HIV infection and cancer in the era of highly active antiretroviral therapy (Review)

The majority of cancers affecting HIV-infected subjects are those established as acquired immunodeficiency syndrome (AIDS)-defining: Kaposi's sarcoma (KS), non-Hodgkin's lymphoma (NHL), and invasive cervical cancer (ICC). However, other types of cancer, such as Hodgkin's disease (HD), anal cancer, lung cancer and testicular germ cell tumors appear to be more common among HIV-infected subjects compared to the general population. While not classified as AIDS-defining, these malignancies have been referred to as AIDS-associated malignancies. The mechanisms by which depressed immunity could increase the risk for cancer are unclear, except for in KS and most subtypes of NHL, where it is strictly associated with a low CD4 count. Although it remains unclear whether HIV-1 acts directly as an oncogenic agent, it may contribute to the development of malignancies through several mechanisms (e.g., infection by oncogenic viruses, impaired immune surveillance, imbalance between cellular proliferation and differentiation). Studies of the effect of highly active antiretroviral therapy (HAART) on the incidence and progression of HIV/AIDS-associated cancers provided contrasting data. While a significant decrease in the incidence of KS has been observed, HAART has not had a significant impact on NHL incidence, particularly systemic NHL, or on ICC, HD, anal cancers and other non-AIDS-defining cancers. Regardless of whether these cancers are directly related to HIV-induced immunodeficiency, treating cancer in HIV-infected patients remains a challenge because of drug interactions, compounded side effects, and the potential effect of chemotherapy on CD4 count and HIV-1 viral load. A better knowledge of viral mechanisms of immune evasion and manipulation will provide the basis for a better management and treatment of the malignancies associated with chronic viral infections.