dihydropyridines and Colonic-Neoplasms

Amooranin (AMR), a plant terpenoid, isolated from Amoora rohituka, was investigated for its ability to overcome multidrug resistance in human leukemia and colon carcinoma cell lines. AMR IC(50) values of multidrug-resistant leukemia (CEM/VLB) and colon carcinoma (SW620/Ad-300) cell lines were higher (1.9- and 6-fold) than parental sensitive cell lines (CEM and SW620). AMR induced G(2)+M phase-arrest during cell cycle traverse in leukemia and colon carcinoma cell lines and the percentage of cells in G(2)+M phase increased in a dose-dependent manner. Coincubation of tumor cells with both DOX and AMR reversed DOX resistance in 104-fold DOX-resistant CEM/VLB and 111-fold DOX-resistant SW620/Ad-300 cell lines with a dose modification factor of 50.9 and 99.6, respectively. Flow cytometric assay showed that AMR causes enhanced cellular DOX accumulation in a dose-dependent manner. AMR inhibits photolabeling of P-glycoprotein (P-gp) with [(3)H]-azidopine and the blocking effect enhanced with increasing concentrations of AMR. Our results show that AMR competitively inhibits P-gp-mediated DOX efflux, suggestive of a mechanism underlying the enhanced DOX accumulation and reversal of multidrug resistance by AMR.

Topics: Affinity Labels; Antineoplastic Agents, Phytogenic; ATP Binding Cassette Transporter, Subfamily B, Member 1; Azides; Carcinoma; Cell Cycle; Cell Survival; Colonic Neoplasms; Dihydropyridines; Dose-Response Relationship, Drug; Doxorubicin; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Humans; Leukemia; Triterpenes; Tumor Cells, Cultured

To gather further insight into the interaction between P-glycoprotein (Pgp) and its substrates, 167 compounds were analyzed in multidrug resistant human colon carcinoma cells. These compounds were selected from the National Cancer Institute Drug Screen repository using computer-generated correlations with known Pgp substrates and antagonists. The compounds were prospectively defined as Pgp substrates if cytotoxicity was increased > or =4-fold by the addition of cyclosporin A (CsA) and as Pgp antagonists if inhibition of efflux increased rhodamine accumulation by 4-fold. Among the 84 agents that met either criterion, 35 met only the criterion for substrates, 42 met only the criterion for antagonists, and only seven met both criteria. Thus, compounds interacting with Pgp form two distinct groups: one comprising cytotoxic compounds that are transported and have poor or no antagonistic activity and a second comprising compounds with antagonistic activity and no evidence of significant transport. Vinblastine accumulation and kinetic studies performed on a subset of 18 compounds similarly differentiated substrates and antagonists, but inhibition of 3H-azidopine labeling and induction of ATPase activity did not. These data support an emerging concept of Pgp in which multiple regions instead of specific sites are involved in drug transport.

Topics: Adenosine Triphosphatases; Affinity Labels; Antineoplastic Agents; Antineoplastic Agents, Phytogenic; ATP Binding Cassette Transporter, Subfamily B, Member 1; Azides; Biological Transport, Active; Colonic Neoplasms; Cyclosporine; Dihydropyridines; Drug Interactions; Drug Resistance, Multiple; Drug Screening Assays, Antitumor; Fluorescent Dyes; Humans; Immunosuppressive Agents; Rhodamines; Stimulation, Chemical; Substrate Specificity; Tritium; Tumor Cells, Cultured; Vinblastine

