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HIV Can Also Be Direct Cause Of Cancer, Researchers Say

By Sheryl Stolberg
Los Angeles Times

Researchers say they have found the first evidence that the human immunodeficiency virus, which causes AIDS, also can cause cancer rather than simply make patients susceptible by weakening their immune system.

In a study at the University of California, San Francisco, involving just four AIDS patients with what may be a previously undiscovered form of lymphoma, the scientists reported that the virus had inserted itself into the DNA of malignant tumors, lodging next to a cancer-causing gene. They theorize that the virus activated this "oncogene," spawning the malignancy. Top experts, however, are skeptical of the findings.

Although lymphoma, or cancer of the lymph system, is common among AIDS patients, previous studies have shown that the cancer is not directly caused by HIV, but occurs because the virus depresses the immune system. If the San Francisco research proves correct, it would mark the first time that scientists have shown that HIV is a direct cause of cancer.

"It's a totally different perspective of what HIV can do," said Dr. Michael McGrath, the senior author of the study, which will appear next week in the journal Cancer Research.

If the research is confirmed, the study could have broad implications for the treatment of AIDS patients and also the development of an AIDS vaccine. The findings suggest that, even if effective treatments for AIDS are developed, those who have HIV could still develop cancer years after being infected with the virus.

The type of lymphoma tumors McGrath and his colleagues studied have never before been identified, and contain different properties than those typically found in AIDS patients. Dr. Alexandra Levine, an expert in AIDS-related cancers at the University of Southern California, said it is possible that what the San Francisco team believes is lymphoma is not a malignancy, but simply an abnormal reaction against HIV.

"I don't believe they have proven in any sense that that they have found a new kind of cancer," Levine said. "It's a scientific curiosity that warrants further study, but they are not discussing classic AIDS lymphoma."

In nearly all AIDS patients who have lymphoma, the malignant tumors are "monoclonal" - meaning they are derived from one type of cell, almost always a B-cell, an immune system cell that makes antibodies. A small number of cases - between 35 and 50 - have been identified in which the cancer derives from other immune system cells called T-cells.

But at San Francisco General Hospital, McGrath said, doctors have been seeing an increasing number of lymphoma that are "polyclonal" - derived from a collection of B-cells, T-cells and also macrophages, a third type of immune system cells.

Over the past decade, McGrath said, he has seen 280 patients with this unusual form of lymphoma. Today, he said, nearly a third of all the hospital's patients with AIDS-related lymphoma have strains that are not derived from B-cells.