A recent study concluded that nicotine promotes growth of blood vessels and therefore promotes lung cancer. What implications does this have for smokeless tobacco users.
Though the biological properties of a chemical are suggestive of possible health effects, the epidemiology shows the actual health effects. For an extended discussion of the toxicology versus the epidemiology issue see this entry in our FAQ pages: http://www.tobaccoharmreduction.org/faq/healtheffectsofst.htm#37. What we know is that there is no increase in overall cancer risk associated with the use of smokeless tobacco.
These angiogenetic properties of nicotine are still under investigation. While it is conceivable that an already existing cancer (lung or otherwise) could be facilitated by such a property, that is not the same thing as initiating it. The fact that Stanford patented the "use of nicotine for therapeutic angiogenesis" implies that under some conditions this property could be beneficial.