March 5 (HealthDay News) -- A drug based on compounds extracted from cruciferous vegetables such as broccoli and cabbage could offer a potent and safe treatment against melanoma, Penn State College of Medicine researchers say.

In mice, a combination of these vegetable compounds (called isothiocyanates) and selenium slowed production and blocked the signaling network of a protein called Akt3 -- which plays a role in melanoma development, -- and reduced tumor growth by 60 percent.

"There are currently no drugs to target the proteins that trigger melanoma. We have developed drugs from naturally occurring compounds that can inhibit the growth of tumors in mice by 50 to 60 percent with a very low dose," Gavin Robertson, an associate professor of pharmacology, pathology and dermatology, said in a Penn State news release.

The potency of isothiocyanates is so low that a useful drug would require impractically large amounts of the compounds. Instead, the researchers altered the vegetable-based compounds by replacing their sulfur bonds with selenium, resulting in a more powerful drug that can be delivered intravenously at low doses. The new drug is called isoselenocyanate.

"Selenium deficiency is common in cancer patients, including those diagnosed with metastatic melanoma. Besides, selenium is known to destabilize Akt proteins in prostate cancer cells," Robertson said.

When the researchers tested the combination drug on different human melanoma cell lines, they found it was from 30 percent to 70 percent effective. Possible human trials of the new drug are still years away.

"We have harnessed something found in nature to target melanoma. And since we only need tiny amounts to kill the cancer cells, it means even less toxic side effects for the patient," said Robertson, who has a provisional patent on the discovery.

The research was published in the March issue of Clinical Cancer Research.

SOURCE: Penn State, news release, March 1, 2009