does nicotine cause cancer?

During class today, there was one question continuously on my mind, does nicotine cause cancer? Others questioned this as well and both yes and no were responses.

According to Robert P. Murray, John E. Connett and Lisa M. Zapawa in their 2009 Oxford Journal article,

"Does nicotine replacement therapy cause cancer? Evidence from the Lung Health Study"

There is no significant evidence indicating that nicotine causes lung cancer. (http://ntr.oxfordjournals.org/content/11/9/1076.short)

Yet, as stated by Wikipedia, (however credible they may be) "While no epidemiological evidence supports that nicotine alone acts as a carcinogen in the formation of human cancer, research over the last decade has identified nicotine's carcinogenicpotential in animal models and cell culture...nicotine increases cholinergic (and adrenergic signaling in the case of colon cancer[62]), thereby impeding apoptosis (programmed cell death), promoting tumor growth, and activating growth factors and cellular mitogenic factors... Nicotine also promotes cancer growth by stimulating angiogenesis and neovascularization.[63][64] In one study, nicotine administered to mice with tumors caused increases in tumor size (twofold increase), metastasis (nine-fold increase), and tumor recurrence (threefold increase)."

There you have it, does nicotine cause cancer? Who knows. But we do know it is bad for us, so lets avoid it and hope that one day every pack of cigarettes will look like this...