Interest in such arthritis drugs, known as cox-2 inhibitors and which include the well known drug Celebrex, stems from the mechanism by which they apparently work against cancerous tumors. According to Adam Dicker, M.D., Ph.D., assistant professor of radiation oncology at Jefferson Medical College of Thomas Jefferson University in Philadelphia and a member of Jefferson's Kimmel Cancer Center, who led the work, the drugs appear to affect angiogenesis, a process by which a tumor's growth is fed by the development of blood vessels. A new field of research on anti-cancer drugs known as angiogenesis inhibitors has sprung up in recent years based on the concept that by blocking the formation of blood vessels, cancers cannot grow or spread without a blood supply to feed them.
Dr. Dicker presents his team's findings November 7 at the American Society for Therapeutic Radiology and Oncology meeting in San Francisco.
According to Dr. Dicker, tumors actually make cox-2, an enzyme, and nearly every tumor "overexpresses," or makes too much of it. It is also present in blood vessels associated with the tumor, though the enzyme's precise role is uncertain.
In animal models, both Vioxx and Celebrex have shown anti-tumor properties, in some cases even shrinking tumors, possibly through an anti-angiogenic effect.
Other researchers have demonstrated in animal models that Celebrex enhances the effects of radiation on tumors. But little had been known, Dr. Dicker explains, about the effects of Vioxx. Dr. Dicker, using various laboratory tests and a number of different models for angiogenesis, showed the drug also enhances the effects of radiation on tumor cells by interfering with angiogenesis.
"People are excited about cox-2 inhibitors because they appear to lower toxicity for patients with arthritis," he says. "In addition, they also enhance radiotherapy effects and have anti-angiogenic activity."
Angiogenesis has become one of the hottest areas of cancer research. Some researchers believe that anti-angiogenesis drugs will expand the armamentarium of drugs that will halt cancer growth, with the disease becoming more a chronic illness patients can live with.
Dr. Dicker is leading a number of clinical trials looking at the use of these inhibitors for the treatment of cancer. At the same time, he chairs the Cox-2 Inhibitor Working Group at the Radiation Therapy Oncology Group, a federally funded cancer clinical trials organization that is conducting trials nationwide on the use of cox-2 and its role in cancer therapy.
"There will be a lot of research in this area - it's an exciting time," Dr. Dicker says.
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