A team of Italian researchers has found that combining two drugs, Herceptin (trastuzumab) and Iressa (ZD1839), appears to control the growth of breast cancer cells far better than either drug used alone-at least in a laboratory.

In many studies, Herceptin has shown a demonstrated effectiveness against breast tumors that "overexpress" a growth factor receptor called HER2/neu, which occurs in about 15 percent of breast cancer cases. The presence of HER2/neu stimulates the production of cancer cells in these patients; Herceptin acts to inhibit HER2/neu's activity.

Iressa, while currently approved only for use in clinical trials on women with advanced breast cancer, appears to act in a similar way to Herceptin. However, Iressa targets a different growth factor receptor called EGFR, which may occur in as many as 70 percent of breast cancers.

Writing in the Annals of Oncology, Dr. Nicola Normanno explained that growth factor receptors act like a cellular "lock and key" mechanism, with cancer growth factors attempting to bind to receptor sites on healthy cells, consequently making them divide out of control. Both Herceptin and Iressa act on enzymes that facilitate this binding activity. However, once HER2/neu and EGFR are disabled, the binding process-and thus cancer growth-are destroyed.

Normanno's study involved cells that both overproduced HER2/neu and produced some EGFR. Those cells were divided into 48 containers and treated with either the drug combination of Herceptin and Iressa or only one of the two drugs. After five days, her team found that the combination treatment was far more likely to control the growth of the cancer cell lines than either drug used alone.

Interestingly, Iressa has already shown promise in treating lung and prostate cancer patients, and a new clinical trial, being sponsored by the National Cancer Institute, is currently looking at the drug 's effectiveness in treating kidney cancer patients as well.

SOURCE:
Annals of Oncology, January 2002; 13:65-72