Merkel cell polyomavirus causes skin cancer in humans. This has a malignant form and is considered aggressive. The virus was first discovered in the early 21st century.
What is Merkel cell polyomavirus?
Merkel cell polyomavirus is responsible for the formation of malignant skin cancer. Merkel cells are among the cells that receive stimuli on the skin of the human body and transmit the information to the brain. For example, Merkel cells perceive the stimuli of a touch as well as pressure on the skin. They are slow adapting. Merkel cell polyomavirus is the fifth of the seven known oncoviruses. Merkel cell polyomavirus is abbreviated with the letters MCPyV. It is detected in approximately 80% of people who have Merkel cell carcinoma. The carcinoma occurs rarely, but is considered a particularly aggressive skin cancer. Merkel cell polyomavirus is frequently found in secretions of the bronchial tubes. For this reason, scientists believe that it can be transmitted and spread through the respiratory tract. The malignant skin cancer is increasingly diagnosed in older people, but can also occur already in children or adolescents. Patients with an immunodeficiency are considered to be particularly at risk.
Incidence, distribution, and characteristics
Merkel cell polyoma virus was discovered in 2008. It has a genetic similarity to the B-lymphotropic polyoma virus. For this reason, scientists believe that it was already present in a similar form in the great apes. It is very likely that it has coexisted since then and was found only a few years ago by laboratory testing. Merkel cell polyoma virus is distributed worldwide and has no sex-specific incidence. Moreover, it can be diagnosed in people of any age group. There is not yet sufficient clarity on the exact form of transmission between humans. However, it is considered highly likely that it is transmitted through respiration. The suspicion arose because physicians have been able to detect it several times in the smears of bronchial secretions in sick people. Merkel cell polyoma virus belongs to the polyomavirus genus and is assigned to the murine polyomavirus genogroup. It is a human polyomavirus that is considered monotypic. The viruses have a size of approximately 50 nm. The very small viruses are envelope-less. They have a genome that consists of 5387 base pairs. In addition, it is a circularly closed double-stranded DNA. The task of the genome includes the coding of the proteins that belong to the polyomaviruses. The coding serves to build the typically complex structure of the protein. Medical experts refer to this process as building the capsid. In addition to the characteristic proteins, the genome also encodes various structural and non-structural proteins. The structural proteins are VP1 and VP2/3, while the non-structural proteins include a small t antigen and a large T antigen. The latter are comparable to the so-called oncogenes. These are genes that can trigger a change from normal cell growth to unrestrained cell growth. The large MCPyV T antigen is a splicing gene that can produce different proteins according to a specific splicing pattern. The large T antigen and the small t antigen both have the ability to convert healthy cells in the body into cancer cells. Both antigens inhibit the retinoblastoma protein. This protein has the task of tumor suppression in the organism. If the protein is restricted in its functional activity, there is no suppression of the growth of cancer cells, and the cell division that takes place leads to a proliferation of tumor cells.
Diseases and medical conditions
Merkel cell polyoma virus causes Merkel cell carcinoma. This is a skin cancer disease that is notable for the very rapid growth of cancer cells. The virus causes this malignant tumor disease in a large number of patients, which is considered to be very aggressive. In most cases, the disease occurs in people over the age of 60. The so-called cutaneous neuroendocrine carcinoma can develop with high exposure to UV rays. For this reason, people at an older age are considered to be more at risk. Because of their age, their skin is more likely to come into contact with UV rays than younger people. Nevertheless, younger people can also develop the carcinoma.The affected patients have a weak immune defense. This can be chronic as well as hereditary or triggered by the administration of drugs. In particular, patients who have an HIV infection or have undergone organ transplantation are considered to be at risk for Merkel cell carcinoma. Nevertheless, it is still unclear whether the risk factors contribute to an increase in skin cancer or whether they can be considered independent of it. The carcinoma is considered to be painless. Small nodules form on the head, neck as well as face. These have a bluish-red coloration or are skin-colored. Since Merkel cell carcinoma is classified as particularly malignant, early detection is very important to maintain good chances of cure. Treatment options include surgery to remove the nodules, followed by chemotherapy or radiation therapy. To minimize the risk of skin cancer, children and adults should apply sunscreen to their skin before exposure to sunlight. This is especially true for people with pale skin, as they are particularly susceptible to sunburn.
