Discipline: Biological Sciences
Subcategory: Cancer Research
Adelina Parral - Seward County Community College
Co-Author(s): Jazmine Snow, Tristan Mcalister, and Nicholas Wallace, Division of Biology Kansas State University, Manhattan, KS
Merkel Cell Carcinoma (MCC) is a rare skin cancer, common among immunosuppressed patients such as the elderly and AIDs patients. About 80% of MCCs are caused by a virus called Merkel Cell Polyomavirus (MCPyV). Researchers have shown the viral protein Large T antigen (MCPyV LT) is present in MCPyV+ MCCs and required for MCPyV replication. To facilitate MCPyV replication, MCPyV LT aberrantly activates the ATR signaling pathway that coordinates repair of UV damage. Productive DNA repair requires coordinated activation and resolution of DNA repair complexes. Because unrepaired DNA damage is toxic to cells, we hypothesize that MCPyV LT sensitizes cells to UV by preventing repair of UV-damaged DNA. To test our hypothesis, we developed an assay to measure cellular sensitivity to UV (0.005-0.0225 mJ/cm^2). This assay showed the first dosage of 0.0005 mJ/cm^2 as being a lethal dose for 20% of cells (LD20). An LD50 was seen at a dosage of 0.005, and the LD90 leveled off at 0.0125. To determine if MCPyV LT could exacerbate impairments to UV-damage repair, we measured UV-sensitivity in XPA(-)fibroblasts. XPA is a protein involved in the nucleotide excision repair pathway (NER). Specifically, it is involved in the early detection of DNA damage induced by UV rays. XPA(-)fibroblasts transfected with a MCPyV LT expression vector were more sensitive to UV than untransfected controls and XPA(-) fibroblast transfected with an empty vector. At 0.0025 mJ/cm^2, the LT transfected cells showed a LD80, while the vector control showed only a LD40. These results have implications for the treatment of MCPyV+ MCCs, as they suggest that these tumors may be sensitive to existing DNA crosslinking chemotherapeutics that cause DNA damage similar to UV (ie cisplatin or mitomycin C). In the future, we will replicate the experiments described here, as well as further elucidate UV-sensitivity when other disruptions to UV-damage repair are combined with MCPyV LT expression. Ultimately, we will test the ability of MCPyV LT to sensitize cells to cisplatin and mitomycin C.
Funder Acknowledgement(s): This work received financial support from Kansas Louis Strokes Alliance for Minority Participation 1305059 and the Johnson Cancer Research Center.
Faculty Advisor: Nicholas Wallace, firstname.lastname@example.org
Role: I was able to replicate the assay using U2OS cells as previously performed by the team. In addition, I was able to UV treat transfected and untransfected XPA (-) cells and compare the results to the U2OS assay. All these experiments were done under the guidance of my mentor, as well as using notes provided by the previous team.