Influence of S9788, a new modulator of multidrug resistance, on the cellular accumulation and subcellular distribution of daunorubicin in p‐glycoprotein‐expressing MCF7 human breast adenocarcinoma cells

Abstract

A triazjnoaminopiperidine derivative synthesized as a modulator of multidrug resistance, S9788, was investigated in the human breast adenocarcinoma MCF7"= cell line expressing P-glycoprotein. In addition to being less sensitive to daunorubicin, the resistant cell line showed dramatic alterations in the subcellular distribution of daunorubicin, as observed via fluorescence microscopy and quantified via tritiated daunorubicin nuclear distribution analysis. Compared to verapamil and cyclosporin A at 2 and 5 pmoyliter, S9788 proved to be more potent in restoring the cellular accumulation and the subcellular distribution of daunorubicin in the resistant cells. Significant activity of S9788 was observed at 2 FmoYliter, which is clinically achievable, and S9788 restored the nuclear distribution of the drug to the level observed in the parental sensitive cell line. Consequently, the restoration of the cytotoxicity of daunorubicin by S9788 was nearly complete (>!lo%) at 2 pmoyliter, whereas cyclosporin A reached this level of activity at 5 VmoVliter, and verapamil was always less active at both concentrations. These results suggest that the modulation of multidrug resistance by S9788 is not only related to the enhancement of the cellular accumulation but also especially by the restoration of the subcellular distribution of the drugs to their nuclear sites of action.

Determination of intracellular organelles implicated in daunorubicin cytoplasmic sequestration in multidrug-resistant MCF-7 cells using fluorescence microscopy image analysis

“…Our results demonstrating that Golgi vesicles containing P-gp could explain mainly intracellular DNR sequestration are in agreement with these data and suggest that functional cytoplasmic P-gp should exist in MCF-7 DXR in addition to surface P-gp (6). From the present study, no clear relationship between DNR sequestration in Golgi vesicles and apoptosis induction can be established.…”

“…2, 1B and 1D). No or few co-localizations of DNR and DiOC 6 , probing endoplasmic reticulum, were detected in …”

“…The filter set to detect daunorubicin and AO (acidic compartment) consisted of a 400 -440 or 460 -490 nm bandpass (BP) excitation filter, a 570 nm dichroic mirror (DM) and a 590 nm long-pass (LP) barrier filter. AO (DNA labeling), NBD and DiOC 6 were detected using a filter set composed of a 460 -490 nm BP excitation filter, a 505 nm DM and a 510 -550 nm BP filter. LB was detected using a filter set composed of a 330 -385 nm BP excitation filter, a 410 nm DM and a 420 -460 nm BP filter.…”

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

“…Our previous results (19) showed that S9788 modulates the intracellular accumulation of daunorubicin. We further suggested that the subcellular targets located in the membrane of vesicular systems are involved in the protection of specific intracellular or nuclear targets in resistant cells—as already suggested for verapamil and daunorubicin (20).…”

Influence of SDZ‐PSC833 on daunorubicin intracellular accumulation in bone marrow specimens from patients with acute myeloid leukaemia

“…We previously reported (Guerci et al, 1995;Merlin et al, 1994) that doublelabelling flow cytometry enables the simultaneous determination of PGP expression and its functionality through IDF. This analytical procedure was validated in demonstrating that IDF correlated with tritiated daunorubicin intracellular accumulation (Merlin et al, 1994) and was used to investigate the modulating activity of second-generation MDR modulators such as S9788 (Merlin et al, 1994(Merlin et al, , 1995a and tiapamil analogues (Abderrabi et al, 1996), as well as non-chemical modulation by liposome-encapsulated daunorubicin (Merlin et al, 1995b). This technique was recently validated through a multicentric assay in a leukaemic cell line .…”