LasBD suppresses BCR/ABL mRNA in primary CML cells and renders normal and CML progenitors MTX-resistant. (A) 1 × 10⁴ normal or CML CD34⁺ HLA-DR⁺ cells were transduced with LasBD or the control vector, LBD containing PA317 supernatants, protamine sulfate, IL-3, IL-6, and SCF in contact with M2-10B4 stromal feeders for 24 hours. Cells were subsequently cultured in serum-free semisolid methylcellulose culture in the presence or absence of 5 × 10⁻⁸ mol/L MTX to determine the percentage of MTX-resistant progenitors. Results are represented as the percentage of CFC surviving 5 × 10⁻⁸ mol/L MTX from 2 patients with CML (with known b3a2 breakpoint) and 3 normal individuals. (B) 5 × 10⁴ LasBD and LBD-transduced CML CD34⁺ HLA-DR⁺ cells were cultured for 14 days in liquid serum-free culture containing 5 × 10⁻⁸ mol/L MTX and cells examined by RT-PCR for the presence of the BCR/ABL mRNA.