Gene Summary

Gene:UCP2; uncoupling protein 2
Aliases: UCPH, BMIQ4, SLC25A8
Summary:Mitochondrial uncoupling proteins (UCP) are members of the larger family of mitochondrial anion carrier proteins (MACP). UCPs separate oxidative phosphorylation from ATP synthesis with energy dissipated as heat, also referred to as the mitochondrial proton leak. UCPs facilitate the transfer of anions from the inner to the outer mitochondrial membrane and the return transfer of protons from the outer to the inner mitochondrial membrane. They also reduce the mitochondrial membrane potential in mammalian cells. Tissue specificity occurs for the different UCPs and the exact methods of how UCPs transfer H+/OH- are not known. UCPs contain the three homologous protein domains of MACPs. This gene is expressed in many tissues, with the greatest expression in skeletal muscle. It is thought to play a role in nonshivering thermogenesis, obesity and diabetes. Chromosomal order is 5'-UCP3-UCP2-3'. [provided by RefSeq, Jul 2008]
Databases:OMIM, HGNC, Ensembl, GeneCard, Gene
Protein:mitochondrial uncoupling protein 2
Source:NCBIAccessed: 31 August, 2019


What does this gene/protein do?
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Cancer Overview

Research Indicators

Publications Per Year (1994-2019)
Graph generated 31 August 2019 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.

Tag cloud generated 31 August, 2019 using data from PubMed, MeSH and CancerIndex

Specific Cancers (6)

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: UCP2 (cancer-related)

Wang Y, Lei T, Yuan J, et al.
GCN2 deficiency ameliorates doxorubicin-induced cardiotoxicity by decreasing cardiomyocyte apoptosis and myocardial oxidative stress.
Redox Biol. 2018; 17:25-34 [PubMed] Free Access to Full Article Related Publications
The clinical use of doxorubicin for cancer therapy is limited by its cardiotoxicity, which involves cardiomyocyte apoptosis and oxidative stress. Previously, we showed that general control nonderepressible 2 (GCN2), an eukaryotic initiation factor 2α (eIF2α) kinase, impairs the ventricular adaptation to chronic pressure overload by affecting cardiomyocyte apoptosis. However, the impact of GCN2 on Dox-induced cardiotoxicity has not been investigated. In the present study, we treated wild type (WT) and Gcn2

Hayashi M, Futawaka K, Matsushita M, et al.
GH directly stimulates UCP3 expression.
Growth Horm IGF Res. 2018; 40:44-54 [PubMed] Related Publications
OBJECTIVE: We evaluated the direct action of GH signaling in energy homeostasis in myocytes.
DESIGN: We investigated the GH-induced expression of UCP3 in human embryonic kidney 293 cells, human H-EMC-SS chondrosarcoma cells, murine C2C12 skeletal muscle myoblasts, and rat L6 skeletal muscle cells, as well as its direct effect on the GHR/JAK/STAT5 pathway using a combination of a reporter assay, real-time quantitative polymerase chain reaction, and western blotting.
RESULTS: We demonstrated that the regulation of energy metabolism by GH involves UCP3 via activated STAT5, a signal transducer downstream of GH. UCP3 expression increased with STAT5 in a dose-dependent manner and was higher than that of UCP2. We confirmed the functional STAT5 binding site consensus sequences at -861 and -507 bp in the UCP3 promoter region.
CONCLUSION: The results suggest that GH stimulates UCP3 directly and that UCP2 and that UCP3 participate in the signal transduction pathway that functions downstream of the GHR/JAK/STAT.

Cox TR, Erler JT, Rumney RMH
Established Models and New Paradigms for Hypoxia-Driven Cancer-Associated Bone Disease.
Calcif Tissue Int. 2018; 102(2):163-173 [PubMed] Free Access to Full Article Related Publications
The five-year survival rate for primary bone cancers is ~ 70% while almost all cases of secondary metastatic bone cancer are terminal. Hypoxia, the deficiency of oxygen which occurs as the rate of tumour growth exceeds the supply of vascularisation, is a key promoter of tumour progression. Hypoxia-driven effects in the primary tumour are wide ranging including changes in gene expression, dysregulation of signalling pathways, resistance to chemotherapy, neovascularisation, increased tumour cell proliferation and migration. Paget's seed and soil theory states that for a metastasising tumour cell 'the seed' it requires the correct microenvironment 'soil' to colonise. Why and how metastasising tumour cells colonise the bone is a complex and intriguing problem. However, once present tumour cells are able to disrupt bone homeostasis through increasing osteoclast activity and downregulating osteoblast function. Osteoclast resorption releases growth factors from the bone matrix that subsequently contribute to the proliferation of invasive tumour cells creating the vicious cycle of bone loss and metastatic cancer progression. Recently, we have shown that hypoxia increases expression and release of lysyl oxidase (LOX) from primary mammary tumours, which in turn disrupts bone homeostasis to favour osteolytic degradation to create pre-metastatic niches in the bone microenvironment. We also demonstrated how treatment with bisphosphonates could block this cancer-induced bone remodelling and reduce secondary bone metastases. This review describes the roles of hypoxia in primary tumour progression to metastasis, with a focus on key signalling pathways and treatment options to reduce patient morbidity and increase survival.

