The Role Of Raptor And Rictor On Disease Progression And Prognosis In Hepatocellular Carcinoma

Hepatocellular Carcinoma(HCC)is the most common type among hepatobiliary malignant tumors in the world.The incidence of HCC is the highest in Asia.Hepatectomy and liver transplantation are still the main treatments for resectable hepatocellular carcinoma.As a target drug approved for the use in advanced HCC.Sorafinib has limited efficacy.mTOR plays a central role in regulating many basical life activities.PI3K/Akt/mTOR signaling pathway is activated among many human cancers with poor prognosis.mTOR combines with Raptor and Rictor to form two different protein complexes,named mTORC1 and mTORC2,respectively.mTORC1 plays an important role in regulating lipid and protein metabolism,while mTORC2 has more advantages in regulating cytoskeletal tissue and cell migration.However,the molecular mechanism of mTOR signaling pathway in HCC has not been fully elucidated.We purchased two tissue arrays from Shanghai Outdo Biotech Co.,Ltd..Every tissue array contains HCC tissues and paracancerous tissues from 90 patients with hepatocellular carcinoma who underwent surgical resection.Immunohistochemical staining was used to detect the expression of Raptor and Rictor protein.We knocked down the expression of Rictor by siRNA in order to explore the role and molecular mechanism of Rictor in HCC.Results:1.Raptor and Rictor proteins were expressed in the cytoplasm of hepatocellular carcinoma and paracancerous liver cells.Raptor expression in cancer tissues and paracancerous tissues were significantly different,and it also significantly correlated with AJCC stage,while Rictor protein was not significantly correlated with clinical factors in HCC patients.2.Both the expression of Raptor and Rictor in cancer tissues had a significant effect on the recurrence-free survival of patients with hepatocellular carcinoma.Meanwhile,Rictor had a significant effect on the overall survival of patients.Univariate Cox regression analysis showed that Raptor and Rictor protein expression,preoperative serum ALT level and AJCC stage were significantly related to the recurrence-free survival of HCC patients,while Rictor expression and AJCC stage to the overall survival.Multivariate survival analysis showed that AJCC stage and Raptor expression were independent prognostic factors for recurrence-free survival of HCC patients,while AJCC stage and Rictor expression were independent prognostic factors for overall survival of HCC patients.The combined analysis showed that the overall prognosis of patients with Raptor high expression and Rictor low expression was significantly better than those with Raptor low expression and Rictor high expression.3.Subgroup analysis showed that in the subgroup with tumor capsule and without portal vein tumor thrombus,HCC patients with high expression of Raptor has significantly better recurrence-free survival when compared with those with low expression of Raptor.The prognosis of HCC patients with low expression of Rictor was significantly better than those with high expression of Rictor in the subgroups with early AJCC stage,with trumor capsule and preoperative serum AFP>20μg/L and TB<20μmol/L.4.Knockdown of Rictor expression inhibited proliferation,migration and invasion in hepatocellular carcinoma cell lines SMMC-7721 and Hep3B.Western blot showed that knockdown of Rictor inhibited the expression of cyclin CCND1,increased the p21 expression.Knocking down Rictor promoted EMT by up-regulating E-cadherin and down-regulating the expression of N-cadhernn and vimentin.Conclusions:1.Raptor and Rictor proteins were expressed in cytoplasm of HCC and paracancerous tissues.2.The expression of Raptor in cancer tissues was significantly correlated with AJCC stage.3.The expression of Raptor in cancer tissues was an independent prognostic factors of recurrence-free survival in patients with hepatocellular carcinoma after surgery,while Rictor was an independent prognostic indicator of overall survival.4.Rictor increased the ability of proliferation,migration and invasion in HCC cell lines by affecting the expression of cyclin related proteins and promoting EMT.