TP53 and neoplasm: We also investigated whether the elevated levels of p53 and p21 might be the related to increased DNA damage, an early event in tumorigenesis and showed that γ-H2AX, the phosphorylated form of the core histone H2AX and a marker for double-stranded DNA breakage, was highly expressed in both Amhr2-Cre;Ctnnb1Δ(ex3)/+ and Amhr2-Cre;Ctnnb1Δ(ex3)/+;PtenΔ/Δ tumor cells compared to control ovarian tissue (Fig. 3 U–W).