Marques D, Ferreira-Costa LR, Ferreira-Costa LL, et al.
Association of insertion-deletions polymorphisms with colorectal cancer risk and clinical features.
World J Gastroenterol. 2017; 23(37):6854-6867 [PubMed] Free Access to Full Article Related Publications
AIM: To investigate the association between 16 insertion-deletions (INDEL) polymorphisms, colorectal cancer (CRC) risk and clinical features in an admixed population.
METHODS: One hundred and forty patients with CRC and 140 cancer-free subjects were examined. Genomic DNA was extracted from peripheral blood samples. Polymorphisms and genomic ancestry distribution were assayed by Multiplex-PCR reaction, separated by capillary electrophoresis on the ABI 3130 Genetic Analyzer instrument and analyzed on GeneMapper ID v3.2. Clinicopathological data were obtained by consulting the patients' clinical charts, intra-operative documentation, and pathology scoring.
RESULTS: Logistic regression analysis showed that polymorphism variations in
CONCLUSION: The INDEL variations in

Fan T, Rong Z, Dong J, et al.
Metabolomic and transcriptomic profiling of hepatocellular carcinomas in Hras12V transgenic mice.
Cancer Med. 2017; 6(10):2370-2384 [PubMed] Free Access to Full Article Related Publications
Activation of the Ras/MAPK pathway is prevalently involved in the occurrence and development of hepatocellular carcinoma (HCC). However, its effects on the deregulated cellular metabolic processes involved in HCC in vivo remain unknown. In this study, a mouse model of HCC induced by hepatocyte-specific expression of the Hras12V oncogene was investigated using an integrative analysis of metabolomics and transcriptomics data. Consistent with the phenotype of abundant lipid droplets in HCC, the lipid biosynthesis in HCC was significantly enhanced by (1) a sufficient supply of acetyl-CoA from enhanced glycolysis and citrate shuttle activity; (2) a sufficient supply of NADPH from enhanced pentose phosphate pathway (PPP) activity; (3) upregulation of key enzymes associated with lipid biosynthesis; and (4) downregulation of key enzymes associated with bile acid biosynthesis. In addition, glutathione (GSH) was significantly elevated, which may result from a sufficient supply of 5-oxoproline and L-glutamate as well as an enhanced reduction in the process of GSSG being turned into GSH by NADPH. The high level of GSH along with elevated Bcl2 and Ucp2 expression may contribute to a normal level of reactive oxygen species (ROS) in HCC. In conclusion, our results suggest that the lipid metabolism, glycolysis, PPP, tricarboxylic acid (TCA) cycle, citrate shuttle activity, bile acid synthesis, and redox homeostasis in the HCC induced by ras oncogene are significantly perturbed, and these altered metabolic processes may play crucial roles in the carcinogenesis, development, and pathological characteristics of HCC.

Omidian K, Rafiei H, Bandy B
Polyphenol inhibition of benzo[a]pyrene-induced oxidative stress and neoplastic transformation in an in vitro model of carcinogenesis.
Food Chem Toxicol. 2017; 106(Pt A):165-174 [PubMed] Related Publications
While dietary polyphenols are widely recognized for cancer-preventing characteristics, the relative effectiveness and mechanisms of action of different polyphenols is not clear. In the present study, we investigated the protective effects of six different polyphenols against benzo[a]pyrene (B[a]P)-induced oxidative stress and neoplastic transformation in the Bhas 42 cell carcinogenesis assay. All of the polyphenols completely prevented the increased intracellular ROS generation by B[a]P at 12 h, and most inhibited after 3 days. B[a]P increased mitochondrial superoxide generation at 12 h, which was inhibited by the anthocyanins and berberine. B[a]P increased expression of genes related to oxidative stress and inflammation (Nrf2, UCP2, and TNF-α) after 24 h. Polyphenols strongly inhibited the increase in TNF-α and also several polyphenols inhibited the increase in UCP2. At 21 days after 72 h treatment, B[a]P produced a large increase in the number of neoplastic colonies. This transformation was inhibited by most polyphenols, and strongly by resveratrol. In summary, all tested polyphenols were able to inhibit B[a]P-induced increases in markers of oxidative stress and inflammation, and to inhibit cellular transformation, with resveratrol being notable for the strongest preventive effect on cell transformation. The results support a role for dietary polyphenols in protecting against B[a]P-induced carcinogenesis.

Torrens-Mas M, González-Hedström D, Abrisqueta M, et al.
PGC-1α in Melanoma: A Key Factor for Antioxidant Response and Mitochondrial Function.
J Cell Biochem. 2017; 118(12):4404-4413 [PubMed] Related Publications
Melanocortin 1 receptor (MC1R) and BRAF are common mutations in melanoma. Through different pathways, they each regulate the expression of PGC-1α, which is a key factor in the regulation of mitochondrial biogenesis and the antioxidant response. Our aim was to study the importance of the different regulatory characteristics of MC1R and BRAF on the pathways they regulate in melanoma. For this purpose, ROS production, levels of gene expression and enzymatic activities were analyzed in HBL and MeWo, with wild-type MC1R and BRAF, and A375 cells with mutant MC1R and BRAF. HBL cells showed a functional MC1R-PGC-1α pathway and exhibited the lowest ROS production, probably because of a better mitochondrial pool and the presence of UCP2. On the other hand, MeWo cells showed elevated levels of PGC-1α but also high ROS production, similar to the A375 cells, along with an activated antioxidant response and significantly low levels of UCP2. Finally, A375 cells are mutant for BRAF, and thus showed low levels of PGC-1α. Consequently, A375 cells exhibited poor mitochondrial biogenesis and function, and no antioxidant response. These results show the importance of the activation of the MC1R-PGC-1α pathway for mitochondrial biogenesis and function in melanoma development, as well as BRAF for the antioxidant response regulated by PGC-1α. J. Cell. Biochem. 118: 4404-4413, 2017. © 2017 Wiley Periodicals, Inc.