The pharmacokinetics of oral dexniguldipine, a new multidrug-resistance-modifying agent under clinical evaluation, and its pyridine metabolite M-1 were determined in plasma, tumor, and renal tissue in Wag/Rij rats bearing a multidrug-resistant CC531 colon adenocarcinoma tumor under the renal capsule. The pharmacokinetics were studied in four experiments. After a single administration of dexniguldipine (30 mg/kg), tumors and kidneys were collected after 5 (experiment 1), 24 (experiment 2), and 48 h (experiment 3). In the fourth experiment, dexniguldipine was given once daily for 3 consecutive days at a dose of 30 mg/kg. In all experiments, plasma samples were collected at regular intervals. The concentrations of dexniguldipine and M-1 could be determined in plasma in most of the rats at up to 32 h after drug administration. The area under the curve (AUC) of dexniguldipine and M-1 varied by a factor of 2-6 in the four experiments. High tumor-tissue concentrations of dexniguldipine were observed. The concentrations were highest in the multiple-dose experiment (2014 +/- 1005 ng/g tissue). High degrees of correlation (> 0.8) were established between the concentrations of dexniguldipine measured in plasma and tumor as well as renal tissue. Overall, tumor-tissue concentrations of M-1 comprised one-third of the dexniguldipine concentrations measured.

Topics: Adenocarcinoma; Animals; Antineoplastic Agents; Colonic Neoplasms; Dihydropyridines; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Humans; Kidney; Neoplasm Transplantation; Pyridines; Rats; Rats, Inbred Strains

The chemosensitizing potency of dexniguldipine hydrochloride (B8509-035) on epidoxorubicin was assessed in a multidrug-resistant (MDR) tumour model, the intrinsic MDR rat colon carcinoma CC531. In vitro in the sulphorhodamine B cell-viability assay the cytotoxicity of epidoxorubicin was increased approximately 15-fold by co-incubation with 50 ng/ml dexniguldipine. In vivo concentrations of dexniguldipine 5 h after a single oral dose of 30 mg/kg were 72 (+/- 19 SD) ng/ml in plasma and 925 (+/- 495 SD) ng/g in tumour tissue. Levels of the metabolite of dexniguldipine, M-1, which has the same chemosensitizing potential, were 26 (+/- 6 SD) ng/ml and 289 (+/- 127 SD) ng/g respectively. The efficacy of treatment with 6 mg/kg epidoxorubicin applied intravenously combined with 30 mg kg-1 day-1 dexniguldipine administered orally for 3 days prior to epidoxorubicin injection was evaluated on tumours grown under the renal capsule. Dexniguldipine alone did not show antitumour effects in vivo. Dexniguldipine modestly, but consistently, potentiated the tumour-growth-inhibiting effect of epidoxorubicin, reaching statistical significance in two out of four experiments. In conclusion, these experiments show that dexniguldipine has potency as an MDR reverter in vitro and in vivo in this solid MDR tumour model.

Topics: Adenocarcinoma; Animals; Antineoplastic Combined Chemotherapy Protocols; Biotransformation; Colonic Neoplasms; Dihydropyridines; Drug Resistance, Multiple; Drug Screening Assays, Antitumor; Drug Synergism; Epirubicin; Male; Neoplasm Transplantation; Rats; Rats, Inbred Strains; Tumor Cells, Cultured

