North Carolina State University researchers said their findings might lead to tobacco products -- especially smokeless ones -- that contain reduced levels of cancer-causing agents.

Professor Ralph Dewey and Assistant Professor Ramsey Lewis teamed with colleagues at the University of Kentucky to knock out a gene known to turn nicotine into nornicotine -- a precursor to the carcinogen N-nitrosonornicotine, or NNN.

The scientists said varying percentages of nicotine are turned into nornicotine as the plant ages, while nornicotine converts to NNN as the tobacco is cured, processed and stored.

Field tests in Kentucky, Virginia and North Carolina compared cured burley tobacco plants with the gene silenced and "control" plant lines with normal levels of gene expression. The researchers found a six-fold decrease in carcinogenic NNN in the genetically modified tobacco plants.

The research that included Anne Jack, Lily Gavilano, Balazs Siminszky and Lowell Bush at University of Kentucky and Jerry Morris, Vincent Robert and Alec Hayes at Philip Morris USA was detailed in the Feb. 14 online issue of The Plant Biotechnology Journal.