PARP1 and neoplasm: Anti-tumour effects of MNA may at the same time arise from its inhibition of NNMT activity [1,31,63,155] and its subsequent effects upon nicotinamide levels, NAD+ synthesis and cellular SAM availability, the consequences of which include decreased activity of NAD+-dependent pro-oncogenic enzymes such as PARP-1 [141,142,143,144] and reversal of pro-oncogenic changes in epigenetic regulation [56,58,59,60], as well as increased production of PGI2.