Gene Summary

Gene:MAD2L1; MAD2 mitotic arrest deficient-like 1 (yeast)
Aliases: MAD2, HSMAD2
Summary:MAD2L1 is a component of the mitotic spindle assembly checkpoint that prevents the onset of anaphase until all chromosomes are properly aligned at the metaphase plate. MAD2L1 is related to the MAD2L2 gene located on chromosome 1. A MAD2 pseudogene has been mapped to chromosome 14. [provided by RefSeq, Jul 2008]
Databases:OMIM, HGNC, GeneCard, Gene
Protein:mitotic spindle assembly checkpoint protein MAD2A
Source:NCBIAccessed: 28 February, 2015


What does this gene/protein do?
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Pathways:What pathways are this gene/protein implicaed in?
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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.

  • HeLa Cells
  • Nuclear Proteins
  • Cell Cycle
  • Apoptosis
  • DNA Mutational Analysis
  • Tumor Markers
  • Bladder Cancer
  • Thyroid Cancer
  • Genes, cdc
  • Chromosome Segregation
  • Cell Proliferation
  • Cell Cycle Proteins
  • Mutation
  • Mitosis
  • Breast Cancer
  • Neoplastic Cell Transformation
  • Ubiquitin-Protein Ligases
  • Aneuploidy
  • Messenger RNA
  • Western Blotting
  • Chromosomal Instability
  • Sex Factors
  • World Health Organization
  • Chromosome 4
  • Protein Kinases
  • Flow Cytometry
  • Ultraviolet Rays
  • Mad2 Proteins
  • Protein-Serine-Threonine Kinases
  • Cancer Gene Expression Regulation
  • Spindle Apparatus
  • Stomach Cancer
  • Transcriptional Activation
  • Molecular Sequence Data
  • Calcium-Binding Proteins
  • Neoplasm Proteins
  • Repressor Proteins
  • Down-Regulation
  • Cdc20 Proteins
Tag cloud generated 28 February, 2015 using data from PubMed, MeSH and CancerIndex

Specific Cancers (4)

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: MAD2L1 (cancer-related)

Ali I, Braun DP
Resveratrol enhances mitomycin C-mediated suppression of human colorectal cancer cell proliferation by up-regulation of p21WAF1/CIP1.
Anticancer Res. 2014; 34(10):5439-46 [PubMed] Related Publications
BACKGROUND/AIM: Studies have shown that natural products could potentially be employed in combination therapies to decrease toxicity to healthy tissues by chemotherapy drugs. No studies however, have investigated the potential modulatory role of resveratrol (RV) on mitomycin C (MMC)-mediated effects on colorectal cancer. The aim of the present study was to investigate the impact of RV on MMC-mediated inhibition of colorectal cancer cell proliferation and to assess the potential mechanisms for such effects.
MATERIALS AND METHODS: Primary cell lines generated from resected colorectal tumor specimens were treated with RV, MMC or RV+MMC and cell proliferation and gene expression analyses were performed.
RESULTS: Suppression of cell proliferation by RV+MMC was significantly greater than individual treatments. RV+MMC synergistically modulated several genes but the up-regulation of p21(WAF1/CIP1) was several-fold greater.
CONCLUSION: The up-regulation of p21(WAF1/CIP1), which inhibits the cell cycle at G0/G1 and G2/M phases, may represent the predominant mechanism for enhancement of MMC-mediated anti-cancer effects by resveratrol.

Schneider C, Setty M, Holmes AB, et al.
MicroRNA 28 controls cell proliferation and is down-regulated in B-cell lymphomas.
Proc Natl Acad Sci U S A. 2014; 111(22):8185-90 [PubMed] Free Access to Full Article Related Publications
Burkitt lymphoma (BL) is a highly aggressive B-cell non-Hodgkin lymphoma (B-NHL), which originates from germinal center (GC) B cells and harbors translocations deregulating v-myc avian myelocytomatosis viral oncogene homolog (MYC). A comparative analysis of microRNAs expressed in normal and malignant GC B cells identified microRNA 28 (miR-28) as significantly down-regulated in BL, as well as in other GC-derived B-NHL. We show that reexpression of miR-28 impairs cell proliferation and clonogenic properties of BL cells by modulating several targets including MAD2 mitotic arrest deficient-like 1, MAD2L1, a component of the spindle checkpoint whose down-regulation is essential in mediating miR-28-induced proliferation arrest, and BCL2-associated athanogene, BAG1, an activator of the ERK pathway. We identify the oncogene MYC as a negative regulator of miR-28 expression, suggesting that its deregulation by chromosomal translocation in BL leads to miR-28 suppression. In addition, we show that miR-28 can inhibit MYC-induced transformation by directly targeting genes up-regulated by MYC. Overall, our data suggest that miR-28 acts as a tumor suppressor in BL and that its repression by MYC contributes to B-cell lymphomagenesis.

Wang P, Wang Y, Yan H, et al.
Genetic variation in the major mitotic checkpoint genes and risk of breast cancer: a multigenic study on cancer susceptibility.
Tumour Biol. 2014; 35(7):6701-5 [PubMed] Related Publications
The mitotic checkpoint system is a mechanism essential for maintaining genomic stability and defects which have been linked to cancer development. We conducted this hospital-based case-control study to investigate whether genetic variants in three major spindle checkpoint genes (BUB3, MAD2L1, and BUB1) had any bearing on an individual risk of breast cancer (BC). A total of 462 incident BC patients and 529 cancer-free controls were enrolled in this study. Results showed that neither variants in BUB3 nor variants in MAD2L1 caused any significant effect on the risk of BC. However, the variant rs12623473 in BUB1 was significantly associated with increased BC risk with the odds ratio (OR) of 1.30 (95 % confidence interval (CI) 1.03-1.64) under the allelic model. The estimated population attributable risk of one copy of the risk allele for developing BC was 10.3 %. The bioinformatics analysis suggested that this variant may regulate the transcriptional ability of BUB1.