Cruz MD, Ledbetter S, Chowdhury S, et al.
Metabolic reprogramming of the premalignant colonic mucosa is an early event in carcinogenesis.
Oncotarget. 2017; 8(13):20543-20557 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Colorectal cancer (CRC) is the second leading cause of cancer-related mortality in the United States. There is an increasing need for the identification of biomarkers of pre-malignant and early stage CRC to improve risk-stratification and screening recommendations. In this study, we investigated the possibility of metabolic and mitochondrial reprogramming early in the pre-malignant colorectal field.
METHODS: Rectal biopsies were taken from 81 patients undergoing screening colonoscopy, and gene expression of metabolic and mitochondrial markers were assessed using real time quantitative PCR. Validation studies were performed in two different animal models of colon carcinogenesis: Pirc rats and AOM-treated rats.
RESULTS: We found evidence of a Warburg effect in the normal-appearing rectal mucosa of patients harboring precancerous lesions elsewhere in the colon compared to control patients, with a significant increase in HIF1α, SLC2A1 (referred to as GLUT1), PKM2, and LDHA. We also found evidence of early mitochondrial changes in the colorectal field of patients harboring pre-cancerous lesions, with significantly increased mitochondrial gene expression of DRP1 (fission), OPA1 (fusion), PGC1-α (biogenesis), UCP2 (uncoupling) and mtND1 (copy number). Similar results were observed in the two different animal models.
CONCLUSIONS: These results demonstrate for the first time evidence of early Warburg-like metabolic changes as well as changes in mitochondrial function, dynamics and mtDNA copy number in endoscopically normal premalignant colorectal mucosal field. These findings provide an opportunity for the development of metabolic biomarkers that could be used for improving screening recommendations and risk-stratification. This also provides a potential target for novel chemopreventive strategies in the pre-malignant colorectal field.

Oleksiewicz U, Liloglou T, Tasopoulou KM, et al.
COL1A1, PRPF40A, and UCP2 correlate with hypoxia markers in non-small cell lung cancer.
J Cancer Res Clin Oncol. 2017; 143(7):1133-1141 [PubMed] Free Access to Full Article Related Publications
PURPOSE: Collagen 1A1 (COL1A1), RNA-binding and pre-mRNA Processing Factor (PRPF40A), and Uncoupling Protein 2 (UCP2) were identified as downstream effectors of cytoglobin (CYGB), which was shown implicated in tumour biology. Although these three genes have been previously associated with cancer, little is known about their status in lung malignancies.
METHODS: Hereby, we investigated the expression and promoter methylation of COL1A1, PRPF40A, and UCP2 in 156 non-small cell lung cancer (NSCLC) and adjacent normal tissues.
RESULTS: We demonstrate that COL1A1 and PRPF40A mRNAs are significantly overexpressed in NSCLC (p < 1 × 10
CONCLUSION: In conclusion, our data revealed that COL1A1, UCP2, and PRPF40A are novel players implicated in the complex network of hypoxia response in NSCLC.

Chang J, Lucas MC, Leonte LE, et al.
Pre-clinical evaluation of small molecule LOXL2 inhibitors in breast cancer.
Oncotarget. 2017; 8(16):26066-26078 [PubMed] Free Access to Full Article Related Publications
Lysyl Oxidase-like 2 (LOXL2), a member of the lysyl oxidase family of amine oxidases is known to be important in normal tissue development and homeostasis, as well as the onset and progression of solid tumors. Here we tested the anti-tumor properties of two generations of novel small molecule LOXL2 inhibitor in the MDA-MB-231 human model of breast cancer. We confirmed a functional role for LOXL2 activity in the progression of primary breast cancer. Inhibition of LOXL2 activity inhibited the growth of primary tumors and reduced primary tumor angiogenesis. Dual inhibition of LOXL2 and LOX showed a greater effect and also led to a lower overall metastatic burden in the lung and liver. Our data provides the first evidence to support a role for LOXL2 specific small molecule inhibitors as a potential therapy in breast cancer.

Wang M, Li G, Yang Z, et al.
Uncoupling protein 2 downregulation by hypoxia through repression of peroxisome proliferator-activated receptor γ promotes chemoresistance of non-small cell lung cancer.
Oncotarget. 2017; 8(5):8083-8094 [PubMed] Free Access to Full Article Related Publications
Hypoxic microenvironment is critically involved in the response of non-small cell lung cancer (NSCLC) to chemotherapy, the mechanisms of which remain largely unknown. Here, we found that NSCLC patients exhibited increased chemotherapeutic resistance when complicated by chronic obstructive pulmonary disease (COPD), a critical cause of chronic hypoxemia. The downregulation of uncoupling protein 2 (UCP2), which is attributed to hypoxia-inducible factor 1 (HIF-1)-mediated suppression of the transcriptional factor peroxisome proliferator-activated receptor γ (PPARγ), was involved in NSCLC chemoresistance, and predicted a poor survival rate of patients receiving routine chemotherapy. UCP2 suppression induced reactive oxygen species production and upregulation of the ABC transporter protein ABCG2, which leads to chemoresistance by promoting drug efflux. UCP2 downregulation also altered metabolic rates as shown by elevated glucose uptake and reduced oxygen consumption. These data suggest that UCP2 is a key mediator of hypoxia-triggered chemoresistance of NSCLCs, which can be potentially targeted in clinical treatment of chemo-refractory NSCLCs.

Burch TC, Rhim JS, Nyalwidhe JO
Mitochondria Biogenesis and Bioenergetics Gene Profiles in Isogenic Prostate Cells with Different Malignant Phenotypes.
Biomed Res Int. 2016; 2016:1785201 [PubMed] Free Access to Full Article Related Publications
Background. The most significant hallmarks of cancer are directly or indirectly linked to deregulated mitochondria. In this study, we sought to profile mitochondria associated genes in isogenic prostate cell lines with different tumorigenic phenotypes from the same patient. Results. Two isogenic human prostate cell lines RC77N/E (nonmalignant cells) and RC77T/E (malignant cells) were profiled for expression of mitochondrial biogenesis and energy metabolism genes by qRT-PCR using the Human Mitochondria and the Mitochondrial Energy Metabolism RT(2) PCR arrays. Forty-seven genes were differentially regulated between the two cell lines. The interaction and regulatory networks of these genes were generated by Ingenuity Pathway Analysis. UCP2 was the most significantly upregulated gene in primary adenocarcinoma cells in the current study. The overexpression of UCP2 upon malignant transformation was further validated using human prostatectomy clinical specimens. Conclusions. This study demonstrates the overexpression of multiple genes that are involved in mitochondria biogenesis, bioenergetics, and modulation of apoptosis. These genes may play a role in malignant transformation and disease progression. The upregulation of some of these genes in clinical samples indicates that some of the differentially transcribed genes could be the potential targets for therapeutic interventions.

