Lactate derived from cancer-associated fibroblasts promotes alternative splicing and castration resistance in prostate cancer.

Lactate in the tumor microenvironment (TME) is typically generated by cells exhibiting high glycolytic flux, exemplified by tumor cells. However, in glycolysis-low malignancies such as prostate cancer, stroma-derived lactate may drive noncanonical signaling and functions that remain unclear. Here, we identified APCDD1+ cancer-associated fibroblasts (CAFs) as a distinct stromal population that secretes lactate into the TME in response to androgen deprivation therapy (ADT). Lactate uptake by prostate cancer cells induces androgen receptor variant 7 expression, thereby conferring resistance to ADT. Mechanistically, lactate-induced lactylation of the spliceosome component SNRPA at Lys123 (K123) enhances its recognition of cis-acting elements, increases chromatin binding, and promotes androgen receptor splicing. Targeting lactate transport with monocarboxylate transporter inhibitors effectively restores ADT sensitivity. These findings reveal a metabolic-epigenetic axis linking lactate in the microenvironment to alternative splicing regulation and suggest a promising therapeutic strategy to overcome ADT resistance.