Reversal effects of Ca2+ antagonists on multidrug resistance via down-regulation of MDR1 mRNA.

In previous reports, the effects of 12 Ca2+ antagonists on a multidrug resistant transporter, P-glycoprotein/MDR1, were evaluated in terms of those on MDR1-mediated transport of [3H]digoxin and the sensitivity of vinblastine sulfate or paclitaxel, and they were able to be classified into 4 subgroups based on their actions, as those with transport inhibition and sensitivity recovery, those with or without transport inhibition but marginal sensitivity recovery, and those without both. In this study, our previous findings were confirmed by the resistance against doxorubicin hydrochloride and daunorubicin hydrochloride, and by the recovery of [3H] vinblastine sulfate accumulation. Furthermore, it was found that the effects of 12 Ca2+ antagonists on the sensitivity recovery were also explained by the down-regulation of MDR1 mRNA, suggesting a novel mechanism to reverse the MDR1-mediated multidrug resistance.

Three-dimensional, but not two-dimensional, culture results in tumor growth enhancement after exposure to anticancer drugs.

Previously, we have adapted a recently developed three-dimensional chemosensitivity test, the collagen gel droplet embedded culture drug sensitivity test (CD-DST), for evaluation of chemosensitivity of 12 anticancer drugs against colorectal adenocarcinoma, and surprisingly, it was found that tumor growth enhancement was occasionally observed even after exposure to anticancer drugs. In this study, the CD-DST was applied for human cervical carcinoma cell line HeLa-Ohio (HeLa) cells and its MDR1/P-glycoprotein-overexpressing subline, Hvr100-6 cells, and 12 anticancer drugs were assessed in terms of chemosensitivity and deterioration of tumor, and the results were compared with those by two-dimensional WST-1 assay. Growth enhancement was observed in Hvr100-6 cells, not in HeLa cells, for mitomycin C with the ratio of total volume of colonies in the treated group to that in the untreated group (T/C%) of 135.

Effects of St John's wort and hypericin on cytotoxicity of anticancer drugs.

St John's wort (SJW) is Hypericum perforatum L., Hypericaceae, a herbaceous perennial plant native to Europe and Asia, and its various preparations are widely used for the treatment of mild-to-moderately severe depressive disorders. With increasingly prevalent use, the interactions with SJW preparations with co-administered drugs have been reported, presumably via MDR1-mediated processes.

Gene expression profiles of ABC transporters and cytochrome P450 3A in Caco-2 and human colorectal cancer cell lines.

Purpose: The mRNA levels of MDR1 (P-glycoprotein), multidrug resistance-associated proteins (MRP1, MRP2), cytochrome P450 3A (CYP3A) and villin in human colorectal cell lines (HCT-15, LoVo DLD-1, HCT-116 and SW620) were quantitatively compared with those in Caco-2 cells.

Methods: The mRNA levels were determined by real time quantitative polymerase chain reaction and expressed as the relative concen trations of MDR1 mRNA to glyceraldehyde-3-phosphate dehydro genase (GAPDH) mRNA. RESULTSl MDR1 mRNA was expressed in HCT-15 LoVo and DLD-1 cells at similar or lower level to Caco-2.

Effects of reactive oxygen species on cell proliferation and death in HeLa cells and its MDR1-overexpressing derivative cell line.

In this paper, the effects of H2O2, a typical reactive oxygen species (ROS), on cell proliferation or death were examined using the human cervical carcinoma cell line HeLa and its MDR1-overexpressing subline, Hvr100-6, which was established by stepwise exposure to vinblastine. It was confirmed that the growth of HeLa cells was enhanced by H2O2 at relatively low concentrations in a concentration-dependent manner, and the growth enhancement was suppressed by antioxidants. Doxorubicin and daunorubicin also enhanced the growth of HeLa cells at concentrations lower than IC50 values, and the antioxidants suppressed this effect, being consistent with the fact that both anticancer drugs generate ROS.

Effects of 12 Ca2+ antagonists on multidrug resistance, MDR1-mediated transport and MDR1 mRNA expression.

The effects of 12 Ca(2+) antagonists on MDR1 were examined by two independent models: the inhibitory effect on MDR1-mediated transport of [(3)H]digoxin using MDR1-overexpressing LLC-GA5-COL150 cell monolayers and the reversal effect on cytotoxicity of vinblastine or paclitaxel using MDR1-overexpressing Hvr100-6 cells. The inhibitory effects on [(3)H]digoxin transport were assessed as the 50% inhibitory concentration during 4 h exposure, and the values were the lowest for nicardipine (4.54 microM), manidipine (4.

Cytotoxic effects of 27 anticancer drugs in HeLa and MDR1-overexpressing derivative cell lines.

The cytotoxic effects of 27 anticancer drugs including amrubicin, vinorelbine, paclitaxel, docetaxel, gemcitabine, and irinotecan were evaluated in human cervical carcinoma HeLa cells, and drug-resistant HeLa-derived Hvrl-1, HvrlO-6, and Hvr100-6 cells, which were newly established by stepwise exposure to vinblastine. FACS and RT-PCR analysis indicated that MDR1 (P-glycoprotein) was induced without any alterations in expression of its related transporters. Hvrl00-6 cells showed 2- to 200-fold higher resistance to anthracyclines than HeLa cells, and unexpectedly showed slight resistance to idarubicin and amrubicin.

Simvastatin and lovastatin, but not pravastatin, interact with MDR1.

The 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, pravastatin, was compared with simvastatin and lovastatin from the viewpoint of susceptibility to interaction with or via the multidrug transporter, MDR1 (P-glycoprotein). This was carried out using the MDR1-overexpressing cell line LLC-GA5-COL150, established by transfection of MDR1 cDNA into porcine kidney epithelial LLC-PK1 cells, and [3H]digoxin, which is a well-documented substrate for MDR1. Pravastatin, at 25-100 microM, had no effect on the transcellular transport of [3H]digoxin whereas simvastatin and lovastatin suppressed the basal-to-apical transport of [3H]digoxin and increased the apical-to-basal transport.

Real-time quantitative polymerase chain reaction for MDR1, MRP1, MRP2, and CYP3A-mRNA levels in Caco-2 cell lines, human duodenal enterocytes, normal colorectal tissues, and colorectal adenocarcinomas.

The expression levels of mRNAs for MDR1 (P-glycoprotein), multidrug resistance-associated proteins (MRP1, MRP2), and cytochrome P450 3A (CYP3A) in Caco-2 cells were quantitatively compared with those in human duodenal enterocytes, normal colorectal tissues, and colorectal adenocarcinomas. Caco-2 cells (passages 36-88) were kindly supplied by several laboratories in Japan. Human duodenal enterocytes were obtained from five healthy male volunteers.