Merkel cell polyomavirus (MCPyV) is a double-stranded DNA virus that has been associated with a rare but aggressive skin cancer, Merkel cell carcinoma (MCC). Two characteristics of MCPyV¿positive MCCs are integration of the viral genome and expression of a truncated version of large T antigen (LT). Considering the well described role of MCPyV in the development of MCC and the widespread prevalence of the virus across the body, the involvement of MCPyV in tumours other than MCC remains to establish. It has been proposed that MCPyV may be associated with some types of non-MCC cancers and several studies reported the frequently detection of MCPyV DNA or transcripts at a varying level in healthy respiratory tissue and in cancer lung tissue. However, many of these examples are not able to clearly demonstrate a direct connection between cellular transformation and the presence of the virus. Since mechanistic studies to fully investigate MCPyV molecular biology and oncogenic mechanisms in malignancies, other than MCC, have been hampered by a lack of adequate cell culture model, a pulmonary cell culture infection system for MCPyV will be established. Building on this model we will focus on the biology of MCPyV in respiratory system's cells and on its potential contribution to triggering a neoplastic transformation in these cells type. Specifically, the state of the viral genome (episomal or integrated) and the expression and contribution of LT and small T (sT) viral proteins to transformation and cancer growth in lung tumour will be determined. Moreover, in parallel, to further study the MCPyV biology and its oncogenic properties in lung tissue, lung organoid culture will be developed.
The first human polyomaviruses (HPyVs) were discovered in 1971 and despite their ability to transform cells and induce tumors in animals, they role in human cancer remains unclear [43-46]. It was until 2008 when the lab of Chang and Moore isolated MCPyV, the first and so far the only HPyV etiologically linked to the development of a specific neoplasia, known as MCC, a rare neuroendocrine cancer of homonymous cells [1]. Although MCPyV is constantly shed from healthy skin, the incidence rates of MCC have dramatically increased in the last years [14]. Moreover, this aggressive malignancy is associated with a poor prognosis and high mortality, exceeding melanoma [15]. Although our knowledge about the MCPyV and MCC has increased, many questions remain unsolved including the plausible contribution of MCPyV to induce tumors other than MCC. Several studies, including our own study [47], reported the frequently detection of MCPyV DNA or transcripts at a varying level in healthy respiratory tissue and in cancer lung tissue. Intriguingly, in some cases of non-small-cell lung carcinomas, a peculiar duality containing both episomal and integrated MCPyV DNA and expressing both the full-length and truncated LT protein, was observed [33]. Mechanistic studies to fully investigate MCPyV molecular biology and oncogenic mechanisms in malignancies, other than MCC, have been hampered by a lack of adequate cell culture model. Liu and co-workers [14] developed a set of protocols for performing and detecting MCPyV infection of primary human skin cells. Starting from this point, these protocols could be set to in vitro explore and identify additional MCPyV-permissive cell types, in which study the guilty or circumstantial contribution of MCPyV infection to tumor development. Identify cell types or cell lines different to fibroblasts from the dermis, could contribute to determine the state of the viral genome (episomal or integrated) and to define the contribution of LT and sT viral protein to transformation and cancer growth in non-MCC tumors. Moreover, since the organoid model represents, to date, the most advanced tool to study the pathogenesis of infectious agents, the challenge of this project will be also to cultivate these multicellular tridimensional structures able to recapitulate the physiologic function of the organ/tissue from which they are derived. Developing this model could represent a suitable platform to further study MCPyV biology and to understand the oncogenic properties of MCPyV in lung tissue. Establish an in vitro lung cells and organoid cultures could contribute to identify specific biomarkers that can be used in cancer diagnosis and prognosis and, finally, since specific therapy to stem the MCPyV infection does not yet exist, these model could by also used to identify potential therapeutic targets versus MCPyV.