We have previously shown that a series of N-alkylated 1,4-dihydropyridines potentiate the therapeutic efficacy of vincristine in vincristine-resistant P388 leukemia. The purpose of this study was to investigate the ability of one of the compounds, AC394, and its enantiomers to potentiate the antitumor activity of adriamycin against colon cancer cells in vitro and in vivo.. The effects of AC394 on potentiation of adriamycin cytotoxicity and enhancement of its accumulation were evaluated using colon 26, HCT-15 and MCF-7 cells. Furthermore, the activities of AC394 and its enantiomers were compared. We also studied the combined effects of (+)-AC394 and adriamycin on subcutaneously (s.c.)-implanted and liver metastasis tumor models.. AC394 potentiated the cytotoxicity of adriamycin and enhanced its accumulation in colon cancer cells (colon 26 and HCT-15), which are known to express P-GP (P-glycoprotein) intrinsically. Enhancement of adriamycin accumulation by AC394 was found in s.c.-implanted colon 26 cells in vivo. Although both enantiomers of AC394 showed equal activity in vitro, (+)-AC394 was more effective than (-)-AC394 given orally. (-)-AC394 was found to be cleared more rapidly from the plasma than (+)-AC394. Thus, (+)-AC394 was evaluated for further study. Administration of (+)-AC394 significantly potentiated the antitumor activities of adriamycin in human colon cancer HCT-15 cells implanted s.c. Furthermore, in the liver metastasis model using colon 26 cells, a model completely resistant to adriamycin, the combination therapy of adriamycin with (+)-AC394 produced superior antitumor effects over adriamycin alone.. A newly synthesized N-alkylated 1,4-dihydropyridine derivative, (+)-AC394, showed superior effects on the potentiation of adriamycin antitumor and antimetastatic activities in vivo. These results suggest that this combination may have therapeutic efficacy not only against primary colon cancers but also against metastatic liver cancer.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Cell Survival; Colon; Colonic Neoplasms; Dihydropyridines; Dose-Response Relationship, Drug; Doxorubicin; Drug Resistance, Neoplasm; Drug Synergism; Female; Humans; Liver Neoplasms; Mice; Mice, Nude; Tumor Cells, Cultured

Two new dihydropyridine derivatives with low calcium channel affinity, S16317 and S16324, were found to fully overcome multidrug resistance in vitro. These two compounds increased doxorubicin cytotoxicity on the human COLO 320DM cell line and completely reversed the vincristine resistance of murine P388/VCR cells. In vivo, S16324 administered p.o. (200 mg/kg on days 1 to 4) or i.p. (50 mg/kg on days 1, 5, 9) in combination with vincristine (i.p.) restored the antitumor activity of vincristine in P388/VCR-bearing mice. S16317 showed a reversing activity when administered p.o., i.v. (days 1 to 4) or i.p. (days 1, 5, 9) at the same dose (25 mg/kg), suggesting a remarkable bioavailability. Moreover, these two compounds potentiated the antitumor activity of vincristine in the sensitive P388 leukemia, increasing the number of long-term survivors. These results suggest that combination chemotherapy using S16317 or S16324 would be effective not only in circumventing multidrug resistance but also in preventing the emergency of a population of resistant tumor cells in sensitive tumors.

Topics: Adenocarcinoma; Animals; Antineoplastic Combined Chemotherapy Protocols; Calcium Channels; Colonic Neoplasms; Dihydropyridines; Doxorubicin; Drug Resistance, Multiple; Drug Screening Assays, Antitumor; Drug Synergism; Felodipine; Female; Humans; Leukemia P388; Mice; Mice, Inbred DBA; Neoplasm Transplantation; Tumor Cells, Cultured; Vincristine

Two human colon carcinoma drug resistant clones (LoVo-IDA-1 and LoVo-IDA-2) were selected by continuous pressure of LoVo parent cell lines to idarubicin (IDA). Both cell sublines exhibited a typical multidrug resistance (MDR) phenotype but, despite IDA selection, the resistance index (RIext) was higher for daunorubicin (DAU) (RIext = 101-112) than for IDA (RIext = 20-23). A similar pattern of cross-resistance was also observed in two (DOX) doxorubicin-selected LoVo cell lines (LoVo-DOX-1 and LoVo-DOX-2). All the MDR cell lines exhibited decreased drug accumulation and increased intracellular drug tolerance as evidenced by the greater intracellular amount of drug required to cause a 50% growth inhibition (IC50int) compared to their parent cell line. The differences between DAU and IDA RIext exhibited by MDR cells were a function of intracellular resistance. DAU IC50int was 13.9 and 14.9 times higher in LoVo-IDA-1,2 and 6.4 and 6.2 in LoVo-DOX-1,2 cell lines, respectively, than in LoVo-sensitive cells, whereas IDA IC50int was only 3.6 and 3.2 times higher in LoVo-IDA-1,2 and 2.2 and 2.3 in LoVo-DOX-1,2 cell lines, respectively. Conversely, variations in IDA accumulation between resistant and sensitive cells were similar to those observed for DAU [the ratios between DAU uptake in sensitive and resistant cells were almost identical (P = NS) to those observed for IDA]. Differences between IDA and DAU intracellular distribution accounted for the relatively higher DAU intracellular resistance. In fact nuclear/cytoplasmic (N/C) DAU fluorescence ratio was higher (P < 0.01) in sensitive (N/C = 3.4 +/- 2.7) than in MDR cells (N/C ranging from 0.31 +/- 0.2 to 0.41 +/- 0.1). In contrast, no significant (P = NS) differences were observed in IDA N/C ratios between sensitive and MDR cells (N/C ranging from 0.16 +/- 0.1 to 0.20 +/- 0.1). In MDR cells, 1-hr VER (10 microM) treatment partially reverted both DAU N/C ratios and intracellular DAU resistance but neither changes in IDA N/C ratios nor variation in intracellular IDA resistance were observed following VER exposure. In conclusion, the greater intracellular drug tolerance that MDR cells show for DAU compared to IDA makes IDA more effective than DAU in MDR cells overexpressing P-glycoprotein (P-gp).

