The human papillomavirus is a DNA virus; that is, the genes of the virus are in molecules of DNA, surrounded by a protein shell. Primarily transmitted through sexual and skin-to-skin contact, it causes warts and cancer. The skin warts are benign, but may be embarrassing to those who have them. Some genital infections, on the other hand, can lead to cancer. A mutation in the human gene that makes the P16 protein is associated with higher cancer rates with HPV infection.
Human Papillomavirus
There are over 100 types of the human papillomavirus, according to Richard Reichman, M.D., director of the Infectious Diseases Division at the University of Rochester School of Medicine in "Harrison's Principles of Internal Medicine." The different types cause specific diseases; for example, the human papillomavirus type 1, or HPV-1, causes warts on the sole of the foot, while HPV-6 causes warts in the genital area and around the anus. HPV-16, HPV-18, HPV-31, HPV-33 and HPV-45 can all cause cervical cancer, although most infections do not develop into cancer. In addition, the virus can cause cancer in the middle area of the throat.
Tumor Suppressor Genes and P16
Genes tell a cell how to make a particular protein. There are several genes involved in making the proteins that stimulate the reproduction of cells and interfere with their reproduction. Tumor-suppressor genes are the genes that interfere with cell reproduction, and all cells have them, as explained in the "Handbook of Pathophysiology" by Elizabeth Corwin, Ph.D., of the Department of Physiology at Pennsylvania State University. P16 is one of the tumor-suppressor genes; a mutation in this gene that makes it inactive can lead to cancer.
P16 and HPV
In the September 2010 issue of "Anticancer Research," Francesca Angiero, M.D., wrote about a research study to determine the role of the P53 and P16 tumor-suppressor genes and the human papillomavirus in changing abnormal tissue into mouth cancer in people who do not drink or smoke. Their results showed there was no P16 in the 31 biopsies of tissue taken from people with mildly abnormal tissue; there was P16 in the 14 biopsies of moderately or severely abnormal tissue and in the 11 biopsies with cancer. All of the tissues that had the virus had too much P16.
P16 and the Virus Capsid
Viruses have an inner area made of RNA or DNA and an outer shell made of protein. The outer shell is called a capsid; it protects the genetic material and helps the virus attach to cells. Tomomi Yoshida, Ph.D. wrote an article in the April 2008 issue of "Cancer Cytopathology" about a study on the relationship between the P16 protein and an L1 protein found in the capsid of HPV. The results determined that the more malignant the tissue sample, the less L1 protein. On the other hand, all of the malignant samples had P16.
References
- "Anticancer Research": Frequency and Role of HPV in the Progression of Epithelial Dysplasia to Oral Cancer; Francesca Angiero, M.D., Luisa Gatta, Rossella Seramondi et al; 2010
- "Cancer Cytopathology": Immunochemical analysis of HPV L1 capsid protein and p16 protein in liquid-based cytology samples from uterine cervical lesions; Tomomi Yoshida, Ph.D., Takaaki Sano, M.D., Tatsuya Kanuma, M.D. et al; 2008
- "Handbook of Pathophysiology"; Elizabeth Corwin, MSN, Ph.D., FNP; 2000
- "Harrison's Principles of Internal Medicine"; Anthony Fauci, M.D., Dennis Kasper, M.D., Dan Longo, M.D. et al; 2008
