Genome-wide analyses of transcription factors and co-regulators across seven cohorts identified reduced PPARGC1A expression as a driver of prostate cancer progression

Defining altered transcription factor (TF) and coregulators that are oncogenic drivers remains a challenge, in part because of the multitude of TFs and coregulators. We addressed this challenge by using bootstrap approaches to test how expression, copy number alterations or mutation of TFs (n = 2662), coactivators (COA; n= 766); corepressor (COR; n = 599); mixed function coregulators (MIXED; n = 511) varied across seven prostate cancer (PCa) cohorts (three of localized and four advanced disease). COAS, CORS, MIXED and TFs all displayed significant down-regulated expression (q.value < 0.1) and correlated with protein expression ({rho} 0.4 to 0.55). Stringent expression filtering identified commonly altered TFs and coregulators including well-established (e.g. ERG) and underexplored (e.g. PPARGC1A, encodes PGC1) in localized PCa. Reduced PPARGC1A expression significantly associated with worse disease-free survival in two cohorts of localized PCa. Stable PGC1 knockdown in LNCaP cells increased growth rates and invasiveness and RNA-Seq revealed a profound basal impact on gene expression (~2300 genes; FDR < 0.05, logFC > 1.5), but only modestly impacted PPAR{gamma} responses. GSEA analyses of the PGC1 transcriptome revealed that it significantly altered the AR-dependent transcriptome, and was enriched for epigenetic modifiers. PGC1-dependent genes were overlapped with PGC1-ChIP-Seq genes and significantly associated in TCGA with higher grade tumors and worse disease-free survival. Together these data demonstrate an approach to identify cancer-driver coregulators in cancer and that PGC1 expression is clinically significant yet underexplored coregulator in aggressive early stage PCa.