Cho YS, Lee JH, Jung KH, et al.
Molecular mechanism of (18)F-FDG uptake reduction induced by genipin in T47D cancer cell and role of uncoupling protein-2 in cancer cell glucose metabolism.
Nucl Med Biol. 2016; 43(10):587-92 [PubMed] Related Publications
INTRODUCTION: Compounds that modulate cancer cell glucose metabolism could open new opportunities for antitumor therapy and for monitoring response using (18)F-FDG PET. Genipin, a natural dietary compound that blocks uncoupling protein 2 (UCP2)-mediated mitochondrial proton leakage, is a potential anticancer agent. We investigated the effect of genipin on glucose metabolism and the mitochondrial function of cancer cells.
METHODS: Breast and colon cancer cells were assessed for effects of genipin on (18)F-FDG uptake. T47D breast cancer cells were further evaluated for time-dependent and dose-dependent effects on (18)F-FDG uptake, lactate release, oxygen consumption rate (OCR), reactive oxygen species (ROS) production, and mitochondrial membrane potential. The effects of UCP2 knockdown were evaluated using specific siRNA.
RESULTS: Cancer cells displayed significant reductions in (18)F-FDG uptake by genipin. T47D cells showed the greatest reduction to 32.6±1.0% of controls by 250μM genipin. The effect occurred rapidly, reaching a plateau by 1h that lasted up to 24h. The effect was dose-dependent with a half-inhibitory concentration of 60.8μM. An accompanying decrease in lactate release was consistent with reduced glycolytic flux. OCR was significantly decreased by genipin to 82.2±11.4% of controls, and ROS generation was increased to 156.7±16.0%. These effects were largely reproduced by UCP2 knockdown with specific siRNA.
CONCLUSIONS: Genipin decreased cancer cell (18)F-FDG uptake by reducing both glycolytic flux and mitochondrial oxidative respiration. This effect appeared to occur by blocking the ability of UCP2 to dissipate energy and restrict ROS production through proton leakage.

Futawaka K, Tagami T, Fukuda Y, et al.
Growth hormone regulates the expression of UCP2 in myocytes.
Growth Horm IGF Res. 2016; 29:57-62 [PubMed] Related Publications
OBJECTIVE: To determine if and how growth hormone (GH) signaling is involved in energy metabolism.
DESIGN: We used human embryonic kidney TSA201 cells, human H-EMC-SS chondrosarcoma cells, rat L6 skeletal muscle cells, and murine C2C12 skeletal muscle myoblasts to investigate GH-induced expression of uncoupling protein2 (UCP2) to the GHR/JAK/STAT5 pathway by a combination of a reporter assay, electrophoretic mobility shift assay (EMSA), real-time quantitative PCR, Western blotting.
RESULTS: We demonstrated that the regulation energy metabolism, which was hypothesized to be directly acted on by GH, involves UCP2 via activated STAT5B, a signal transducer downstream of GH. We also showed that the sequence at the -586 'TTCnGA' may function as a novel putative consensus sequence of STAT5s.
CONCLUSION: The results suggest that GH regulates energy metabolism directly in myocytes and that UCP2 participates in the signal transduction pathway that functions downstream of the GHR/JAK/STAT.

Yu G, Wang J, Xu K, Dong J
Dynamic regulation of uncoupling protein 2 expression by microRNA-214 in hepatocellular carcinoma.
Biosci Rep. 2016; 36(3) [PubMed] Free Access to Full Article Related Publications
Gemcitabine (GEM), a commonly used chemotherapeutic agent in hepatocellular carcinoma (HCC) patients, uses oxidative stress induction as a common effector pathway. However, GEM alone or in combination with oxaliplatin hardly renders any survival benefits to HCC patients. We have recently shown that this is part due to the overexpression of the mitochondrial uncoupling protein 2 (UCP2) that in turn mediates resistance to GEM in HCC patients. However, not much is known about regulatory mechanisms underlying UCP2 overexpression in HCC. Differential protein expression in HCC cell lines did not show a concomitant change in UCP2 transcript level, indicating post-transcriptional or post-translational regulatory mechanism. In situ analysis revealed that UCP2 is a putative target of miR-214 miR-214 expression is significantly down-regulated in HCC patient samples as compared with normal adjacent tissues and in cell line, human hepatoblastoma cells (HuH6), with high UCP2 protein expression. We demonstrated using miR-214 mimic and antagomir that the miRNA targeted UCP2 expression by directly targeting the wild-type, but not a miR-214 seed mutant, 3' UTR of UCP2 Overexpression of miR-214 significantly attenuated cell proliferation. Finally, analysis in 20 HCC patients revealed an inverse correlation in expression of UCP2 and miR-214 (Pearson's correlation coefficient, r=-0.9792). Cumulatively, our data indicate that in the context of HCC, miR-214 acts as a putative tumour suppressor by targeting UCP2 and defines a novel mechanism of regulation of UCP2.

Calgani A, Delle Monache S, Cesare P, et al.
Leptin contributes to long-term stabilization of HIF-1α in cancer cells subjected to oxygen limiting conditions.
Cancer Lett. 2016; 376(1):1-9 [PubMed] Related Publications
Leptin, a cytokine produced by the adipose tissue in response to food intake, is a key player in the regulation of energy balance and body weight control. Physiological action of leptin in modulating the metabolic adaptation of different peripheral tissues supports the hypothesis that it could also exert a direct effect on cancer cells. In vitro, treatment with leptin up-regulated HIF-1α and stimulated adhesion and invasion of prostate cancer cells cultured in hypoxia. Leptin action was effective in both low and high glycolytic cancer cell lines, and determined the up-regulation of lactate exporter MCT4 and its associated protein CD147. HIF-1α stabilization was oligomycin-independent and was associated with an important modulation of mitochondrial homeostasis. In fact, leptin treatment produced mitochondrial biogenesis, stabilization of mitochondrial membrane potential and increased uncoupled respiration through the up-regulation of UCP2. Furthermore, leptin counteracted the downmodulation of SIRT1 induced by hypoxia, and persistent high levels of SIRT1 were directly involved in HIF-1α stabilization. Leptin can sustain cancer progression in hypoxic environment and when mitochondrial respiration is impaired. Leptin signaling axis, including the new proposed intermediate SIRT1, could represent a new diagnostic and therapeutic target in prostate cancer.

