Modulation of daunorubicin cellular resistance by combination of P-glycoprotein blockers acting on drug efflux and intracellular drug sequestration in Golgi vesicles

Abstract

Background S9788 and PSC833 were developped as P‐glycoprotein (Pgp) blockers and found to act additionally on daunorubicin subcellular distribution, involving different putative targets. On this basis, combinations of S9788 and PSC833 were evaluated in Pgp‐expressing MCF7DXR cells in which we recently demonstrated that daunorubicin was sequestered in Golgi vesicles (Bour‐Dill et al.: Cytometry, 39: 16–25, 2000). Methods Combinations of S9788 and PSC833 consisted in complementary fractions of iso‐effective concentrations (IEC) leading to 90% (IEC90) and median (IEC50) reversion of daunorubicin resistance. Resistance modulation was assessed using cytotoxicity assays, flow cytometry determination of intracellular daunorubicin, and fluorescence microscopy analysis of daunorubicin subcellular distribution. Results Individually, both S9788 and PSC833 were found to be very potent with IEC90 of 5 and 15 μmol/l, and IEC50 of 0.1 and 0.2 μmol/l, respectively, for S9788 and PSC833. When combined, synergistic cytotoxicity was observed for both IEC90 and IEC50 combinations while intracellular daunorubicin fluorescence was only synergistically increased for IEC90 combinations. For IEC50 combinations, no increase in intracellular fluorescence was observed, and fluorescence microscopy examination of the cells suggested that daunorubicin sequestration in Golgi vesicles could be modulated at concentrations that do not significantly increase daunorubicin cellular concentration. Using immunofluorescence and reverse transcription‐polymerase chain reaction analyses, multidrug resistance‐associated protein, major vault lung‐resistance protein, and anthracycline‐resistance associated protein were not found to be implicated. Conclusions Synergistic combinations of S9788 and PSC833 might offer alternative ways to decrease the toxicity generated by high‐dose Pgp‐blockers without altering the efficacy of the resistance modulation. Cytometry 41:62–72, 2000 © 2000 Wiley‐Liss, Inc.

Imaging recognition of inhibition of multidrug resistance in human breast cancer xenografts using 99mTc-labeled sestamibi and tetrofosmin

“…The results of washout kinetics and biodistribution analysis in this study further show that accumulation of either MIBI or TF in PSC833-treated MCF7/AdrR tumors might be restored to the level of MCF7/WT. These findings are consistent with those in a cell model in which PSC833 blocked Pgp function almost completely and restored cell sensitivity to daunorubicin [34].…”

Acute Doxorubicin Insult in the Mouse Ovary Is Cell- and Follicle-Type Dependent

“…It is unclear whether these structures play a role in the apparent sensitivity of granulosa cells to DXR-induced DNA damage or are in fact a defense mechanism. One frequently observed feature of multidrug resistant cancer cells is compartmentalization of DXR and other chemotherapy agents into acidic intracellular compartments [31], [35], [61], [63], [65], [66], [67], [68], [69], [70], [71], [72], [73], [74], [75], [76], [77], [78], [79], [80], [81], [82], [83], [84], [85], [86], [87], [88], [89], [90], [91], [92], [93], [94], [95], [96], [97]; this compartmentalization is directly linked to limiting nuclear accumulation of DXR and therefore decreasing chemotherapy toxicity. Exceptions exist, however, such as the uterine drug-sensitive MES-SA cell line which accumulates DXR in lysosomes where the drug-resistant MES-SA/Dx5 cell line does not [76].…”

Improvement of nonviral p53 gene transfer in human carcinoma cells using glucosylated polyethylenimine derivatives

“…29 Briefly, cell suspensions containing 2.10 4 viable cells/mL were plated into 96 -well dishes and allowed to attach for 48 hours at 378C in a 5% CO 2 atmosphere. The culture medium was then removed and the cells were incubated for 2 hours at 378C in culture medium containing PEI or PEI ±DNA complexes.…”