Washington, DC -- A family of compounds found in cruciferousvegetables, such as broccoli, cauliflower, and watercress, blocked lungcancer progression in both animal studies and in tests with human lungcancer cells, report researchers from Georgetown University MedicalCenter and the Institute for Cancer Prevention.
They say the results, published in a set of papers in the September 15 issue of Cancer Research,suggest that these chemicals -- put into a veggie pill of sorts --might some day be used to help current and former smokers ward offdevelopment of lung cancer, the leading cause of cancer death inAmericans.
"These studies provides significant insight into the mechanismsof lung cancer prevention and suggests ways the process can be sloweddown after exposure has already occurred," said the study's principalinvestigator Fung-Lung Chung, Ph.D., Professor of Oncology in theLombardi Cancer Center at the Georgetown University Medical Center. Heworked with researchers from the Institute for Cancer Prevention, inValhalla, New York, and with other scientists in Illinois, Minnesotaand New York on the studies.
"We still need to do more research, but it may be that an agentcontaining these ingredients could, to some degree, help protect peoplewho have developed early lung lesions due to smoking," Chung said. "Inany case, we know that eating vegetables is generally good for us, andthat some studies have shown they help lower a person's risk ofdeveloping cancer."
One of the two new studies being reported was the first to test whetherthese compounds, derived from naturally occurring isothiocyanates,could have an impact on the stages of cancer development specificallyafter exposure to cancer-causing elements . To test that, theresearchers induced lung tumor development in experimental mice byexposing them to tobacco carcinogens, and then they fed one group ofmice the veggie compounds. They found that, indeed, use of thechemicals resulted in a reduced development of benign (harmless) lungtumors to malignant tumors, compared to mice that did not receive thecompound.
Chung cautions, however, that it is difficult to draw anydirect comparisons between human consumption of these vegetables andthe effects seen in the mice studies. "Because the amount ofcarcinogens we used to induce tumors was very high, we needed to use avery high dose of isothiocyanates to see any effect," he said. "Thisanimal model will give us data for the potential use of such agents ina human clinical trial."
The second new study looked at the effect of the same compoundon human lung cancer cells, which were forced to grow quickly (ascancer does) because of insertion of a gene known to be involved incell growth and regulation. The laboratory test showed that thederivative of isothiocyanate significantly pushed the human lung cellsto commit "suicide," compared to cells that did not have the gene,suggesting that its use may stop fast growing lung cancer cells fromthe outset. This study provides some insight onto "one of the possiblemechanisms of action" by which the compounds may offer some protectionagainst lung cancer development, the researchers said.
These studies were continuation of a 20-year research effort byChung and his team, much of it conducted while Chung was at theInstitute for Cancer Prevention before moving to Georgetown UniversityMedical Center. The body of research they have established on theconnection between cruciferous vegetables and lung cancer is one of themost detailed available. Chung earlier identified the isothiocyanatesmay be responsible for the beneficial effects of these vegetables, andhe had shown they were effective in hindering development of lungcancer cells.
The study was funded by a grant from the National Institutes ofHealth. Co-authors include C. Clifford Conaway, PhD, from the Institutefor Cancer Prevention, who served as senior investigator on the mousestudy, and Yang-Ming Yang, PhD, also from the Institute, who was firstauthor on the lung cell study. Other co-authors include, from theInstitute for Cancer Research, Meena Jhanwar-Uniyal, PhD, JoelSchwartz, MD, Chung-Xiou Wang, MD, and Brian Pittman, MS; Defa Tian,MD, from Georgetown University; H. Dorota Halicka, PhD, and FrankTraganos, PhD, from New York Medical College; and Edward McIntee, PhD,and Stephen Hecht, PhD, from the University of Minnesota.
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