Cox TR, Gartland A, Erler JT
Lysyl Oxidase, a Targetable Secreted Molecule Involved in Cancer Metastasis.
Cancer Res. 2016; 76(2):188-92 [PubMed] Related Publications
Secondary metastatic cancer remains the single biggest cause of mortality and morbidity across most solid tumors. In breast cancer, 100% of deaths are attributed to metastasis. At present, there are no "cures" for secondary metastatic cancer of any form and there is an urgent unmet clinical need to improve the tools available in our arsenal against this disease, both in terms of treatment, but also prevention. Recently, we showed that hypoxic induction of the extracellular matrix modifying enzyme lysyl oxidase (LOX) correlates with metastatic dissemination to the bone in estrogen receptor negative breast cancer and is essential for the formation of premetastatic osteolytic lesions. We showed that in models of breast cancer metastasis, targeting LOX, or its downstream effects, significantly inhibited premetastatic niche formation and the resulting metastatic burden, offering preclinical validation of this enzyme as a therapeutic target for metastatic breast cancer. Our work is the latest in an emerging body of work supporting the targeting of LOX and calls for greater efforts in developing therapeutics against this extracellular secreted factor in the prevention of cancer progression across multiple solid tumor types.

Yu X, Luo A, Liu Y, et al.
MiR-214 increases the sensitivity of breast cancer cells to tamoxifen and fulvestrant through inhibition of autophagy.
Mol Cancer. 2015; 14:208 [PubMed] Free Access to Full Article Related Publications
BACKGROUND: Tamoxifen (TAM) and fulvestrant (FUL) are the major drugs for patients with estrogen receptor-positive (ER(+)) breast cancers. However, the development of endocrine resistance is the impediment for successful treatment. We aimed to explore the mechanisms of endocrine resistance and therapeutic strategy for overcoming resistance against TAM and FUL.
METHODS: Experiments were performed in ER(+) and estrogen/TAM-sensitive MCF7 cells and antiestrogen-resistant MCF7/LCC9 cells. The expression of miR-214 and uncoupling protein 2 (UCP2) was determined by RT-qPCR and Western blot in breast cancer cells and human breast cancer tissue specimens. Cell autophagy was examined by fluorescent probe monodansyl cadaverine (MDC) and GFP-LC3-II-positive punctate identified by confocal microscopy. Apoptotic cells were determined by Annexin V-FITC/PI staining. The potential regulatory target of miR-214 was determined by prediction tool, target protein expression and luciferase reporter assay.
RESULTS: 4-OHT/FUL treatment resulted in induction of apoptosis as well as autophagy in breast cancer cells. Autophagy might be the major cause of endocrine resistance to 4-OHT or FUL. MiR-214 increased the sensitivity of breast cancer cells to the 4-OHT/FUL-induced apoptosis through inhibition of autophagy. Importantly, a negative correlation was established between miR-214 and UCP2 in human breast cancer tissue specimens assayed by RT-qPCR. UCP2 was identified to be a direct target of miR-214. Further study in MCF7/LCC9 cells indicated that endocrine resistance might arise from activation of the PI3K-Akt-mTOR pathway, thereby inducing autophagy by overexpression of UCP2.
CONCLUSION: MiR-214 increased the sensitivity of breast cancer cells to TAM and FUL through inhibition of autophagy by targeting UCP2. MiR-214 shows potential as a novel therapeutic strategy for overcoming endocrine resistance in ER(+) breast cancers.

Hima S, Sreeja S
Regulatory role of estrogen-induced reactive oxygen species in the modulatory function of UCP 2 in papillary thyroid cancer cells.
IUBMB Life. 2015; 67(11):837-46 [PubMed] Related Publications
Oxidative stress is postulated as one of the mechanisms underlying the estrogen's carcinogenic effect in thyroid cancer. But the fundamental mechanisms behind this carcinogenic effect remain elusive. Physiologically attainable concentrations of estrogen or estrogen metabolites have been made known to cause reactive oxygen species (ROS). It is envisioned that estrogen-induced ROS mediated signaling is a key congruent mechanism that drives the modulation of uncoupled proteins in papillary thyroid carcinoma cells. The present study investigates that estrogens may increase mitochondrial ROS production by repressing uncoupling proteins, which offers a new perspective on the understanding of why thyroid cancer occurs three times more often in females than in males, and the occurrence decreases after menopause.

