dihydropyridines and Leukemia-P388

Aminoalkyl-substituted monomeric and dimeric dihydrodipyridopyrazines have been synthesized and evaluated as antitumor agents. Potent cytotoxic compounds were identified in both series. Biochemical and biophysical studies indicated that all these compounds strongly stabilized the duplex structure of DNA and some of them elicited a selectivity for GC-rich sequences. Sequence recognition by of the dimeric dihydrodipyridopyrazines is reminiscent of that of certain antitumor bisnaphthalimides. Compared to monomers, corresponding dimeric derivatives showed higher affinity for DNA. This property was attributed to a bisintercalative binding to DNA. This assumption was indirectly probed by electric linear dichroism and DNA relaxation experiments. DNA provides a bioreceptor for these dihydrodipyridopyrazine derivatives, but no poisoning of human topoisomerases I or II was detected. Most of the compounds efficiently inhibited the growth of L1210 murine leukemia cells and perturbed the cell cycle progression (with a G2/M block in most cases). A weak but noticeable in vivo antitumor activity was observed with one of the dimeric compounds. This studies identifies monomeric and dimeric dihydrodipyridopyrazines as a new class of DNA-targeted antitumor agents.

Topics: Animals; Antineoplastic Agents; Cell Line, Tumor; Dihydropyridines; DNA; DNA Topoisomerases, Type I; DNA Topoisomerases, Type II; DNA, Superhelical; Drug Screening Assays, Antitumor; Humans; Intercalating Agents; Leukemia P388; Mice; Pyrazines; Structure-Activity Relationship

Multidrug resistance has been a major problem in cancer chemotherapy. In this study, in vitro and in vivo modulations of MDR by ginsenoside Rg(3), a red ginseng saponin, were investigated. In flow cytometric analysis using rhodamine 123 as an artificial substrate, Rg(3) promoted accumulation of rhodamine 123 in drug-resistant KBV20C cells in a dose-dependent manner, but it had no effect on parental KB cells. Additionally Rg(3) inhibited [3H]vinblastine efflux and reversed MDR to doxorubicin, COL, VCR, and VP-16 in KBV20C cells. Reverse transcriptase-polymerase chain reaction and immuno-blot analysis after exposure of KBV20C cells to Rg(3) showed that inhibition of drug efflux by Rg(3) was due to neither repression of MDR1 gene expression nor Pgp level. Photo-affinity labeling study with [3H]azidopine, however, revealed that Rg(3) competed with [3H]azidopine for binding to the Pgp demonstrating that Rg(3) competed with anticancer drug for binding to Pgp thereby blocking drug efflux. Furthermore, Rg(3) increased life span in mice implanted with DOX-resistant murine leukemia P388 cells in vivo and inhibited body weight increase significantly.

Topics: Affinity Labels; Animals; ATP Binding Cassette Transporter, Subfamily B, Member 1; Azides; Biological Transport; Dihydropyridines; Disease Models, Animal; Drug Resistance, Multiple; Fluorescent Dyes; Ginsenosides; Humans; KB Cells; Leukemia P388; Mice; Rhodamine 123; Tritium; Tumor Cells, Cultured; Vinblastine

The structure activity relationships were studied on newly synthesized 1,4-dihydropyridine derivatives possessing a 1-pentyl group at the 4-position, and 3-pyridylpropylester was found to be one of the effective fragments for overcoming P-glycoprotein mediated multidrug-resistance (MDR) in cultured human cancer cells, in vitro. 3-Pyridylpropylester was also found to be one of the effective fragments for increasing the life span of P-glycoprotein overexpressing MDR P388 leukemia-bearing mice, in vivo. All compounds had weak calcium antagonistic activities, but there appeared no relationship between MDR reversing effect and calcium antagonistic activity.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; ATP Binding Cassette Transporter, Subfamily B, Member 1; Calcium; Combinatorial Chemistry Techniques; Dihydropyridines; Drug Resistance, Multiple; Humans; Inhibitory Concentration 50; Leukemia P388; Mice; Structure-Activity Relationship; Survival Rate; Transfection; Tumor Cells, Cultured; Vincristine

Newly synthesized 1,4-dihydropyridine derivatives possessing alkyl chains at the 4-position screened whether they could overcome P-glycoprotein-mediated multidrug resistance in cultured cancer cells and also leukemia-bearing animals. Of these derivatives, some could overcome drug resistance to doxorubicin and vincristine in multidrug resistant human cancer cell lines. Combined administration of vincristine and some of the derivatives significantly increased the life span of P-glycoprotein overexpressing multidrug-resistant P388 leukemia-bearing mice. The calcium antagonistic activities, an undesirable effects, were weaker than that of verapamil. These results suggested that the introduction of alkyl groups at the 4-position were effective for both overcoming multidrug resistance and reducing the calcium antagonistic activity.

