Colony formation and long-term self-renewal of HSPCs is impaired in MM patients. Equal numbers of HSPCs from the BM of 4 healthy donors and 8 MM patients were seeded in semisolid ready-to-use methylcellulose growth medium, and colonies (CFU-E, BFU-E, CFU-G/CFU-M/CFU-GM, CFU-GEMM) were counted after 14 days. □ and ■ represent data for healthy donors and MM patients, respectively. Means of (A) absolute numbers and (B) proportions of colonies are shown. For LTC-IC assays, HSPCs from the BM of 6 healthy donors and 6 MM patients were plated in limiting dilutions (22 replicates per concentration: 180, 60, 20, 7.5 cells/well) onto irradiated confluent AFT024 feeder layers and maintained in liquid medium. After 5 weeks, the liquid medium was replaced by methylcellulose medium and wells were scored for the presence of secondary colony-forming cells after 2 weeks. (C) The absolute frequency of LTC-ICs was calculated using Lda STAT software. Error bars represent SEM. The Student t test was used to detect statistically significant differences. *P < .05; **P < .01.