The retinoblastoma tumor suppressor protein pRb restricts cell growth through inhibition of cell cycle progression. Increasing evidence suggests that pRb also promotes differentiation, but the mechanisms are poorly understood, and the key question remains as to how differentiation in tumor cells can be enhanced in order to diminish their aggressive potential. Previously, we identified the histone demethylase KDM5A (lysine [K]-specific demethylase 5A), which demethylates histone H3 on Lys4 (H3K4), as a pRB-interacting protein counteracting pRB's role in promoting differentiation. Here we show that loss of Kdm5a restores differentiation through increasing mitochondrial respiration. This metabolic effect is both necessary and sufficient to induce the expression of a network of cell type-specific signaling and structural genes. Importantly, the regulatory functions of pRB in the cell cycle and differentiation are distinct because although restoring differentiation requires intact mitochondrial function, it does not necessitate cell cycle exit. Cells lacking Rb1 exhibit defective mitochondria and decreased oxygen consumption. Kdm5a is a direct repressor of metabolic regulatory genes, thus explaining the compensatory role of Kdm5a deletion in restoring mitochondrial function and differentiation. Significantly, activation of mitochondrial function by the mitochondrial biogenesis regulator Pgc-1α (peroxisome proliferator-activated receptor γ-coactivator 1α; also called PPARGC1A) a coactivator of the Kdm5a target genes, is sufficient to override the differentiation block. Overexpression of Pgc-1α, like KDM5A deletion, inhibits cell growth in RB-negative human cancer cell lines. The rescue of differentiation by loss of KDM5A or by activation of mitochondrial biogenesis reveals the switch to oxidative phosphorylation as an essential step in restoring differentiation and a less aggressive cancer phenotype. ; This work was supported by R01CA138631 (to E.V.B.) and R01GM094220 (to J.R.) from the National Institutes of Health, educational grant SAF2009-06954 (to N.L.-B.) from the Spanish Ministry of Science, and a fellowship from the Agencia de Gestió d'Ajuts Universitaris i de Recerca of the Catalonian Government, Spain (to A.B.M.M.K.I.)
Abstract Background Epstein-Barr virus (EBV) infection is a well characterized etiopathogenic factor for a variety of immune-related conditions, including lymphomas, lymphoproliferative disorders and autoimmune diseases. EBV-mediated transformation of resting B cells to proliferating lymphoblastoid cells occurs in early stages of infection and is an excellent model for investigating the mechanisms associated with acquisition of unlimited growth. Results We investigated the effects of experimental EBV infection of B cells on DNA methylation profiles by using high-throughput analysis. Remarkably, we observed hypomethylation of around 250 genes, but no hypermethylation. Hypomethylation did not occur at repetitive sequences, consistent with the absence of genomic instability in lymphoproliferative cells. Changes in methylation only occurred after cell divisions started, without the participation of the active demethylation machinery, and were concomitant with acquisition by B cells of the ability to proliferate. Gene Ontology analysis, expression profiling, and high-throughput analysis of the presence of transcription factor binding motifs and occupancy revealed that most genes undergoing hypomethylation are active and display the presence of NF-κB p65 and other B cell-specific transcription factors. Promoter hypomethylation was associated with upregulation of genes relevant for the phenotype of proliferating lymphoblasts. Interestingly, pharmacologically induced demethylation increased the efficiency of transformation of resting B cells to lymphoblastoid cells, consistent with productive cooperation between hypomethylation and lymphocyte proliferation. Conclusions Our data provide novel clues on the role of the B cell transcription program leading to DNA methylation changes, which we find to be key to the EBV-associated conversion of resting B cells to proliferating lymphoblasts. ; This work was supported by grants PI081346 (FIS) and SAF2011-29635 from the Spanish Ministry of Science and Innovation (MICINN) and grant 2009SGR184 from AGAUR (Catalan Government). AI was supported by fellowship from AGAUR, Government of Catalonia, Spain. MP is supported by Ramon y Cajal Programme. ; Peer Reviewed