Suraokar MB, Nunez MI, Diao L, et al.
Expression profiling stratifies mesothelioma tumors and signifies deregulation of spindle checkpoint pathway and microtubule network with therapeutic implications.
Ann Oncol. 2014; 25(6):1184-92 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
BACKGROUND: Malignant pleural mesothelioma (MPM) is a lethal neoplasm exhibiting resistance to most treatment regimens and requires effective therapeutic options. Though an effective strategy in many cancer, targeted therapy is relatively unexplored in MPM because the therapeutically important oncogenic pathways and networks in MPM are largely unknown.
MATERIALS AND METHODS: We carried out gene expression microarray profiling of 53 surgically resected MPMs tumors along with paired normal tissue. We also carried out whole transcriptomic sequence (RNA-seq) analysis on eight tumor specimens. Taqman-based quantitative Reverse-transcription polymerase chain reaction (qRT-PCR), western analysis and immunohistochemistry (IHC) analysis of mitotic arrest deficient-like 1 (MAD2L1) was carried out on tissue specimens. Cell viability assays of MPM cell lines were carried out to assess sensitivity to specific small molecule inhibitors.
RESULTS: Bioinformatics analysis of the microarray data followed by pathway analysis revealed that the mitotic spindle assembly checkpoint (MSAC) pathway was most significantly altered in MPM tumors with upregulation of 18 component genes, including MAD2L1 gene. We validated the microarray data for MAD2L1 expression using quantitative qRT-PCR and western blot analysis on tissue lysates. Additionally, we analyzed expression of the MAD2L1 protein by IHC using an independent tissue microarray set of 80 MPM tissue samples. Robust clustering of gene expression data revealed three novel subgroups of tumors, with unique expression profiles, and showed differential expression of MSAC pathway genes. Network analysis of the microarray data showed the cytoskeleton/spindle microtubules network was the second-most significantly affected network. We also demonstrate that a nontaxane small molecule inhibitor, epothilone B, targeting the microtubules have great efficacy in decreasing viability of 14 MPM cell lines.
CONCLUSIONS: Overall, our findings show that MPM tumors have significant deregulation of the MSAC pathway and the microtubule network, it can be classified into three novel molecular subgroups of potential therapeutic importance and epothilone B is a promising therapeutic agent for MPM.

Niimi K, Murakumo Y, Watanabe N, et al.
Suppression of REV7 enhances cisplatin sensitivity in ovarian clear cell carcinoma cells.
Cancer Sci. 2014; 105(5):545-52 [PubMed] Related Publications
Human REV7 (also known as MAD2L2 and MAD2B) is involved in DNA repair, cell cycle regulation, gene transcription, and carcinogenesis. In this study, we evaluated the expression of REV7 in epithelial ovarian cancer (EOC) and analyzed the association between its expression and chemosensitivity in ovarian clear cell carcinoma (CCC) cells. Expression of REV7 in human EOC tissues was assessed by immunohistochemical staining. Expression was detected in the majority of EOCs (92.0%) with especially high levels of expression frequently observed in CCCs (73.5%) compared with that of non-CCCs (53.4%). Enhanced immunoreactivity to REV7 was associated with poor prognosis represented by reduced progression-free survival in advanced stage (stage II-IV) EOC as assessed using Kaplan-Meier curves and log-rank tests. The effects of REV7 knockdown on cell proliferation and chemosensitivity in CCC cells were also analyzed in vitro and in vivo. Knockdown of REV7 in CCC cells decreased cell proliferation without affecting cell cycle distribution. Additionally, the number of apoptotic cells and DNA damaged cells were increased after cisplatin treatment. In a nude mouse tumor xenograft model, inoculated REV7-knockdown tumors showed significantly reduced tumor volumes after cisplatin treatment compared with those of the control group. These findings indicate that depletion of REV7 enhances sensitivity to cisplatin treatment in CCC, suggesting that REV7 is a candidate molecular target in CCC management.

Hell MP, Thoma CR, Fankhauser N, et al.
miR-28-5p promotes chromosomal instability in VHL-associated cancers by inhibiting Mad2 translation.
Cancer Res. 2014; 74(9):2432-43 [PubMed] Related Publications
Chromosomal instability enables tumor development, enabled in part by aberrant expression of the mitotic checkpoint protein Mad2. Here we identify a novel regulatory mechanism for Mad2 expression involving miR-28-5p-mediated inhibition of Mad2 translation, and we demonstrate that this mechanism is triggered by inactivation of the tumor suppressor VHL, the most common event in clear cell renal cell carcinoma (ccRCC). In VHL-positive cancer cells, enhanced expression of miR-28-5p diminished Mad2 levels and promoted checkpoint weakness and chromosomal instability. Conversely, in checkpoint-deficient VHL-negative renal carcinoma cells, inhibition of miR-28-5p function restored Mad2 levels, mitotic checkpoint proficiency, and chromosomal stability. Notably, chromosome missegregation errors and aneuploidy that were produced in a mouse model of acute renal injury (as a result of kidney-specific ablation of pVHL function) were reverted in vivo also by genetic inhibition of miR-28-5p. Finally, bioinformatic analyses in human ccRCC associated loss of VHL with increased miR-28-5p expression and chromosomal instability. Together, our results defined miR-28-5p as a critical regulator of Mad2 translation and mitotic checkpoint function. By identifying a potential mediator of chromosomal instability in VHL-associated cancers, our work also suggests a novel microRNA-based therapeutic strategy to target aneuploid cells in VHL-associated cancers.

Bian Y, Kitagawa R, Bansal PK, et al.
Synthetic genetic array screen identifies PP2A as a therapeutic target in Mad2-overexpressing tumors.
Proc Natl Acad Sci U S A. 2014; 111(4):1628-33 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
The spindle checkpoint is essential to ensure proper chromosome segregation and thereby maintain genomic stability. Mitotic arrest deficiency 2 (Mad2), a critical component of the spindle checkpoint, is overexpressed in many cancer cells. Thus, we hypothesized that Mad2 overexpression could specifically make cancer cells susceptible to death by inducing a synthetic dosage lethality defect. Because the spindle checkpoint pathway is highly conserved between yeast and humans, we performed a synthetic genetic array analysis in yeast, which revealed that Mad2 overexpression induced lethality in 13 gene deletions. Among the human homologs of candidate genes, knockdown of PPP2R1A, a gene encoding a constant regulatory subunit of protein phosphatase 2, significantly inhibited the growth of Mad2-overexpressing tumor cells. PPP2R1A inhibition induced Mad2 phosphorylation and suppressed Mad2 protein levels. Depletion of PPP2R1A inhibited colony formation of Mad2-overexpressing HeLa cells but not of unphosphorylated Mad2 mutant-overexpressing cells, suggesting that the lethality induced by PP2A depletion in Mad2-overexpressing cells is dependent on Mad2 phosphorylation. Also, the PP2A inhibitor cantharidin induced Mad2 phosphorylation and inhibited the growth of Mad2-overexpressing cancer cells. Aurora B knockdown inhibited Mad2 phosphorylation in mitosis, resulting in the blocking of PPP2R1A inhibition-induced cell death. Taken together, our results strongly suggest that PP2A is a good therapeutic target in Mad2-overexpressing tumors.

