Diabetes and risk of Kaposi's sarcoma: effects of high glucose on reactivation and infection of Kaposi's sarcoma-associated herpesvirus

Patients with diabetes are generally prone to pathogen infection and tumor progression. Here, we investigated the potential association between diabetes and Kaposi's sarcoma (KS), a tumor linked to infection with Kaposi's sarcoma-associated herpesvirus (KSHV). By using Taiwan's National Health Insurance Research Database, we found that diabetes is statistically associated with increased risk of KS in a casecontrol study. Since a high level of blood sugar is the hallmark of diabetes, we determined whether high glucose promotes both KSHV reactivation and infection, which are crucial for KS pathogenesis. Our results showed that high glucose significantly increases lytic reactivation of KSHV but not Epstein-Barr virus, another related human oncogenic gammaherpesvirus, in latently infected cells. Activation of the transcription factor AP1 by high glucose is critically required for the onset of KSHV lytic reactivation. We also demonstrated that high glucose enhances susceptibility of various target cells to KSHV infection. Particularly, in endothelial and epithelial cells, levels of specific cellular receptors for KSHV entry, including integrin alpha 3 beta 1 and xCT/CD98, are elevated under high glucose conditions, which correlate with the enhanced cell susceptibility to infection. Taken together, our studies implicate that the high-glucose microenvironment may be an important predisposing factor for KS development.