Down-regulated expression of ATG5 in colorectal cancer.

The role of autophagy in tumor development is paradoxical. Although some genetic evidence has indicated that autophagy has as a tumor suppressor function, it also provides some advantages to tumors under metabolic stress conditions. Autophagy is regulated by several autophagy-related gene (ATG) proteins. In mammals, 16 different ATG genes have been identified. To investigate the clinicopathological role of ATG5 in colorectal cancer, we firstly investigated its expression in patients with sporadic colorectal cancer. Expression analysis revealed ATG5 to be strongly down-regulated in colorectal cancer (38/40 patients). Interestingly, immunohistochemical analysis of colorectal cancer tissues indicated that increased ATG5 expression is associated with lymphovascular invasion (p=0.035). The findings in our limited clinical cohort indicate that ATG5 could be a potential prognostic or diagnostic biomarker.