Biochemical parameters of resistance of an adriamycin-resistant subline of P388 leukemia to emetine, an inhibitor of protein synthesis.

The effects of emetine on protein and DNA synthesis in vitro and in vivo were compared in P388 leukemia cells (P388/S) and in an adriamycin-resistant subline of P388 leukemia (P388/ADR), which was completely cross-resistant in vivo to emetine. In P388/ADR cells in vitro no apparent resistance to emetine was found; no difference in cytotoxicity was evident in P388/S or P388/ADR cells exposed to emetine in vitro for 1 or 6 hours. Protein and DNA synthesis was inhibited to a similar extent in P388/S and P388/ADR cells at equivalent concentrations of the drug. However, inhibition of protein synthesis by emetine in P388/ADR cells was more reversible than in P388/S cells when the cells were exposed to emetine and subsequently incubated in drug-free medium for 1 hour prior to addition of labeled L-leucine. Differences between P388/S and P388/ADR cells were evident in vivo. The duration of inhibition (greater than 90%) of protein and DNA synthesis in P388/ADR cells was about 8 hours compared to 24 hours in P388/S cells following administration of a therapeutic dose of 25 mg emetine/kg to tumor-bearing mice. The level of radioactivity in the P388/ADR cells 24 hours after in vivo administration of the emetine analog, (+/-)-[3'-14C]2,3-dehydroemetine, was only 26% of that in P388/S cells. This evidence suggests that the resistance of P388/ADR to emetine is due to decreased retention of the drug.

Circumvention of adriamycin resistance: effect of 2-methyl-1,4-naphthoquinone (vitamin K3) on drug cytotoxicity in sensitive and MDR P388 leukemia cells.

The effect of vitamin K3 (2-methyl-1,4-naphthoquinone) on Adriamycin (ADR) induced growth inhibition of drug sensitive and multidrug resistant P388 leukemia cells was evaluated. Exposure to ADR concentrations of 100-5000 ng simultaneously with 1 microM vitamin K3 elicited an enhanced inhibition of tumor cell survival. The effect of treatment with ADR alone, or in combination with vitamin K3 on DNA and RNA biosynthesis in the sensitive and resistant tumor cells, was also assessed. DNA and RNA biosynthesis inhibition was increased in P388/S (the parental cell line) and P388/ADR cells (the ADR resistant cell line which exhibits the multidrug resistant (MDR) phenotype) exposed to ADR after pretreatment for 3 h with vitamin K3. Concurrent administration in vivo of vitamin K3 and ADR illustrated a therapeutically significant increase (P less than 0.05) in the life span of sensitive and resistant tumor cell bearing animals. Vitamin K3 caused a depletion of the intracellular glutathione (GSH) levels in P388/S and P388/ADR leukemia cells but at concentrations greater than those that enhanced ADR cytotoxicity. Pretreatment of the tumor cells with 1 microM vitamin K3 induced a 35-50% (P less than 0.001) elevation in the intracellular ADR accumulation in MDR P388 leukemia cells, while such an effect was absent in P388/S tumor cells. DNA binding studies performed utilizing calf thymus DNA, indicated that vitamin K3 enhanced the intercalation potential of ADR and also altered the equilibrium between the free and bound form of ADR in a cell free system. These factors and their possible effects on the potentiation of ADR cytotoxicity and the therapeutic significance of utilizing vitamin K3 as an adjuvant in the chemotherapy of MDR tumors is discussed.

Potentiation of hydroxyurea cytotoxicity in human chronic myeloid leukemia cells by iron-chelating agent.

