An Exploratory Investigation Of Combination Therapy For Virus-resistant Cancer With Oncolytic Virus OHSV-1 And Small Molecule Inhibitors

In the last forty years,the pattern of cancer treatment has undergone tremendous changes.Traditional or conventional treatment options for cancer patients include surgery,radiation and chemotherapy,all of which serve as the pillars of cancer therapy.In the recent past,however,immunotherapy in particular has started to become more important in treatment plans.Since oncolytic virotherapy has been reported in the Science Journal in 1991,after unremitting efforts and renovations by scientists,it has become one of the most promising therapeutic drugs for cancer treatment.At present,more than 20 oncolytic viruses have entered the clinical stage,clinical trials have confirmed good safety profiles and therapeutic efficacy for oncolytic viruses.According to the results of clinical trials,the efficacy of oncolytic virotherapy is still limited mainly due to the heterogeneity and complex regulatory mechanisms of cancer.At present,two strategies were employed to improve the therapeutic efficacy of oncolytic virus for cancer treatment.The first strategy is to reconstruct engineered viruses arming with exogenously enhanced genes,such as the first FDA approved oncolytic virus T-VEC,which arms with GM-CSF genes;The second strategy is to seek other treatment options for combination therapy,such as the combination of small molecule inhibitors,radio-chemotherapy agents,or immune checkpoint blockers to treat cancer.Among them,small molecule inhibitors in combination with oncolytic viruses exhibit a variety of advantages due to their broad range of action,convenient access to target sites,high purity,and oral administration.Many studies focusing on the combination therapy with oncolytic viruses and small molecule inhibitors are still in progress.The current trend and future direction for cancer treatment is the combination therapy.The purpose of this study was to screen some small molecule inhibitors that can be used as oncolytic virotherapy potentiators to impove the cell killing ability of oncolytic viruses in virus-resistant tumors.For this purpose,the following work was carried out.First,using the trypan blue exclusion test we established a cell platform for in vitro evaluation of cell killing ability of oncolytic viruses,then the oncolytic effect of oHSV-1 was evaluated by a panel of cancer cell lines consisting of 38 different cell lines.Among them,6 cell lines were proved to be virus-resistant tumor cells.Subsequently,several small molecule inhibitors that may increase the killing effect of oncolytic virus oHSV-1 in virus-resistant tumor cells were selected by their mechanism of action and evaluated in combination therapy with oHSV-1.Small molecule inhibitors that can impove the cell killing ability of oncolytic viruses were screened by using WST-1 cell proliferation and cytotoxicity assays.Two small molecule inhibitors,rapamycin and PF-573228 were verified as oncolytic virotherapy potentiators.Then we focus on the efficacy of combination therapy with oHSV-1 and Rapamycin in established nude mice models xenografted with virus-resistant cancer cell lines,such as human endometrial adenocarcinoma cell line(HEC-1B)and human cervical cancer cell line(SiHa).It was revealed that the efficacy of combination therapy was better than monotherapy.Finally the oncolytic mechanism of combination therapy with oHSV-1 and rapamycin in virus-resistant cancer cells were investigated by Wesertern blotting and RT-qPCR.It was concluded that rapamycin can improve the oHSV-1 replication in virus-resistant cancer cells by inhibiting the interferon-mediated antiviral responses.However,the underlying mechanism still need to be further investigated.In summary,we have screened 2 small molecule inhibitors that can potentially improve the oncolytic effect of oHSV-1 in virus-resistance cancer cells,and the efficacy of combination therapy with oHSV-1 and rapamycin was evaluated both in vitro and invivo mouse xenograft models.In addition,the mechanism of combination therapy was also preliminarily explored.This study laid the solid foundation for the future clinical application of combination therapy with oHSV-1 and small molecule inhibitors for the treatment of cancer.