Critical BRCA1 role as a transcriptional regulator in prostate cancer DNA damage response

DE LUCA P; MOIOLA C; ZALAZAR F; GUERON G; COTIGNOLA J; VAZQUEZ E; GARDNER K; DE SIERVI A

Orlando, Florida, Estados Unidos

Congreso; 102nd Annual Meeting American Association for Cancer Research; 2011

American Association for Cancer Research

Loss or mutation of the BRCA1 gene is associated with nearly 5% of all breast cancers. Since many cases of sporadic cancers that also show decreased BRCA1 expression are often associated with higher grade tumors, significant interest has developed in defining mechanisms of BRCA1 regulation at the level of transcription. BRCA1 plays numerous roles in regulating genome integrity. It interacts with crucial proteins and is considered a gene-specific transcriptional co-regulator; however, BRCA1’s role in the transcriptional response to DNA damage is poorly understood. In this study we show that BRCA1 plays a central role in the transcriptional response to genotoxic stress in prostate cancer. Using BRCA1-depleted or BRCA1-overexpressing human prostate cancer cell lines, we found that BRCA1 mediates apoptosis, cell cycle arrest and decreased viability in response to doxorubicin treatment. Furthermore, xenograft studies using human prostate carcinoma PC3 cells demonstrate that BRCA1 depletion results in increased tumor growth. In addition, genome-wide screens using the combined application of chromatin immunoprecipitation and microarray technology (ChIP-chip) reveals that BRCA1 is highly enriched at the promoters of greater than 1300 genes. Gene Ontology (GO) analysis of this “BRCA1 ChIP signature” reveals a significant enrichment in genes that function in cell cycle regulation and the response to DNA damage including “M phase”' and “Mitotic checkpoint” terms, suggesting a specific role for BRCA1 in controlling mitotic events following genotoxic stress. We have validated multiple members of this BRCA1 ChIP signature including: BLM, FEN1, DDB2, H3F3B, BRCA2, CCNB2, MAD2L1, GADD153 and ATM. Further focused analysis reveals that BRCA1 occupancy at the ATM promoter increases its transcription and H2AX phosphorylation. Notably, following doxorubicin exposure, BRCA1 is released from the ATM promoter and redistributed to other genes like GADD153 where it induces expression, apoptosis and cell cycle arrest. RNAi depletion of GADD153 blocks BRCA1-dependent apoptosis and cell cycle arrest in response to doxorubicin, suggesting that GADD153 is required for BRCA1 mediated drug sensitivity. These findings define a novel mechanism through which BRCA1 influences cell fate decisions in response to genotoxic insult through direct transcriptional control of genes, including GADD153 and ATM. Thus, tumors with absent or reduced expression of BRCA1 are likely to show a marked resistance to chemotherapy for prostate cancer.BLM, FEN1, DDB2, H3F3B, BRCA2, CCNB2, MAD2L1, GADD153 and ATM. Further focused analysis reveals that BRCA1 occupancy at the ATM promoter increases its transcription and H2AX phosphorylation. Notably, following doxorubicin exposure, BRCA1 is released from the ATM promoter and redistributed to other genes like GADD153 where it induces expression, apoptosis and cell cycle arrest. RNAi depletion of GADD153 blocks BRCA1-dependent apoptosis and cell cycle arrest in response to doxorubicin, suggesting that GADD153 is required for BRCA1 mediated drug sensitivity. These findings define a novel mechanism through which BRCA1 influences cell fate decisions in response to genotoxic insult through direct transcriptional control of genes, including GADD153 and ATM. Thus, tumors with absent or reduced expression of BRCA1 are likely to show a marked resistance to chemotherapy for prostate cancer.ATM promoter increases its transcription and H2AX phosphorylation. Notably, following doxorubicin exposure, BRCA1 is released from the ATM promoter and redistributed to other genes like GADD153 where it induces expression, apoptosis and cell cycle arrest. RNAi depletion of GADD153 blocks BRCA1-dependent apoptosis and cell cycle arrest in response to doxorubicin, suggesting that GADD153 is required for BRCA1 mediated drug sensitivity. These findings define a novel mechanism through which BRCA1 influences cell fate decisions in response to genotoxic insult through direct transcriptional control of genes, including GADD153 and ATM. Thus, tumors with absent or reduced expression of BRCA1 are likely to show a marked resistance to chemotherapy for prostate cancer.GADD153 where it induces expression, apoptosis and cell cycle arrest. RNAi depletion of GADD153 blocks BRCA1-dependent apoptosis and cell cycle arrest in response to doxorubicin, suggesting that GADD153 is required for BRCA1 mediated drug sensitivity. These findings define a novel mechanism through which BRCA1 influences cell fate decisions in response to genotoxic insult through direct transcriptional control of genes, including GADD153 and ATM. Thus, tumors with absent or reduced expression of BRCA1 are likely to show a marked resistance to chemotherapy for prostate cancer.