence of allele *5 or *10 did not correlate with clinical factors such as onset of hepatotoxicity within 2 months, grade ≥ 3 serum transaminase elevation, and tolerability to dose reduction or rechallenge of gefitinib. However, in 7 patients taking CYP3A4-inhibitory drugs, rechallenge of gefitinib again caused hepatotoxicity in 4 patients with allele *5 or *10 but not in 3 patients with normal alleles (P = .029). Moreover, switching to erlotinib did not cause hepatotoxicity in any of 17 patients with allele *5 or *10 but did in 3 of 8 patients without these alleles (P = .024).
CONCLUSION: Reduced function of CYP2D6 may partly account for gefitinib-induced hepatotoxicity when CYP3A4 is inhibited. Erlotinib could be safely used in patients with decreased CYP2D6 activity even after they experienced gefitinib-induced hepatotoxicity.

Li J, Wang Y, Zhu Y, Oupický D
Recent advances in delivery of drug-nucleic acid combinations for cancer treatment.
J Control Release. 2013; 172(2):589-600 [PubMed] Free Access to Full Article Related Publications
Cancer treatment that uses a combination of approaches with the ability to affect multiple disease pathways has been proven highly effective in the treatment of many cancers. Combination therapy can include multiple chemotherapeutics or combinations of chemotherapeutics with other treatment modalities like surgery or radiation. However, despite the widespread clinical use of combination therapies, relatively little attention has been given to the potential of modern nanocarrier delivery methods, like liposomes, micelles, and nanoparticles, to enhance the efficacy of combination treatments. This lack of knowledge is particularly notable in the limited success of vectors for the delivery of combinations of nucleic acids with traditional small molecule drugs. The delivery of drug-nucleic acid combinations is particularly challenging due to differences in the physicochemical properties of the two types of agents. This review discusses recent advances in the development of delivery methods using combinations of small molecule drugs and nucleic acid therapeutics to treat cancer. This review primarily focuses on the rationale used for selecting appropriate drug-nucleic acid combinations as well as progress in the development of nanocarriers suitable for simultaneous delivery of drug-nucleic acid combinations.

Rigalli JP, Reuter T, Herold-Mende C, et al.
Minor role of pregnane-x-receptor for acquired multidrug resistance in head and neck squamous cell carcinoma in vitro.
Cancer Chemother Pharmacol. 2013; 71(5):1335-43 [PubMed] Related Publications
PURPOSE: Acquired multidrug resistance (MDR) has been linked to overexpression of drug-metabolising and transporting proteins mediated by pregnane-x-receptor (PXR). The aim of this work was to establish the relevance of PXR for MDR in head and neck squamous cell carcinoma (HNSCC).
METHODS: Using eight HNSCC cell lines, we determined the efficacy of paclitaxel, cisplatin and 5-fluorouracil (5-FU) via proliferation assays and determined the expression and activity of PXR through quantitative real-time polymerase chain reaction, western blotting and luciferase-based reporter gene assay. PXR knockdown approaches using shRNA-encoding vectors were applied to estimate the role of PXR for native MDR.
RESULTS: Drug resistance ranged between 5.2 and 620 nM for paclitaxel, varied between 4.5 and 58 μM for cisplatin, and varied between 1.1 and 5,467 μM for 5-FU. Lack of PXR mRNA expression was mostly accompanied by the absence of mRNA expression of cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (P-gp, ABCB1) expression. Neither mRNA nor protein expression of PXR correlated with drug resistance. However, PXR activity tended to correlate with IC50 values of paclitaxel (p = 0.08). Knockdown of PXR in one of the cell lines had a slight but not significant impact on paclitaxel efficacy compared to scrambled sequence control. Surprisingly, only in two cell lines, PXR activity was increased by the well-known inductor rifampicin.
CONCLUSION: This study suggests a malfunctioning of PXR and thus a minor relevance for iatrogenic chemotherapy resistance in HNSCC.