Topics: Animals; ATP Binding Cassette Transporter, Subfamily B, Member 1; Calcium Channel Blockers; Dihydropyridines; Doxorubicin; Drug Design; Drug Resistance, Multiple; Humans; KB Cells; Leukemia P388; Mice; Models, Molecular; Molecular Conformation; Molecular Structure; Structure-Activity Relationship; Tumor Cells, Cultured; Vincristine

New N-alkylated 1,4-dihydropyridine derivatives were synthesized and their ability to overcome multidrug resistance was examined in vincristine-resistant P388 cells (P388/VCR cells). Compounds that possessed an arylalkyl substituent on the dihydropyridine ring nitrogen were more potent than verapamil in potentiating the cytotoxicity of vincristine against P388/VCR cells. However, neither drug effectively enhanced the antitumor activity of vincristine in tumor-bearing mice. Introduction of basic nitrogen-containing substituents on the side chain of 1,4-dihydropyridines gave improved activity in vitro and in vivo. The piperazine derivative 12c and 12o were more than 10 times as potent as verapamil in vitro. Four compounds selected for in vivo testing showed superior antitumor activity in P388/VCR-bearing mice in combination with vincristine. The structure-activity relationships of the compounds are discussed.

Topics: Alkylation; Animals; Chemical Phenomena; Chemistry, Physical; Dihydropyridines; Drug Resistance, Multiple; Drug Resistance, Neoplasm; Female; Leukemia P388; Magnetic Resonance Spectroscopy; Mice; Mice, Inbred BALB C; Mice, Inbred DBA; Stereoisomerism; Structure-Activity Relationship; Tumor Cells, Cultured; Verapamil; Vincristine

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

The clinical use of Ca++ antagonist agents as modulators of multidrug resistance is limited by their strong vasodilator activity. This study reports data obtained by testing a series of new 1,4 dihydropyridine derivatives (DHPs) for their in vitro resistance modulating activity and their Ca++ antagonist effect. All the tested DHPs are active to increase doxorubicin activity with dose modifying factor values ranging between 2 and 47 on P388/DX cells and 12 and 36 on LoVo/DX cells. Their resistance modulating action is exerted through an increase of DX intracellular level. The Ca++ antagonist activity of DHPs, evaluated as capacity to inhibit the KCl-induced contractions in isolated Guinea pig ileum strips, is not related to their resistance modulating activity. This finding makes it possible to select, for further in vivo evaluations, compounds IX, X and XI, which have strong ability to overcome multidrug resistance and low Ca++ antagonist effect.

Topics: Animals; Calcium; Dihydropyridines; Doxorubicin; Drug Resistance, Multiple; Drug Screening Assays, Antitumor; Drug Synergism; Guinea Pigs; Ileum; In Vitro Techniques; Leukemia P388; Tumor Cells, Cultured

The effects of a newly synthesized compound, N-ethoxycarbonyl-7-oxo-staurosporine (NA-382), on multidrug resistance in tumor cells were investigated. Protein kinase-inhibitory activity of NA-382 was lower but more selective to Ca2+/phospholipid-dependent protein kinase than that of staurosporine. NA-382 at noncytotoxic concentrations effectively reversed in vitro multidrug resistance of Adriamycin-resistant P388 (P388/ADR) cells, without influencing the drug sensitivity of sensitive P388 cells. NA-382 inhibited extrusion of vinblastine (VBL) and increased intracellular accumulation of VBL, more in P388/ADR cells than in sensitive P388 cells, with higher potency than staurosporine. This compound also reduced VBL resistance of other multidrug-resistant cell lines, AH66 and K562/ADR, by inhibiting VBL efflux and promoting VBL accumulation. NA-382 also dose dependently potentiated the effects of VBL and Adriamycin in P388/ADR-bearing mice. The toxicity of staurosporine was too high to use the combination with VBL in vitro and in vivo. NA-382 accumulated VBL in P388/ADR cells even after desensitization of Ca2+/phospholipid-dependent protein kinase by treatment with 12-O-tetradecanoylphorbol-13-acetate and 18 h, while being suppressed by 12-O-tetradecanoylphorbol-13-acetate added simultaneously or shortly before NA-382. Both staurosporine and NA-382 inhibited the photolabeling of [3H]azidopine on M(r) 140,000 P-glycoprotein in the plasma membrane from P388/ADR cells. These results indicate that this new staurosporine analogue, NA-382, reverses multidrug resistance by directly inhibiting the drug binding to P-glycoprotein, but not by Ca2+/phospholipid-dependent protein kinase inhibitory action.

