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

## TL;DR

This study shows that the CUL5 protein helps bladder cancer cells avoid immune attack, and removing CUL5 makes cancer cells more vulnerable to immune therapy.

## Contribution

The study identifies CUL5 as a novel regulator of immune evasion in bladder cancer through autophagy inhibition.

## Key findings

- CUL5 knockout increases bladder cancer cell sensitivity to CD8+ T cell-mediated killing.
- CUL5 loss inhibits autophagy by regulating RUBCN splicing through PTBP1 ubiquitination.
- CUL5 knockout improves anti-PD-1 immunotherapy efficacy in a xenograft model.

## Abstract

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.

CD8+ T cells can specifically target and eliminate malignant tumor cells, but tumors are known to develop resistance mechanisms to escape CD8+ T-cell-mediated killing. This study shows that loss of the E3 ubiquitin ligase CUL5 enhances CD8+ T cell cytotoxicity and anti PD-1 efficacy by inhibiting autophagy.