RRM2 and cancer: It was observed that mRNA levels of RRM2 were elevated in a wide range of cancers, including bladder, central nervous system (CNS) tumors, breast, cervical, colorectal, esophageal, gastric, head and neck, kidney, liver, lung, lymphoma, melanoma, ovarian, pancreatic, and sarcoma when compared to their normal tissue counterparts, as highlighted in Fig. (4A).