Minakawa Y, Kasamatsu A, Koike H, et al.
Kinesin family member 4A: a potential predictor for progression of human oral cancer.
PLoS One. 2013; 8(12):e85951 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
BACKGROUND: Kinesin family member 4A (KIF4A), a microtubule-based motor protein, was implicated in regulation of chromosomal structure and kinetochore microtubule dynamics. Considering the functions of KIF4A, we assumed that KIF4A is involved in progression of oral squamous cell carcinomas (OSCCs) via activation of the spindle assembly checkpoint (SAC). However, little is known about the relevance of KIF4A in the behavior of OSCC. We investigated the KIF4A expression status and its functional mechanisms in OSCC.
METHODS: The KIF4A expression levels in seven OSCC-derived cells were analyzed by quantitative reverse transcriptase-polymerase chain reaction and immunoblotting analyses. Using a KIF4A knockdown model, we assessed the expression of (SAC)-related molecules (BUB1, MAD2, CDC20, and cyclin B1), cell-cycle, and cellular proliferation. In addition to in vitro data, the clinical correlation between the KIF4A expression levels in primary OSCCs (n = 106 patients) and the clinicopathologic status by immunohistochemistry (IHC) also were evaluated.
RESULTS: KIF4A mRNA and protein were up-regulated significantly (P < 0.05) in seven OSCC-derived cells compared with human normal oral keratinocytes. In the KIF4A knockdown cells, SAC activation was observed via increased BUB1 expression on the kinetochores, appropriate kinetochore localization of MAD2, down-regulation of CDC20, up-regulation of cyclin B1, and cell-cycle arrested at G2/M phase. The results showed that cellular proliferation of KIF4A knockdown cells decreased significantly (P < 0.05) compared with control cells. IHC showed that KIF4A expression in primary OSCCs was significantly (P < 0.05) greater than in the normal oral counterparts and that KIF4A-positive OSCCs were correlated closely (P < 0.05) with tumoral size.
CONCLUSIONS: Our results proposed for the first time that KIF4A controls cellular proliferation via SAC activation. Therefore, KIF4A might be a key regulator for tumoral progression in OSCCs.

Ikawa-Yoshida A, Ando K, Oki E, et al.
Contribution of BubR1 to oxidative stress-induced aneuploidy in p53-deficient cells.
Cancer Med. 2013; 2(4):447-56 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
DNA aneuploidy is observed in various human tumors and is associated with the abnormal expression of spindle assembly checkpoint (SAC) proteins. Oxidative stress (OS) causes DNA damage and chromosome instability that may lead to carcinogenesis. OS is also suggested to contribute to an increase in aneuploid cells. However, it is not clear how OS is involved in the regulation of SAC and contributes to carcinogenesis associated with aneuploidy. Here we show that an oxidant (KBrO3) activated the p53 signaling pathway and suppressed the expression of SAC factors, BubR1, and Mad2, in human diploid fibroblast MRC5 cells. This suppression was dependent on functional p53 and reactive oxygen species. In p53 knockdown cells, KBrO3 did not suppress BubR1 and Mad2 expression and increased both binucleated cells and cells with >4N DNA content. BubR1 and not Mad2 downregulation suppressed KBrO3-induced binucleated cells and cells with >4N DNA content in p53 knockdown cells, suggesting that BubR1 contributes to enhanced polyploidization by a mechanism other than its SAC function. In analysis of 182 gastric cancer specimens, we found that BubR1 expression was significantly high when p53 was positively stained, which indicates loss of p53 function (P = 0.0019). Moreover, positive staining of p53 and high expression of BubR1 in tumors were significantly correlated with DNA aneuploidy (P = 0.0065). These observations suggest that p53 deficiency may lead to the failure of BubR1 downregulation by OS and that p53 deficiency and BubR1 accumulation could contribute to gastric carcinogenesis associated with aneuploidy.

Date DA, Burrows AC, Venere M, et al.
Coordinated regulation of p31(Comet) and Mad2 expression is required for cellular proliferation.
Cell Cycle. 2013; 12(24):3824-32 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
p31(Comet) is a well-known interacting partner of the spindle assembly checkpoint (SAC) effector molecule Mad2. At the molecular level it is well established that p31(Comet) promotes efficient mitotic exit, specifically the metaphase-anaphase transition, by antagonizing Mad2 function. However, there is little knowledge of how p31(Comet) is regulated or the physiological importance of controlling p31(Comet). Here, we show that the Rb-E2F pathway regulates p31(Comet) expression. In multiple tumor types (including breast and lung) p31(Comet) expression is increased along with Mad2. Expression of this antagonist-target pair is coordinated in cells and correlated in cancer. Moreover, a narrow range of p31(Comet):Mad2 ratios is compatible with cellular viability. Our data suggest that coordinate regulation is important for the outgrowth of oncogenic cell populations. Our findings suggest that altered p31(Comet):Mad2 expression ratios may provide new insight into altered SAC function and the generation of chromosomal instability in tumors.

Tang T, Song X, Liu YF, Wang WY
PEITC reverse multi-drug resistance of human gastric cancer SGC7901/DDP cell line.
Cell Biol Int. 2014; 38(4):502-10 [PubMed] Related Publications
Gastric cancer is one of the leading causes of cancer death in the world and nearly all patients who respond initially to cisplatin later develop drug resistance, indicating multi-drug resistance is an essential aspect of the failure of treatment. Phenethyl isothiocyanate (PEITC) has been implicated in inhibiting metastasis of several types of human cancer. However, the effect and potential mechanism of PEITC reversed multi-drug resistance of human gastric cancer is not fully clear. We have identified the role of PEITC in multi-drug resistance reversal of human gastric cancer SGC7901/DDP cell line. PEITC inhibited cisplatin-resistant human SGC7901/DDP cell growth in a dose-dependent manner, causing increased apoptosis, ROS generation, glutathione depletion, accumulation of Rhodamine-123, decreased expression of P-glycoprotein and cell cycle arrest. mRNA and protein expression of the multi-drug resistance gene (MDR1), multi-drug resistance-associated protein (MRP1), excision repair cross-complementing gene 1 (ERCC1), survivin, and Mad2 was decreased, and phosphorylation of Akt and transcriptional activation of NF-κB were suppressed. PEITC may be useful as the therapeutic strategy for overcoming multi-drug resistance through suppressing the PI3K-Akt pathway in human gastric cancer.

