CCPG1-mediated reticulophagy promotes tumorigenesis and cisplatin resistance in bladder cancer.

Reticulophagy, a selective macroautophagy/autophagy process targeting endoplasmic reticulum fragments via receptors, plays a critical role in cellular homeostasis. This study reveals that CCPG1, a reticulophagy receptor, drives bladder cancer (BLCA) tumorigenesis and confers cisplatin resistance. We observed elevated reticulophagy activity in BLCA cells compared to normal counterparts, particularly under conditions of nutrient stress. CCPG1 expression was significantly upregulated in BLCA patient samples and correlated with poor prognosis. Functional studies demonstrated that CCPG1 knockdown suppressed reticulophagy, leading to decreased cell proliferation and increased apoptosis. Conversely, overexpression of the wild-type CCPG1, but not a MAP1LC3/LC3-binding-deficient variant, rescued reticulophagy and promoted tumor growth. Notably, we found that cisplatin treatment inhibited reticulophagy by downregulating CCPG1 expression through the ATM-CHEK2/Chk2 signaling pathway. CCPG1 knockdown synergistically enhanced cisplatin cytotoxicity to BLCA cells, while CCPG1 overexpression conferred resistance. These findings highlight CCPG1-mediated reticulophagy as a driver of BLCA progression and as a potential prognostic biomarker and therapeutic target.