Utilizing a Trp53- and Brca2-null ID8 syngeneic mouse model (ID8 Trp53−/−Brca2−/−; ref. 43), we next examined the effect of Cbx2 knockdown on tumor progression (Fig. 5A) with three experimental arms: Cbx2 intact (shCTRL), Cbx2 knockdown #1 (shCbx2#1), and Cbx2 knockdown #2 (shCbx2#2). Here, CBX2 is linked to neoplasm.