Abstract B046: Exploring the potential of commensal polyomavirus as a promising approach for breast cancer treatment
Authors: XIA YUN 
Published: February 2024

Abstract
Cancer is a leading cause of mortality worldwide, accounting for nearly one in six deaths. Our understanding of the immune system role in cancer control has increased dramatically in recent decades, facilitating the recent development of effective cancer immunotherapies, which have significantly improved the survival of cancer patients. However, current immunotherapies can induce overactive immune responses with severe even fatal outcomes. Moreover, immunotherapy may not work in every scenario, especially in ‘cold’ tumors that lack immune cell infiltration. Thus, more effective immunotherapies with fewer side effects are under active investigation. Viruses are one of the most abundant biological entities in the world; about 12% to 20% of human cancers are associated with viral infections. Viral antigens can increase tumor immunogenicity, triggering T cell immunity against tumor cells. Polyomaviruses are small, nonenveloped double-stranded DNA viruses that are widespread. In immunocompetent hosts, polyomaviruses remain at a low persistent level in the host after the primary infection, which appears to cause little or no symptoms. Previous studies have shown high polyomavirus seroprevalence and the frequent presence of polyomavirus-specific T cells in healthy adult blood donors. In the elderly population, Merkel cell polyomavirus (MCPyV) infection is linked to Merkel cell carcinoma (MCC), a rare, aggressive skin cancer associated with immunosuppression. MCPyV integration into the genome is the primary oncogenic event in ~80% of MCC cases, and the remaining virus-negative MCC cases are associated with ultraviolet (UV) radiation. MCPyV-induced MCCs are associated with more intratumor immune cells and better responses to cancer therapy. Moreover, BK and JC polyomavirus positive lymphoma patients showed a trend toward significantly better overall survival. These clinical data suggest that polyomavirus in tumors may increase tumor immunogenicity. Thus, polyomavirus presents an intriguing opportunity to develop a novel strategy to enhance cancer immunogenicity. We utilized mouse polyomavirus (MPyV) to colonize typically ‘cold’ breast tumor cell line E0771 breast cancer cells in mice. MPyV infection blocked the growth of tumors in immunocompetent mice and promoted immune cell infiltration when intratumorally delivered to the tumor. The tumor rejection activity of polyomavirus is depend on CD4 and CD8 T cells. Unlike conventional oncolytic viruses which directly lyse the infected cells and trigger a nonspecific inflammatory response, polyomavirus does not lyse the colonized cells, and it induces a relatively low level of inflammation. Instead, polyomavirus stimulates viral antigen expression in tumors that boosts T cell response leading to epitope spreading to tumor-associated antigens. The outcomes of this research will establish the utility of commensal polyomavirus as a novel agent for cancer immunotherapy.
Citation Format: YUN XIA. Exploring the potential of commensal polyomavirus as a promising approach for breast cancer treatment [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Breast Cancer Research; 2023 Oct 19-22; San Diego, California. Philadelphia (PA): AACR; Cancer Res 2024;84(3 Suppl_1):Abstract nr B046.