PIKfyve inhibition upregulates surface expression of MHC class I to enhance immune responses in cancer

Despite the remarkable clinical success of immunotherapies in a subset of cancer patients, many fail to respond to treatment and exhibit primary resistance. Here, we found thatgenetic or pharmacologic inhibitionof the lipid kinase PIKfyve, a regulator of autophagic flux and lysosomal biogenesis,upregulated surface expression of major histocompatibility complex class I (MHC-I) in cancer cells via impairing autophagic flux, resulting in enhanced cancer cell killing mediated by CD8+ T cells. Genetic depletion or pharmacologic inhibition of PIKfyve elevated tumor-specific MHC-I surface expression, reduced tumor proliferation, and increased intratumoral functional CD8+T cellsinsyngeneic mouse models. Importantly, enhanced antitumor responses by Pikfyve-depletion was CD8+T cell- and MHC-I-dependent,as CD8+ T cell depletion or B2m knockout rescued tumor growth. Furthermore, PIKfyve inhibition improved response to various immunotherapies, including immune checkpoint blockade (ICB), adoptive cell therapy, and therapeutic vaccines. High expression of PIKFYVE was also predictive of poor response to ICB and prognostic of poor survival in ICB-treated cohorts. Collectively, our findings show that targeting PIKfyve enhances immunotherapies by elevating surface expression of MHC-I in cancer cells, and PIKfyve inhibitors have potential as novel agents to increase immunotherapy response in cancer patients. Overall design: To compare the transcriptomic changes in pancreatic tumors established by Pikfvye-null KPC1361 versus control KPC1361 in C57BL/6