The effect of hydroxyurea (HU) was studied in 15 cases of human chronic myeloid leukemia cells (CML) in combination with iron-chelating agent, 2,2-bipyridine (bipyridine). The extent of (3H)thymidine incorporation in CML cells in vitro was taken as an index for the measurement of cytotoxicity. In the present study, we observed a potentiation in HU cytotoxicity by hydrophobic iron-chelator bipyridine (p less than 0.001) resulting in complete DNA biosynthesis inhibition. Both HU and bipyridine were used at a relatively non-toxic concentrations of 10(-4) M and 10 micrograms/ml, respectively. This inhibition was found to be partially reversible and a partial protective action by iron is also demonstrated. The various other metal chelators failed to sensitise CML cells to HU cytotoxicity. Implications with respect to the efficacy in cancer treatment is discussed.

Enhancement of the in vitro cytotoxicity of bouvardin by verapamil alone and combined with hyperthermia in Sarcoma 180 and Ehrlich ascites carcinoma cells.

The cytotoxic effect of bouvardin (BVD) a protein synthesis inhibitor was studied separately and in combination with verapamil (VRP), a vasodilator and hyperthermia (43 degrees C) against Sarcoma 180 (S 180) and Ehrlich ascites carcinoma (EAC) tumour cells in vitro. S 180 cells exhibited natural resistance to hyperthermia and BVD, whereas EAC tumour cells were found to be sensitive. VRP alone did not show cytotoxicity to either tumour cells. A combination of BVD and VRP at an elevated temperature resulted in a greater cell kill in the EAC tumour cell line whereas the natural resistance of S 180 tumour cells to the drug BVD and hyperthermia was circumvented by combination with VRP. Combination of BVD, hyperthermia and VRP resulted in greater cell kill, compared to separate treatment with the single agents. The cytotoxicity was evaluated by comparing the inhibition of incorporation of 3H-thymidine in treated cells to that in untreated cells.

Studies on high-dose chemotherapy of amygdalin in murine P388 lymphocytic leukaemia and P815 mast cell leukaemia.

The anti-tumor activity of amygdalin (NSC 251222), commercially known as Laetrile, was investigated using P388 lymphocytic leukaemia and P815 mast-cell leukaemia in BDF1 mice. Doses varying from 200 mg/kg to 2,000 mg/kg were used following the days 1 and 5 and days 1, 5 and 9 schedules. Despite treatment with high doses of amygdalin there was no prolongation in the life-span of mice bearing either P388 or P815 tumor.

Reversal of natural resistance to bouvardin (NSC 259968) in sarcoma 180 cells in vitro and in vivo by verapamil.

Reversal of natural resistance to bouvardin (NSC 259968) has been attained in vitro and in vivo, by the calcium influx blocker verapamil in sarcoma 180 cells insensitive to bouvardin. Verapamil increased the in vitro lethality of the tumor cells following exposure with cells for 1 and 3 h as a result of the cytotoxic effect of bouvardin. Similar results were observed in vivo when the tumor cells were exposed to verapamil and then treated with bouvardin, showing a significant percent increase in the lifespan to 30% and 45%. This suggested that this calcium channel blocker had interacted with tumor cell membrane to modulate the response of the cells, and make them more amenable to the drug action.

Synthesis, spectroscopic, and cytotoxicity studies of some diamine and diimine platinum(II) complexes of diethyldithiocarbamate.

Four new water soluble complexes of the formula [Pt(DA)(DDTC)]NO3 (where DA is 2,2'-bipyridine, 1,10-phenanthroline, 1,2-diaminopropane, or 1,2-diaminocyclohexane, and DDTC is diethyldithiocarbamate anion) have been synthesized by reaction of platinum-diamine/diimine diaqua complex with sodium diethyldithiocarbamate in molar ratio of 1:1. These complexes have been characterized by the chemical analysis, and ultraviolet-visible, infra-red and 1H NMR spectroscopy. The infrared and 1H NMR spectral studies of these complexes have ascertained the modes of binding of diamine/diimine and diethyldithiocarbamate to platinum. The molar conductance values of these platinum complexes in conductivity water suggest them to be 1:1 electrolytes. These four complexes and two other complexes containing ethylenediamine and 1,3-diaminopropane ligands have been tested against P-388 lymphocytic leukemic cells. Out of them only 2,2'-bipyridine and 1,10-phenanthroline complexes show 1.D.50 values less than cisplatin.