Topics: Alkaloids; Animals; ATP Binding Cassette Transporter, Subfamily B, Member 1; Azides; Dihydropyridines; Doxorubicin; Drug Resistance; Drug Synergism; Female; Humans; In Vitro Techniques; Leukemia P388; Membrane Glycoproteins; Mice; Staurosporine; Tetradecanoylphorbol Acetate; Tumor Cells, Cultured; Vinblastine

The effect of thaliblastine (TBL, NSC-68075), a plant alkaloid, in over-coming multidrug resistance was investigated in doxorubicin (ADR)-resistant murine leukemic P388/R-84 cells. In the soft agar clonogenic assay, a nontoxic concentration of TBL (2 microM) reduced the 50% inhibitory dose of ADR (1-h exposure) from 10.8 to 1.4 microM with a dose modification factor of 7.7. Continuous treatment of P388/R-84 cells with ADR and TBL for 24 h further lowered the 50% inhibitory dose from 3.5 to 0.07 microM, the resistance level being decreased from 233-fold in the absence of TBL to 4.7-fold in the presence of TBL as compared to the parental P388 cells. Although ADR or TBL individually had no detectable effects on cell cycle traverse, the combination of the two drugs caused a significant G2 block. Flow cytometric analysis showed that TBL enhanced ADR retention in P388/R-84 cells in a dose- and time-dependent manner. TBL partially blocked the photolabeling of P-glycoprotein with [3H]azidopine, and this blocking effect was further enhanced in combination with ADR. Our results indicate that TBL can reverse multidrug resistance by direct interaction with P-glycoprotein, thereby increasing cellular ADR retention.

Topics: Affinity Labels; Animals; Antineoplastic Agents, Phytogenic; Aporphines; ATP Binding Cassette Transporter, Subfamily B, Member 1; Azides; Benzylisoquinolines; Carrier Proteins; Cell Cycle; Dihydropyridines; DNA, Neoplasm; Doxorubicin; Drug Resistance; Isoquinolines; Leukemia P388; Membrane Glycoproteins; Mice

Activities of a newly synthesized compound, N-ethoxycarbonyl-7-oxo-staurosporine (NA-382), on cyclic AMP-dependent protein kinase (A-kinase), Ca2+/phospholipid dependent protein kinase (C-kinase), and drug resistance were investigated and compared with those of staurosporine. Protein kinase-inhibitory activity of NA-382 was lower but more selective to C-kinase than that of staurosporine. NA-382 was less toxic to P388 cells and at a non-cytotoxic concentration completely reversed the vinblastine (VBL) resistance of Adriamycin-resistant P388 (P388/ADR) cells without influence on the effect of VBL on the parental P388/S cells. However, the cytotoxicity of staurosporine was too high to give the combination effect with VBL. NA-382 dose-dependently increased VBL-accumulation and inhibited VBL-efflux in P388/ADR with higher potency than staurosporine. Both compounds inhibited the photolabeling of [3H]azidopine on 140-kDa P-glycoprotein in the plasma membrane from the resistant cells. These results suggest that a staurosporine analog, NA-382, reverses multidrug resistance by inhibiting the drug-efflux system or P-glycoprotein.

Topics: Affinity Labels; Alkaloids; Animals; ATP Binding Cassette Transporter, Subfamily B, Member 1; Azides; Cell Division; Cell Line; Cell Membrane; Dihydropyridines; Dose-Response Relationship, Drug; Doxorubicin; Drug Resistance; Leukemia P388; Membrane Glycoproteins; Protein Kinase C; Staurosporine; Vinblastine

