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By Karla Gale
NEW ORLEANS, Mar 26 (Reuters Health) - HIV-infected whites are more likely to develop non-Hodgkin's lymphoma, a type of cancer, than HIV-infected blacks, and now researchers think they may know the reason why.
It seems that a gene variation that affects production of interleukin 6 (IL-6), an immune system signaling molecule, is five times as common in whites as blacks, researchers reported on Sunday at the American Association for Cancer Research meeting here. IL-6 helps fight infection by stimulating the growth and maturation of white blood cells.
Dr. Charles S. Rabkin, of the National Cancer Institute in Bethesda, Maryland, and his colleagues looked at six immune system genes in approximately 2,500 people with advanced HIV infection.
The investigators found that carriers of a certain variation in the IL-6 gene--known as IL-6-174C--were twice as likely to develop non-Hodgkin's lymphoma during the 2-year study as other patients. Those with IL-6-174C produce less IL-6 than those with other variations of the gene.
The genetic variant was carried by five times as many whites as African Americans, which according to Rabkin may explain lower incidence of non-Hodgkin's lymphoma in sub-Saharan Africa. Non-Hodgkin's lymphoma is a cancer that develops in lymphoid tissue, such as the lymph nodes or spleen.
One unexpected finding was that patients with Kaposi's sarcoma who had the IL-6-174C gene were actually less--not more--likely to develop non-Hodgkin's lymphoma.
"These results are not so odd," Rabkin told Reuters Health, "because we've seen a number of other paradoxes where cancers in HIV infection seem to have different associations." He pointed out that Kaposi's sarcoma, which occurs early in the course of HIV infection, is related to stimulation of the immune system, whereas non-Hodgkin's lymphoma "is more tightly linked to loss of immune control and destruction of immune pathways."
The question remains whether HIV-negative patients with non-Hodgkin's lymphoma are also more likely to carry IL-6-174C. Rabkin and his colleagues plan to address this issue in future studies.
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