HUMAN HOMOLOG OF THE RAT CHONDROITIN SULFATE PROTEOGLYCAN, NG2, DETECTED BY MONOCLONAL-ANTIBODY 7.1, IDENTIFIES CHILDHOOD ACUTE LYMPHOBLASTIC LEUKEMIAS WITH T(4-11)(Q21-Q23) OR T(11-19)(Q23-P13) AND MLL GENE REARRANGEMENTS

Monoclonal antibody 7.1, which recognizes the chondroitin sulfate prot eoglycan molecule NG2, was used to screen prospectively blast cells fr om 104 consecutive children at initial presentation with acute lymphob lastic leukemia (ALL). Reactivity with this antibody was found in 9 ca ses (8.6%), of whom 5 had a t(4;11)(q21;q23) and 4 had a t(11;19)(p13; q23). None of the NG2(-) cases had either translocation. Southern blot analysis disclosed MLL gene rearrangement in only the 9 cases with 7. 1 reactivity plus the t(4;11)(q21;q23) or t(11;19)(q23;p13) translocat ion. MLL gene rearrangements were not detected in 89 patient leukemic samples that did not express NG2, including 7 patients with del(ll)(q2 3) or inv(11)(p13q23). As expected from the association with t(4;11) a nd t(11;19), NG2(+) cases were significantly more likely to be infants , to have hyperleukocytosis and central nervous system involvement, to be CD10(-), and to express myeloid-associated antigens CD15 and CD65. Despite short follow-up duration, 3 of the NG2(+) cases have relapsed while the other 101 patients remain in remission. Thus, blast cell su rface expression of NG2 is useful for identifying patients with ALL ha ving t(4;11) or t(11;19) translocations that are associated with poor prognosis, especially in the infant age group. (C) 1996 by The America n Society of Hematology.