AKT1 and lung cancer: Nicotine's carcinogenic metabolites have also been shown to promote cell proliferation in lung cancer cells via serotonin-induced stimulation of the Raf-1/MAPK/c-myc pathway (Schuller and Orloff, 1998; Jull et al., 2001) and the Akt pathway (West et al., 2003; Tsurutani et al., 2005).