The LEDGF/p75 Integrase Binding Domain Interactome Contributes to the Survival, Clonogenicity, and Tumorsphere Formation of Docetaxel-Resistant Prostate Cancer Cells

Patients with prostate cancer (PCa) receiving docetaxel chemotherapy invariably develop chemoresistance. The transcription co-activator lens epithelium-derived growth factor p75 (LEDGF/p75), also known as DFS70 and PSIP1, is upregulated in several human cancers, including PCa and promotes resistance to docetaxel and other drugs. The C-terminal region of LEDGF/p75 contains an integrase binding domain (IBD) that tethers nuclear proteins, including the HIV-1 integrase and transcription factors, to active chromatin to promote viral integration and transcription of cellular survival genes. Here, we investigated the contribution of the LEDGF/p75 IBD interactome to PCa chemoresistance. Quantitative immunoblotting revealed that LEDGF/p75 and its IBD-interacting partners are endogenously upregulated in docetaxel-resistant PCa cell lines compared to docetaxel-sensitive parental cells. Using specific human autoantibodies, we co-immunoprecipitated LEDGF/p75 with its endogenous IBD-interacting partners JPO2, menin, MLL, IWS1, ASK1, and PogZ, as well as transcription factors c-MYC and HRP2, in docetaxel-resistant cells, and confirmed their nuclear co-localization by confocal microscopy. Depletion of LEDGF/p75 and selected interacting partners robustly decreased the survival, clonogenicity, and tumorsphere formation capacity of docetaxel-resistant cells. These results implicate the LEDGF/p75 IBD interactome in PCa chemoresistance and could lead to novel therapeutic strategies targeting this protein complex for the treatment of docetaxel-resistant tumors.