Cancer Testing on Animals: Not Accurate
"Nicotine promotes metastasis in animals with implanted tumors, speculated to be a result of enhanced angiogenesis (Heeschen et al., 2001; Cooke, 2007). Nicotine has been demonstrated to affect cellular signal transduction in several critical pathways that involve inhibition of apoptosis and stimulation of cellular proliferation (West et al., 2003; Dasgupta et al., 2006). These studies concerning inhibition of apoptosis, stimulation of angiogenesis and cellular proliferation by nicotine have been done in animals. Relevant human data are not available. The generally negative results in animal carcinogenicity tests lead to the conclusion that nicotine itself is not a significant direct, cause of cancer in people who use tobacco products, although nicotine could possibly promote cancer once initiated."