Cross-resistance to the synthetic retinoid CD437 in a paclitaxel-resistant human ovarian carcinoma cell line is independent of the overexpression of retinoic acid receptor-gamma

Treatment of ovarian carcinomas with the antimitotic antitumor drug paclitaxel is highly efficacious. However, development of drug resistance presents a major obstacle. The common cellular phenotypes associated with paclitaxel resistance are an increased expression of the drug transport protein P-glycoprotein (P-gp), an alteration in the levels of beta-tubulin isotypes, and/or changes in the drug binding affinity of the microtubules. We established two paclitaxel-resistant human ovarian carcinoma cell lines. The 2008/17/4 cells exhibited a "classic" multidrug-resistant phenotype (overexpression of P-gp associated with cross-resistance to natural product drugs), whereas the 2008/13/4 cells were an atypical multidrug-resistant subline (no overexpression of P-gp). In addition to being paclitaxel resistant (250-fold), the 2008/13/4 cells were also cross-resistant to etoposide (39-fold) and vincristine (460-fold). To identify the alterations in the gene expression profile associated with the development of atypical paclitaxel resistance, we used the Clontech Atlas Human Cancer cDNA Microarray (spotted with 588 genes). The expression of retinoic acid receptor (RAR)-gamma was significantly higher in the paclitaxel-resistant (2008/13/4 and 2008/17/4) cells than in the parental (2008) cells. Northern blotting analysis demonstrated that the expression of RAR-gamma was 7-fold higher in the 2008/13/4 and 2008/17/4 cells than in the 2008 cells, whereas the expression of RAR-alpha and RAR-beta was not observed in any cell line. Whereas the 2008, 2008/13/4, and 2008/17/4 cells were found to resist the antiproliferative effects of all-trans-retinoic acid, the paclitaxel-resistant cells were 6- to 7-fold cross-resistant to the antiproliferative effects of CD437 (a synthetic RAR-gamma-selective agonist; 6-[-(1-admantyl)-4-hydroxyphenyl]-2-naphthalenecarboxylic acid) compared with the sensitivity of the parental cells. To further understand the association of paclitaxel and CD437 resistance with the observed RAR-gamma overexpression, we transfected the 2008 cells with a full-length RAR-gamma cDNA construct. Two transfectants with increased expression of the RAR-gamma mRNA and protein were isolated and subjected to growth inhibition assays in the presence of various concentrations of paclitaxel, etoposide, vincristine, and CD437. The sensitivity of the 2008 transfected clones (displaying increased expression of RAR-gamma) to the cytotoxic effects of paclitaxel, etoposide, vincristine, and CD437 was similar to that observed in the parental 2008 cells. These results suggest that the overexpression of RAR-gamma (observed in the 2008/13/4 and 2008/17/4 cells) by itself is not capable of inducing paclitaxel and CD437 resistance (or resistance to etoposide and vincristine).

Expression of the cisplatin resistance phenotype in a human ovarian carcinoma cell line segregates with chromosomes 11 and 16

Many mechanisms have been proposed to explain cisplatin resistance, suggesting that this phenomenon is multifactorial. In an attempt to define the chromosome(s) responsible for cisplatin resistance in the human ovarian carcinoma 2008/C13* cell lines, somatic cell hybrids were obtained following fusion of the cisplatin-resistant 2008/C13* cells with an A9 rodent fibroblast cell line. The hybrids were then analyzed for segregation of the human chromosomes with the drug-resistant phenotype. Chromosomes 11 and 16 were present in all of the resistant somatic cell hybrids, with the highest concordance for chromosome 16. The role of both of these chromosomes was further established with microcell hybrids. Microcell hybrids of A9 cells with chromosome 16 from the 2008/C13* cells did not exhibit cisplatin resistance, but the presence of a normal chromosome 11 with chromosome 16 (derived from cisplatin-resistant 2008/C13* cells and not from the cisplatin-sensitive 2008 cells) resulted in increased resistance to cisplatin. In addition, loss of chromosome 11 from a resistant somatic cell hybrid resulted in the hybrid becoming sensitive to cisplatin, implicating this chromosome in maintaining the resistant phenotype. The results demonstrate that resistance to cisplatin is a dominant trait in the 2008/C13* human ovarian cells, and both chromosomes 11 and 16 are required for its expression.

