Does Merkel cell polyomavirus cause Merkel cell carcinoma?
A qualified yes (see our website for description). Scientists from around the world have looked at over 500 tumors in over 20 different studies and that show an average 75% infection rate. When present, the virus has a “clonal” pattern in the cancer cells indicating that MCV infected and integrated into the very first cancer cell before it began growing into a tumor. The virus in cancer cells also has tumor-specific mutations that contribute to its ability to initiate cancer. When the virus’ proteins are inhibited (“knocked down”) in cancer cells in the laboratory, the cancer cells die indicating that they are dependent on the virus for their survival. However, MCV infection alone does not cause MCC and other factors are also required. MCV is a common infection that does not cause any disease in most people. It is clear that MCV is just one factor that contributes to MCC and other factors, like mutations from sun exposure or immunosuppression, appear to also be critical.