De Keersmaecker K, Porcu M, Cox L, et al.
NUP214-ABL1-mediated cell proliferation in T-cell acute lymphoblastic leukemia is dependent on the LCK kinase and various interacting proteins.
Haematologica. 2014; 99(1):85-93 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
The NUP214-ABL1 fusion protein is a constitutively active protein tyrosine kinase that is found in 6% of patients with T-cell acute lymphoblastic leukemia and that promotes proliferation and survival of T-lymphoblasts. Although NUP214-ABL1 is sensitive to ABL1 kinase inhibitors, development of resistance to these compounds is a major clinical problem, underlining the need for additional drug targets in the sparsely studied NUP214-ABL1 signaling network. In this work, we identify and validate the SRC family kinase LCK as a protein whose activity is absolutely required for the proliferation and survival of T-cell acute lymphoblastic leukemia cells that depend on NUP214-ABL1 activity. These findings underscore the potential of SRC kinase inhibitors and of the dual ABL1/SRC kinase inhibitors dasatinib and bosutinib for the treatment of NUP214-ABL1-positive T-cell acute lymphoblastic leukemia. In addition, we used mass spectrometry to identify protein interaction partners of NUP214-ABL1. Our results strongly support that the signaling network of NUP214-ABL1 is distinct from that previously reported for BCR-ABL1. Moreover, we found that three NUP214-ABL1-interacting proteins, MAD2L1, NUP155, and SMC4, are strictly required for the proliferation and survival of NUP214-ABL1-positive T-cell acute lymphoblastic leukemia cells. In conclusion, this work identifies LCK, MAD2L1, NUP155 and SMC4 as four new potential drug targets in NUP214-ABL1-positive T-cell acute lymphoblastic leukemia.

Sun W, Dong WW, Mao LL, et al.
Overexpression of p42.3 promotes cell growth and tumorigenicity in hepatocellular carcinoma.
World J Gastroenterol. 2013; 19(19):2913-20 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
AIM: To investigate the association of p42.3 expression with clinicopathological characteristics and the biological function of p42.3 in human hepatocellular carcinoma (HCC).
METHODS: We used reverse transcription-polymerase chain reaction (RT-PCR), quantitative real-time RT-PCR and western blotting to detect p42.3 mRNA and protein expression in hepatic cell lines. We examined primary HCC samples and matched adjacent normal tissue by immunohistochemistry to investigate the correlation between p42.3 expression and clinicopathological features. HepG2 cells were transfected with a pIRES2-EGFP-p42.3 expression vector to examine the function of the p42.3 gene. Transfected cells were analyzed for their viability and malignant transformation abilities by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, colony formation assay, and tumorigenicity assay in nude mice.
RESULTS: p42.3 is differentially expressed in primary HCC tumors and cell lines. Approximately 69.6% (96/138) of cells were p42.3-positive in hepatic tumor tissues, while 30.7% (35/114) were p42.3-positive in tumor-adjacent normal tissues. Clinicopathological characteristics of the HCC specimens revealed a significant correlation between p42.3 expression and tumor differentiation (P = 0.031). However, p42.3 positivity was not related to tumor tumor-node-metastasis classification, hepatitis B virus status, or hepatoma type. Regarding p42.3 overexpression in stably transfected HepG2 cells, we discovered significant enhancement of cancer cell growth and colony formation in vitro, and significantly enhanced tumorigenicity in nude mice. Western blot analysis of cell cycle proteins revealed that enhanced p42.3 levels promote upregulation of proliferating cell nuclear antigen, cyclin B1 and mitotic arrest deficient 2.
CONCLUSION: p42.3 promotes tumorigenicity and tumor growth in HCC and may be a potential target for future clinical cancer therapeutics.

Zhang ZR, Al Zaharna M, Wong MM, et al.
Taxifolin enhances andrographolide-induced mitotic arrest and apoptosis in human prostate cancer cells via spindle assembly checkpoint activation.
PLoS One. 2013; 8(1):e54577 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
Andrographolide (Andro) suppresses proliferation and triggers apoptosis in many types of cancer cells. Taxifolin (Taxi) has been proposed to prevent cancer development similar to other dietary flavonoids. In the present study, the cytotoxic and apoptotic effects of the addition of Andro alone and Andro and Taxi together on human prostate carcinoma DU145 cells were assessed. Andro inhibited prostate cancer cell proliferation by mitotic arrest and activation of the intrinsic apoptotic pathway. Although the effect of Taxi alone on DU145 cell proliferation was not significant, the combined use of Taxi with Andro significantly potentiated the anti-proliferative effect of increased mitotic arrest and apoptosis by enhancing the cleavage of poly(ADP-ribose) polymerase, and caspases-7 and -9. Andro together with Taxi enhanced microtubule polymerization in vitro, and they induced the formation of twisted and elongated spindles in the cancer cells, thus leading to mitotic arrest. In addition, we showed that depletion of MAD2, a component in the spindle assembly checkpoint (SAC), alleviated the mitotic block induced by the two compounds, suggesting that they trigger mitotic arrest by SAC activation. This study suggests that the anti-cancer activity of Andro can be significantly enhanced in combination with Taxi by disrupting microtubule dynamics and activating the SAC.

Gogolin S, Batra R, Harder N, et al.
MYCN-mediated overexpression of mitotic spindle regulatory genes and loss of p53-p21 function jointly support the survival of tetraploid neuroblastoma cells.
Cancer Lett. 2013; 331(1):35-45 [PubMed] Related Publications
High-risk neuroblastomas often harbor structural chromosomal alterations, including amplified MYCN, and usually have a near-di/tetraploid DNA index, but the mechanisms creating tetraploidy remain unclear. Gene-expression analyses revealed that certain MYCN/MYC and p53/pRB-E2F target genes, especially regulating mitotic processes, are strongly expressed in near-di/tetraploid neuroblastomas. Using a functional RNAi screening approach and live-cell imaging, we identified a group of genes, including MAD2L1, which after knockdown induced mitotic-linked cell death in MYCN-amplified and TP53-mutated neuroblastoma cells. We found that MYCN/MYC-mediated overactivation of the metaphase-anaphase checkpoint synergizes with loss of p53-p21 function to prevent arrest or apoptosis of tetraploid neuroblastoma cells.

