Staining with Hoechst 33342 and rhodamine 123: an attempt to detect multidrug resistant phenotype cells in leukemia.

Development of resistance is the major cause of failure in chemotherapeutic treatments. We have previously shown that the level of labeling with Hoechst 33342 and rhodamine 123 in established cell lines was decreased in cells with 'classic' MDR phenotype. This functional test was carried out using fluorescence image cytometry on living cells. We applied this protocol to patients with chronic lymphocytic leukemia. Although a large variability of the labeling is observed in cells from healthy donors, this approach seems to be useful for early detection of P-gp-dependent resistance in leukemia cells and for identification of new reversing agents on patient lymphocytes.