Background: More than 50% of adults with acute lymphoblastic leukemia (ALL) actually die with resistant leukemia. The multidrug resistance (MDR) related P170 glycoprotein may be involved in treatment failure.
Methods: P170 content of leukemic cells was assayed by immunocytochemistry with the MRK-16 monoclonal antibody in 41 consecutive cases of adult ALL (27 at onset and 14 at relapse).
Results: Positive cells were found in 11/14 cases at relapse and in 18/27 cases at onset. All cases with a high WBC, FAB L3, B-mature phenotype, and t(9; 22) were positive. In the 27 patients who were studied at onset and were treated with the same protocol, the overall failure rate was 44% in negative cases and 83% in positive cases.
Conclusion: P170 overexpression may contribute to drug resistance and to chemotherapy failure in adult ALL.