Effect of Epstein-Barr virus (EBV) LMP1 and RPMS1 proteins on the regulation of genes coding immune checkpoint proteins in human cells cultured in vitro

Abstract

Based on data from the World Health Organization (WHO), approximately 2 million new cases of cancers related to microorganism infections are estimated worldwide. The majority of the adult population has latent Epstein-Barr virus (EBV) infection, which is recognized as potentially carcinogenic to humans. EBV is found in neoplastic cells of virtually all cases of the African endemic form of Burkitt's lymphoma and undifferentiated nasopharyngeal carcinoma. Additionally, EBV infection is also associated with the development of other cancers, especially lymphomas. The latent state of EBV's biological cycle is characterized by a restriction of the expression of some viral products, which favors its immune evasion and persistent infection in the host. Moreover, the expression of some EBV genes during its latent cycle can regulate immune checkpoints, indicating that EBV can also benefit carcinogenesis by this mechanism. There are some evidence indicating the role of the viral oncoprotein LMP1 on the expression of PD-L1 and CTLA-4, but little is known about its possible regulatory activity on the expression of other molecules which are important for regulating lymphocyte response and its potential effects on EBV-associated lymphomagenesis. Also, data about other EBV viral products, such as RPMS1, on the regulation of immune checkpoints are scarce. Thus, this study aims to evaluate the effects of EBV's LMP1 and RPMS1 expression on the regulation of immune checkpoint molecules using EBV-positive neoplastic cell lines derived from lymphomas, as well as to verify possible phenotypic effects of this regulation in cells cultured in vitro. The expression profile of selected immune checkpoint molecules will be initially evaluated in cell lines by qPCR. Subsequently, inhibition of the expression of LMP1 and RPMS1 will be performed by interference RNA (RNAi) to evaluate their possible effects on the expression of the immune checkpoint molecules investigated. Lastly, cell lines with and without inhibition of the molecules regulated by the expression of LMP1 and RPMS1 will be evaluated for cell viability, cytotoxicity, apoptosis and cell invasion in vitro. At the end of the experiments, it is expected that the information gathered could elucidate the role of LMP1 and RPMS1 on the regulation of immune checkpoint molecules, as well as the role of these molecules in cellular phenotype in vitro, providing a better understanding of the oncogenic properties of EBV. (AU)