Abrogation of Hn RNP L enhances anti-PD-1 therapy efficacy via diminishing PD-L1 and promoting CD8^(+) T cell-mediated ferroptosis in castration-resistant prostate cancer

Owing to incurable castration-resistant prostate cancer(CRPC)ultimately developing after treating with androgen deprivation therapy(ADT),it is vital to devise new therapeutic strategies to treat CRPC.Treatments that target programmed cell death protein 1(PD-1)and programmed death ligand-1(PD-L1)have been approved for human cancers with clinical benefit.However,many patients,especially prostate cancer,fail to respond to anti-PD-1/PD-L1 treatment,so it is an urgent need to seek a support strategy for improving the traditional PD-1/PD-L1 targeting immunotherapy.In the present study,analyzing the data from our prostate cancer tissue microarray,we found that PD-L1 expression was positively correlated with the expression of heterogeneous nuclear ribonucleoprotein L(Hn RNP L).Hence,we further investigated the potential role of Hn RNP L on the PD-L1 expression,the sensitivity of cancer cells to T-cell killing and the synergistic effect with anti-PD-1 therapy in CRPC.Indeed,Hn RNP L knockdown effectively decreased PD-L1 expression and recovered the sensitivity of cancer cells to T-cell killing in vitro and in vivo,on the contrary,Hn RNP L overexpression led to the opposite effect in CRPC cells.In addition,consistent with the previous study,we revealed that ferroptosis played a critical role in T-cell-induced cancer cell death,and Hn RNP L promoted the cancer immune escape partly through targeting YY1/PD-L1 axis and inhibiting ferroptosis in CRPC cells.Furthermore,Hn RNP L knockdown enhanced antitumor immunity by recruiting infiltrating CD8^(+)T cells and synergized with anti-PD-1 therapy in CRPC tumors.This study provided biological evidence that Hn RNP L knockdown might be a novel therapeutic agent in PD-L1/PD-1 blockade strategy that enhanced anti-tumor immune response in CRPC.