Usukura K, Kasamatsu A, Okamoto A, et al.
Tripeptidyl peptidase II in human oral squamous cell carcinoma.
J Cancer Res Clin Oncol. 2013; 139(1):123-30 [PubMed] Related Publications
PURPOSE: Tripeptidyl peptidase II (TPP2), a member of the family of eukaryotic serine peptidase, has been implicated in DNA repair, cellular division, and apoptosis. The aim of this study was to examine TPP2 expression and its functional mechanisms in oral squamous cell carcinoma (OSCC).
METHODS: TPP2 mRNA and protein expression in seven OSCC-derived cells (Ca9-22, HSC-2, HSC-3, HSC-4, HO-1-N-1, H1, and Sa3) was analyzed by quantitative reverse transcriptase-polymerase chain reaction and immunoblotting analyses. Since previous studies indicated that TPP2 might control chromosomal division, we investigated cellular proliferation and spindle assembly checkpoint (SAC) molecules, MAD2 and CCNB1. In addition, we evaluated the correlation between TPP2 expression levels in primary OSCCs (n = 108 specimens) and the clinicopathologic status by immunohistochemistry (IHC).
RESULTS: TPP2 mRNA and protein were significantly (P < 0.05) up-regulated in OSCC-derived cells compared with human normal oral keratinocytes. Suppression of TPP2 expression with shRNA significantly (P < 0.05) inhibited cellular proliferation compared with the control cells. In addition, appropriate localization of MAD2 and up-regulation of CCNB1 were observed in TPP2 knockdown OSCC cells. IHC showed that TPP2 expression in primary OSCCs was significantly (P < 0.001) greater than that in the normal oral counterparts, and the TPP2-positive cases were significantly (P < 0.05) correlated with tumor size.
CONCLUSION: The current study showed that overexpression of TPP2 occurs frequently during oral carcinogenesis and might be associated with OSCC progression via SAC activation.

Kim S, Kon M, DeLisi C
Pathway-based classification of cancer subtypes.
Biol Direct. 2012; 7:21 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
BACKGROUND: Molecular markers based on gene expression profiles have been used in experimental and clinical settings to distinguish cancerous tumors in stage, grade, survival time, metastasis, and drug sensitivity. However, most significant gene markers are unstable (not reproducible) among data sets. We introduce a standardized method for representing cancer markers as 2-level hierarchical feature vectors, with a basic gene level as well as a second level of (more stable) pathway markers, for the purpose of discriminating cancer subtypes. This extends standard gene expression arrays with new pathway-level activation features obtained directly from off-the-shelf gene set enrichment algorithms such as GSEA. Such so-called pathway-based expression arrays are significantly more reproducible across datasets. Such reproducibility will be important for clinical usefulness of genomic markers, and augment currently accepted cancer classification protocols.
RESULTS: The present method produced more stable (reproducible) pathway-based markers for discriminating breast cancer metastasis and ovarian cancer survival time. Between two datasets for breast cancer metastasis, the intersection of standard significant gene biomarkers totaled 7.47% of selected genes, compared to 17.65% using pathway-based markers; the corresponding percentages for ovarian cancer datasets were 20.65% and 33.33% respectively. Three pathways, consisting of Type_1_diabetes mellitus, Cytokine-cytokine_receptor_interaction and Hedgehog_signaling (all previously implicated in cancer), are enriched in both the ovarian long survival and breast non-metastasis groups. In addition, integrating pathway and gene information, we identified five (ID4, ANXA4, CXCL9, MYLK, FBXL7) and six (SQLE, E2F1, PTTG1, TSTA3, BUB1B, MAD2L1) known cancer genes significant for ovarian and breast cancer respectively.
CONCLUSIONS: Standardizing the analysis of genomic data in the process of cancer staging, classification and analysis is important as it has implications for both pre-clinical as well as clinical studies. The paradigm of diagnosis and prediction using pathway-based biomarkers as features can be an important part of the process of biomarker-based cancer analysis, and the resulting canonical (clinically reproducible) biomarkers can be important in standardizing genomic data. We expect that identification of such canonical biomarkers will improve clinical utility of high-throughput datasets for diagnostic and prognostic applications.

Choi HJ, Zhu BT
Critical role of cyclin B1/Cdc2 up-regulation in the induction of mitotic prometaphase arrest in human breast cancer cells treated with 2-methoxyestradiol.
Biochim Biophys Acta. 2012; 1823(8):1306-15 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
Earlier studies showed that 2-methoxyestradiol (2ME(2)), an endogenous nonpolar metabolite of estradiol-17β, is a strong inducer of G(2)/M cell cycle arrest (based on analysis of cellular DNA content) in human cancer cell lines. The present study sought to investigate the molecular mechanism underlying 2ME(2)-induced cell cycle arrest. We found that 2ME(2) can selectively induce mitotic prometaphase arrest, but not G(2) phase arrest, in cultured MDA-MB-435s and MCF-7 human breast cancer cells. During the induction of prometaphase arrest, there is a time-dependent initial up-regulation of cyclin B1 and Cdc2 proteins, occurring around 12-24h. The strong initial up-regulation of cyclin B1 and Cdc2 matches in timing the 2ME(2)-induced prometaphase arrest. The 2ME(2)-induced prometaphase arrest is abrogated by selective knockdown of cyclin B1 and Cdc2, or by pre-treatment of cells with roscovitine, an inhibitor of cyclin-dependent kinases, or by co-treatment of cells with cycloheximide, a protein synthesis inhibitor that was found to suppress the early up-regulation of cyclin B1 and Cdc2. In addition, we provided evidence showing that MAD2 and JNK1 are important upstream mediators of 2ME(2)-induced up-regulation of cyclin B1 and Cdc2 as well as the subsequent induction of mitotic prometaphase arrest. In conclusion, treatment of human cancer cells with 2ME(2) causes up-regulation of cyclin B1 and Cdc2, which then mediate the induction of mitotic prometaphase arrest.