Synthesis, characterization, DNA binding, and cytotoxic studies of some mixed-ligand palladium(II) and platinum(II) complexes of alpha-diimine and amino acids.

The syntheses of nine palladium(II) complexes of type [Pd(phen)(AA)]+ (where AA is an anion of glycine, L-alanine, L-leucine, L-phenylalanine, L-tyrosine, L-tryptophan, L-valine, L-proline, or L-serine) have been achieved. These palladium(II) complexes have been characterized by ultraviolet-visible, infrared, and 1H NMR spectroscopy. The binding studies of several complexes [M(NN)(AA)]+ (where M is Pd(II) as Pt(II), NN is 2,2'-bipyridine or 1,10-phenanthrodine, and AA is an anion of amino acid) with calf thymus DNA have been carried out using UV difference absorption and fluorescence spectroscopy. The mode of binding of the above complexes to DNA suggests the involvement of the hydrogen bonding between them. Several complexes [M(phen)(AA)]+ (where M is Pd(II) or Pt(II) and AA is an anion of amino acid) have also been screened for cytotoxicity in P388 lymphocytic cells. Of them, only two complexes, [Pd(Phen)(Gly)]+ and [Pd(phen)(Val)]+, show comparable cytotoxicity, as cisplatin does.

Some mixed-ligand palladium(II) complexes of 2,2'-bipyridine and amino acids as potential anticancer agents.

Eight new palladium complexes of the formula [Pd(bipy)(AA)]Cl 1 or 2 H2O (where bipy is 2,2'-bipyridine and AA is an anion of glycine, L-alanine, L-leucine, L-proline, L-serine, L-lysine, L-asparagine, or L-glutamine) have been synthesized by reaction of [Pd(bipy)Cl2] with an appropriate mono sodium salt of amino acid in water. These complexes have been characterized by chemical analysis and by visible, infrared, and 1H NMR spectroscopy. The detailed 1H NMR and infrared spectral studies of these complexes ascertain the mode of binding of amino acids to palladium through nitrogen of terminal -NH2 group and oxygen of terminal -COO- group. The molar conductance values of these complexes in water suggest them to be 1:1 electrolytes. These complexes have also shown growth inhibition against L1210 lymphoid leukemic, P388 lymphocytic leukemic, Sarcoma 180, and Ehrlich ascitic tumor cells. Some of these complexes show better 50% inhibitory dose values than cis-diamminedichloroplatinum(II).

Some potential anticancer palladium(II) complexes of 2,2'-bipyridine and amino acids.

Nine new palladium(II) complexes of the formula [Pd(bipy)(AA)]n+ (where bipy is 2,2'-bipyridine, AA is an anion of L-cysteine, L-aspartic acid, L-glutamic acid, L-methionine, L-histidine, L-arginine, L-phenylalanine, L-tyrosine, or L-tryptophan, and n = 0 or 1) have been synthesized by interaction of [Pd(bipy)Cl2] with an appropriate sodium salt of amino acid in water. These palladium(II) complexes have been characterized by chemical analysis and by visible, infrared, and 1H NMR spectroscopy. The modes of binding of amino acids in these palladium complexes have been ascertained by infrared and 1H NMR spectroscopy. The molar conductances of these complexes in water suggest that they are either nonelectrolytes or 1:1 electrolytes. These palladium complexes have shown growth inhibition against L1210 lymphoid leukemic, P388 lymphocytic leukemic, Sarcama 180, and Ehrlich ascites tumor cells. Some of these complexes show I.D.50 values comparable to or lower than cis-diamminedichloroplatinum(II).

Cytotoxicity and DNA binding studies of several platinum (II) and palladium (II) complexes of the 2,2'-bipyridine and an anion of 2-pyridinecarboxylic/2-pyrazinecarboxylic acid.

