RRM2B and breast carcinoma: Ribonucleotide reductase M2B (RRM2B), also known as p53R2, was believed to play essential roles in DNA repair, mtDNA synthesis, and protection against oxidative stress (34) and has been reported to be associated with tumorigenesis of several cancer types, including colorectal cancer (35), hepatocellular carcinoma (36), esophageal squamous cell carcinoma (37), and breast cancer (38).