INTRODUCTION: Endocrine therapies targeting cell proliferation and survival mediated by estrogen receptor alpha (ERalpha) are among the most effective systemic treatments for ERalpha-positive breast cancer. However, most tumors initially responsive to these therapies acquire resistance through mechanisms that involve ERalpha transcriptional regulatory plasticity. Here, we identify VAV3 as a critical component in this process. METHODS: A cell-based chemical compound screen was carried out to identify therapeutic strategies against resistance to endocrine therapy. Binding to ERalpha was evaluated by molecular docking analyses, an agonist fluoligand assay, and short-hairpin (sh) RNA-mediated protein depletion. Microarray analyses were performed to identify altered gene expression. Western blot of signaling and proliferation markers and shRNA-mediated protein depletion in viability and clonogenic assays were performed to delineate the role of VAV3. Genetic variation in VAV3 was assessed for association with the response to tamoxifen. Immunohistochemical analyses of VAV3 were carried out to determine the association with therapy response and different tumor markers. An analysis of gene expression association with drug sensitivity was carried out to identify a potential therapeutic approach based on differential VAV3 expression. RESULTS: The compound YC-1 was found to comparatively reduce the viability of cell models of acquired resistance. This effect was probably not due to activation of its canonical target (soluble guanylyl cyclase) but instead a result of binding to ERalpha. VAV3 was selectively reduced upon exposure to YC-1 or ERalpha depletion and, accordingly, VAV3 depletion comparatively reduced the viability of cell models of acquired resistance. In the clinical scenario, germline variation in VAV3 was associated with response to tamoxifen in Japanese breast cancer patients (rs10494071 combined P value = 8.4 x 10-4). The allele association combined with gene expression analyses indicated that low VAV3 expression predicts better clinical outcome. Conversely, high nuclear VAV3 expression in tumor cells was associated with poorer endocrine therapy response. Based on VAV3 expression levels and the response to erlotinib in cancer cell lines, targeting EGFR signaling may be a promising therapeutic strategy. CONCLUSIONS: This study proposes VAV3 as a biomarker and rationale signaling target to prevent and/or overcome resistance to endocrine therapy in breast cancer. ; We wish to thank all study participants and their clinicians for their valuable contributions. This work was supported by grants from the Eugenio Rodriguez Pascual Foundation (2012, to MAP), the Government of Catalonia (2009-SGR283, to AV and MAP), the National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health (R01 DK015556, to JAK), the Red Cooperative Research Thematic Network on Cancer (RTICC) (12/0036/0002 to XRB and 12/0036/0008 to XRB and MAP) and the Spanish Ministry of Health, Fund for Health Research-Institute of Health Carlos III (11/00951 to AU and 12/01528 to MAP).
While interplay between BRCA1 and AURKA-RHAMM-TPX2-TUBG1 regulates mammary epithelial polarization, common genetic variation in HMMR (gene product RHAMM) may be associated with risk of breast cancer in BRCA1 mutation carriers. Following on these observations, we further assessed the link between the AURKA-HMMR-TPX2-TUBG1 functional module and risk of breast cancer in BRCA1 or BRCA2 mutation carriers. Forty-one single nucleotide polymorphisms (SNPs) were genotyped in 15,252 BRCA1 and 8,211 BRCA2 mutation carriers and subsequently analyzed using a retrospective likelihood approach. The association of HMMR rs299290 with breast cancer risk in BRCA1 mutation carriers was confirmed: per-allele hazard ratio (HR) = 1.10, 95% confidence interval (CI) 1.04 - 1.15, p = 1.9 x 10(-4) (false discovery rate (FDR)-adjusted p = 0.043). Variation in CSTF1, located next to AURKA, was also found to be associated with breast cancer risk in BRCA2 mutation carriers: rs2426618 per-allele HR = 1.10, 95% CI 1.03 - 1.16, p = 0.005 (FDR-adjusted p = 0.045). Assessment of pairwise interactions provided suggestions (FDR-adjusted p(interaction) values greater than 0.05) for deviations from the multiplicative model for rs299290 and CSTF1 rs6064391, and rs299290 and TUBG1 rs11649877 in both BRCA1 and BRCA2 mutation carriers. Following these suggestions, the expression of HMMR and AURKA or TUBG1 in sporadic breast tumors was found to potentially interact, influencing patients survival. Together, the results of this study support the hypothesis of a causative link between altered function of AURKA-HMMR-TPX2-TUBG1 and breast carcinogenesis in BRCA1/2 mutation carriers. ; Funding Agencies|National Cancer Institute [UM1 CA164920]; Lithuania (BFBOCC-LT): Research Council of Lithuania grant [LIG-07/2012]; Hereditary Cancer Association (Paveldimo vezio asociacija); LSC grant [10.0010.08]; ESF [2009/0220/1DP/1.1.1.2.0/09/APIA/VIAA/016]; Liepajas municipal council; Cancer Association of South Africa (CANSA); Morris and Horowitz Familes Endowed Professorship; NEYE Foundation; Spanish Association against Cancer [AECC08, RTICC 06/0020/1060, FISPI08/1120]; Mutua Madrilena Foundation (FMMA); COH-CCGCRN: City of Hope Clinical Cancer Genetics Community