CUL5 E3 ubiquitin ligase regulates the evasion of bladder cancer cells to CD8+ T cell-mediated killing by inhibiting autophagy

CD8+ T cells are capable of specifically targeting and eliminating malignant tumor cells, but tumor cells can develop resistance mechanisms to escape CD8+ T cell-mediated killing. Here, we performed a whole genome CRISPR-Cas9 knockout screen under CD8+ T cells pressure and identified the E3 ubiquitin ligase CUL5 as an essential factor required for escaping CD8+ T cells killing in bladder cancer cells. We found that CUL5 knockout promoted the sensitivity of bladder cancer cells to CD8+ T cell-mediated killing both in vivo and in vitro. Mechanistically, CUL5 loss reduced the ubiquitination of PTBP1, which regulated alternative splicing of RUBCN pre-mRNA and led to an increase in the levels of the RUBCN-S isoform, thereby preventing immune evasion of bladder cancer cells by inhibiting autophagy. Importantly, CUL5 knockout significantly enhanced the efficacy of anti-PD-1 immunotherapy in a xenograft model. Collectively, these findings reveal a novel mechanism of bladder cancer immune evasion, providing potential targets for cancer immunotherapy. Overall design: Considering that PTBP1 acts as a classical splicing factor, we conducted high-throughput sequencing of RNA (RNA-Seq) on the CUL5-WT and CUL5-KO T24 cells to analyze the changes of alternative splicing (AS).