Bedewy AM, El-Maghraby SM
Do SLCO1B3 (T334G) and CYP3A5*3 polymorphisms affect response in Egyptian chronic myeloid leukemia patients receiving imatinib therapy?
Hematology. 2013; 18(4):211-6 [PubMed] Related Publications
BACKGROUND: Imatinib has so far been the first-choice treatment in chronic myeloid leukemia (CML) with excellent results. However, only a proportion of patients achieve major molecular response. Hence, the need to find whether there are some factors that affect the response to treatment is essential. This study aimed to investigate the allele and genotype frequencies of single nucleotide polymorphisms (SNPs) of SLCO1B3 (T334G) and CYP3A5*3 in CML patients undergoing imatinib treatment and to determine whether SNPs of these two genes could predict the response of imatinib therapy in CML patients.
SUBJECTS AND METHODS: We investigated SLCO1B3 (T334G) and CYP3A5*3 polymorphisms by Polymerase Chain Reaction-restriction fragment length polymorphism in 86 Philadelphia positive newly diagnosed Egyptian CML patients (78 patients in chronic phase and 8 patients in accelerated phase). All patients received imatinib therapy and were followed for at least one and half years. The response to imatinib therapy was evaluated by recording the hematological response, cytogenetic response, and molecular response according to the European Leukemia Net criteria.
RESULTS: This study included 86 Philadelphia positive newly diagnosed CML patients, 78 in the early chronic phase and 8 in the accelerated phase. In the chronic phase patients, no association between SLCO1B3 (T334G) exon 3 polymorphism and response to imatinib therapy was detected (P = 0.938) while CYP3A5*3 gene polymorphism was associated with inferior outcome (P < 0.001). In the group of accelerated phase patients, the SLCO1B3 polymorphic variants (TG) and (GG) were detected equally with none of the patients in this group having the homozygous wild form (TT). The homozygous state for the CYP3A5*3 allele was the most frequent (50%) and the homozygous state for the CYP3A5*1 allele was the least frequent (12.5%) in this group.
CONCLUSION: CYP3A5*3 polymorphism was associated with imatinib efficacy while the SNP SLCO1B3 (T334G) was not associated with the response to imatinib treatment in Egyptian patients with CML in chronic phase. These results prompt us to explore the effect of CYP3A5*3 in CML patients taking imatinib in a larger scale study.

Motohashi S, Mino Y, Hori K, et al.
Interindividual variations in aprepitant plasma pharmacokinetics in cancer patients receiving cisplatin-based chemotherapy for the first time.
Biol Pharm Bull. 2013; 36(4):676-81 [PubMed] Related Publications
The pharmacokinetics of aprepitant, a neurokinin-1 receptor antagonist, have not been fully evaluated in clinical settings. The aim of this study was to characterize the plasma pharmacokinetics of aprepitant and reveal their influence of laboratory tests and cytochrome P450 (CYP) 3A5 gene polymorphisms in cancer patients. Forty-four Japanese cancer patients receiving cisplatin-based chemotherapy for the first time following oral aprepitant (125 mg on day 1 and 80 mg on days 2 and 3) were enrolled. The patients did not have gastrointestinal disease and the clinical laboratory values were within their normal reference levels. The plasma concentrations of aprepitant 24 (day 2 predose), 72, and 120 h after the first aprepitant administration were determined using LC-MS/MS. The relationships between plasma exposure to aprepitant and body weight, clinical laboratory values, age, gender, or CYP3A5*3 were investigated. The median and interquartile ranges of the 120-h area under the plasma concentration time curve (AUC)(0-120) of aprepitant were 73215 and 55518-91121 ng h/mL. The coefficient of variation value for aprepitant AUC(0-120) was 53%. The AUC(0-120) of aprepitant was correlated with the levels of total bilirubin and serum albumin, respectively (r=0.454, p<0.01 and r=0.287, p=0.06), but not with other non-genetic factors and CYP3A5 genetic variants in a univariate analysis. The AUC(0-120) of aprepitant was significantly correlated with the level of total bilirubin (adjusted R(2)=0.187, p<0.01) in a multivariate analysis. In conclusion, the plasma pharmacokinetics of aprepitant varied markedly in cancer patients receiving cisplatin-based chemotherapy for the first time and were correlated with the level of total bilirubin.