de Groen FL, Timmer LM, Menezes RX, et al.
Oncogenic Role of miR-15a-3p in 13q Amplicon-Driven Colorectal Adenoma-to-Carcinoma Progression.
PLoS One. 2015; 10(7):e0132495 [PubMed] Free Access to Full Article Related Publications
Progression from colorectal adenoma to carcinoma is strongly associated with an accumulation of genomic alterations, including gain of chromosome 13. This gain affects the whole q arm and is present in 40%-60% of all colorectal cancers (CRCs). Several genes located at this amplicon are known to be overexpressed in carcinomas due to copy number dosage. A subset of these genes, including the mir-17~92 cluster, are functionally involved in CRC development. The present study set out to explore whether apart from mir-17~92, other miRNAs located at the 13q amplicon show a copy number dependent dosage effect that may contribute to 13q-driven colorectal adenoma-to-carcinoma progression. Integration of publically available miRNA expression, target mRNA expression and DNA copy number data from 125 CRCs yielded three miRNAs, miR-15a, -17, and -20a, of which high expression levels were significantly correlated with a 13q gain and which influenced target mRNA expression. These results could be confirmed by qRT-PCR in a series of 100 colon adenomas and carcinomas.Functional analysis of both mature miRNAs encoded by mir-15a, i.e. miR-15a-5p and miR-15a-3p, showed that silencing of miR-15a-3p significantly inhibited viability of CRC cells. Integration of miR-15a expression levels with mRNA expression data of predicted target genes identified mitochondrial uncoupling protein 2 (UCP2) and COP9 signalosome subunit 2 (COPS2) as candidates with significantly decreased expression in CRCs with 13q gain. Upon silencing of miR-15a-3p, mRNA expression of both genes increased in CRC cells, supporting miR-15a-3p mediated regulation of UPC2 and COPS2 expression. In conclusion, significant overexpression of miR-15a-3p due to gain of 13q is functionally relevant in CRC, with UCP2 and COPS2 as candidate target genes. Taken together our findings suggest that miR-15a-3p may contribute to adenoma-to-carcinoma progression.

Creixell P, Reimand J, Haider S, et al.
Pathway and network analysis of cancer genomes.
Nat Methods. 2015; 12(7):615-621 [PubMed] Free Access to Full Article Related Publications
Genomic information on tumors from 50 cancer types cataloged by the International Cancer Genome Consortium (ICGC) shows that only a few well-studied driver genes are frequently mutated, in contrast to many infrequently mutated genes that may also contribute to tumor biology. Hence there has been large interest in developing pathway and network analysis methods that group genes and illuminate the processes involved. We provide an overview of these analysis techniques and show where they guide mechanistic and translational investigations.

Yuan Y, Yao YF, Hu SN, et al.
MiR-133a Is Functionally Involved in Doxorubicin-Resistance in Breast Cancer Cells MCF-7 via Its Regulation of the Expression of Uncoupling Protein 2.
PLoS One. 2015; 10(6):e0129843 [PubMed] Free Access to Full Article Related Publications
The development of novel targeted therapies holds promise for conquering chemotherapy resistance, which is one of the major hurdles in current breast cancer treatment. Previous studies indicate that mitochondria uncoupling protein 2 (UCP-2) is involved in the development of chemotherapy resistance in colon cancer and lung cancer cells. In the present study we found that lower level of miR133a is accompanied by increased expression of UCP-2 in Doxorubicin-resistant breast cancer cell cline MCF-7/Dox as compared with its parental cell line MCF-7. We postulated that miR133a might play a functional role in the development of Doxorubicin-resistant in breast cancer cells. In this study we showed that: 1) exogenous expression of miR133a in MCF-7/Dox cells can sensitize their reaction to the treatment of Doxorubicin, which is coincided with reduced expression of UCP-2; 2) knockdown of UCP-2 in MCF-7/Dox cells can also sensitize their reaction to the treatment of Doxorubicin; 3) intratumoral delivering of miR133a can restore Doxorubicin treatment response in Doxorubicin-resistant xenografts in vivo, which is concomitant with the decreased expression of UCP-2. These findings provided direct evidences that the miR133a/UCP-2 axis might play an essential role in the development of Doxorubicin-resistance in breast cancer cells, suggesting that the miR133a/UCP-2 signaling cohort could be served as a novel therapeutic target for the treatment of chemotherapy resistant in breast cancer.

Pons DG, Nadal-Serrano M, Torrens-Mas M, et al.
UCP2 inhibition sensitizes breast cancer cells to therapeutic agents by increasing oxidative stress.
Free Radic Biol Med. 2015; 86:67-77 [PubMed] Related Publications
Modulation of oxidative stress in cancer cells plays an important role in the study of the resistance to anticancer therapies. Uncoupling protein 2 (UCP2) may play a dual role in cancer, acting as a protective mechanism in normal cells, while its overexpression in cancer cells could confer resistance to chemotherapy and a higher survival through downregulation of ROS production. Thus, our aim was to check whether the inhibition of UCP2 expression and function increases oxidative stress and could render breast cancer cells more sensitive to cisplatin (CDDP) or tamoxifen (TAM). For this purpose, we studied clonogenicity, mitochondrial membrane potential (ΔΨm), cell viability, ROS production, apoptosis, and autophagy in MCF-7 and T47D (only the last four determinations) breast cancer cells treated with CDDP or TAM, in combination or without a UCP2 knockdown (siRNA or genipin). Furthermore, survival curves were performed in order to check the impact of UCP2 expression in breast cancer patients. UCP2 inhibition and cytotoxic treatments produced a decrease in cell viability and clonogenicity, in addition to an increase in ΔΨm, ROS production, apoptosis, and autophagy. It is important to note that CDDP decreased UCP2 protein levels, so that the greatest effects produced by the UCP2 inhibition in combination with a cytotoxic treatment, with regard to treatment alone, were observed in TAM+UCP2siRNA-treated cells. Moreover, this UCP2 inhibition caused autophagic cell death, since apoptosis parameters barely increased after UCP2 knockdown. Finally, survival curves revealed that higher UCP2 expression corresponded with a poorer prognosis. In conclusion, UCP2 could be a therapeutic target in breast cancer, especially in those patients treated with tamoxifen.

