EXPRESSION OF CD25 (INTERLEUKIN-2 RECEPTOR-ALPHA CHAIN) IN ADULT ACUTE LYMPHOBLASTIC-LEUKEMIA PREDICTS FOR THE PRESENCE OF BCR ABL FUSION TRANSCRIPTS - RESULTS OF A PRELIMINARY LABORATORY ANALYSIS OF ECOG/MRC INTERGROUP STUDY E2993/

Of 144 adult Eastern Cooperative Oncology Group (ECOG) patients with a cute lymphoblastic leukemia (ALL) entered on study E2993 at the time o f analysis, 104 had informative immunophenotypes and molecular analysi s by polymerase chain reaction for BCR/ABL fusion transcripts, In 23 p atients (22%), BCR/ABL transcripts were detected: the ALL-typical e1a2 alone in 12, e1a2 + b2a2/b3a2 in five, and b2a2 and/or b3a2 in six. O f BCR/ABL-positive patients, 83% had early pre-B ALL, one patient had pre-T ALL, while half of the BCR/ABL-negative patients had early pre-B ALL, 18% had CD10-negative pro-B ALL and 21% were pre-T. When antibod ies to both the interleukin-2 receptor alpha (CD25) and beta chain (CD 122) were tested, CD25 was expressed significantly more frequently in BCR/ABL-positive (median 23% positive blast cells, range 1-84%) than B CR/ABL-negative patients (median 3%, range 0-69%) (P=0.00006). There w as no corelation with CD122 expression. Therefore, CD25 expression may serve as a surrogate marker for BCR/ABL positivity (Philadelphia chro mosome), the major poor prognostic parameter in adult ALL.