Effect of e1a2Mz transduction on primary leukemia cells from Ph⁺ ALL patients. (A) Transduction efficiencies of primary leukemia cells from a Ph⁺ ALL-1 patient. Expression of CD2 (transgene) and CD19 (natively expressed gene) in cells transduced with or without the indicated vectors was determined by FCM on day 3. (B) Cobblestone area formation of primary leukemia cells from Ph⁺ ALL-1 patients on day 17. Primary leukemia cells were cocultured with mouse stroma cells, and cobblestone areas were formed about 2 weeks after transduction (original magnification, × 100). The image was acquired using an inverted microscope (Diaphot TMD 300; Nikon, Tokyo, Japan) with a digital camera (DXM 1200; Nikon). The acquired image was processed using ACT-1 software (Nikon). The objective lenses used were Nikon NCF Plan ELWD DM 20×/0.40. (C) Number of cobblestone areas derived from primary leukemia cells of the Ph⁺ ALL-4 patient. Cells were transduced with the indicated vectors at an MOI of 20, and cobblestone areas were counted 17 days after transduction. The results represent means ± SDs of duplicate experiments. (D) Apoptosis of primary leukemia cells from Ph⁺ ALL-1 patients. Apoptosis was determined by annexin V assay on day 7 as performed for the cell lines. ^*In panels A and D, the numbers in the plot indicate the percentage of cells in that quadrant.