Moreover, compared to the WT tumor, Ubr5−/− tumor exhibited increased apoptosis by TUNEL staining (Figs. 3H and S5A) and elevated levels of cleaved caspase-3 and cleaved PARP1 by immunohistochemistry (IHC) staining (Fig. S5B, C), respectively. Here, PARP1 is linked to neoplasm.