Single-cell image analysis to assess ABC-transporter-mediated efflux in highly purified hematopoietic progenitors.

BACKGROUND: Normal and malignant hematopoietic stem cells are characterized by their capacity to actively extrude fluorescent dyes. The contribution of different ATP-binding cassette (ABC) transporters to this phenomenon is largely unknown due to the small stem cell numbers limiting the use of standard methods to assess functional efflux. METHODS: We used epifluorescence microscopy (EFM) in combination with single-cell image analysis to study ABC-transporter-mediated efflux in highly purified, viable, CD34+CD38- cells sorted on an adhesive biolayer. P-glycoprotein and multidrug-resistant protein (MRP)-mediated efflux were quantitated using fluorescent substrates (rhodamine-123 and calcein acetoxymethyl ester [calcein-AM]) and specific inhibitors (verapamil and probenecid, respectively). RESULTS: The feasibility, sensitivity, and reproducibility of rhodamine-123 efflux quantitation using single-cell EFM was shown in cell lines and compared with standard flow cytometric assessment. P-glycoprotein-mediated transport was higher in CD34+CD38- cells than in more differentiated progenitors (mean efflux index = 2.24 +/- 0.35 and 1.14 +/- 0.11, respectively; P = 0.01). P-glycoprotein-mediated transport was the main determinant of the rhodamine "dull" phenotype of these cells. In addition, significant MRP-mediated efflux was demonstrated in CD34+CD38- and CD38+ cells (mean efflux index = 1.42 +/- 0.19 and 1.28 +/- 0.18, respectively). CONCLUSION: The described method is a valuable tool for assessing ABC-transporter-mediated efflux in highly purified single cells. Both P-glycoprotein and MRP-mediated efflux are present in human CD34+CD38- hematopoietic stem cells.

Lung-resistance-related protein expression is a negative predictive factor for response to conventional low but not to intensified dose alkylating chemotherapy in multiple myeloma.

This study was undertaken to assess the significance of lung-resistance related protein (LRP) expression in plasma cells from untreated multiple myeloma (MM) patients and to determine whether LRP was associated with a poor response and survival in patients treated with different dose regimens of melphalan. Seventy untreated patients received conventional oral dose melphalan (0.25 mg/kg, day 1 to 4) combined with prednisone (MP) or intravenous intermediate-IDM; 70 mg/m2) or high- (140 mg/m2) dose Melphalan (HDM). LRP expression was assessed with immunocytochemistry using the LRP-56 monoclonal antibody. LRP expression was found in 47% of patients. In the MP treated patients, LRP expression was a significant prognostic factor regarding response induction (P < .05), event free survival (P < .003), and overall survival (P < .001). In the intensified dose melphalan treated patients LRP did not have a prognostic value. The response rates of LRP-positive patients to MP and IDM/HDM were 18% versus 81%, respectively (P < .0001). We conclude that LRP is frequently expressed in untreated MM patients and is an independent predictor for response and survival in patients treated with MP. Pretreatment assessment of LRP identifies a subpopulation of patients with a poor probability of response to conventional dose melphalan. Dose intensification of melphalan is likely to overcome LRP-mediated resistance.

MDR-1 expression and response to vincristine, doxorubicin, and dexamethasone chemotherapy in multiple myeloma refractory to alkylating agents.

PURPOSE: To assess whether the presence of enhanced multiple drug resistance (MDR)-1 gene expression in multiple myeloma (MM) patients predicts survival, as well as response to vincristine, doxorubicin, and dexamethasone (VAD) chemotherapy. PATIENTS AND METHODS: Sixty-three MM patients refractory to alkylating therapy were studied. The presence of the MDR-1 gene product, a 170-kd glycoprotein (P-170), was analyzed in bone marrow plasma cells by means of the alkaline phosphatase (APAAP) technique using the P-170-specific monoclonal antibody (MoAb) C219. The prognostic value of MDR-1 gene expression, examined before VAD treatment, was compared with other established prognostic factors including beta 2-microglobulin, albumin, lactate dehydrogenase (LDH), and the plasma cell labeling index. RESULTS: Fifty-nine percent of all samples were P-170-positive. No association could be demonstrated between response to VAD and MDR-1 gene expression (chi 2 P = .359), in contrast to high serum beta 2-microglobulin levels, which were positively correlated with response (P = .006). P-170-positive and -negative patients showed a median survival duration of 23 and 22 months, respectively, a difference that was not statistically significant (P = .9). beta 2-microglobulin, LDH, albumin, and the plasma cell labeling index were all significantly correlated with survival. CONCLUSION: These results indicate that other mechanisms of resistance must be involved in MM apart from MDR. The role of MDR status at this stage of disease may be biased by the major contribution of dexamethasone to induction of response by VAD in MM patients.