PCNA and neoplasm: Additionally, we examined the proliferative index of Ki-67 and proliferating cell nuclear antigen (PCNA) by immunohistochemistry (IHC) staining of the tumor graft, finding that the frequency of cells positive for Ki-67 and PCNA was significantly lower (P < 0.01) in the PATU8988-NONHSAT105177 tumor than in the PATU8988-lnc-NC tumor.