Analysis of mCG-PR^+/− × Rara^+/− and mCG-PR^+/− × Rara^+/+ leukemia cells. (A) Expression array profiling of leukemic spleen cells from 5 mCG-PR^+/− × Rara^+/− and 5 mCG-PR^+/− × Rara^+/+ mice using Affymetrix Exon 1.0 arrays. Tumors did not cluster by genotype using an unsupervised analysis. (B-D) Ex vivo ATRA sensitivity. (B) Experimental schema. (C) Cryopreserved spleen cells from 9 mCG-PR^+/− × Rara^+/− and 9 mCG-PR^+/− × Rara^+/+ independent tumors were thawed and cultured for 48 hours in liquid medium containing IL-3, IL-6, and SCF ± 1μM ATRA. Viable cells were counted and plated in methylcellulose containing IL-3, IL-6, and SCF. After 7 days, colonies (C) were counted and pairwise assessed for ATRA sensitivity (D).