Dai Y, Tang Y, He F, et al.
Screening and functional analysis of differentially expressed genes in EBV-transformed lymphoblasts.
Virol J. 2012; 9:77 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
BACKGROUND: Epstain-Barr virus (EBV) can transform human B lymphocytes making them immortalized and inducing tumorigenic ability in vitro, but the molecular mechanisms remain unclear. The aim of the present study is to detect and analyze differentially expressed genes in two types of host cells, normal human lymphocytes and coupled EBV-transformed lymphoblasts in vitro using gene chips, and to screen the key regulatory genes of lymphocyte transformation induced by EB virus.
METHODS: Fresh peripheral blood samples from seven healthy donors were collected. EBV was used to transform lymphocytes in vitro. Total RNA was extracted from 7 cases of the normal lymphocytes and transformed lymphoblasts respectively, marked with dihydroxyfluorane after reverse transcription, then hybridized with 4 × 44 K Agilent human whole genome microarray. LIMMA, String, Cytoscape and other softwares were used to screen and analyze differentially expressed genes. Real-time PCR was applied to verify the result of gene expression microarrays.
RESULTS: There were 1745 differentially expressed genes that had been screened, including 917 up-regulated genes and 828 down-regulated genes. According to the results of Generank, String and Cytoscape analyses, 38 genes may be key controlled genes related to EBV-transformed lymphocytes, including 22 up-regulated genes(PLK1, E2F1, AURKB, CDK2, PLCG2, CD80, PIK3R3, CDC20, CDC6, AURKA, CENPA, BUB1B, NUP37, MAD2L1, BIRC5, CDC25A, CCNB1, RPA3, HJURP, KIF2C, CDK1, CDCA8) and 16 down-regulated genes(FYN, CD3D, CD4, CD3G, ZAP70, FOS, HCK, CD247, PRKCQ, ITK, LCP2, CXCL1, CD8A, ITGB5, VAV3, CXCR4), which primarily control biological processes such as cell cycle, mitosis, cytokine-cytokine pathway, immunity response and so on.
CONCLUSIONS: Human lymphocyte transformation induced by EB virus is a complicated process, involving multiple-genes and -pathways in virus-host interactions. Global gene expression profile analysis showed that EBV may transform human B lymphocytes by promoting cell cycle and mitosis, inhibiting cell apoptosis, hindering host immune function and secretion of cytokines.

Oki E, Hisamatsu Y, Ando K, et al.
Clinical aspect and molecular mechanism of DNA aneuploidy in gastric cancers.
J Gastroenterol. 2012; 47(4):351-8 [PubMed] Related Publications
The biological characteristics of cancers depend mostly on genetic alterations in the cancer cells of individuals. Gastric cancers show a high frequency of DNA aneuploidy, a phenotype of chromosomal instability. Compared to diploid tumors, gastric carcinomas with aneuploidy have been shown to have high proliferative activity and high metastatic or invasive potential; these characteristics lead to a poor prognosis. It has been suggested that an abnormal spindle assembly checkpoint is involved in DNA aneuploidy, but the underlying mechanism is still unclear. This review, in order to determine whether gastric carcinomas that display aneuploidy are associated with a poorer prognosis than diploid tumors, and to discuss the biological mechanisms that induce aneuploidy, summarizes the results of studies on DNA ploidy in gastric cancer published in the English literature. Analysis of DNA ploidy in gastric cancer may provide clinically useful information from diagnostic, therapeutic, and prognostic standpoints. Further investigations may be needed to clarify the relationship between chromosome instability and DNA ploidy.

Kawabata T, Tanimura S, Asai K, et al.
Up-regulation of pro-apoptotic protein Bim and down-regulation of anti-apoptotic protein Mcl-1 cooperatively mediate enhanced tumor cell death induced by the combination of ERK kinase (MEK) inhibitor and microtubule inhibitor.
J Biol Chem. 2012; 287(13):10289-300 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
Blockade of the ERK signaling pathway by ERK kinase (MEK) inhibitors selectively enhances the induction of apoptosis by microtubule inhibitors in tumor cells in which this pathway is constitutively activated. We examined the mechanism by which such drug combinations induce enhanced cell death by applying time-lapse microscopy to track the fate of individual cells. MEK inhibitors did not affect the first mitosis after drug exposure, but most cells remained arrested in interphase without entering a second mitosis. Low concentrations of microtubule inhibitors induced prolonged mitotic arrest followed by exit of cells from mitosis without division, with most cells remaining viable. However, the combination of a MEK inhibitor and a microtubule inhibitor induced massive cell death during prolonged mitosis. Impairment of spindle assembly checkpoint function by RNAi-mediated depletion of Mad2 or BubR1 markedly suppressed such prolonged mitotic arrest and cell death. The cell death was accompanied by up-regulation of the pro-apoptotic protein Bim (to which MEK inhibitors contributed) and by down-regulation of the anti-apoptotic protein Mcl-1 (to which microtubule and MEK inhibitors contributed synergistically). Whereas RNAi-mediated knockdown of Bim suppressed cell death, stabilization of Mcl-1 by RNAi-mediated depletion of Mule slowed its onset. Depletion of Mcl-1 sensitized tumor cells to MEK inhibitor-induced cell death, an effect that was antagonized by knockdown of Bim. The combination of MEK and microtubule inhibitors thus targets Bim and Mcl-1 in a cooperative manner to induce massive cell death in tumor cells with aberrant ERK pathway activation.

Yan H, Zhu S, Song C, et al.
Bone morphogenetic protein (BMP) signaling regulates mitotic checkpoint protein levels in human breast cancer cells.
Cell Signal. 2012; 24(4):961-8 [PubMed] Related Publications
Aberrant expression of mitotic checkpoint genes compromises mitotic checkpoint, leads to chromosome instability and tumorigenesis. However, the cell signals that control mitotic checkpoint gene expression have not been reported so far. In the present study we show that, in human breast cancer cells, chemical inhibition of Bone morphogenetic proteins (BMPs), but not Transforming Growth Factor-β (TGF-β), abrogates the mitotic arrest induced by nocodazole. Protein expression analysis reveals that inhibition of BMP signaling dramatically down regulates protein levels of mitotic checkpoint components BUB3, Hec1, TTK and MAD2, but inhibition of TGF-β has relatively minor effect on the expression of these proteins. Activation of BMP signaling specifically up regulates BUB3, and activation of Activin A signaling globally down regulates these proteins level. Furthermore, overexpressing MAD2, TTK, BUB3 or Hec1 significantly rescues the mitotic arrest defect caused by BMP inhibition. Our results demonstrated for the first time that TGF-β family cytokines are cellular signals regulating mitotic checkpoint and perturbations in intrinsic BMP signaling could lead to suppression of mitotic checkpoint signaling by downregulating key checkpoint proteins. The results suggest a possible mechanism by which dysregulation of TGF-β signaling causes mitotic checkpoint defects and drives tumorigenesis. The finding also provides a potential and more specific strategy for cancer prevention by targeting BMP and mitotic checkpoint connection.

