FOXA1 and prostate neoplasm: In addition to tumors with ETS fusions, the Cancer Genome Atlas (TCGA) network further classified primary prostate tumors in three additional molecular subtypes on the basis of mutations in SPOP, FOXA1, and IDH1. Both SPOP and FOXA1 are key regulators of the AR, and tumors carrying mutations in SPOP and FOXA1 possess enhanced AR transcriptional activity.