AML cells express the SHIP and PTEN phosphatases. MO7e cells in log phase growth (lane 1), purified CD34⁺ cells (lane 2), or CD34-depleted MNCs (lane 3), and patient samples were lysed in 1% Triton X-100 lysis buffer (A,B). Protein lysates were quantitated and 100 μg protein loaded for analysis by SDS-PAGE. (A) Blot was probed for expression of PTEN (upper panel). Blot was separated and lower portion separately probed for expression of p38 MAP kinase as a loading control (lower panel). (B) The upper portion of the same blot as in A was probed for SHIP. (C) In a separate experiment, samples were thawed, pelleted by centrifugation, and immediately lysed by boiling in 10% SDS with 2-mercaptopurine present. Samples were equalized to 1 million cells per lane. Proteins were again analyzed by SDS-PAGE using the same antibody to probe for SHIP expression. In contrast to panel B, SHIP expression was present in all samples analyzed.