Crbn^I391Vcells heterozygous for Csnk1a1 are more sensitive to lenalidomide in vitro and in vivo. (A) An in vitro competition experiment was performed by isolating CD45.2⁺ c-Kit⁺ cells of the listed genotypes, mixing them in a 1:1 ratio with CD45.1⁺ c-Kit⁺ cells of the same Crbn genotype, treating the cells with vehicle or 10 μM lenalidomide, and following the percentage of CD45.1⁺ and CD45.2⁺ cells in the cultures over time by flow cytometry. The data are given as the ratio of the percentage of CD45.2⁺ cells to the percentage of CD45.1⁺ cells at each time point, normalized to the value of the DMSO-treated sample at that time point. n = 4. (B-C) Peripheral blood chimerism over time in transplanted mice treated with vehicle or 50 mg/kg lenalidomide twice per day. Data are given as a ratio of the percentage of CD45.2⁺ cells (test genotype) in the peripheral blood relative to the sum of the percentage of CD45.1⁺/CD45.2⁺ (competitor) and CD45.2⁺ (test genotype) cells. This method of data analysis excludes any CD45.1⁺ cells arising from residual recipient-derived hematopoiesis. (D) Chimerism in hematopoietic stem and progenitor compartments of transplanted mice after 41 days of treatment with vehicle or 50 mg/kg lenalidomide twice per day. Lineage markers are CD3, B220, CD11b, Gr1, and Ter119. Dark shading represents the vehicle and light shading represents lenalidomide. (E) Peripheral blood chimerism results for in vivo competition experiment with cells heterozygous for both Csnk1a1 and Rps14. Mice were treated twice per day with vehicle of 50 mg/kg lenalidomide for 41 days. Data are expressed as in panel B. For all in vivo experiments, n = 4 and results are representative of 2 independent experiments.