Abstract: Background and purpose: Hepatocellular carcinoma (HCC) is a primary liver cancer with extremely high mortality, and the mechanism of its malignant transformation is not yet clear. In recent years, with the deep research on autophagy, it has been found that autophagy can ensure the high energy demand of tumor growth and increase the adaptability of tumor cells to extreme hypoxia and chemotherapeutic drugs. Thus autophagy is closely related to the malignant process of the tumor. The aim of this study was to investigate the expression of autophagy related gene 5 (Atg5) in the ubiquitous connection system Atgl2-Atg5-Atgl6 in HCC and its relationship with clinicopathological parameters. Methods: HCC and adjacent tissues from 110 patients treated in Cancer Hospital of China Medical University from March 2015 to June 2017 were collected retrospectively. The immunohistochemical staining method was used to detect the expression of Atg5 protein in these HCC and adjacent tissues. Moreover, we analyzed the relationship between Atg5 protein expression and clinicopathological parameters in HCC tissues. Western blot and real-time fluorescent quantitative polymerase chain reaction (RTFQ-PCR) were used to detect the expression of Atg5 protein and its mRNA in 46 of 110 patients’ HCC and adjacent tissues. Results: The immunohistochemical results showed that the positive rate of Atg5 protein in HCC tissues was 71.82% (79/110), which was significantly higher than that in adjacent tissues ［20.09% (23/110), P<0.05］. The expression of Atg5 protein in HCC tissues was correlated with tumor size, alpha fetoprotein (AFP) level and vascular invasion (P<0.05). Furthermore, when clinicopathological parameters in HCC tissues were tumor size ≥5 cm, AFP level ≥200 ng/mL and combined with vascular invasion, the positive rate of Atg5 protein expression was higher. The expression of Atg5 protein was 1.25±0.25 in HCC tissues, and 0.47±0.12 in the adjacent tissues. The expression of Atg5 protein in HCC tissues was higher than that in adjacent tissues (P<0.05). RTFQ-PCR results showed that the relative expression level of Atg5 mRNA in HCC was 4.37 times that of the adjacent tissues (P<0.05). Conclusions: The gene expression and protein level of Atg5 in HCC is significantly increased. Furthermore, the activation of Atg5 may be closely related to the occurrence and development of HCC tissues.

Key words: Autophagy-related gene 5, Hepatocellular carcinoma, Adjacent tissue