RRM2 increases tumorigenic potential via cooperating with a variety of oncogenes, whereas RRM1 has malignancy-suppressing activity.20,21 Metastasis-suppressing potential of RRM2B is found in human cancer patients.22 Moreover, RRM2 is an independent prognostic factor and predicts poor survival of CRC. This evidence concerns the gene RRM2B and colorectal carcinoma.