'Eat Your Vegetables,' Says Researcher -- Cancer Cell Division Is Blocked By Chemical In Carrots, Cornell Biologists Show

The chemical is retinoic acid, a product of vitamin A, which thebody manufactures from carotenes, the compounds found in a wide assortmentof yellow-orange vegetables and fruits, from carrots and sweet potatoes topumpkins and apricots.

Retinoic acid reverses the growth-promoting effects of oncogenes,the mutated genetic material that induces cancer, says Andrew Yen, aprofessor of pathology and director of one of the Cancer BiologyLaboratories in Cornell University's College of Veterinary Medicine.

The finding, which to date has been restricted to the test-tubelevel, could lead to enhanced therapies for those cancers, includingleukemia, that seem to respond to retinoic acid. The research alsohighlights the cancer-prevention role of carotenes.

"This is one more reason," Yen says, "to listen to your mother andeat your vegetables."

Yen reported the cell growth-arresting function of retinoic acidMarch 30 in New Orleans at the annual meeting of the American Associationfor Cancer Research. More details are in an article prepared for theassociation's journal, "Cancer Research". Previously, progress by Yen'slaboratory in explaining the role of retinoic acid was reported in a seriesof articles in several journals, including "Blood", "European Journal ofCell Biology" and "Experimental Cell Research.

" Retinoic acid is a metabolic product of retinol, the active form ofvitamin A. The compound had been shown by other researchers to regulatenormal cell growth and differentiation. Yen's latest results -- usingtransforming proteins to switch on proto-oncogenes, the precursors tooncogenes -- demonstrate how retinoic acid can use the samechemical-signalling cascades that cause cell growth instead to arrestgrowth.

"Retinoic acid can reverse the defect in growth control that wascaused by the viral agent and result in cell-growth arrest," Yen says,describing his experiments with cell cultures. "Now we need a deeperunderstanding of how retinoic acid causes these changes -- and exactlywhich molecules are affected by retinoic acid. In my dreams there is asingle effector, but it's more likely there are several."

Ongoing studies in the Yen laboratory, supported in part by theNational Cancer Institute and the U.S. Department of Agriculture's Programin Human Nutrition, aim to explain exactly how retinoic acid works ononcogenes and whether other, related compounds would be more effective inchemotherapy. As a result, oncologists might be able to fine-tune thechemotherapy cocktails given not only to leukemia patients but also topatients with other types of cancer, Yen suggests.

"In the meantime," he says, "I think we're adding evidence that anadequate supply of carotene in the diet is obviously beneficial for anyonewho wishes to stay healthy and avoid cancer."