The differential expression of cytokeratin 18 in cisplatin-sensitive and -resistant human ovarian adenocarcinoma cells and its association with drug sensitivity

DNA is the primary target of cis-diamminedichloroplatinum (cisplatin), but the drug also interacts with the cellular cytoskeleton composed of microtubules and intermediate filaments. It was found that the cisplatin-resistant 2008/C13* cell line contained markedly lower levels (6-fold) of cytokeratin 18, when compared to the cisplatin-sensitive 2008 cell line. Northern blot analysis revealed a markedly decreased level of cytokeratin 18 mRNA in the resistant cell line. Southern blot analysis of the DNA extracted from the two cell lines and then digested with HpaII and its methylation-sensitive isoschizomer, MspI, revealed no detectable differences in the methylation status of the cytokeratin gene. Neither 5-azacytidine (5 microM) nor retinoic acid (1 microM) treatment enhanced the expression of cytokeratin 18 in the resistant cell line. However, transfection of full-length cytokeratin 18 cDNA into the cisplatin-resistant 2008/C13* cells resulted in clones with increased levels of cytokeratin 18, which was accompanied in the majority of clones by a marked increase in their sensitivity to cisplatin. These results demonstrate that modulating the expression of an intermediate filament protein results in sensitization of a drug-resistant human ovarian cell line to cisplatin.

NADPH-dependent enzyme-catalyzed reduction of aldophosphamide, the pivotal metabolite of cyclophosphamide

One of the metabolites found in the urine of mammals given the prodrug cyclophosphamide is alcophosphamide, an alcohol. It is most probably generated from cyclophosphamide via aldophosphamide, an aldehyde which otherwise can directly give rise to phosphoramide mustard; the latter effects the cytotoxic action of cyclophosphamide and other oxazaphosphorines. It has already been demonstrated that horse liver alcohol dehydrogenase catalyzes the reduction of aldophosphamide to alcophosphamide. Herein, we report that aldose reductase and aldehyde reductase purified from human placenta also catalyze this reaction. The Km values for aldose reductase- and aldehyde reductase-catalyzed reduction of aldophosphamide to alcophosphamide were 0.15 and 1.6 mM, respectively. Aldose reductase and aldehyde reductase accounted for 94 and 6%, respectively, of total placental pyridine nucleotide-dependent enzyme-catalyzed aldophosphamide (160 microM) reduction. Aldose reductase-catalyzed reduction of aldophosphamide appeared to be noncompetitively inhibited by sorbinil; the Ki value was 0.4 microM. The in vivo significance of these observations is uncertain but could be of some magnitude since alcophosphamide is known to be only weakly cytotoxic.

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.

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.

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.

Effect of alterations in permeability by nonionic surfactants on adriamycin cytotoxicity in murine tumor models in vitro

Differential effects of adriamycin cytotoxicity and its cellular uptake were assessed in murine tumor models utilising adriamycin alone and in combination with nontoxic concentrations of nonionic polyoxyethylated lauryl ether surfactants Brij 30 and Brij 35. Parental P388 murine leukemia cell line sensitive to adriamycin, subline of P388 murine leukemia resistant to adriamycin, sarcoma-180 and Ehrlich ascites tumor were employed in this study. The results indicate an enhanced DNA biosynthesis inhibition by adriamycin when used in combination with Brij 30 or Brij 35 in all the murine tumor models. The increase in adriamycin cytotoxicity was due to an increased accumulation of adriamycin observed in the tumor models used. The present investigation demonstrates the necessity of utilising surface-active drug-response modulators to enhance the cytotoxicity of anticancer drugs and circumvent drug resistance.

Prenatal mortality and its effects on subsequent fertility in purebred and crossbred Gir cows

A study was conducted on 851 cows (Gir cows and their crossbreeds) between 1971 and 1984 at the Livestock Farm of the All India Coordinated Research Project on Cattle in Jabalpur, India. The cows were impregnated with frozen or fresh semen from 90 bulls and a total of 2699 pregnancies resulted. An overall incidence of prenatal mortality was recorded at 4.89%. A significantly higher (P / 0.01) incidence of prenatal mortality was encountered in three breed crosses in comparison with Gir cows and their first generation crossbreeds. Parity of dam had no effect on prenatal mortality. However, effects of season and individual sires on prenatal mortality were documented. It was observed that reproductive performance was improved significantly after prenatal mortality.