Network from the National Cancer Institute and the Office of the Director, National Institutes of Health; Hereditary Cancer Research Registry from the National Cancer Institute and the Office of the Director, National Institutes of Health [RC4CA153828]; Fondazione IRCCS Istituto Nazionale Tumori; Cancer Research-United Kingdom grant [C12292/A11174, C1287/ A10118]; NHMRC Program Grant; DKFZ; European Union (European Social Fund-ESF); Greek national funds through the Operational Program "Education and Lifelong Learning" of the National Strategic Reference Framework (NSRF)-Research Funding Program of the General Secretariat for Research and Technology: ARISTEIA; European Social Fund; Cancer Research United Kingdom Grants [C1287/A10118, C1287/A11990]; National Institute of Health Research (NIHR) grant; NIHR grant; Royal Marsden NHS Foundation Trust; Cancer Research United Kingdom Grant [C5047/A8385]; University of Kansas Cancer Center [P30 CA168524]; Kansas Bioscience Authority Eminent Scholar Program; Chancellors Distinguished Chair in Biomedical Sciences Professorship; AKG [5U01CA113916, R01CA140323]; German Cancer Aid [109076]; Center for Molecular Medicine Cologne (CMMC); Ligue National Contre le Cancer; Association "Le cancer du sein, parlonsen!" Award; Canadian Institutes of Health Research; Fund for Scientific Research Flanders (FWO); National Cancer Institute grant [CA 27469]; GOG Statistical and Data Center [CA 37517]; GOGs Cancer Prevention and Control Committee [CA 101165]; Intramural Research Program, NCI; ISCIII (Spain) [RD12/00369/0006, 12/00539]; European Regional Development FEDER funds; Helsinki University Central Hospital Research Fund; Academy of Finland [132473]; Finnish Cancer Society; Sigrid Juselius Foundation; Dutch Cancer Society grant [NKI1998-1854, NKI2004-3088, NKI2007-3756]; Netherlands Organization of Scientific Research [NWO 91109024]; Pink Ribbon grant [110005]; BBMRI grant [NWO 184.021.007/CP46]; Hungarian Research Grant [KTIA-OTKA CK-80745]; Norwegian EEA Financial Mechanism [HU0115/NA/2008-3/OP-9]; Spanish Ministry of Health ISCIII FIS [PI10/01422, PI12/01528, PI13/00285]; RTICC [RD12/0036/0008]; Ramon Areces (XV) Foundation; Eugenio Rodriguez Pascual Foundation; Roses Contra el Cancer Foundation; Spanish Association Against Cancer (AECC); AGAUR Generalitat de Catalunya [2009-SGR290, 2009-SGR293]; Polish Foundation of Science; Icelandic Association "Walking for Breast Cancer Research"; Nordic Cancer Union; Landspitali University Hospital Research Fund; Canadian Institutes of Health Research for the "CIHR Team in Familial Risks of Breast Cancer" program; Canadian Breast Cancer Research Alliance-grant [019511]; Ministry of Economic Development, Innovation and Export Trade-grant [PSR-SIIRI-701]; Ministero dellIstruzione, dellUniversita e della Ricerca and Ministero della Salute; Liga Portuguesa Contra o Cancro; National Breast Cancer Foundation; National Health and Medical Research Council (NHMRC); Queensland Cancer Fund; Cancer Council of New South Wales; Cancer Council of Victoria; Cancer Foundation of Western Australia; Cancer Councils of Tasmania; National Institutes of Health grant [CA128978]; NCI Specialized Program of Research Excellence (SPORE) in Breast Cancer [CA116201]; United States Department of Defence Ovarian Cancer Idea award [W81XWH-10-1-0341]; Breast Cancer Research Foundation; Jewish General Hospital Weekend; Quebec Ministry of Economic Development, Innovation and Export Trade; Cancer Councils of South Australia; European Regional Development Fund; State Budget of the Czech Republic (RECAMO) [CZ.1.05/2.1.00/03.0101]; MH CZ-DRO (MMCI) [00209805]; Niehaus Family Genetics Research Fund; STARR Cancer Consortium Grant; NAROD [1R01 CA149429-01]; NCI Intramural Research Program, National Institutes of Health [NO2-CP-11019-50, N02-CP-65504]; Westat, Inc, Rockville, Maryland; Clalit Health Services in Israel; Israel Cancer Association; Breast Cancer Research Foundation (BCRF), New York; Russian Federation for Basic Research [11-04-00227, 12-04-00928, 12-04-01490]; Federal Agency for Science and Innovations, Russia [02.740.11.0780]; Canadian Institutes of Health Research for the "CIHR Team in Familial Risks of Breast Cancer" program and grant from the National Cancer Institute [UM1 CA164920]; Breast Cancer Family Registry (BCFR); United States Government or the BCFR; Ohio State University Comprehensive Cancer Center; Isreal cancer association; Israeli Inherited breast cancer consortium; Swedish Cancer Society; Ralph and Marion Falk Medical Research Trust; Entertainment Industry Fund National Womens Cancer Research Alliance; National Institutes of Health (NIH) [R01-CA102776, R01-CA083855]; Rooney Family Foundation; Susan G. Komen Foundation for the cure, Basser Research Center; American Cancer Society Early Detection Professorship [SIOP-06-258-01-COUN]; SAF2010-20493; [PBZ_KBN_122/P05/2004]