Divergent FOXA1 mutations drive prostate tumorigenesis and therapy-resistant cellular plasticity.

FOXA1 is altered in 10 to 40% of prostate cancers, yet its oncogenic mechanisms remain uncharacterized in vivo. We developed knock-in mouse models representing distinct classes of FOXA1 mutations. Histopathological and multi-omic analyses of prostate tissues and organoids revealed that Class 1 mutations, in conjunction with inactivation, drive androgen-dependent adenocarcinomas through co-activation of mTORC1/2 and oncogenic AR signaling stemming from chimeric AR-half enhancers. In contrast, Class 2 mutations induce intra-luminal plasticity by reprogramming differentiated luminal cells into a progenitor-like state through activation of KLF5 and AP-1 neo-enhancer circuitries, which enables enhanced survival and proliferation even under castrate androgen levels. Our findings establish FOXA1 as a multifaceted oncogene, with distinct mutational classes divergently evolving to drive prostate tumorigenesis or therapy-resistant progression.