Feedback loop between fatty acid transport protein 2 and receptor interacting protein 3 pathways promotes polymorphonuclear neutrophil myeloid-derived suppressor cells-potentiated suppressive immunity in bladder cancer

Background Polymorphonuclear myeloid-derived suppressor cells (PMN-MDSCs) promote tumor immune tolerance and cause tumor immunotherapy failure. In this study, we found that high PMN-MDSCs infiltration, overexpressed fatty acid transporter protein 2 (FATP2) and underexpressed receptor-interacting protein kinase 3 (RIPK3) existed in the mouse and human bladder cancer tissues. However, the related mechanisms remain largely unknown. Methods and results Both FATP2 and RIPK3 expressions were associated with clinical stage. FATP2 knockout or up-regulating RIPK3 reduced the synthesis of prostaglandin E2 (PGE2) in PMN-MDSCs, attenuated the suppressive activity of PMN-MDSCs on CD8(+) T cells functions and inhibited the tumor growth. There was a PGE2-mediated feedback loop between FATP2 and RIPK3 pathways, which markedly promoted the immunosuppressive activity of PMN-MDSCs. Combination therapy with inhibition of FATP2 and activation of RIPK3 can effectively inhibit tumor growth. Conclusions This study demonstrated that a feedback loop between FATP2 and RIPK3 pathways in PMN-MDSCs significantly promoted the synthesis of PGE2, which severely impaired the CD8(+) T cell functions. This study may provide new ideas for immunotherapy of human bladder cancer.

Automated summary

This study discovered a feedback loop between FATP2 and RIPK3 pathways in PMN-MDSCs, which significantly promoted the synthesis of PGE2 and impaired the CD8(+) T cell functions. Combination therapy with inhibition of FATP2 and activation of RIPK3 effectively inhibited tumor growth.