Elens L, Nieuweboer A, Clarke SJ, et al.
CYP3A4 intron 6 C>T SNP (CYP3A4*22) encodes lower CYP3A4 activity in cancer patients, as measured with probes midazolam and erythromycin.
Pharmacogenomics. 2013; 14(2):137-49 [PubMed] Related Publications
AIM: The CYP3A4*22 allele was recently reported to be associated with reduced CYP3A4 activity. We investigated the impact of this allele on the metabolism of the CYP3A-phenotyping probes, midazolam (MDZ) and erythromycin.
PATIENTS & METHODS: Genomic DNA from 108 cancer patients receiving intravenous MDZ and 45 undergoing the erythromycin breath test was analyzed for CYP3A4*22 (rs35599367 C>T) and CYP3A5*3.
RESULTS: The MDZ metabolic ratio (1´-OH-MDZ:MDZ) was 20.7% (95% CI: -36.2 to -6.2) lower for CYP3A4*22 carriers compared with CYP3A4*1/*1 patients (p = 0.01). Combining CYP3A4*22 and CYP3A5*3 genotypes showed a 38.7% decrease (95% CI: -50.0 to -27.4; p < 0.001) in 1´-OH-MDZ:MDZ for poor (CYP3A4*22-CYP3A5*3/*3) and 28.0% (95% CI: -33.3 to -22.6; p < 0.001) for intermediate (CYP3A4*1/*1-CYP3A5*3/*3) metabolizers, compared with extensive (CYP3A4*1/*1-CYP3A5*1) CYP3A metabolizers. CYP3A4 erythromycin N-demethylation activity was 40% lower in CYP3A4*22 carriers compared with CYP3A4*1/*1 patients (p = 0.032).
CONCLUSION: The CYP3A4*22 allele is associated with decreased CYP3A4-mediated metabolism, as verified by CYP3A-phenotyping probes.

Altés A, Paré L, Esquirol A, et al.
Pharmacogenetic analysis in the treatment of Hodgkin lymphoma.
Leuk Lymphoma. 2013; 54(8):1706-12 [PubMed] Related Publications
About 15-20% of patients with Hodgkin lymphoma (HL) treated with doxorubicin, bleomycin, vinblastine and dacarbazine (ABVD) chemotherapy ± radiotherapy still die following relapse or progressive disease. The outcome might be influenced by gene polymorphisms influencing chemotherapy metabolism. We studied 126 patients with HL treated with the ABVD regimen. We analyzed glutathione S-transferases (GSTT1, GSTM1 and GSTP1), cytochromes P450 (CYP3A4 and CYP2D6), UGT1A1 and BLMH gene polymorphisms and their association with clinical and outcome variables. Patients with a GSTM1 genotype associated with extensive or ultrahigh activity had a probability of 93.8% to achieve a complete response, while the remainder of the patients had a probability of 82.3% (p = 0.04). This variable maintained its statistical significance in multivariate analysis (hazard ratio 3.7, 95% confidence interval 1-13, p = 0.05). Patients with an extensive or ultrahigh GSTM1 genotype had better prognostic factors than those with poor or intermediate genotypes (hemoglobin level, p = 0.003; serum albumin, p = 0.05; and International Prognostic Score, p = 0.038). Thus, in the treatment of HL, clinical determinants might be more relevant than the pharmacogenetic parameters analyzed to date.

Sivertsson L, Edebert I, Palmertz MP, et al.
Induced CYP3A4 expression in confluent Huh7 hepatoma cells as a result of decreased cell proliferation and subsequent pregnane X receptor activation.
Mol Pharmacol. 2013; 83(3):659-70 [PubMed] Related Publications
We have previously shown that confluent growth of the human hepatoma cell line Huh7 substantially induces the CYP3A4 mRNA, protein, and activity levels. Here, the mechanisms behind were investigated, and a transcriptome analysis revealed significant up-regulation of liver-specific functions, whereas pathways related to proliferation and cell cycle were down-regulated in the confluent cells. Reporter analysis revealed that the CYP3A4 gene was transcriptionally activated during confluence in a process involving pregnane X receptor (PXR). PXR expression was increased, and PXR protein accumulated in the nuclei during confluent growth. The PXR ligand rifampicin further increased the expression of CYP3A4, and siRNA-mediated knock-down of PXR in confluent cells resulted in decreased CYP3A4 expression. Cyclin-dependent kinase 2 (CDK2), a known modulator of the cell cycle and a negative regulator of PXR, was more highly expressed in proliferating control cells. Trypsinization of the confluent cells and replating them subconfluent resulted in a decrease in CYP3A4 and PXR expression back to levels observed in subconfluent control cells, whereas the CDK2 levels increased. Knock-down of CDK2 in proliferating control cells increased the CYP3A4 and PXR protein levels. Moreover, the CDK inhibitor roscovitine stimulated the expression of CYP3A4. A phosphorylation-deficient mutation (S350A) in the PXR protein significantly induced the CYP3A4 transcription. In conclusion, the data strongly suggest that the increased CYP3A4 expression in confluent Huh7 cells is caused by the endogenous induction of PXR as a result of cell-cell contact inhibited proliferation and subsequent decreased CDK2 activities, indicating an endogenous, non-ligand-dependent regulation of PXR and CYP3A4, possibly of physiologic and pharmacological significance.

