RRM2 and neoplasm: Immunostaining of the xenograft tumor sections revealed that, in comparison to the WT + cis group, the KO + cis group exhibited significant downregulation of SIRT7, cleaved-PARP1 and cleaved-caspase3 expression and substantial upregulation of RRM2 and Pan-cr expression, which is in line with our in vitro findings (Figure 7D).