Díaz-Rodríguez E, Álvarez-Fernández S, Chen X, et al.
Deficient spindle assembly checkpoint in multiple myeloma.
PLoS One. 2011; 6(11):e27583 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
Multiple myeloma (MM) is a hematological disease characterized by an abnormal accumulation of plasma cells in the bone marrow. These cells have frequent cytogenetic abnormalities including translocations of the immunoglobulin heavy chain gene and chromosomal gains and losses. In fact, a singular characteristic differentiating MM from other hematological malignancies is the presence of a high degree of aneuploidies. As chromosomal abnormalities can be generated by alterations in the spindle assembly checkpoint (SAC), the functionality of such checkpoint was tested in MM. When SAC components were analyzed in MM cell lines, the RNA levels of most of them were conserved. Nevertheless, the protein content of some key constituents was very low in several cell lines, as was the case of MAD2 or CDC20 in RPMI-8226 or RPMI-LR5 cells. The recovery of their cellular content did not substantially affect cell growth, but improved their ability to segregate chromosomes. Finally, SAC functionality was tested by challenging cells with agents disrupting microtubule dynamics. Most of the cell lines analyzed exhibited functional defects in this checkpoint. Based on the data obtained, alterations both in SAC components and their functionality have been detected in MM, pointing to this pathway as a potential target in MM treatment.

Furlong F, Fitzpatrick P, O'Toole S, et al.
Low MAD2 expression levels associate with reduced progression-free survival in patients with high-grade serous epithelial ovarian cancer.
J Pathol. 2012; 226(5):746-55 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
Epithelial ovarian cancer (EOC) has an innate susceptibility to become chemoresistant. Up to 30% of patients do not respond to conventional chemotherapy [paclitaxel (Taxol®) in combination with carboplatin] and, of those who have an initial response, many patients relapse. Therefore, an understanding of the molecular mechanisms that regulate cellular chemotherapeutic responses in EOC cells has the potential to impact significantly on patient outcome. The mitotic arrest deficiency protein 2 (MAD2), is a centrally important mediator of the cellular response to paclitaxel. MAD2 immunohistochemical analysis was performed on 82 high-grade serous EOC samples. A multivariate Cox regression analysis of nuclear MAD2 IHC intensity adjusting for stage, tumour grade and optimum surgical debulking revealed that low MAD2 IHC staining intensity was significantly associated with reduced progression-free survival (PFS) (p = 0.0003), with a hazard ratio of 4.689. The in vitro analyses of five ovarian cancer cell lines demonstrated that cells with low MAD2 expression were less sensitive to paclitaxel. Furthermore, paclitaxel-induced activation of the spindle assembly checkpoint (SAC) and apoptotic cell death was abrogated in cells transfected with MAD2 siRNA. In silico analysis identified a miR-433 binding domain in the MAD2 3' UTR, which was verified in a series of experiments. Firstly, MAD2 protein expression levels were down-regulated in pre-miR-433 transfected A2780 cells. Secondly, pre-miR-433 suppressed the activity of a reporter construct containing the 3'-UTR of MAD2. Thirdly, blocking miR-433 binding to the MAD2 3' UTR protected MAD2 from miR-433 induced protein down-regulation. Importantly, reduced MAD2 protein expression in pre-miR-433-transfected A2780 cells rendered these cells less sensitive to paclitaxel. In conclusion, loss of MAD2 protein expression results in increased resistance to paclitaxel in EOC cells. Measuring MAD2 IHC staining intensity may predict paclitaxel responses in women presenting with high-grade serous EOC.

Huang C, Tang H, Zhang W, et al.
Integrated analysis of multiple gene expression profiling datasets revealed novel gene signatures and molecular markers in nasopharyngeal carcinoma.
Cancer Epidemiol Biomarkers Prev. 2012; 21(1):166-75 [PubMed] Related Publications
PURPOSE: To identify the novel gene signatures and molecular markers of nasopharyngeal carcinoma (NPC) by integrated bioinformatics analysis of multiple gene expression profiling datasets.
EXPERIMENTAL DESIGN: Seven published gene expression profiling studies and one of our unpublished works were reanalyzed to identify the common significantly dysregulated (CSD) genes in NPC. Overrepresentation analysis of cytogenetic bands, Gene Ontology (GO) categories, pathways were used to explore CSD genes functionally associated with carcinogenesis. The protein expressions of selected CSD genes were examined by immunohistochemistry on tissue microarrays, and the correlations of their expressions with clinical outcomes were evaluated.
RESULTS: Using the criteria (genes reported deregulated in more than one study), a total of 962 genes were identified as the CSD genes in NPC. Four upregulated (BUB1B, CCND2, CENPF, and MAD2L1) and two downregulated (LTF and SLPI) genes were markedly reported in six studies. The enrichments of chromosome aberrations were 2q23, 2q31, 7p15, 12q15, 12q22, 18q11, and 18q12 in upregulated genes and 14q32 and 16q13 in downregulated genes. The activated GO categories and pathways related to proliferation, adhesion, invasion, and downregulated immune response had been functionally associated with NPC. SLPI significantly downregulated in nasopharyngeal adenocarcinoma. Furthermore, the high expression of BUB1B or CENPF was associated with poor overall survival of patients.
CONCLUSION: It was first clearly identified the dysregulated expression of BUB1B and SLPI in NPC tissues.
IMPACT: Further studies of the CSD genes as gene signatures and molecular markers of NPC might improve the understanding of the disease and identify new therapeutic targets.

