(A) Abnormal expression of TRKC protein in t(12;15) leukemic cells. Total cell lysates were prepared from NBTM, t(12;15) leukemic cells, HL60 and K562. Wild-type TRK expression is detected in NBTM and weakly in K562. On the other hand, 52-kD abnormal protein is detected only in the t(12;15) leukemic cells. Anti-TRK antibody detects carboxy terminal of the TRK gene family. (B) ETV6/TEL expression in leukemic cells. Western blotting analysis using anti–N-TEL antibody detects a 52-kD band corresponding to the normal ETV6 protein in t(12;15) leukemic cells, HL60, and K562. C-1 ETV6-TRKC protein in t(12;15) leukemic cells is also detected as the 52-kD band. The t(12;15) leukemic cells express a 38-kD protein corresponding to the C-2 and C-3 ETV6-TRKC protein.