Four water soluble complexes of the type [M(bpy)(a-x)]NO3, where M is Pd(II) or Pt(II), bpy is 2,2-bipyridine, and a-x is anion of 2-pyridinecarboxylic acid or 2-pyrazinecarboxylic acid, have been found to bind calf thymus DNA, possibly through hydrogen binding. [M(bpy)(2-py)]NO3 complexes (2-py is an anion of 2-pyridinecarboxylic acid) show I.D.50 values smaller than cisplatin whereas [M(bpy)(2-pyz)]NO3 complexes (2-pyz is an anion of 2-pyrazinecarboxylic acid) show I.D.50 values larger than cisplatin against P388 cancer cells.

Synthesis, spectroscopic, cytotoxic, and DNA binding studies of binuclear 2,2'-bipyridine-platinum(II) and -palladium(II) complexes of meso-alpha,alpha'-diaminoadipic and meso-alpha,alpha'-diaminosuberic acids.

Four new binuclear complexes of formula [M2(bipy)2(BAA)]Cl2 (where M is Pt(II) or Pd(II), bipy is 2,2'-bipyridine, and BAA is a dianion of meso-alpha-alpha'-diaminoadipic acid (DAA) or meso-alpha,alpha'-diaminosuberic acid (DSA) have been synthesized. These complexes have been characterized by chemical analysis and ultraviolet-visible, infrared, and 1H NMR spectroscopy. The mode of binding of ligands in these complexes has been ascertained by infrared and detailed 1H NMR spectroscopy. These complexes are 1:2 electrolyte in conductivity water. They have also been tested against P388 lymphocytic leukemia cells and their target is DNA molecules. [Pt2(bipy)2(DSA)]Cl2, [Pd2(bipy)2(DSA)Cl2, and [Pd2(bipy)2(DAA)]Cl2 show I.D.50 values comparable or lower than cis-diamminedichloroplatinum(II) and [Pt(bipy)(Ala)]Cl. In addition, binding studies of [Pt2(bipy)2(DSA)]Cl2 and [Pd2(bipy)2(DAA)]Cl2 to calf thymus DNA have been carried out and the mode of binding seems to be hydrogen bonding, as suggested earlier for analogous mononuclear amino acid-DNA complexes.

Syntheses and spectroscopic studies of potential antitumor copper(II) complexes with 5-phenylazo-3-methoxy salicylidene thiosemicarbazone and N4 substituted thiosemicarbazones.

Five new copper(II) complexes of 5-phenylazo-3-methoxy salicylidene thiosemicarbazone and N4 substituted thiosemicarbazones have been synthesized. They have been characterized by chemical analyses, magnetic, conductance data, and by ultraviolet (UV)--visible, infrared, and electron spin resonance spectra. The complexes have the general formula CuL2, where HL is the ligand. One representative complex has been screened in vitro and in vivo against P388 lymphocytic leukemia cells sensitive and resistant to adriamycin (P388/S and P388/R). It has shown promising growth inhibition activity. We are reporting here for the first time the antineoplastic activity of this complex against experimental tumor systems.

Synthesis, characterization, and cytotoxic studies of alpha-diimine/1,2-diamine platinum(II) and palladium(II) complexes of selenite and tellurite and binding of some of these complexes to DNA.

Eleven new complexes of formula [M(NN)(XO3)] (where M is Pd(II) or Pt(II); NN is 2,2'-bipyridine, 1,10-phenanthroline, 2,2'-dipyridylamine, ethylenediamine or (+-)trans-1,2-diaminocyclohexane, and XO3(2-) is SeO3(2-) or TeO3(2-)) have been synthesized. These water soluble complexes have been characterized by chemical analysis and conductivity measurements as well as ultraviolet-visible and infrared spectroscopy. In these complexes the selenite or tellurite ligand coordinates to platinum(II) or palladium(II) as bidentate with two oxygen atoms. These complexes inhibit the growth of P 388 lymphocytic leukemia cells, their targets are DNA. The selenite complexes invariably show I.D.50 values less than cisplatin. However, the I.D.50 values of the tellurite complexes are usually higher than cisplatin, except that of [Pd(dach)(TeO3)] which has comparable I.D.50 values, as compared to cisplatin. [Pt(bipy)(SeO3)] and [Pd(bipy)(SeO3)] have been interacted with calf thymus DNA and bind to DNA through a coordinate covalent bond.

