DHFR and cancer: Both TS and DHFR are well-known molecular targets in anti-cancer chemotherapy, whereas CK2 has recently emerged as a target (Borgo et al., 2021), and the enzyme inhibitor, CX-4945 (5-(3-chlorophenylamino)benzo [c][2,6]naphthyridine-8-carboxylic acid), also known as silmitasertib (Pierre et al., 2011; Kim and Kim, 2012; Chon et al., 2015) undergoes phase I and phase II clinical studies for cancer treatment.