One way to address this question is to observe whether cancer affects those species which do not express NNMT but use NADA instead, for example Drosophila. NADA hydrolyses nicotinamide, producing nicotinic acid which then enters the NAD+ synthetic pathway via nicotinic acid adenylyltransferase (NaMNAT) [189,190] (Figure 2). Here, NNMT is linked to cancer.