Topics: Affinity Labels; ATP Binding Cassette Transporter, Subfamily B, Member 1; Azides; Biological Transport; Cell Membrane; Cell Nucleus; Clone Cells; Colonic Neoplasms; Daunorubicin; Dihydropyridines; DNA Topoisomerases, Type II; Drug Resistance, Multiple; Fluorescence; Humans; Idarubicin; Tumor Cells, Cultured

A new triazinoaminopiperidine derivative, Servier 9788 (S9788), was investigated for its ability to increase Adriamycin (ADR) accumulation and retention in two rodent (P388/ADR and DC-3F/AD) and three human (KB-A1, K562/R and COLO 320DM) cell lines displaying the P-glycoprotein (P-gp)-mediated multidrug resistance (MDR) phenotype. Depending on the cell line S9788 was shown to be two to five times more active and five to 15 times more potent than Verapamil (VRP) in increasing ADR accumulation in resistant cells. ADR retention in KB-A1 cells maintained in a concentration of 10 microM S9788 was twice that in VRP-treated cells, and similar to that measured in the untreated sensitive KB-3-1 cells. Although 5 microM S9788 and 50 microM VRP gave the same values of ADR uptake in KB-A1 cells, S9788 was shown to induce a greater ADR retention following cell wash and post-incubation in resistance modifier- and ADR-free medium. Taking into account that S9788 had no effects on ADR accumulation and retention in sensitive KB-3-1 cells, it can be suggested that S9788 inhibits specifically the P-gp dependent ADR efflux, and in a manner less reversible than that observed with VRP. Moreover, [3H]azidopine photolabeling of P-gp, in P388/ADR plasma membranes, was completely inhibited by 100 microM S9788. Although S9788, as VRP, had no effect on the cell cycle of P388 cells, 5 microM S9788 increased 700-fold the efficacy of ADR to block P388/ADR cells in the G2+M phase of the cell cycle. Together, these results show that the sensitization, by S9788, of cell lines resistant to ADR is mainly due to an increase in ADR accumulation and retention, leading to an increase in the number of resistant cells blocked in the G2+M phase.

Topics: Adenocarcinoma; Animals; Antineoplastic Agents; ATP Binding Cassette Transporter, Subfamily B, Member 1; Azides; Carcinoma, Squamous Cell; Cell Cycle; Cell Membrane; Cells, Cultured; Colonic Neoplasms; Cricetinae; Cricetulus; Dihydropyridines; Doxorubicin; Drug Resistance; Flow Cytometry; Fluorescence; Humans; Kinetics; Leukemia P388; Leukemia, Myeloid, Acute; Lung; Membrane Glycoproteins; Mice; Piperidines; Sensitivity and Specificity; Triazines; Tritium; Tumor Cells, Cultured; Verapamil