Establishment and characterization of an in vitro model of human Polyomavirus BK (BKV) infected prostate normal cells

Introduction: Prostate cancer (PCa) is one of the most common male neoplasm in the Western word, being the most commonly diagnosed non-skin cancer and the second leading cause of cancer death. Various potential risk factors exist for the initial triggering events, including exposure to infectious agents, such as the human Polyomavirus BK (BKV). BKV is a good candidate as risk factor of PCa because it naturally infects the human reno-urinary tract, it establishes latency, and encodes oncoproteins that interfere with tumor suppressors pathways, thus altering the normal progression of cell cycle. The aim of the study is to establish an in vitro model of infection and to investigate the possible co-factorial role of BKV in PCa onset and progression. Materials and Methods: To investigate the potential relationship between BKV infection and PCa, an vitro model was established using the normal epithelial prostate cell line RWPE-1. The titration of the viral load was performed by means of BKV specific-quantitative real time PCR (qPCR) and droplet digital PCR (ddPCR). 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay was performed at different time points to evaluate the effect of BKV infection on the growth of RWPE-1 cells. The expression profiles of a panel of 48 cytokines/chemokines were analyzed to identify differences in their kinetics in infected and uninfected cells by multiplex assay. To assess whether BKV infection was able to modify the cells morphology, ultrastructural analysis and analysis of epithelial-mesenchymal transition (EMT) markers in BKV infected, uninfected and cleared cells were conducted. Preliminary results: RWPE-1 cell line was found to be both susceptible and permissive to BKV infection, reaching a peak of infection after 3 days (3.9*10^6 copies/mL) and the infection lasted for 14 days. The infected cells showed an higher rate of proliferation than the uninfected cells ranging from +37% to +18%. The expression of IL-6, -9 -18 and TNF-α was higher in the infected cells than in the uninfected. Regarding the EMT markers, E-cadherin was expressed in some uninfected RWPE-1 at cell boundaries and upon BKV infection, E-cadherin expression was mainly located in the cytoplasm and in the perinuclear region. Moreover, after infection some big multinucleated cells could be detected. This pattern was maintained also after 30 days post infection. Conclusions: The RWPE-1 cell line could be used as a model of BKV infection. The viral infection induces molecular and morphological changes in the cells, but the possible cancer progression due to the virus needs to be still elucidated.