Experimental evaluation of novel therapy approaches against the virally induced Merkel cell carcinoma (MCC)
Merkel cell carcinoma (MCC) is a rare but highly aggressive neuroendocrine skin cancer, often associated with a life-threatening prognosis due to its strong metastatic potential. The occurrence of MCC is mainly caused by the expression of a truncated version of the large T antigen (truncLT) originating from the Merkel cell polyomavirus (MCPyV). The truncation disrupts the viral lytic replication cycle while preserving the retinoblastoma (Rb) binding motif, which promotes carcinogenesis. Thus, the viral oncoprotein is assumed to drive carcinogenesis by dysregulating multiple cellular regulatory processes like cell cycle progression and immune response. Although immune checkpoint inhibition targeting PD-1 or PD-L1 has emerged as a major advancement in MCC treatment, still a substantial proportion of patients shows limited response and compromised long-term survival. This indicates the urgent need to investigate alternative therapy approaches and expand the present treatment panel.
Given the clinical success of adoptive cell therapies in hematological cancers and their emerging efficacy against solid tumors, we aim to identify alternative therapeutic targets on MCC tumor cells. In this project, novel chimeric antigen receptors (CARs) will be evaluated to enable antigen-specific MCC cell recognition, immune cell stimulation, and tumor cell lysis. RNA sequencing data will therefore provide insights into the transcriptome of MCC tumor cells to examine suitable surface and/or transmembrane proteins via an established AI-based in silico analysis pipeline followed by verifying surface expression of promising candidates on MCC cells. Improved immune response towards MCC cells will be evaluated after inducing CAR expression on primary cytotoxic T lymphocytes via mRNA electroporation. To confirm preliminary findings from in vitro co-culture experiments, a chorioallantoic membrane (CAM) assay in which human tumors are grown in fertilized chicken eggs will be utilized to investigate the CAR-T cells tumor tissue infiltration capacity and tumor cell clearance in an in vivo tumor model.
Additionally, dysregulated signaling pathways supporting carcinogenesis, disclosed by analyzing bulk-RNA sequencing data from large T knockdown MCC cells, will further unveil the functions of the viral oncogene. Thereof, therapeutically promising intervention points within critical signaling pathways will be defined to reconstruct the functionality of cell cycle regulation or disrupted cell death mechanisms via antibody or small molecule treatment. Resulting effects on MCC cell proliferation or killing susceptibility will be initially investigated in vitro, followed by a profound investigation in the CAM model system.
