Abstract: Objective To investigate the effects of mTOR inhibitor combined with ursodeoxycholic acid (UDCA) on the inhibition of growth, immune escape and Ras/ERK signaling pathway of hepatocellular carcinoma (HCC) in rats. Methods A total of 50 SPF grade of SD male rats were randomly divided into a normal (NO) group, a model (MO) group, a mTOR inhibitor (MI) group, a UDCA (UD) group, and a mTOR inhibitor combined with UDCA (UN) group, with 10 rats in each group. HCC model was established by intraperitoneally injection of Diethylnitrosamine (DMN) in each group of rats except the NO group. After successful modeling, the MI group was administrated with 2 mg/kg of mTOR inhibitor sirolimus, the UD group was given 30 mg/kg of UDCA, and the UN group was given 2 mg/kg of mTOR inhibitor sirolimus and 30 mg/kg of UDCA. The tumor growth in rats of NO group and MO group was observed and recorded by intragastric administration of the same volume of normal saline. The pathological morphology of liver tissue was detected by H&E staining. The immune escape related factors were detected by enzyme linked immunosorbent assay (ELISA), and the expression of Ras/ERK signaling pathway related proteins was detected by Western blotting. Results Compared with the NO group, the body weight of the MO group was significantly decreased (P<0.05), and the liver weight and liver coefficient were significantly increased (P<0.05). Compared with the MO group, the body weight of the MI group was significantly increased (P<0.05), and the liver weight and liver coefficient were significantly decreased (P<0.05). There were no significant differences in body weight, liver weight and liver coefficient in the UD group (P>0.05). Compared with the UD group, the body weight of rats in the UN group was significantly increased (P<0.05), and liver weight and liver coefficient were significantly decreased (P<0.05). While the tumor inhibition curve of the MI group was significantly increased compared with the MO group (P<0.05), there was no significantly difference between those of the UD group and the MI group (P>0.05). Compared with the UD group, the tumor inhibition curve of the UN group was significantly increased (P<0.05). The liver morphology of rats in NO group showed clear and intact liver lobular structure, radiate out in a clear demarcation without cell hyperplasia, death and inflammatory cells infiltration. The liver tissues of MO group showed that the liver cable structure was unclear, with disordered swelling cells, visible cancer nests and a large number of inflammatory cells infiltration. When compared with the MO group, the pathological structure of MI group, UD group, and UN group obviously improved, Inflammatory cells and cancer cells decreased. The serum levels of IL-4, IL-10 and TGF-β1 in rats of MO group were significantly higher than those of rats in the NO, MI, UD and UN groups (P<0.05). There was no difference between the UD group and the MI group (P>0.05), and the UN group was significantly lower than the UD group (P<0.05). The expressions of Ras protein in NO group, MO group, MI group, UD group and UN group were 1.16±0.11, 2.26±0.29, 1.51±0.17, 1.55±0.18, 1.19±0.14, respectively. The expression of P-ERK protein was 1.05±0.10, 2.94±0.28, 1.66±0.14, 1.68±0.16, 1.14±0.11, respectively. The expressions of Ras and P-ERK proteins in liver tissue of rats in MO group was significantly increased when compared with those of the NO group (P<0.05), The protein expressions of Ras and P-ERK in the liver tissues of rats in MI, UD and UN groups were significantly decreased compared with those of the MO group (P<0.05). There was no difference between the UD group and the MI group (P>0.05), but the expressions in the UN group was significantly decreased compared with the UD group (P<0.05). Conclusion mTOR inhibitor combined with ursodeoxycholic acid (UDCA) can significantly inhibit tumor growth, immune escape and the activation of Ras/ERK signaling pathway in HCC rats.

Key words: mTOR inhibitor, Ursodeoxycholic acid (UDCA), Hepatocellular carcinoma. Immune escape, Ras/ERK signaling pathway