Project Summary Merkel cell polyomavirus (MCPyV) is a ubiquitous skin infection that can cause Merkel cell carcinoma (MCC), a highly aggressive form of skin cancer. Immune suppression is one of the most important risk factors for developing MCPyV-associated MCC. MCPyV has a far greater chance to induce cancer development among immunocompromised individuals, including HIV-infected patients. However, both the MCPyV life cycle and oncogenic mechanisms remain poorly understood. The incidence of MCC has tripled over the past twenty years, but effective treatments are lacking. Therefore, a better understanding of the MCPyV life cycle and oncogenic mechanisms is needed for developing more effective treatments. In MCPyV-infected cells, the early promoter (EP) supports the transcription of early genes and plays a critical role in maintaining persistent infection. In the majority of MCCs, MCPyV DNA is clonally integrated into the cancer genome, where the EP drives the expression of viral oncogenes, large and small T antigens, to promote MCC tumor growth. MCPyV EP transcription therefore is also critical for supporting MCC oncogenesis. However, very little is known about the mechanisms that regulate MCPyV EP during either MCPyV infection or MCC development. This gap in our knowledge is largely because, until recently, the cellular tropism of MCPyV was unknown and there was a lack of a biologically relevant culture system for studying MCPyV. We recently identified human dermal fibroblast (HDF) as a natural host cell for MCPyV infection. We found that MCPyV entry is a promiscuous process, whereas its transcription is the key determinant for MCPyV host cell tropism, persistent infection, and oncogenic potential. Building on the in vitro and ex vivo infection models developed in our recent studies, we propose to discover the epigenetic mechanisms (Aim 1) as well as host cellular factors and cis-acting viral DNA elements (Aim 2) that regulate MCPyV early gene transcription. We will also apply the recently developed lipid nanoparticle (LNP) technology to abolish MCPyV oncogene transcription and obliterate MCC tumorigenesis (Aim 3). Our studies will fill a significant knowledge gap in understanding the mechanisms that regulate MCPyV early transcription during the viral life cycle and MCC tumorigenic development. Moreover, our investigation will provide important insights into the virology and oncogenic mechanism of this new human tumor virus, and identify novel targets for developing better strategies to treat the highly lethal MCC skin cancers with a rapidly rising incidence. As demonstrated by the success of COVID-19 vaccines, the highly potent LNPs have shown great promise for therapeutic applications. Therefore, the superb in vivo delivery power of LNPs affords a viable platform for translating our findings into clinical setting.

Project narrative Merkel cell polyomavirus (MCPyV) can cause one of the most aggressive skin cancers, Merkel cell carcinoma (MCC). This proposal seeks to investigate the largely unknown mechanism of MCPyV early gene transcription, which drives MCPyV infection and MCC tumorigenesis. The findings obtained from these studies may facilitate the development of virus-targeted novel therapeutic strategy for treating the highly lethal MCC cancer, which contributes significantly to HIV/AIDS-associated malignancies.