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

A newly synthesized dihydropyridine analogue, 2-[benzyl(phenyl)amino]ethyl 1,4-dihydro-2,6-dimethyl-5-(5,5-dimethyl-2-oxo-1,3,2-dioxaphosphorina n-2-yl)-1- (2-morpholinoethyl)-4-(3-nitrophenyl)-3-pyridinecarboxylate (PAK-200), at 1 microM completely reversed the resistance to vincristine in vincristine-resistant P388 mouse leukemia cells (P388/VCR), in vitro. PAK-200 at 2 microM inhibited the efflux of [3H]vincristine from P388/VCR and increased the accumulation of [3H]vincristine in P388/VCR to a level similar to that in P388 cells. P-Glycoprotein in membrane vesicles from P388/VCR cells was photolabeled with [3H]azidopine. The labeling was completely inhibited by 10 microM PAK-200. The calcium antagonistic activity of PAK-200 was about 1000 times lower than that of another dihydropyridine analogue, nicardipine. Experiments with P388 and P388/VCR-bearing mice showed that PAK-200 enhanced the effect of vincristine on both leukemia cells in vivo. These results suggest that PAK-200 interacts with P-glycoprotein and reverses drug resistance in P388 mouse leukemia cells in vitro, and that PAK-200 has an ability to potentiate the effect of vincristine on P388 mouse leukemia cells in vivo.

Topics: Animals; Blood Pressure; Dihydropyridines; Drug Resistance; Drug Synergism; Leukemia P388; Male; Mice; Nicardipine; Vincristine

To predict the clinical effect on leukemic disease of a combination regimen developed to circumvent multidrug resistance (MDR), we tested various antitumor agents in the presence and absence of AHC-52, a sensitizing agent for multidrug-resistant cells, in the i.v.-i.v. model of murine leukemia. In this model system, sensitive and resistant P388 murine leukemia cells are inoculated i.v. into mice, and each antitumor agent is injected via the i.v. route. Vincristine (VCR) had no effect on the survival of mice bearing VCR-resistant P388, a relatively poorly resistant subline, when given either as a single agent or in combination with AHC-52. In contrast, adriamycin (ADR) alone had no effect on these mice, but its combination with AHC-52 resulted in significant survival, the maximal value achieved being 196% (treated mice/control animals, T/C). Etoposide (VP-16) strongly enhanced survival, even when used alone, and this effect was markedly potentiated by AHC-52. Combination of any antitumor drug with AHC-52 was ineffective in mice bearing ADR-resistant P388, a highly resistant subline. On the other hand, AHC-52 strongly augmented the therapeutic efficacy of these antitumor agents in mice bearing the sensitive parent P388 leukemia, producing some curative effects. On the basis of these results, the feasibility of this type of combination therapy is discussed.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Dihydropyridines; Doxorubicin; Drug Resistance; Drug Synergism; Etoposide; Female; Leukemia P388; Mice; Mice, Inbred BALB C; Mice, Inbred DBA; Pyrazoles; Vincristine

Newly synthesized quinoline derivatives were investigated for their efficacy to reverse multidrug resistance (MDR). In this study, one of the most effective quinoline derivatives, MS-073, was compared with verapamil with regard to its ability to overcome MDR in vitro and in vivo. MS-073 at 0.1 microM almost completely reversed in vitro resistance to vincristine (VCR) in VCR-resistant P388 cells. The compound also reversed in vitro VCR, adriamycin (ADM), etoposide, and actinomycin D resistance in ADM-resistant human myelogenous leukemia K562 (K562/ADM) cells, ADM-resistant human ovarian carcinoma A2780 cells, and colchicine-resistant human KB cells. MS-073 administered i.p. daily for 5 days with VCR enhanced the chemotherapeutic effect of VCR in VCR-resistant P388-bearing mice. Increases in life span of 19-50% were obtained by the combination of 100 micrograms/kg of VCR with 3-100 mg/kg of MS-073, as compared to the control. The ability of MS-073 to reverse MDR was remarkably higher, especially at low MS-073 doses, than that of verapamil, both in vitro and in vivo. MS-073 enhanced accumulation of [3H]VCR in K562/ADM cells. Photolabeling of P-glycoprotein with 200 nM [3H]azidopine in K562/ADM plasma membranes was completely inhibited by 10 microM MS-073, indicating that MS-073 reverses MDR by competitively inhibiting drug binding to P-glycoprotein.

