AML cells cultured in GM-CSF, IL-4, and TNF- express the inv(16) gene product. AML cells from patient 14 were cultured for 14 days in GM-CSF + IL-4 + TNF-. Triton X-100 lysates of freshly isolated and cultured AML cells were separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and then analyzed by Western blotting using antibodies against the N-termini (C2) and C-termini (AH107) of the CBFB-MYH11 inv(16) gene product. Lysates from K562 cell line served as a negative control.