Effects And Underlying Mechanisms For Oncolytic Vaccinia Virus Inhibiting Human Hepatocellular Carcinoma Cell Lines

Background:Hepatocellular carcinoma(HCC)is a highly lethal disease and the sixth most frequently diagnosed malignancy worldwide.Novel drugs or methods targeting the invasion and metastasis of HCC offer better therapeutic effects.Vaccinia virus(VV)is intensively studied and widely used for cancer gene therapy.Compared with other virus species,VV has been shown possessing many inherent advantages to be engineered vectors for cancer gene therapy.Since most tumors are highly heterogeneous,better understanding the mechanisms of action of VW will help the development of rational and successful gene therapeutic strategies.VW targets and destroys cancer cells by multiple complementary mechanisms,which may vary by different viral strains and/or tumor cell types.Besides the immune-mediated cell death and the tumor vasculature shut-down,apoptosis and necrosis are likely involved in destroying tumor cells by VV.Virus hijack host cell machinery to produce viral protein,however,not much is known regarding ER stress responses to vaccinia virus infection.Therefore,the mechanisms on VV action remains to be further investigated.Methods:We constructed a thymidine kinase(TK)gene insertional inactivated VV,named VV-Onco,tested the effect on cell viatbility,apoptosis and colony formation ability of hepatocellular carcinoma cell lines Hep3B,SMMC7721 and highly metastatic human hepatocellular carcinoma cell line MHCC97-H,and investigated the potential cell signal pathways involved in this action.Finally,the antitumor efficacy of VV-Onco was evaluated with MHCC97-H-luc hepatomaleft flank xenograft model established in nude mice.Furthermore,the effects of VV-Onco on different drug-resistant chronic myeloid leukemia cell lines were tested.Results:Compared with oncolytic adenovirus ZD55,VV-Onco induced strong cytotoxicity,apoptosis effect on hepatocellular carcinoma cell lines Hep3B,SMMC7721 and MHCC97-H,and inhibited the colony formation of Hep3BM and HCC97-H cells.The MHCC97-H cell apoptosis induced by VV-Onco is likely mediated via endoplasmic reticulum(ER)stress,autophagy and Wnt signaling pathways.The downregulation of survivin and c-Myc may also play a role in VV-Onco induced cell death.The once intratumoral injection of VV-Onco showed obvious antitumor effct in animal model with the established tumor by MHCC97-H-luc.The additional cell ability tests show that VV-Onco may inhibit different drug-resistant chronic myeloid leukemia cell lines differently.Conclusions:Our results may provide new insight into the mechanisms of VV-inducedtumor cell death.The engineered recombinant VV containing optimized therapeutic transgenes may provide a new avenue for cancer gene therapy.