Topics: Affinity Labels; Animals; Antineoplastic Combined Chemotherapy Protocols; ATP Binding Cassette Transporter, Subfamily B, Member 1; Azides; Dihydropyridines; Drug Administration Schedule; Drug Resistance; Drug Screening Assays, Antitumor; Drug Synergism; Female; Leukemia P388; Membrane Glycoproteins; Mice; Mice, Inbred BALB C; Mice, Inbred DBA; Piperazines; Quinolines; Tumor Cells, Cultured; Verapamil; Vincristine

We recently reported that six 1,4-dihydropyridine derivatives out of 57 screened effectively over-came vincristine (VCR)-resistance in VCR-resistant (P388/VCR) leukaemia-bearing mice when the dihydropyridines and VCR were administered intraperitoneally (i.p.). Furthermore, among the six dihydropyridine derivatives, two compounds, NK-250 and NK-252, most effectively overcame VCR-resistance while exhibiting relatively low calcium antagonistic activity and toxicity. In this study, we examined whether NK-250 and NK-252 could potentiate the antitumour activities of etoposide in mice with drug-sensitive (P388/S) or VCR-resistant (P388/VCR) leukaemia cells when the anticancer agents and tumour cells were administered by various routes. In both groups of mice inoculated i.p. with P388/S- and P388/VCR-leukaemia cells, the oral (p.o.) administration of NK-250 combined with i.p. or intravenously (i.v.) administration of etoposide (ip-po-ip trials and ip-po-iv trials) dramatically potentiated the antitumour activity of etoposide. Although etoposide alone was less effective in treating mice inoculated i.v. with P388/S- and P388/VCR-leukaemia cells, p.o. administration of NK-250 combined with i.p. or i.v. administration of etoposide (iv-po-ip trials and iv-po-iv trials) potentiated the antitumour activity of etoposide to similar levels as in treating mice inoculated i.p. with leukaemia cells. These 1,4-dihydropyridines were therefore highly effective in potentiating anticancer drugs against both drug-sensitive and drug-resistant tumours.

Topics: Administration, Oral; Animals; Antineoplastic Combined Chemotherapy Protocols; Cell Line; Dihydropyridines; Dioxins; Drug Resistance; Drug Synergism; Etoposide; Injections, Intraperitoneal; Injections, Intravenous; Leukemia P388; Male; Mice

Newly synthesized 1,4-dihydropyridine derivatives (NK-compounds) were screened to determine whether they could overcome vincristine (VCR) resistance in VCR-resistant (P388/VCR) leukemia-bearing mice. Among the 57 NK-compounds examined, six compounds had strong reversing ability (Grade A), 18 partially overcame the resistance (Grade B), and 33 did not reverse the resistance (Grade C). The ability to overcome resistance varied considerably with the nature of substituents at positions 3.5 of the 1,4-dihydropyridine, and the most suitable substituents were the pyridylalkyl-including esters. Calcium antagonistic activity of NK-compounds having pyridylalkyl-including esters at positions 3.5 and dithiene ring at position 4 of the 1,4-dihydropyridine was greater than in those compounds having the dioxene ring at position 4. NK-242, which was assessed at Grade A and had no calcium antagonistic activity, improved therapeutic effects in both VCR-sensitive (P388/S) leukemia- and P388/VCR leukemia-bearing mice when combined with VCR. Fourteen NK-compounds were screened to determine whether they could inhibit photoaffinity labeling of the P-glycoprotein (Mr 170,000 glycoprotein) in a multidrug-resistant cell line by [3H]azidopine. All six compounds of Grade A and two of the three compounds of Grade B almost completely inhibited the labeling of Mr 170,000 glycoprotein at 1 to 10 microM. Thus there was a good correlation between the ability to reverse VCR resistance in vivo and the inhibition of photoaffinity labeling of Mr 170,000 glycoprotein.

Topics: Affinity Labels; Animals; ATP Binding Cassette Transporter, Subfamily B, Member 1; Azides; Blood Pressure; Calcium Channel Blockers; Dihydropyridines; Drug Resistance; Leukemia P388; Male; Membrane Glycoproteins; Mice; Mice, Inbred BALB C; Mice, Inbred DBA; Structure-Activity Relationship; Vincristine

We investigated whether two representative 1,4-dihydropyridine derivatives, NK-250 and NK-252, could potentiate the antitumor activity of multiple anticancer agents including vincristine (VCR), vinblastine, vindesine and actinomycin D in drug-resistant tumor cells and their parental drug-sensitive tumor cells. NK-250 and NK-252 at 5-10 microM almost completely reversed VCR resistance in cultured VCR-resistant P388/VCR cells derived from the mouse drug-sensitive P388/S leukemia cell line and also potentiated the cytocidal activity of VCR in drug-sensitive P388/S cells. NK-250 and NK-252 at 1-10 microM inhibited the photoaffinity labeling by [3H]azidopine of the cell-surface 170,000-molecular-weight P-glycoprotein. In chemotherapeutic experiments with leukemia-bearing mice, NK-250 or NK-252 was orally administered in combination with different drugs of the MDR phenotype administered intraperitoneally. The antitumor activity of the various combinations was found to be augmented in mice bearing P388/S- and P388/VCR-leukemia. Among the combinations examined, the combination of NK-250 and VCR was the most effective. These two 1,4-dihydropyridines, NK-250 and NK-252, are unique compounds because they were effective not only in circumventing the drug resistance, but also in potentiating the action of antitumor drugs against drug-sensitive tumors.

