TP53BP1 and neoplasm: Furthermore, the tumour size was significantly reduced when HCT116 xenograft mice were co-treated with DXR and ARV825 as compared to DXR treatment alone, coincident with a significant reduction of p21Waf1/Cip1/Sdi1 expression and 53BP1 foci formation, senescence markers (Fig. 3c–e).