β-Catenin–mediated lymphomagenesis requires Rag activity. (A) Kaplan-Meyer tumor-free survival curves of LckCre-Ctnnb^Δex3, CD4Cre-Ctnnb^Δex3, LckCre-Ctnnb^Δex3-TCR(CL4)-Rag2^−/−, LckCre-Ctnnb^Δex3-TCR(6.5)-Rag2^−/−, and CD4Cre-Ctnnb^Δex3-pTα^−/− mice. Mice were observed for 160 days after birth. The median latency of lymphoma development in LckCre-Ctnnb^Δex3, CD4Cre-Ctnnb^Δex3, and CD4Cre-Ctnnb^Δex3-pTα^−/− mice was 99, 114, and 104 days, respectively, with a penetrance of 88%, 66%, and 53%, respectively. Log-rank tests indicated that CD4Cre-Ctnnb^Δex3 and LckCre-Ctnnb^Δex3 mice had significantly different disease-free survival curves (P = .007), while LckCre-Ctnnb^Δex3 and CD4Cre-Ctnnb^Δex3-pTa^−/− mice have similar disease-free survival curves (P = .88). No lymphomas developed in LckCre-Ctnnb^Δex3-Rag2^−/−, LckCre-Ctnnb^Δex3-TCR(CL4)-Rag2^−/−, and LckCre-Ctnnb^Δex3-TCR(6.5)-Rag2^−/− mice during the same period. (B) CD4/CD8profiles of lymphomas from the indicated mice. (C) (Histogram overlay left) Intracellular levels of β-catenin. (Histogram overlay right) Surface expression of TCRβ. The profiles presented are representative of 3 independent experiments.