Topics: Administration, Oral; Animals; Antineoplastic Combined Chemotherapy Protocols; ATP Binding Cassette Transporter, Subfamily B, Member 1; Azides; Dactinomycin; Dihydropyridines; Dioxins; Drug Resistance; Drug Synergism; Leukemia P388; Male; Membrane Glycoproteins; Mice; Mice, Inbred Strains; Tritium; Vinblastine; Vincristine; Vindesine

A novel compound partially analogous to nifedipine, AHC-52, was found to sensitize multidrug-resistant tumor cells. AHC-52 at 0.5 microgram/ml completely reversed the in vitro resistance to vincristine (VCR) in VCR-resistant P388 cells (P388/VCR). Of various regimens examined for the in vivo treatment of P388/VCR-bearing mice, the combination of 0.05 mg/kg of VCR with 100 mg/kg twice a day of AHC-52 daily demonstrated the best result with a 206% increase in life prolongation. This result was comparable with that observed in parental P388-bearing mice treated with the optimal dose of VCR alone, indicating almost complete circumvention of resistance by combination VCR-AHC-52 therapy. In addition, the combination of both agents exhibited therapeutic effects in the treatment of P388-bearing mice with some long term survivors. This result was presumably due to the elimination of heterogeneity of VCR sensitivity in this cell population. These results suggest that combination chemotherapy using a sensitizing agent such as AHC-52 will be effective in not only circumvention of multidrug resistance but also retardation of its occurrence.

Topics: Animals; Dihydropyridines; Drug Resistance; Drug Synergism; Female; Leukemia P388; Leukemia, Experimental; Mice; Mice, Inbred BALB C; Mice, Inbred DBA; Nifedipine; Pyrazoles; Vincristine

The disodium salt of 2,6-dimethyl-1,4-dihydropyridine-3,5-bis-carbonyl hydroxyacetic acid (I) used in the mg/kg dose decreases the cyclophosphane toxicity in mice and potentiates the cytostatic activity of cyclophosphane, 5-fluorouracil and arabinosyl cytosine against leukemia P388, murine sarcoma 37 and Walker's carcinosarcoma. Administered alone I exhibits no antitumour activity. The potentiation of the antitumour effect of drugs appears independent of the administration schedule. Biochemical evidence indicates that I does not block DNA synthesis in leukemic cells in vitro, but significantly enhances the DNA-blocking effect of cyclophosphane in the same cells in vivo.

Topics: Animals; Antineoplastic Agents; Cells, Cultured; Dihydropyridines; DNA, Neoplasm; Drug Synergism; Lethal Dose 50; Leukemia P388; Male; Mice; Neoplasms, Experimental; Pyridines; Sarcoma 37

Six new 1,4-dihydropyridine derivatives were evaluated in vitro for antimicrobial and cytotoxic effects and in vivo for antineoplastic activity. These compounds inhibited the growth of most of Gram-positive and Gram-negative bacteria at concentrations of 50 and 100 micrograms/ml. Concentrations effective against fungi were somewhat lower (25-50 micrograms/ml). The growth of mycobacteria was inhibited at concentrations of 3.1-25 micrograms/ml. Compound IV inhibited the growth of pathogenic mycobacteria including M. tuberculosis resistant to SM and INH at 3.1 or 6.2 micrograms/ml. In cytotoxicity assays, compound II, IV and V appeared the most active. However, none of the 1,4-dihydropyridine derivatives affected the survival time of mice with P388 and L1210 leukemias or melanoma B16. The growth of subcutaneous tumors of sarcoma 180 was inhibited by compounds I, III, IV and V. The effect was dose related.

Topics: Animals; Anti-Bacterial Agents; Anti-Infective Agents; Antineoplastic Agents; Bacteria; Dihydropyridines; Drug Evaluation, Preclinical; Fungi; Leukemia L1210; Leukemia P388; Melanoma; Mice; Pyridines; Species Specificity; Structure-Activity Relationship