According to cancer researchers, compounds extracted from green vegetables such as broccoli and cabbage could be a potent treatment against melanoma skin cancer, a form of cancer that begins in melanocytes (cells that make the pigment melanin).
Tests on mice suggest that these compounds, when combined with selenium, target tumors more safely and effectively than conventional therapy.
“There are currently no drugs to target the proteins that trigger melanoma skin cancer,” said Gavin Robertson, author of 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.”
Robertson and his colleagues previously showed the therapeutic potential of targeting the Akt3 protein in inhibiting the development of melanoma. The search for a drug to block the protein led them to a class of compounds called isothiocyanates.
These naturally occurring chemicals found in cruciferous vegetables are known to have certain cancer fighting properties. However, the potency of these compounds is so low that a successful treatment would require large impractical amounts of these compounds.
Instead, the researchers rewired the compounds by replacing their sulfur bonds with selenium. The result, they believe, is a more potent drug that can be delivered intravenously in low doses.
“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.”
To study the effectiveness of the new drug, isoselenocyanate, researchers separated mice with cancer into two groups. They were treated with either the vegetable compounds or the compounds supplemented with selenium.
“We found that the selenium-enhanced compounds significantly reduced the production of Akt3 protein and shut down its signaling network,” explained Robertson, who is also leader of the experimental therapeutics program at Penn State Hershey Cancer Institute. The modified compounds also reduced the growth of tumors by 60 percent, compared to the vegetable-based compounds alone.
When the researchers exposed three different human melanoma cell lines to the two compounds, the selenium-enhanced treatment worked better on some cell lines than others. The efficiency was from 30 to 70 percent depending on the cell line.
The exact mechanism of how selenium inhibits cancer remains unclear. However Robertson 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.”
References:
1. Gavin Robertson, et al. Penn State.
