CD7 EXPRESSION IN ACUTE MYELOID-LEUKEMIA

The clinical significance of the expression of CD7 antigen on the blas ts of 207 consecutive patients with de novo acute myeloid leukemia (AM L) was evaluated. For this purpose, fifty-three CD7+ patients (23 fema les and 30 males; mean age 52 years) were analyzed and classified into the following subtypes according to French-American-British (FAB) cla ssification: 7 MD, 13 M1, 9 M2, 1 M3, 9 M4, 14 M5. Immunophenotypic st udies were carried out by flow cytometry and blast cells were selected on the basis of forward light scatter gating and pan-myeloid marker, either CD13 or CD33. All the CD7+ patients were negative for surface C D3 and T-cell-receptor (TCR) molecules. We found no correlation betwee n CD7 expression and sex, age, hepatosplenomegaly and/or central nervo us system involvement. The immaturity of CD7+leukemic cells was suppor ted by the high expression of CD34 (P = 0.001), CD7 positivity was sig nificantly associated with a white blood cell count (WBC) greater than 100 x 10(9)/L (P = 0.003). P-Glycoprotein (P-170) expression was also evaluated in 135 patients by a flow-cytometric assay: there was a clo se relationship between CD7 and P-170 positivity (P < 0.001), For remi ssion induction, all patients received therapeutic regimens routinely used for AML, The complete remission (CR) rate was significantly lower in CD7+ cases (32% vs 74%, P = 0.001). The overall survival and disea se free survival rate of CD7+ AML was lower than those of CD7- patient s (P < 0.001 and = 0.002, respectively). CD7+ AML with coexpression of CD14 had a particularly unfavourable response and prognosis in compar ison with CD7+ patients without CD14. These clinical findings in CD7AML subtype could be explained by the convergence of the following unf avourable prognostic factors: 1) co-expression of immaturity markers ( CD34); 2) frequent monocytic differentiation (CD14); 3) strict correla tion with P-170 phenotype. These findings may require an effort to dra w up a more useful diagnostic formulation of AML in clinical managemen t.