ScienceDaily for August 24, 2010 reported on vitamin D and our health.
While smoking is a well-known risk factor for a broad range of cancer types, non-nicotine components of tobacco have generally been thought to be the carcinogens, so little is known about how nicotine acts on cells to promote cancer cell growth. For breast cancer in particular, some large epidemiological studies have suggested that smoking is related to increased breast cancer risk, but they have not been accompanied by molecular biology studies on how that actually works.