HUMAN PAPILLOMAVIRUSES

During the past 17 years 73 genotypes of human pathogenic papillomavir uses (HPV) have been identified. Most of them are found in benign prol iferations; however, several have been discovered in malignant tumors. Specifically; cancer of the cervix, other anogenital cancers, but als o some cancers of the skin, the oral and nasal cavity, and the rare pe riungual carcinomas have been linked to specific HPV infections. The p athogenesis of cancer of the cervix has been particularly well studied . Specific viral genes (E6 and E7) of high risk HPVs (types 16, 18, an d others) act as oncogenes. Their expression emerges as necessary but not sufficient factors for malignant conversion. Besides stimulating c ell proliferation, they are responsible for the genetic instability of the infected cells. Their transcriptional and functional activity is regulated by host cell genes. Mutational modifications of the latter a ppear to be required for malignant progression.