Jabir RS, Naidu R, Annuar MA, et al.
Pharmacogenetics of taxanes: impact of gene polymorphisms of drug transporters on pharmacokinetics and toxicity.
Pharmacogenomics. 2012; 13(16):1979-88 [PubMed] Related Publications
Interindividual variability in drug response and the emergence of adverse drug effects are the main causes of treatment failure in cancer therapy. Functional membrane drug transporters play important roles in altering pharmacokinetic profile, resistance to treatment, toxicity and patient survival. Pharmacogenetic studies of these transporters are expected to provide new approaches for optimizing therapy. Taxanes are approved for the treatment of various cancers. Circulating taxanes are taken up by SLCO1B3 into hepatocytes. The CYP450 enzymes CYP3A4, CYP3A5 and CYP2C8 are responsible for the conversion of taxanes into their metabolites. Ultimately, ABCB1 and ABCC2 will dispose the metabolites into bile canaliculi. Polymorphisms of genes encoding for proteins involved in the transport and clearance of taxanes reduce excretion of the drugs, leading to development of toxicity in patients. This review addresses current knowledge on genetic variations of transporters affecting taxanes pharmacokinetics and toxicity, and provides insights into future direction for personalized medicine.

Zhou LP, Yao F, Luan H, et al.
CYP3A4*1B polymorphism and cancer risk: a HuGE review and meta-analysis.
Tumour Biol. 2013; 34(2):649-60 [PubMed] Related Publications
CYP450 3A4 (CYP3A4), encoded by the CYP3A4 gene, is a major enzyme catalyzing the metabolism of both endogenous and exogenous agents that may play a role in the etiology of carcinogenesis. Several potentially functional polymorphisms of the CYP3A4 gene have been implicated in cancer risk, but individually published studies have shown inconclusive results. The aim of this Human Genome Epidemiology (HuGE) review and meta-analysis was to investigate the association between CYP3A4*1B (rs2740574 A > G) polymorphism and cancer risk. Eleven studies were included with a total of 3,810 cancer patients and 3,173 healthy controls. We found that the G allele and GG genotype of CYP3A4*1B polymorphism were associated with increased risk of cancers using the fixed effects model (allele model: odds ratio (OR) = 1.24, 95 %CI: 1.09-1.42, P = 0.001; recessive model: OR = 1.77, 95 %CI: 1.30-2.41, P < 0.001; homozygous model: OR = 1.72, 95 %CI: 1.19-2.47, P = 0.004). Subgroup analyses by cancer type showed that the G allele and G carrier (AG + GG) of CYP3A4*1B polymorphism had significant associations with increased risk of prostate cancer, but not with breast cancer, leukemia, or other cancers. With further subgroup analysis based on different ethnicities, the results indicated that the GG genotype of CYP3A4*1B polymorphism might increase the risk of cancer among African populations. However, similar associations were not observed among Caucasian and Asian populations. Results from the current meta-analysis indicate that the G allele and GG genotype of CYP3A4*1B polymorphism might be associated with increased cancer risk, especially for prostate cancer among African populations.

Wang D, Li L, Yang H, et al.
The constitutive androstane receptor is a novel therapeutic target facilitating cyclophosphamide-based treatment of hematopoietic malignancies.
Blood. 2013; 121(2):329-38 [PubMed] Free Access to Full Article Related Publications
Cyclophosphamide (CPA) is one of the most widely used chemotherapeutic prodrugs that undergoes hepatic bioactivation mediated predominantly by cytochrome P450 (CYP) 2B6. Given that the CYP2B6 gene is primarily regulated by the constitutive androstane receptor (CAR, NR1I3), we hypothesize that selective activation of CAR can enhance systemic exposure of the pharmacologically active 4-hydroxycyclophosamide (4-OH-CPA), with improved efficacy of CPA-based chemotherapy. In this study, we have developed a unique human primary hepatocyte (HPH)-leukemia cell coculture model; the chemotherapeutic effects of CPA on leukemia cells can be directly investigated in vitro in a cellular environment where hepatic metabolism was well maintained. Our results demonstrated that activation of CAR preferentially induces the expression of CYP2B6 over CYP3A4 in HPHs, although endogenous expression of these enzymes in leukemia cells remains negligible. Importantly, coadministration of CPA with a human CAR activator led to significantly enhanced cytotoxicity in leukemia cells by inducing the apoptosis pathways, without concomitant increase in the off-target hepatotoxicity. Associated with the enhanced antitumor activity, a time and concentration-dependent increase in 4-OH-CPA formation was observed in the coculture system. Together, our findings offer proof of concept that CAR as a novel molecular target can facilitate CPA-based chemotherapy by selectively promoting its bioactivation.

