P-glycoprotein expression and in vitro reversion of doxorubicin resistance by verapamil in clinical specimens from acute leukaemia and myeloma.

The expression of the P-giycoprotein which is associated with the development of multidrug resistance in various cell lines was investigated in 87 fresh acute leukaemia and multiple myeloma samples using the specific mouse monoclonal antibody MRK16 in an indirect immunofluorescence assay. Considering a 10% positive cell cut-off value, a heterogeneous expression of P-glycoprotein was observed in 5122 (22.7%) de novo acute leukaemias, 7122 (31.8%) relapse or secondary acute leukaemias, 14127 (51.8%) acute transformation of myeloproliferative or myelodysplastic syndromes and 5116 (31.2%) multiple myelomas