Effect of retinoic acid on myeloid antigen expression and clonal growth of leukemic cells from children with acute non lymphocytic leukemia--a Pediatric Oncology Group Study.

We have used a panel of 5 monoclonal antibodies against normal myeloid-differentiation antigens to determine retinoic acid-induced changes in cell surface antigens on ANLL bone marrow cells from 24 children at the time of diagnosis. Two of these antibodies (T5A7 and 5F1) detect antigens expressed on normal mature granulocytes and on all monocytes, respectively. The percentage of positive cells for each monoclonal antibody was determined by indirect immunofluorescence. After 5 days incubation with 1 microM RA in liquid culture, cells from 11 of 24 patients showed substantially increased expression of one or both antigens detected by T5A7 and 5F1. Leukemic bone marrow cells from these patients were also cultured in methylcellulose medium with and without 1 microM RA for one week, and cells from 16 of 24 patients showed clonal growth. Cultures from 10 of these 16 patients showed RA-induced inhibition of colony growth; of these 10 patients, cultures from six patients showed RA-induced increases in antigens associated with maturing myeloid cells. This suggests that the RA-induced inhibition of clonal growth observed with leukemic cells from these patients may be accompanied by the increased expression of maturation-associated myeloid antigens by these cells in the presence of RA.