CD44 is not required for R26-βcat leukemia development or engraftment. (A) CD44 expression on DP cells from pretransformed R26-βcat (6-week-old) and leukemic mice compared with control mice (solid gray). (B) Phenotype of a CD44-deficient R26-βcat tumor compared with control thymuses from CD44 deficient or heterozygote mice. Left panels show the CD25 and CD44 expression of DN thymocytes. Right panels show the CD4 and CD8 expression of total thymocytes. (C,D) Kaplan-Meier plot showing the survival curves of (C) CD44-deficient R26-βcat, CD44^+/+R26-βcat, or CD44-deficient control mice and (D) mice transplanted with 10⁴ cells from 2 distinct CD44-deficient R26-βcat or CD44^+/+R26-βcat tumors. (E) BM and thymus of mice transplanted with CD44-deficient R26-βcat tumor cells were evaluated for CD45.1 and CD45.2 to identify CD45.2⁺ tumor cells and with CD4 and CD8 to analyze the tumor phenotype (gated on CD45.2⁺ cells).