Experiments with mice suggest that these compounds, when combined with selenium, target tumors more safely and effectively than conventional therapies. Although human trials of the new drug are still years away, the researchers are hopeful that it could be delivered either intravenously, or added to sunscreen lotion.
“There are currently no drugs to target the proteins that trigger melanoma,” Gavin Robertson, associate professor of pharmacology, pathology and dermatology at the Penn State College of Medicine, was quoted in a release announcing the study. “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.”
Previously, Robertson and his colleagues had demonstrated the therapeutic potential of focusing on the Akt3 protein in inhibiting the onset of melanoma. Looking for a drug to block the protein led the research team to a class of compounds called isothiocyanates, which are found in cruciferous vegetables (edible members of the cabbage family) and are known to contain certain anti-cancer properties. But any successful drug would call for impractically huge amounts of the compound, so the Penn State researchers rewired the compounds by switching their sulfur bonds to selenium.
“Selenium deficiency is common in cancer patients, including those diagnosed with metastatic melanoma,” explained Robertson, whose findings appear in the March edition of Clinical Cancer Research. “Besides, selenium is known to destabilize Akt proteins in prostate cancer cells.”
Researchers injected mice with 10 million cancer cells. When the rodents developed large tumors six days later, they were split into two groups and treated with either the vegetable compounds or the compounds supplemented with selenium. The selenium-enhanced compounds significantly reduced the production of Akt3 protein and reduced the growth of tumors by 60 percent, in relation to the treatments with vegetable-based compounds alone.
In further tests, the selenium-enhanced drug worked better on some human melanoma cell lines than others, boasting efficiency rates from 30 to 70 percent depending on the cell line. Robertson, who has filed a provisional patent on the discovery, is convinced that the use of naturally occurring compounds that target cancer-causing proteins could lead to more effective ways of treating melanoma.
“We have harnessed something found in nature to target melanoma,” said Robertson. “And since we only need tiny amounts to kill the cancer cells, it means even less toxic side effects for the patient.
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