Role of the Human Papillomavirus Early Proteins in the Carcinogenesis

Abstract

Introduction: The Human Papillomavirus (HPV) is an epitheliotropic agent which has more than 100 genotypes. Among these, some are considered high-risk due to the potential to induce the onset of malignant lesions, such as cervical carcinoma whose percentage of association with the HPV is around 90%. In the infected cells, two viral proteins play important role in tumorigenesis. Objective: A review of papers found in the worldwide scientific literature focusing on the role of HPV viral proteins in carcinogenesis. Method: The articles used in the present review were selected and obtained in full from the electronic portals “Pubmed” and “Portal de periodicos da Capes”. The key-words used in the search included: Human Papillomavirus, HPV, viral proteins, E5, E6 and E7. Results: The E6 and E7 viral proteins are widely known for promoting degradation of the p53 and pRb cellular proteins, respectively, effect which accounts for the much of the oncogenic potential of the high-risk genotype of HPV, being functionally equivalent to mutations of the mentioned cellular genes, which are commonly observed in several tumors. However, new studies have demonstrated that these proteins are also involved in many other tumor pathways, denoting again their relevance in this process. In addition, some studies have pointed the E5 as an adjuvant in carcinogenesis. Conclusion: The diverse effects related to early proteins culminate in the promotion of uncontrolled cell proliferation, immortalization, regulation of the cell differentiation, susceptibility to metastasis and escape from the immune surveillance.