WEDNESDAY, June 7 (HealthDay News) -- The cancer drug Gleevec stops the spread of prostate malignancies in mice by attacking the tumor's blood vessels, a new U.S. study reports.

Typically used to treat certain leukemias and more recently gastrointestinal tumors, Gleevec also seemed effective against otherwise drug-resistant prostate tumors when tested in mice, the research team said.

"Why, then, did it work so well in the animal? Because we didn't attack the tumor, we attacked the blood vessels," senior study author Dr. Isaiah J. Fidler, director of the Cancer Metastasis Research Center at the University of Texas M.D. Anderson Cancer Center, said in a prepared statement. "We target and destroy the vasculature that provides oxygen and nutrients to tumor cells."

The results, reported in the June 7 issue of the Journal of the National Cancer Institute, show that the drug was most potent when combined with paclitaxel (Taxol). Although paclitaxel is already used to treat prostate cancer, the drug tends to become ineffective once drug-resistant cancer cells continue to divide.

This two-drug treatment reduced bone metastases and the size of the tumors in mice with the drug-resistant cancer. Only four of the 18 mice injected with the cancer cells developed tumors, and the cancer spread in only three of those mice. Average size of the tumors was one-tenth of a gram.

In the control group of mice who did not receive the drug therapy, all 19 mice developed tumors that spread to the lymph notes. Average size of the tumors was 1.3 grams.

According to the researchers, Gleevec killed the blood vessels by stunting the activation of platelet-derived growth factor receptors (PDGF-R) on the cancer cells. When PDGF receptors are deactivated, new blood vessels cannot form, and cancerous cells cannot divide and migrate. Instead, a natural process called apoptosis -- a type of cell suicide -- occurs.

"Here, we attack the soil. The seeds can be resistant. Kill the endothelial cell, you kill the soil," said Fidler.

More information

Learn more about prostate cancer from the Prostate Cancer Foundation.