To investigate the impact of administration of the NNMT inhibitors on sensitivity to chemotherapy, OS and MCC cell lines were subjected to single and combined treatment with CDDP (1 nM and 10 nM) and 100 μM of each compound and further subjected to MTT assay in order to evaluate metabolic activity of cancer cells at 24 h, 48 h and 72 h after treatment. Here, NNMT is linked to Merkel cell skin cancer.