Oncogenic Viruses in Organ Transplantation: Implications of Virus-Host Interactions for Cancer Development.

Organ transplantation significantly enhances the survival and quality of life for recipients. However, multiple dependent and independent variables can adversely affect life expectancy after transplantation. Cancer is one of the most common causes of morbidity and mortality for long-term organ transplant recipients. The incidence of cancer in transplanted tissues can be twice as high in approximately 32 distinct cancer types. Oncogenic viruses present in graft tissues may contribute to the etiology of various cancers in transplant recipients. Such oncogenic viruses include hepatitis viruses, papillomaviruses, Epstein-Barr virus, Kaposi's sarcoma, Merkel cell virus, JC virus, BK virus, and human T-lymphotropic virus type 1, all of which have been associated with various malignancies in these patients. To mitigate this risk, a comprehensive viral screening protocol should be integrated into the transplantation process. Depending on the type of graft, diagnostic methods, control strategies, and post-transplantation care may vary considerably. To efficiently implement any strategy to inhibit viral oncogenicity, a comprehensive understanding of viral-host interactions involving oncogenic viruses within graft tissue is essential. The current view of tumor biology is that changes in the tumor microenvironment and immune signaling influence evolutionary selection pressures. Such interactions ultimately promote conditions that favor uncontrolled host-cell proliferation and malignant transformation. This review examines these viral-host interactions and their role in cancer development among transplant recipients.