Researchers from the University of Pittsburgh Cancer Center, reporting in the journal Science, illustrate how Kaposi's sarcoma-associated herpesvirus (KSHV) inhibits the body's immune system and causes cancer cells to grow. The virus allows cancer to develop through a technique called immune evasion by secreting a hormone-like substance called viral IL-6 that not only inhibits immune function but also directly stimulates KS cancer cells to grow. IL-6 also works to prevent the cancer cells from naturally dying through a process called apoptosis. People with healthy immune systems can usually overcome the effects of IL-6 on the body and thwart the disease, but those with compromised immune systems often find themselves unable to beat back the effects of the compound, the researchers say. This helps explain why healthy people are able to be infected with KSHV and not develop Kaposi's sarcoma while AIDS patients are prone to developing the cancer.
"The importance of this finding is that it demonstrates that there is an overlap between the immune system and tumor suppressor pathways that are targeted by KSHV," said lead researcher Patrick S. Moore. "It further demonstrates that viruses that inhibit immune function also can, under some circumstances, induce tumor cells to grow because these viruses are attacking pathways that are important in both immunity and suppression of tumor growth."
The researchers believe that the IL-6 compound could be a promising target for new therapies designed to prevent or treat Kaposi's sarcoma in HIV-positive people. They also hope their discovery will lead to treatments for lymphoma and Castelman's disease, ailments that also may be affected by IL-6 production in the body.