NAT2 and colonic neoplasm: For example, the human NAT2*4 rapid acetylator allele, whose expression in CHO cells increases HAA-associated mutations more than that of NAT2 slow acetylator alleles (Probst-Hensch et al. 1995; Grant et al. 1997; Fretland et al. 2001), is a colon cancer risk factor among Caucasians (Butler et al. 2008) and smokers (Slattery et al. 1998; Nöthlings et al. 2009).