Tang NL, Liao CD, Wang X, et al.
Role of pharmacogenetics on adjuvant chemotherapy-induced neutropenia in Chinese breast cancer patients.
J Cancer Res Clin Oncol. 2013; 139(3):419-27 [PubMed] Related Publications
BACKGROUND: Breast cancer patients regularly undergo adjuvant chemotherapies following surgery. However, these treatments are largely associated with chemotherapeutic toxicities ranging from nausea to severe myelosuppression. In this investigation, we examined the effects of four SNPs in NR1I2, CYP3A4 and CYP3A5 genes on chemotherapy-induced severe neutropenia in 311 female Chinese breast cancer patients undergoing a standard adjuvant chemotherapy regimen.
METHODS: Patients were monitored for adverse reactions throughout the treatment, then divided into "none or mild" (80 %) or "severe" (20 %) toxicity groups according to whether they suffered grade 4 neutropenia defined as having an absolute neutrophil counts (ANC) of less than 0.5 × 10(9)/L anytime during the treatment. DNA was extracted from patients' peripheral blood samples, then genotyped using allele-specific Tm-shift PCR and melting analysis.
RESULTS: Logistic regression revealed that rs776746 or CYP3A5*3 strongly associated with grade 4 neutropenia (OR = 2.56, P = 0.023) after adjustment for covariates, one of which more significant factor was baseline ANC (OR = 0.68, P = 0.020). Although univariate analysis in all patients did not reveal any association at first, further analysis indicated that rs776746 is significantly associated with severe neutropenia in subgroup of breast cancer patients with normal baseline ANC (≥2.0 × 10(9)/L). These carriers of A-allele have 3.14-fold increased risk of developing severe neutropenia (P = 0.004).
CONCLUSION: Our results suggested that polymorphisms in CYP3A5 might be useful pharmacogenetic markers for the prediction of severe neutropenia during chemotherapy, however, only after screening patients by their baseline ANC in the presence of gene-environmental interaction. We demonstrate an approach of pharmacogenetic analysis, in which the genetic data should be analyzed in the perspective of other clinical parameters.

Sliva D, Loganathan J, Jiang J, et al.
Mushroom Ganoderma lucidum prevents colitis-associated carcinogenesis in mice.
PLoS One. 2012; 7(10):e47873 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Epidemiological studies suggest that mushroom intake is inversely correlated with gastric, gastrointestinal and breast cancers. We have recently demonstrated anticancer and anti-inflammatory activity of triterpene extract isolated from mushroom Ganoderma lucidum (GLT). The aim of the present study was to evaluate whether GLT prevents colitis-associated carcinogenesis in mice.
METHODS/PRINCIPAL FINDINGS: Colon carcinogenesis was induced by the food-borne carcinogen (2-Amino-1-methyl-6-phenylimidazol[4,5-b]pyridine [PhIP]) and inflammation (dextran sodium sulfate [DSS]) in mice. Mice were treated with 0, 100, 300 and 500 mg GLT/kg of body weight 3 times per week for 4 months. Cell proliferation, expression of cyclin D1 and COX-2 and macrophage infiltration was assessed by immunohistochemistry. The effect of GLT on XRE/AhR, PXR and rPXR was evaluated by the reporter gene assays. Expression of metabolizing enzymes CYP1A2, CYP3A1 and CYP3A4 in colon tissue was determined by immunohistochemistry. GLT treatment significantly suppressed focal hyperplasia, aberrant crypt foci (ACF) formation and tumor formation in mice exposed to PhIP/DSS. The anti-proliferative effects of GLT were further confirmed by the decreased staining with Ki-67 in colon tissues. PhIP/DSS-induced colon inflammation was demonstrated by the significant shortening of the large intestine and macrophage infiltrations, whereas GLT treatment prevented the shortening of colon lengths, and reduced infiltration of macrophages in colon tissue. GLT treatment also significantly down-regulated PhIP/DSS-dependent expression of cyclin D1, COX-2, CYP1A2 and CYP3A4 in colon tissue.
CONCLUSIONS: Our data suggest that GLT could be considered as an alternative dietary approach for the prevention of colitis-associated cancer.

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