MOLECULAR ANALYSIS OF CD2 GENE-EXPRESSION IN ACUTE MYELOBLASTIC-LEUKEMIA EXPRESSING T-LINEAGE ASSOCIATED SURFACE-ANTIGENS

CD2 is a surface marker of T cells and NK cells, and is not normally e xpressed on human myeloid cells, but is found on a significant minorit y of cases of acute myeloid leukemia (AML). Molecular studies were per formed on bone marrow myeloblasts from two patients with CD2 surface p ositive AML. No abnormality of the CD2 gene was detected on Southern b lot analysis. On Northern blots, CD2 mRNA of normal size was present. The CD2 gene contained a site which was unmethylated, consistent with active transcription, in a CD2 positive AML case, and in a CD2 positiv e T cell line, but methylated in CD2 negative AML cells. The evidence does not support the hypothesis that inappropriate surface expression of lineage markers is due to leukemia-related genetic changes, such as amplification or rearrangement, of the CD2 gene itself. Rather, the r esults are consistent with the hypothesis that mixed lineage leukaemia arises from rare normal bone marrow progenitors with multilineage phe notypes.