Ren J, Wang Y, Gao Y, et al.
FAT10 mediates the effect of TNF-α in inducing chromosomal instability.
J Cell Sci. 2011; 124(Pt 21):3665-75 [PubMed] Related Publications
Tumor necrosis factor-alpha (TNF-α) plays important roles in chronic inflammation-associated tumorigenesis but the mechanisms involved remain poorly understood. Previously, we reported that high levels of FAT10 led to chromosomal instability that is mediated by an abbreviated mitotic phase. Here, we show that TNF-α induces FAT10 gene expression through TNF receptor 1 (TNFR1) and activates the NF-κB pathway in HCT116 and SW620 cells. TNF-α treatment also leads to an abbreviated mitotic phase that can be reversed by inhibiting FAT10 expression. This abbreviated mitotic phase is correlated with a TNF-α-induced reduction in the kinetochore localization of MAD2 during prometaphase which, again, can be reversed by inhibiting FAT10 gene expression. There is greater variability of chromosome numbers in HCT116 and SW620 cells treated with TNF-α than in untreated cells, which can be reversed by the introduction of short hairpin RNA (shRNA) against FAT10. The more stable chromosome numbers in HCT116 cells expressing FAT10 shRNA can revert to greater variability with the addition of a mutant FAT10 that is not recognized by the FAT10 shRNA. Upon TNF-α stimulation, higher cell death is observed when FAT10 expression is inhibited by shRNA. These data strongly suggest that FAT10 plays an important role in mediating the function of TNF-α during tumorigenesis by inducing cell cycle deregulation and chromosomal instability, and by inhibiting apoptosis.

Bie L, Zhao G, Cheng P, et al.
The accuracy of survival time prediction for patients with glioma is improved by measuring mitotic spindle checkpoint gene expression.
PLoS One. 2011; 6(10):e25631 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
Identification of gene expression changes that improve prediction of survival time across all glioma grades would be clinically useful. Four Affymetrix GeneChip datasets from the literature, containing data from 771 glioma samples representing all WHO grades and eight normal brain samples, were used in an ANOVA model to screen for transcript changes that correlated with grade. Observations were confirmed and extended using qPCR assays on RNA derived from 38 additional glioma samples and eight normal samples for which survival data were available. RNA levels of eight major mitotic spindle assembly checkpoint (SAC) genes (BUB1, BUB1B, BUB3, CENPE, MAD1L1, MAD2L1, CDC20, TTK) significantly correlated with glioma grade and six also significantly correlated with survival time. In particular, the level of BUB1B expression was highly correlated with survival time (p<0.0001), and significantly outperformed all other measured parameters, including two standards; WHO grade and MIB-1 (Ki-67) labeling index. Measurement of the expression levels of a small set of SAC genes may complement histological grade and other clinical parameters for predicting survival time.

Yu L, Guo W, Zhao S, et al.
Knockdown of Mad2 induces osteosarcoma cell apoptosis-involved Rad21 cleavage.
J Orthop Sci. 2011; 16(6):814-20 [PubMed] Related Publications
BACKGROUND: Besides Mad2's role in carcinogenesis, recent study has shown that it is essential in cell survival. Here we found that knockdown of Mad2 causes osteosarcoma cell death through apoptosis, with the apoptotic signal resulting from Rad21 cleavage.
METHODS: U2OS and MG63 cells were divided into three groups: the Mad2 siRNA group, mock group and normal control group; the Mad2 siRNA group and mock group are transfected with Mad2 shRNA plasmid and mock plasmid, respectively. G418 was used to increase the transfection efficacy, which was evaluated by GFP fluorescence. Quantitative PCR and Western blotting analyses were used to detect the transcription and expression of Mad2, Rad21 and caspase-3, respectively. Flow cytometry assay using PE-labeled Annexin-V and PI, TUNEL assay and Hoechst 33258 staining were used to evaluate cell apoptosis.
RESULTS: We successfully achieved knockdown of Mad2 expression in cancer cells using RNA interference. We observed obvious apoptosis in the Mad2 siRNA group compared with the Mock and control group. We found that the apoptosis induced by Mad2 knockdown correlated with Rad21 cleavage.
CONCLUSION: These results confirmed that knockdown of Mad2 causes osteosarcoma cell death through apoptosis and provides evidence that the apoptotic signal resulted from Rad21 cleavage. This study suggested that Mad2 has potential to be a novel target for cancer therapy.

De Luca P, Vazquez ES, Moiola CP, et al.
BRCA1 loss induces GADD153-mediated doxorubicin resistance in prostate cancer.
Mol Cancer Res. 2011; 9(8):1078-90 [PubMed] Related Publications
BRCA1 plays numerous roles in the regulation of genome integrity and chemoresistance. Although BRCA1 interaction with key proteins involved in DNA repair is well known, its role as a coregulator in the transcriptional response to DNA damage remains poorly understood. In this study, we show that BRCA1 plays a central role in the transcriptional response to genotoxic stress in prostate cancer. BRCA1 expression mediates apoptosis, cell-cycle arrest, and decreased viability in response to doxorubicin treatment. Xenograft studies using human prostate carcinoma PC3 cells show that BRCA1 depletion results in increased tumor growth. A focused survey of BRCA1-regulated genes in prostate carcinoma reveals that multiple regulators of genome stability and cell-cycle control, including BLM, FEN1, DDB2, H3F3B, BRCA2, CCNB2, MAD2L1, and GADD153, are direct transcriptional targets of BRCA1. Furthermore, we show that BRCA1 targets GADD153 promoter to increase its transcription in response to DNA damage. Finally, GADD153 depletion significantly abrogates BRCA1 influence on cell-cycle progression and cell death in response to doxorubicin treatment. These findings define a novel transcriptional pathway through which BRCA1 orchestrates cell fate decisions in response to genotoxic insults, and suggest that BRCA1 status should be considered for new chemotherapeutic treatment strategies in prostate cancer.

Schvartzman JM, Duijf PH, Sotillo R, et al.
Mad2 is a critical mediator of the chromosome instability observed upon Rb and p53 pathway inhibition.
Cancer Cell. 2011; 19(6):701-14 [PubMed] Article available free on PMC after 01/06/2015 Related Publications
Multiple mechanisms have been proposed to explain how Rb and p53 tumor suppressor loss lead to chromosome instability (CIN). It was recently shown that Rb pathway inhibition causes overexpression of the mitotic checkpoint gene Mad2, but whether Mad2 overexpression is required to generate CIN in this context is unknown. Here, we show that CIN in cultured cells lacking Rb family proteins requires Mad2 upregulation and that this upregulation is also necessary for CIN and tumor progression in vivo. Mad2 is also repressed by p53 and its upregulation is required for CIN in a p53 mutant tumor model. These results demonstrate that Mad2 overexpression is a critical mediator of the CIN observed upon inactivation of two major tumor suppressor pathways.

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