Smoking Affects Breast Cancer through Unknown Biological Mechanisms“This is one of the largest studies yet to look at smoking among women diagnosed with breast cancer, and among the first to show such a significant association,” Braithwaite said. Previous studies might have been less likely to clearly identify an association because they were too small, or because researchers relied on past clinical records rather than following women in real time, according to Braithwaite. “We do not fully understand the biological mechanisms through which smoking affects breast cancer outcome,” Braithwaite said. She noted that animal studies have shown that chemicals in tobacco smoke can get into breast tissue and that exposure to tobacco smoke increases metastasis -- the spread of cancer to other tissues, and an event that most often leads to cancer deaths. In addition, Braithwaite said, studies on mice led by Stanton Glantz, PhD, a UCSF tobacco researcher, showed that exposure to tobacco smoke stimulated tumors to grow. “Her study is very well conducted,” said Glantz, director of the Center for Tobacco Control Research and Education. “What our work is showing is that there is something in tobacco smoke -- probably not nicotine -- that facilitates tumor growth. It’s very angiogenic, and generating new blood vessels to feed tumors is very important to cancer.” In their studies of second-hand smoke exposure, Glantz and colleagues found that drugs that block nicotine did not interfere with the angiogenic effects of tobacco smoke. On the other hand, statins reduced angiogenesis in the exposed mice, which suggested to Glantz that the angiogenic response to smoke probably was triggered by inflammation.
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UCSF News Release, September 24, 2010