Breast cancer: epidemiology and viral ethology associated with human papillomavirus and mouse mammary tumor virus

Oncoviruses are involved in approximately 12% of all human cancers. The interaction between the host and viral factors is a complex process that creates a microenvironment that is conducive to oncogenesis. In this chapter the molecular biology and oncogenic pathways of established human oncoviruses will be discussed. Human herpesvirus 8 (HHV-8), also known as Kaposi sarcoma–associated herpesvirus, is a member of the herpesvirus family and is best known for its association with Kaposi sarcoma. HHV-8 has been implicated in two B cell lymphoproliferative diseases: multicentric Castleman disease and primary effusion lymphoma. Human T cell lymphotropic virus 1 (HTLV-1) is a delta RNA retrovirus that was first isolated in 1979. HTLV-1 is notably the cause of adult T cell lymphoma (ATLL) and is also associated with polymyositis and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). There are approximately 5–20 million HTLV-1 carriers worldwide, and approximately 3%–5% of carriers develop ATLL.