What Causes Merkel Cell Carcinoma (MCC)?

Although we know of some factors that can increase a person’s risk of Merkel cell carcinoma (MCC), it’s not clear exactly how these things might cause MCC.

Gene changes and cancer

Cells are the basic building blocks of all living things, including our bodies. Genes  control how cells function. DNA is the chemical in our cells that makes up those genes. Our DNA, which comes from both our parents, affects more than just how we look.

Different genes have different functions in our bodies. When they’re working as they should, certain genes help control when our cells grow, divide to make new cells, or repair mistakes in DNA. They also cause cells to die when they’re supposed to.

Cancer is caused by changes in the DNA inside our cells.

If these genes aren’t working properly, it can lead to cells growing out of control. For example:

• Changes in genes that normally help cells grow, divide, or stay alive can lead to these genes being more active than they should be, causing them to become oncogenes. These genes can result in cells growing out of control.
• Genes that normally help keep cell division under control or cause cells to die at the right time are known as tumor suppressor genes. Changes that turn off these genes can result in cells growing out of control.
• Some genes normally help repair mistakes in a cell’s DNA. Changes that turn off these DNA repair genes can result in the buildup of DNA changes within a cell, which might lead to them growing out of control.

Any of these types of DNA changes might lead to cells growing out of control and forming a tumor. To learn more, see Oncogenes, Tumor Suppressor Genes, and DNA Repair Genes.

Scientists are looking for the specific DNA changes inside MCC cells to help explain what causes it. A better understanding of how damaged DNA leads to MCC might also be used to design better treatments for it.

Gene changes in Merkel cell carcinoma

Merkel cell cancers are very rarely related to DNA changes that are inherited from a parent. Instead, most of these changes seem to be acquired during a person’s life. Sometimes these changes might just be random events that happen inside cells, without having an outside cause. But sometimes the cause might be something specific, like long-term sun exposure or infection with the Merkel cell polyomavirus (MCV).

Ultraviolet (UV) radiation and Merkel cell carcinoma

Ultraviolet (UV) radiation can damage the DNA inside skin cells. Sometimes this damage affects certain genes that control how and when cells grow and divide, which may be the first step on the path to cancer.

Merkel cell polyomavirus infection and Merkel cell carcinoma

How infection with MCV plays a role in the development of Merkel cell cancer (MCC) isn't clear. But researchers have found that the virus can get inside cells and cause them to make a protein that turns off tumor suppressor genes, which might lead to MCC.

MCV infection might help explain why people with weakened immune systems have a higher risk of MCC. It might be that the virus normally is kept in check (but not killed) by the immune system. A weakened immune system could then allow the virus to grow and flourish, which in turn might raise the risk of MCC.