Some potential antitumor 2,2'-dipyridylamine Pt(II)/Pd(II) complexes with amino acids: their synthesis, spectroscopy, DNA binding, and cytotoxic studies.

Four new palladium(II) and platinum(II) complexes of formula [M(dipy)(AA)]+ (where dipy is 2,2'-dipyridylamine, AA is an anion of glycine or L-alanine, and M is Pd(II) or Pt(II)) have been synthesized and characterized with amino acids binding as bidentate ligands. These complexes are 1:1 electrolyte in conductivity water. Of the above four complexes, the two L-alanine complexes show ID50 values against P388 lymphocytic leukemia cells lower than cis-diamminedichloroplatinum(II), whereas the two glycine complexes show ID50 values higher than cisplatin. The interaction of calf thymus DNA with the above complexes shows significant spectral changes in the presence of [Pt(dipy)(gly)]Cl, [Pd(dipy)(ala)]Cl, and [Pt(dipy)(ala)]Cl and the mode of binding between these complexes and DNA seems to be noncovalent.

Synthesis and spectroscopic studies of potential anticancer [platinum(II)(2,2'-bipyridine)(amino acid)]n+ (n = 1 or 2) complexes.

Six new platinum complexes of the formula [Pt(2,2'-bipyridine)(amino acid)]n+, where n = 1 to 2 and amino acid is an anion of L-histidine, L-lysine, L-asparagine, L-phenylalanine, L-tryptophan, or L-tyrosine, have been prepared by interaction of [Pt(2,2'-bipyridine)Cl2] and an appropriate amino acid (sodium salt) in water or water-methanol mixture. They have been characterized by chemical analyses and spectral methods such as ultraviolet-visible, infrared, and 1H NMR spectroscopy. The 1H NMR studies of these complexes ascertain the modes of binding of amino acids to platinum. The histidine binds to platinum through the nitrogen of a -NH2 group and another nitrogen of heterocyclic ring. All other amino acids bind to platinum through nitrogen of a -NH2 group and oxygen of a -COO- group. The mode of binding of some amino acids to platinum in these complexes has been further confirmed by infrared spectroscopy, and the formulations of these complexes have been supported by conductivity measurements. These six amino acid complexes and also other complexes of glycine, alanine, leucine, serine, cysteine, methionine, and glutamine have shown growth inhibition against P-388 lymphocytic leukemic cells.

Synthesis, characterization, cytotoxic, and DNA binding studies of some platinum (II) complexes of 1,2-diamine and alpha-diimine with 2-pyridinecarboxylate anion.

