Clinical correlates of key autophagic markers, ATG4B, LC3 and p62 in urothelial carcinoma of bladder patients.

Impaired autophagy could contribute to genetic heterogeneity, differential cellular response to drugs and disease relapse in bladder cancer. Among key autophagy related genes, ATG4B, cleaves pro- microtubule-associated protein1 light chain 3 (LC3) to LC3-I, enabling its conjugation to phosphatidylethanolamine (PE) to form membrane-bound LC3-II. LC3-II binds to adaptor protein p62 which facilitates autophagic degradation in lysosomes. Current study determined clinical implications of autophagic markers in non-muscle invasive bladder cancer (NMIBC) and muscle invasive bladder cancer (MIBC) patients. Gene and immuno-expressions of ATG4B, LC3B and p62 were examined by RT-qPCR, western and immunohistochemical staining and their associations with clinicohistopathological characteristics and survival outcomes of 47 NMIBC and 37 MIBC patients. Transmission electron microscopy (TEM) evaluated autophagy/ autophagic vesicles in tumor stage/grade-dependent manner. Observed higher LC3 mRNA showed significances with smoking status and tumor size in MIBC cohort. Increased cytoplasmic LC3-II/LC3-I exhibited significances with tumor type in NMIBC and MIBC and size in MIBC patients. Study reported reduction in gene and protein levels of ATG4B and p62 with increase in tumor stage and grade. TEM studies examined increase in autophagic vesicles with tumor stage and grade. Cox regression identified tumor size and cytoplasmic LC3 as predictors of short PFS and RFS respectively in NMIBC patients. Kaplan Meier analysis established LC3 as an independent predictor of short RFS in NMIBC patients. To the best of our knowledge, this is the first study exploring the clinical implications of ATG4B, LC3 and p62 in urothelial tumorigenesis. Studies are required to validate their relevances in larger cohort.