PCNA and neoplasm: The experimental results showed that the tumor volume and weight of the RRM2 overexpression group were significantly higher than those of the control group, and immunohistochemistry showed up-regulation of the expression of proliferation markers (e.g., Ki67, PCNA), which was in line with the previous observation that RRM2 promotes cell proliferation in tumors such as breast and lung cancers, and further corroborated the promotional role of RRM2 in tumorigenesis and development.