Artesunate Affects T Antigen Expression and Survival of Virus-Positive Merkel Cell Carcinoma.

Bhavishya Sarma,Laura Angerer,David Schrama,Jürgen C Becker,Christian Adam,Christoph Willmes,Roland Houben,Thibault Kervarrec

doi:10.3390/cancers12040919

Abstract

Merkel cell carcinoma (MCC) is a rare and highly aggressive skin cancer with frequent viral etiology. Indeed, in about 80% of cases, there is an association with Merkel cell polyomavirus (MCPyV); the expression of viral T antigens is crucial for growth of virus-positive tumor cells. Since artesunate—a drug used to treat malaria—has been reported to possess additional anti-tumor as well as anti-viral activity, we sought to evaluate pre-clinically the effect of artesunate on MCC. We found that artesunate repressed growth and survival of MCPyV-positive MCC cells in vitro. This effect was accompanied by reduced large T antigen (LT) expression. Notably, however, it was even more efficient than shRNA-mediated downregulation of LT expression. Interestingly, in one MCC cell line (WaGa), T antigen knockdown rendered cells less sensitive to artesunate, while for two other MCC cell lines, we could not substantiate such a relation. Mechanistically, artesunate predominantly induces ferroptosis in MCPyV-positive MCC cells since known ferroptosis-inhibitors like DFO, BAF-A1, Fer-1 and β-mercaptoethanol reduced artesunate-induced death. Finally, application of artesunate in xenotransplanted mice demonstrated that growth of established MCC tumors can be significantly suppressed in vivo. In conclusion, our results revealed a highly anti-proliferative effect of the approved and generally well-tolerated anti-malaria compound artesunate on MCPyV-positive MCC cells, suggesting its potential usage for MCC therapy.

Highlights

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine skin cancer with increasing incidence and mortality rates [1]
Due to the viral carcinogenesis of most MCCs, we tested in an initial experiment, the effect of artesunate on a panel of Merkel cell polyomavirus (MCPyV)-positive classical MCC cell lines and some non-classical MCPyV-negative MCC cell lines
While growth and survival of primary fibroblasts and melanoma cell lines was largely unaffected at the given concentration, in particular the MTS signals of the MCPyV-positive MCC cell lines WaGa and MKL-1 were largely reduced (Supplementary Figure S1)

Summary

Introduction

Merkel cell carcinoma (MCC) is an aggressive neuroendocrine skin cancer with increasing incidence and mortality rates [1]. Cancers 2020, 12, 919 cells [6], and subsequent studies confirmed that approximately 80% of all MCC cases are associated with MCPyV [7]. The integration patterns suggest that clonal expansion of the tumor cells occurs after MCPyV integration sustaining the assumption that viral proteins are causal for tumorigenesis [6,8,9]. In MCPyV-positive MCC cells, expression of the viral oncoproteins small and Large T-antigen (sT and LT) can be detected, and these proteins are essential for growth of the tumor cells [10,11] qualifying them as potential therapeutic targets

Methods

Results

Conclusion