Seven new water-soluble cationic complexes of general formula [Pt(2-pyc)(N-N)]+ (where N-N is 2NH3, ethylenediamine (en), 1,2-diaminopropane (1,2-dap), 1,3-diaminopropane (1,3-dap), (+/-) trans-1,2-diaminocyclohaxane (dach), 2,2'-dipyridylamine (dpa) or 1,10-phenanthroline (phen), and 2-pyridinecarboxylate anion) have been prepared. These complexes have been characterized by conductance measurements, and by ultraviolet-visible, infrared (IR), and 1H nuclear magnetic resonance (NMR) spectroscopy. The COSY (correlated spectroscopy) spectra of [Pt(2-pyc)(dpa)]+ and [Pt(2-pys)(dpa)]+ further support the structures of the above complexes with three nitrogen and one oxygen donor atoms in the first coordination sphere of platinum(II) with 1,2-diamine or alpha-diimine and 2-pyridinecarboxylate anion behaving as bidentate ligands. One of the compounds, [Pt(2-pyc)(dpa)]Cl, also shows a birefringence property in water. These compounds inhibit the growth of P388 lymphocytic leukemia cells. [Pt(2-pyc)(dpa)]+ shows I.D.50 value comparable to cisplatin. However, six other complexes show higher I.D.50 values than cisplatin. In addition, the inhibition studies also suggest that their target is DNA. Therefore, the interactions of four of the above complexes with calf thymus DNA have been studied by ultraviolet and fluorescence spectral methods. These studies suggest that [Pt(2-pyc)(NH3)2]+ and [Pt(2-pyc)(1,2-dap)+ bind to DNA by noncovalent interactions. On the other hand, [Pt(2-pyc)(dpa)]+ and [Pt(2-pyc)(phen)]+ bind to DNA by covalent monofunctional binding. The latter two complexes have also been interacted with PUC19 DNA. The gel electrophoresis studies of these interactions suggest that these complexes bind to DNA, and this binding leads to a conformational change in DNA.

Mitoxantrone & adriamycin cytotoxicity enhanced by reserpine in human chronic myeloid leukaemia cells.

The effect of reserpine was studied alone and in combination with anticancer drugs on human chronic myeloid leukaemia (CML) cells. To study the effect of reserpine on anthracycline antibiotic adriamycin and anthracenedione mitoxantrone the extent of 3H-thymidine incorporation into the DNA was taken as the measure of cytotoxicity. The results indicate that reserpine enhances the cytotoxicity of mitoxantrone and adriamycin in mildly toxic concentrations (1 and 10 micrograms respectively), in CML cells. The mechanism of enhancement in drug sensitivity by reserpine in CML cells is due to enhanced intracellular accumulation of drug.

Hyperthermia blocks reversibility of hydroxyurea and bipyridine induced synergistic inhibition of DNA biosynthesis in P388 murine leukemia cells.

The influence of hyperthermia (42 degrees C) on the reversibility of hydroxyurea- and the iron-chelator 2,2'-bipyridine-induced synergistic inhibition of DNA biosynthesis was studied in intact P388 murine lymphocytic leukemia cells in vitro. The cytotoxicity caused by hydroxyurea alone and in combination with bipyridine for 3 h at 37 degrees C and 42 degrees C was found to be completely reversible. However, the inhibition of DNA biosynthesis was irreversible when hydroxyurea- and iron-chelate-treated and washed cells at 37 degrees C were subjected to hyperthermia at 42 degrees C. A potentiation in DNA biosynthesis was also observed when the P388 cells were subjected to hyperthermia along with the combination of hydroxyurea and 2,2'-bipyridine. These effects are probably due to the heat-sensitive nature of the ribonucleotide reductase enzyme, the target site of the effect of hydroxyurea and 2,2'-bipyridine.

Modulation of in vitro chemosensitivity by extracellular Ca++ in adriamycin sensitive and resistant P388 leukemic cells.

P388 mouse lymphocytic leukemia cells sensitive (P388/S) and resistant to adriamycin (P388/Adr), respectively, were exposed in vitro to 3 dose concentrations of adriamycin, mitoxantrone, vincristine and cisplatin in the presence and absence of extracellular Ca++ at 37 degrees C for 1 h. The absence of extracellular Ca++ enhanced the cytotoxicity of all the four drugs by 25 to 30% in P388/S cells. P388/Adr cells retained their resistance to adriamycin irrespective of the presence or absence of Ca++, however, vincristine and cisplatin to which P388/Adr cells, in normal course, show cross-resistance, exhibited a 30-40% enhancement of cytotoxicity in the absence of extracellular Ca++. Cross-resistance of P388/Adr to mitoxantrone was totally circumvented in the absence of extracellular Ca++.