Relative expression of proapoptotic Bax, Bid, and cytochrome c mRNA is higher in low-risk MDS. Relative expression of Bax, Bid, and cytochrome c mRNA was measured in freshly isolated CD34⁺ cells obtained from 6 RARS, 2 RA, and 13 NBM samples and normalized against 18S rRNA and using NBM as calibrator. The relative expression of Bax and Bid was higher in MDS compared with NBM (Bax: 3.73 [1.15-9.75] vs 1.69 [0.31-3.84]; Bid: 5.44 [1.78-9.45] vs 1.85 [0.21-3.17]). The relative expression of cytochrome c was nearly 4-fold higher in MDS (5.66 [1.49-13.41] vs 1.57 [0.2-4.19]). We also investigated the genes encoding Bax and Bid, 2 proapoptotic proteins implicated in mitochondrial apoptosis signaling, in MDS and NBM in freshly isolated stem cells (CD34⁺) and at day 7 (intermediate phase, CD36⁺ cells) and day 14 (GpA⁺ cells). Higher expression of Bax and Bid was recorded in MDS at day 0 (P = .07 and P = .006, respectively), and a similar pattern was seen at days 7 and 14 (data not shown).