While mechanisms of anti-tumor effects have been reported for PARP inhibitors that target the inhibition of DNA repair as a point of action, anti-tumor effects targeting transcription, chromatin, and epigenomic regulations have not been fully elucidated, while the combination of PARP inhibitor with MEK inhibitors in cancer patients with KRAS mutations was reported to involve transcriptional changes [26]. This evidence concerns the gene PARP1 and cancer.