THE HUMAN HOMOLOG OF RAT NG2, A CHONDROITIN SULFATE PROTEOGLYCAN, IS NOT EXPRESSED ON THE CELL-SURFACE OF NORMAL HEMATOPOIETIC-CELLS BUT ISEXPRESSED BY ACUTE MYELOID-LEUKEMIA BLASTS FROM POOR-PROGNOSIS PATIENTS WITH ABNORMALITIES OF CHROMOSOME BAND 11Q23

In our efforts to produce monoclonal antibodies that recognize cell-su rface antigens expressed by hematopoietic precursor and stromal cells, we generated a monoclonal antibody, 7.1, which recognizes a 220- to 2 40-kD cell-surface protein whose N-terminal amino acid sequence is ide ntical to the rat NG2 chondroitin sulfate proteoglycan molecule. This chondroitin sulfate proteoglycan, previously reported to be expressed by human melanoma cells, was not found to be expressed by normal hemat opoietic cells, nor was it expressed on the cell surface of cell lines of hematopoietic origin including cell lines with 11q23 abnormalities . It was found on the cell surface of acute myeloid leukemia (AML) bla sts and cell lines derived from nonhematopoietic tissues. Samples of l eukemic marrow from 166 children with AML enrolled on Childrens Cancer Group protocol 213 were evaluated for cell-surface expression of this proteoglycan molecule. In 18 of 166 (11%) patient samples, greater th an 25% of leukemic blasts expressed the NG2 molecule. These 18 patient s had a poorer outcome with respect to survival (P = .002) and event-f ree survival (P = .035) with an actuarial survival at 4 years of 16.7% . Blast cell expression of the NG2 molecule was strongly associated wi th French-American-British M5 morphology (P < .0001) and abnormalities in chromosome band 11q23, site of the MLL gene. These results show th at the NG2 molecule is expressed by malignant hematopoietic cells that have abnormalities in chromosome band 11q23, suggesting that antibody 7.1 may be useful in the rapid identification of this group of poor-p rognosis patients. (C) 1996 by The American Society of Hematology.