Correlation of rhodamine 123 efflux by neoplastic plasma cells with clinical and biological characteristics of multiple myeloma

Abstract

Although a variable proportion of multiple myeloma patients can achieve response with conventional chemotherapy, residual tumor cells, which are refractory, finally reemerge leading to disease progression. The expression of the multidrug resistance protein (MDR1) has been one of the most extensively explored mechanisms of drug resistance and has been related to a poor response to chemotherapy in several human tumors. Nevertheless, a careful analysis of the literature on MDR1 expression in multiple myeloma (MM) shows the existence of disturbing discrepancies as regards both the incidence of MDR1 over-expression and its clinical value. A prerequisite for the assessment of MDR1 in tumor cells should be the identification of the neoplastic cells present in the sample. This is particularly important in MM, where the percentage of tumor cells in bone marrow (BM) is relatively low. In the present study we have analyzed the functional expression of MDR1 in BM plasma cells (PC), from a group of 40 untreated MM patients. For that purpose, the rhodamine 123 efflux assay was used in combination with specific staining for plasma cells (CD38 strong+). The mean fluorescence channel (MFC) of rhodamine 123 in myelomatous PC from MM patients was 311 and 110 after incubating cells with this fluorochrome for 15 and 60 min, respectively. The median percentage of rhodamine 123 elimination by BM PC was of 61% (range: 0.29 to 88%). Upon analyzing the relationship between the ability of myelomatous PC to eliminate rhodamine 123 and other clinical and biological disease characteristics we found that, within the group of patients displaying high MDR1 expression (>61% rhodamine efflux), there was a higher incidence of cases with bone disease (P = 0.014) and advanced clinical stages (P = 0.031), greater calcium (P = 0.007) and creatinine serum levels (P = 0.061), and lower levels of albumin in serum (P = 0.015). All these parameters are usually associated with a poor prognosis. When we analyzed the possible relationship between the ability of BM PC to eliminate rhodamine 123 and the presence of numerical chromosome abnormalities we observed that a low MDR1 expression was related to a higher incidence of trisomies of chromosomes 6 and 17, although these differences did not reach statistical significance (P = 0.06). In spite of these associations, from the prognostic point of view, MDR1 expression did not correlate with other relevant prognostic factors, response to treatment (P = 0.38) or overall survival (P = 0.12).

Nature and uses of fluorescent dyes for drug transporter studies

“…P-glycoprotein activity has thus been investigated in clinical samples from patients suffering from acute myeloid leukemia [135][136][137], acute lymphoblastic leukemia [138], B-cell chronic lymphocytic leukemia [139], myeloma [140] and lymphoma [141]. Data suggest a prognostic impact of P-glycoprotein activity in acute myeloid leukemias [142,143] but not in acute lymphoblastic leukemias [144].…”

Single‐cell tracking with a reversing flow cytometer

“…Since the goal of chemotherapy is to kill all individuals in a tumor the population mean is a poor proxy for individual cell behavior. Such behavior may be responsible for the disagreement in literature between studies advocating for the monoclonal antibody based detection of PgP (24) and functional tests of PgP (i.e., R123, calcein AM staining) in clinical settings (25)(26)(27).…”

Functional Imaging of Multidrug Resistant Phenotype by 99mTc-MIBI Scan in Patients with Multiple Myeloma

“…23 Variable results have been published on the prognostic role of Pgp in myeloma patients at the time of diagnosis; high levels of Pgp have been reported in a quite variable percentage of patients, up to 60%. [24][25][26][27][28] Also, increasing Pgp levels, depending on the dose of anthracyclines and vinca alkaloids administered, have been reported. 24 Beyond the well-established role of Pgp in drug efflux, other non-Pgp membrane transporter proteins, such as MDR-related protein (MRP) and lung resistance protein (LRP), have also been implicated in the development of an MDR phenotype in multiple myeloma.…”