Tobacco Helps Cancer Cells Evade Destruction New research suggests that tobacco not only promotes cancer development, but also helps early cancer cells evade detection by the immune system, which might otherwise mop up harmful cells before they reproduce and spread. Dr. Jane A. McCutcheon and her colleagues at New York University in New York City discovered that cells exposed to tobacco have fewer substances on their surfaces used to signal whether or not the cell is dangerous and should be destroyed by the immune system. As such, McCutcheon suggested in an interview with Reuters Health, cells with fewer of these warning devices, if they become cancerous, would be more likely to evade detection by the immune system, grow and spread throughout the body. The cellular warning devices are known as HLA class 1 molecules, which are usually unique to each person. These molecules sit on the surface of cells and present a protein to the outside environment. If this protein is derived from harmless substances inside the cell, immune system components known as killer T cells will bypass the cell, considering it to pose no threat to the body. However, if the protein inside a class 1 molecule was made as a result of a cancer inside the cell, or comes from a virus, the T cells hone in on the cell and destroy it. In a recent issue of the Journal of Immunology, McCutcheon and her colleagues presented the results of experiments in which they found that cells exposed to tobacco showed fewer HLA class 1 molecules. Further experiments revealed that cells exposed to tobacco show lower levels of a particular protein that forms a link in the chain that assembles HLA class 1 molecules inside the cell. Reductions in this protein, known as TAP1, likely lead to lower amounts of HLA class 1 on the cell surface, the authors suggest.In an interview with Reuters Health, McCutcheon cautioned that these changes do not cause cancer, but simply allow the cancer to thrive in the body once it appears. The class 1 is gone before the cell becomes cancerous," she said. "If those cells become cancerous, there isn't enough class 1 for T cells to kill them." McCutcheon noted that tobacco has a lot of ingredients, and she and her colleagues remain unsure about which particular ingredients might interfere with the cells' production of HLA class 1. In the meantime, she noted that all tobacco-containing substances-not just those that people smoke-would likely have the same effect. "If you just sucked on a cigarette it could do this to you," she said. McCutcheon 。" In the future, McCutcheon predicted, it may be possible to design a product that smokers could suck or somehow ingest that could help restore healthy HLA class 1 levels. Tobacco still triggers cancer, she said, but boosting the body's ability to destroy early cancers might help smokers fight off more cases of the disease than they would otherwise. However, the bottom line remains the same, McCutcheon noted: "Cigarettes are bad."
