Human papilloma virus (HPV) and cervical cancer.

Epidemiological and experimental studies have clearly shown that high-risk HPV infection is the main etiologic factor for cervical cancer. Recent studies have indicated that the E6 and E7 gene products play a critical role in cervical carcinogenesis. The E6 and E7 products interfere with the p53 and pRB functions, respectively, and deregulate the cell cycle. The HPV DNA is integrated into the host's chromosomes with disruption of the E2 gene. This disruption promotes the expression of E6 and E7, leading to the accumulation of DNA damage and the development of cervical cancer. The study of the immune response against HPV has been hampered by the lack of a cell culture system for the virus. A breakthrough was made by the discovery that a major capsid protein L1 self-assembles into virus-like particles (VLP) when expressed in eukaryotic systems. Clinical trials of VLP-based vaccines are in progress, and DNA vaccines for the HPV surface protein genes are under development. The E7 and E6 oncoproteins are attractive targets for cancer immunotherapy because their expression is required to maintain the oncogenicity of cervical cancer cells. Cancer immunotherapy for cervical cancer with vaccinations of E7 peptides or dendritic cell-based immunotherapy is moving toward clinical trials.