The Role of Oncogenic DNA Viruses in Penile Cancer Development

Penile cancer is a relatively rare neoplasia in developed countries, with significant morbidity and mortality in developing countries. Penile cancer can be subdivided into human papillomavirus (HPV)-positive and HPV-negative cases. Worldwide, the HPV prevalence in penile cancer samples is around 50%, and HPV16 is the most prevalent genotype. Although HPV is an important factor for cancer development, other oncogenic factors may be associated with carcinogenesis. Some of these factors can be infectious, such as the Epstein-Barr virus (EBV), as well as the Merkel cell polyomavirus (MCPyV). The prevalence rates of nearly 50% for both HPV and EBV infections indicate an important role of these viruses in penile tissue malignancy, reinforcing the idea of a multifactorial etiology of the disease. Although the HPV role is better understood, EBV is thought to facilitate persistence, integration, and mutations. Recent studies on the Merkel cell polyomavirus have not shown a relevant prevalence in penile cancer samples, but its presence indicates the opportunistic infectious potential of this virus. Regarding HPV-negative cases, the literature suggests a link with younger age and epigenetic alterations, mainly through the p16INK4a pathway. Recently, several biomarkers that might act as prognostic tools (e.g., Ki-67, squamous cell carcinoma antigen, among others) have been proposed, but the results remain controversial. In addition, other risk factors have also been associated with penile carcinogenesis, such as the presence of phimosis, noncircumcision, chronic inflammation, and number of sexual partners. Further studies are needed to develop tools for early detection and epidemiological surveillance of penile cancer.