Lou J, Wang Y, Wang X, Jiang Y
Uncoupling protein 2 regulates palmitic acid-induced hepatoma cell autophagy.
Biomed Res Int. 2014; 2014:810401 [PubMed] Free Access to Full Article Related Publications
Mitochondrial uncoupling protein 2 (UCP2) is suggested to have a role in the development of nonalcoholic steatohepatitis (NASH). However, the mechanism remains unclear. Autophagy is an important mediator of many pathological responses. This study aims to investigate the relationship between UCP2 and hepatoma cells autophagy in palmitic acid- (PA-) induced lipotoxicity. H4IIE cells were treated with palmitic acid (PA), and cell autophagy and apoptosis were examined. UCP2 expression, in association with LC3-II and caspase-3, which are indicators of cell autophagy and apoptosis, respectively,was measured. Results demonstrated that UCP2 was associated with autophagy during PA-induced hepatic carcinoma cells injury. Tests on reactive oxygen species (ROS) showed that UCP2 overexpression strongly decreases PA-induced ROS production and apoptosis. Conversely, UCP2 inhibition by genipin or UCP2 mRNA silencing enhances PA-induced ROS production and apoptosis. Autophagy partially participates in this progress. Moreover, UCP2 was associated with ATP synthesis during PA-induced autophagy. In conclusion, increasing UCP2 expression in hepatoma cells may contribute to cell autophagy and antiapoptotic as result of fatty acid injury. Our results may bring new insights for potential NASH therapies.

Esteves P, Pecqueur C, Ransy C, et al.
Mitochondrial retrograde signaling mediated by UCP2 inhibits cancer cell proliferation and tumorigenesis.
Cancer Res. 2014; 74(14):3971-82 [PubMed] Related Publications
Cancer cells tilt their energy production away from oxidative phosphorylation (OXPHOS) toward glycolysis during malignant progression, even when aerobic metabolism is available. Reversing this phenomenon, known as the Warburg effect, may offer a generalized anticancer strategy. In this study, we show that overexpression of the mitochondrial membrane transport protein UCP2 in cancer cells is sufficient to restore a balance toward oxidative phosphorylation and to repress malignant phenotypes. Altered expression of glycolytic and oxidative enzymes mediated the effects of this metabolic shift. Notably, UCP2 overexpression increased signaling from the master energy-regulating kinase, adenosine monophosphate-activated protein kinase, while downregulating expression of hypoxia-induced factor. In support of recent new evidence about UCP2 function, we found that UCP2 did not function in this setting as a membrane potential uncoupling protein, but instead acted to control routing of mitochondria substrates. Taken together, our results define a strategy to reorient mitochondrial function in cancer cells toward OXPHOS that restricts their malignant phenotype.

Du GJ, Li JH, Liu WJ, et al.
The combination of TRPM8 and TRPA1 expression causes an invasive phenotype in lung cancer.
Tumour Biol. 2014; 35(2):1251-61 [PubMed] Related Publications
Our recent studies have shown that hypothermic microenvironment promotes tumor progression and that the molecular sensors for cold are the transient receptor potential (TRP) channels TRPM8 and TRPA1. To evaluate the contribution of TRPM8 and TRPA1 to cancer malignancy, we screened cell subpopulations from Lewis lung cancer (LLC) using limiting dilutions and Western blotting. We identified that LLC-1 cells express 3-fold more TRPM8 than TRPA1, LLC-2 cells express TRPM8 at levels similar to TRPA1, and LLC-3 cells express TRPM8 at one-third the level of TRPA1. LLC-2 cells showed greater adhesion, migration, invasiveness and resistance to hypothermia than LLC-1 and LLC-3 cells, although LLC-2 cells had a longer doubling time. TRPM8 or TRPA1 knockdown using siRNA promoted cell proliferation and decreased adhesion and invasiveness in LLC-2 cells. When assessed for UCP2 staining, LLC-1 cells showed increased staining compared to LLC-2 cells, both of which had more UCP2-positive cells than the LLC-3 subpopulation. In an autophagy assay, hypothermia induced substantially less autophagy in LLC-1 cells than in LLC-2 cells, which displayed decreased autophagy compared to LLC-3 cells. Moreover, mice injected with LLC-2 cells had significantly more spontaneous and experimental lung metastases and a shorter overall survival time than mice injected with LLC-1 or LLC-3 cells. Importantly, LLC-2 cells were also more resistant to activated spleen CTL and the chemotherapeutic drug doxorubicin than LLC-1 and LLC-3 cells in vitro. Collectively, our data suggest that TRPM8 induces UCP2 to trigger metabolic transformation, whereas TRPA1 induces autophagy during adverse conditions, and the combination of both genes contributes directly to an invasive phenotype in lung cancer.

Hu X, Yuan P, Yan J, et al.
Gene Polymorphisms of ADIPOQ +45T>G, UCP2 -866G>A, and FABP2 Ala54Thr on the Risk of Colorectal Cancer: A Matched Case-Control Study.
PLoS One. 2013; 8(6):e67275 [PubMed] Free Access to Full Article Related Publications
As insulin resistance (IR) is an established risk factor for colorectal cancer (CRC), we explored the association between each of the IR-related gene polymorphisms of adiponectin (ADIPOQ) rs2241766, uncoupling protein 2 (UCP2) rs659366, and fatty acid-binding protein (FABP2) rs1799883 and CRC risk. Genotyping of blood samples and collection of lifestyle and dietary habits were performed for 400 case-control pairs. Unconditional logistic regression (ULR) was applied to assess the effects of the three single nucleotide polymorphisms (SNP), environmental factors. Both ULR and generalized multifactor dimensionality reduction (GMDR) were used to test the gene-gene and gene-environment interactions on CRC risk. Subjects carrying the ADIPOQ rs2241766 TG+GG genotype had a higher CRC risk than those carrying the TT genotype (OR = 1.429, 95% CI 1.069-1.909). The additive and multiplicative interactions between ADIPOQ rs2241766 and FABP2 rs1799883 on CRC were found by ULR (RERI = 0.764, 95%CI 0.218∼1.311, AP = 0.514, 95%CI 0.165∼0.864, S = -1.745, 95%CI is unachievable, and Pmulti = 0.017, respectively). Furthermore, the high order gene-gene interaction of the three SNPs were found by GMDR (P = 0.0107). A significant dosage effect with an increasing number of risk genotypes was observed as the risk of CRC increased (Ptrend = 0.037). In GMDR, the gene-environment interaction among the three SNPs and red meat consumption on CRC risk was significant (P = 0.0107). Compared with subjects with low red meat consumption and null risk genotypes, those with high-red meat consumption and three risk genotypes had 3.439-fold CRC risk (95% CI 1.410-8.385). In conclusion, the results showed that the ADIPOQ rs2241766 TG+GG genotype increased CRC risk. Given the complexity of the carcinogen for CRC, ADIPOQ rs2241766, UCP2 rs659366, FABP2 rs1799883 and red meat consumption potentially worked together in affecting CRC risk.

Hossein-Nezhad A, Mirzaei K, Keshavarz SA, et al.
Evidences of dual role of vitamin D through cellular energy homeostasis and inflammation pathway in risk of cancer in obese subjects.
Minerva Med. 2013; 104(3):295-307 [PubMed] Related Publications
AIM: The underlying molecular mechanisms of the role obesity plays in increasing the risk of cancer are not well illuminated. Several mechanisms are proposed for vitamin D as an anti-cancer agent in various malignancies which may be attributed to both its both its anti-inflammatory characteristics as well as its mediatory role in cellular energy homeostasis. This study evaluates the expression of PBMCs' genes which are involved in cellular energy homeostasis such as VDR, PPARγ, PGC1a and UCP2. Moreover, considering the possible role of vitamin D in the inflammation mechanisms, we also aimed at measurement of some inflammatory mediators such as TNF-α, IL-1β, IL4, IL-6, IL10, IL13 and IL17 in inflammatory state in samples obtained from obese persons with and without positive family history of cancer. Moreover, to expand the study to a clinical context, we assessed the correlation of the resting metabolic rate with the evaluated gene.
METHODS: A total of 274 obese women were included in the current cross-sectional study. All of participants were class I obese. By constructing a pedigree that includes 3 generations, twenty-one subjects were at increased risk because of a positive family history of colorectal cancer. Accordingly, current study's analysis was based on positive and negative family history of colorectal cancer.
RESULTS: The concentration of Insulin and PTH were significantly high in group with positive history of cancer. 25 (OH) vitamin D, REE/kg and REE/FFM statuses in two groups; the level of mentioned terms were lower in group with positive history of cancer compared to group with negative history of cancer. We found significantly lower REE/kg in deficiency of vitamin D and higher REE/kg in sufficiency status. Our results demonstrated significant higher concentrations of IL1β, IL17, TNFα and IL6 in group with positive history of cancer compared to group with negative history of cancer. The concentrations of IL13, IL10 and IL4 were significantly lower in group with positive history of cancer compared to group with negative history of cancer. The relative expression of VDR, PGC1αand PPARγ gene was significantly lower in group with positive history of cancer. The relative expression of UCP2 was almost significantly lesser in group with positive history of cancer also.
CONCLUSION: The observed mutual alteration in the levels of inflammatory markers and relative expression of important gene in energy homeostasis may be caused by vitamin D deficiency among the obese subjects with positive history of colorectal cancer.

Liu Y, Jiang H, Xing FQ, et al.
Uncoupling protein 2 expression affects androgen synthesis in polycystic ovary syndrome.
Endocrine. 2013; 43(3):714-23 [PubMed] Related Publications
The roles of uncoupling protein-2 (UCP2) on the androgen synthesis of granulosa cells derived from patients with polycystic ovary syndrome (PCOS) and normal subjects were explored. Primary human granulosa cells from 18 patients who received in vitro fertilization (IVF) were examined; nine patients had PCOS with hyperandrogenism. Primary cultures were treated with genipin, a proton leak inhibitor, guanosine diphosphate (GDP), an UCP inhibitor, and triiodothyronine (T3), an inducer of UCP gene expression. Mitochondrial membrane potential was determined using the JC-1 assay. T3 induced P450scc and UCP2 expressions and testosterone synthesis in both normal and PCOS granulosa cells. Their expressions in response to T3 treatments were correlated in the PCOS group. Differences in testosterone synthesis were observed between normal and PCOS cells in response to genipin. Increased mitochondrial membrane potential was observed in response to genipin and GDP; while T3 decreased it. Increased ovarian UCP2 expression in response to T3 treatment in PCOS may alter pregnenolone synthesis by influencing P450scc expression, thus altering testosterone production. Further in vivo studies are necessary to fully elucidate the role of UCP2 in the hyperandrogenism commonly observed in PCOS.

Dalla Pozza E, Fiorini C, Dando I, et al.
Role of mitochondrial uncoupling protein 2 in cancer cell resistance to gemcitabine.
Biochim Biophys Acta. 2012; 1823(10):1856-63 [PubMed] Related Publications
Cancer cells exhibit an endogenous constitutive oxidative stress higher than that of normal cells, which renders tumours vulnerable to further reactive oxygen species (ROS) production. Mitochondrial uncoupling protein 2 (UCP2) can mitigate oxidative stress by increasing the influx of protons into the mitochondrial matrix and reducing electron leakage and mitochondrial superoxide generation. Here, we demonstrate that chemical uncouplers or UCP2 over-expression strongly decrease mitochondrial superoxide induction by the anticancer drug gemcitabine (GEM) and protect cancer cells from GEM-induced apoptosis. Moreover, we show that GEM IC(50) values well correlate with the endogenous level of UCP2 mRNA, suggesting a critical role for mitochondrial uncoupling in GEM resistance. Interestingly, GEM treatment stimulates UCP2 mRNA expression suggesting that mitochondrial uncoupling could have a role also in the acquired resistance to GEM. Conversely, UCP2 inhibition by genipin or UCP2 mRNA silencing strongly enhances GEM-induced mitochondrial superoxide generation and apoptosis, synergistically inhibiting cancer cell proliferation. These events are significantly reduced by the addition of the radical scavenger N-acetyl-l-cysteine or MnSOD over-expression, demonstrating a critical role of the oxidative stress. Normal primary fibroblasts are much less sensitive to GEM/genipin combination. Our results demonstrate for the first time that UCP2 has a role in cancer cell resistance to GEM supporting the development of an anti-cancer therapy based on UCP2 inhibition associated to GEM treatment.

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