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PubMed1991

Alkylating agent hypersensitivity in poly(adenosine diphosphate-ribose) polymerase deficient cell lines.

Starting with the V79 cell line, two poly(ADP-ribose) polymerase deficient mutants, designated ADPRT 54 and ADPRT 351, had been shown to be hypersensitive to x- and UV-irradiation and to topoisomerase I inhibitors but to be resistant to topoisomerase II inhibitors (Chatterjee, S.; Cheng, M. F.; Berger, N. A. Hypersensitivity to clinically useful alkylating agents and radiation in poly(ADP-ribose) polymerase-deficient cell lines. Cancer Commun. 2:401-407;1990). We now report that these mutants were hypersensitive to a series of different alkylating agents, including alkylsufonates, alkylnitrosoureas, and nitrosoguanidine. In addition, they were hypersensitive to the UV-mimetic agent 4-nitroquinoline-1-oxide. Our findings provide strong evidence that poly(ADP-ribose) polymerase was involved in the repair of alkylating agent induced DNA damage as well as in the damage induced by UV- and x-irradiation and radiomimetic agents. The poly(ADP-ribose) polymerase deficient cell lines showed a marked decrease in the shoulder region of their survival curves, suggesting that poly(ADP-ribose) polymerase was involved in the repair of alkylating agent induced sublethal damage.

4-Nitroquinoline-1-oxide↗
PubMed1998

Enzymatic deacylation of teicoplanin followed by reductive alkylation: synthesis and antibacterial activity of new glycopeptides.

Novel glycopeptides derived from teicoplanin were prepared and evaluated for activity against antibiotic-resistant gram-positive pathogens. Removal of the fatty acid sidechains of teicoplanin was accomplished by enzymatic deacylation. The resulting deacylated teicoplanin was subjected to reductive alkylation resulting in mono- and di-alkylated compounds at the 2 possible primary amines. Deacylated teicoplanin was less active than teicoplanin against enterococci and staphylococci (MIC > or =32 microg/ml). All mono- and di-alkylated products regained some activity, and some had potent activity against both staphylococci and glycopeptide-resistant enterococci. MICs of the most potent di-alkylated compounds ranged from 0.25 approximately 2 microg/ml against glycopeptide-resistant enterococci.

Alkylation↗
PubMed1976

Studies with 2,5-piperazinedione, 3,6-bis(5-chloro-2-piperidyl)-,dihydrochloride. II. Effects on macromolecular synthesis in cell culture and evidence for alkylating activity.

2,5-Piperazinedione, 3,6-bis(5-chloro-2-piperidyl)-,dihydrochloride (NSC-135758) inhibited DNA synthesis but not RNA and protein synthesis in Adenocarcinoma 755 cells in culture. The expression of such inhibition was delayed in time; it was necessary to expose tumor cells to NSC-135758 for 10-12 hours before measuring the macromolecular synthesis in order to demonstrate selective inhibition of DNA synthesis. Inhibition of DNA synthesis was demonstrated to be irreversible in human epidermoid carcinoma cells in culture. Exposure of cells in suspension culture to NSC-135758 or to melphalan for 1-4 hours, and then incubation of cells in the absence of an inhibitor for 20 hours, resulted in preferential inhibition of DNA synthesis; inhibition of RNA synthesis was observed under these conditions but was less pronounced. Chemical evidence for alkylating activity of NSC-135758 and of the bis-aziridine derived from it (NSC-201424) was obtained by demonstrating their reaction with 4-(p-nitrobenzyl)pyridine. NSC-135758 was more potent as a cytotoxic agent than was its derivative, a result which suggests that NSC-135758 is the active alkylating agent. Reaction of NSC-135758 with diethylamine was examined; the product obtained upon alkylation of diethylamine by NSC-135758 was identified from its proton magnetic resonance spectrum and by field desorption mass spectral analysis. These results support the view that NSC-135758 acts as an alkylating agent in inhibiting DNA synthesis and cell proliferation of tumor cells in culture.

Adenocarcinoma↗
PubMed1976

O- and N-alkylation with "Meerwein's reagent": the unusual behaviour of two lactams.

Usually tertiary oxonium salts are excellent O-alkylating agents of lactams; in some cases indiscriminate O- and N-alkylations have been described. In this paper the particular behaviour towards Meerwein's reagent of two isomers with a lactamic structure is pointed out: in one case the usual O-alkylation occurs, in the other N-alkylation is the only reaction that takes place.

Alkylation↗
PubMed1975

The role of drug transport in resistance to nitrogen mustard and other alkylating agents in L518Y lymphoblsts.

An investigation was undertaken of the mechanism of resistance to nitrogen mustard (HN2) and other alkylating agents, with particular emphasis on the interaction between cross-resistance and drug transport mechanisms in L5178Y lymphoblasts. Dose-survival curves demonstrated that the D0 for HN2-sensitive cells (L5178Y) treated with HN2 in vitro was 9.79 ng/ml and the D0 for HN2-resistant cells (L5178Y/HN2) was 181.11 ng/ml; thus, sensitive cells were 18.5-fold more responsive than were resistant cells and the difference was highly significant (p less than 0.001). A similar evaluation of 5 additional alkylating agents, including chlorambucil, melphalan, 1,3-bis(2-chloroethyl)-l-nitrosourea, Mitomycin C, and 2,3,5-tris(ethyleneimino)-1,4-benzoquinone, revealed that L5178Y/HN2 cells were also cross-resistant, in part, to each of these compounds. Furthermore, the degree of cross-resistance was remarkably similar; for each drug, dose-survival studies showed that HN2-resistant cells were approximately 2- to 3-fold more resistant to therapy than were sensitive cells. L5178Y/HN2 cells were also cross-resistant to cyclophosphamide in vivo; after treatment with cyclophosphamide, DBA/2 female mice that were given inoculations of L5178Y cells, but not those given transplants of L5178Y/HN2 cells, showed a significant prolongation of survival time (p less than 0.01). Transport of HN2, hydrolyzed derivative of HN2 and choline by L5178Y lymphoblasts in vitro was not competitively inhibited by any of the other alkylating agents, suggesting that transport of these compounds was by an independent mechanism. These findings suggest that the mechanism whereby L5178Y/HN2 cells are cross-resistant to other alkylating agents may involve nontransport factors and that these other drugs may bypass a major portion of HN2 resistance by using independent transport systems.

Alkylating Agents↗
PubMed2000

Effect of O6-benzylguanine on alkylating agent-induced toxicity and mutagenicity. In Chinese hamster ovary cells expressing wild-type and mutant O6-alkylguanine-DNA alkyltransferases.

The DNA repair protein O6-alkylguanine-DNA alkyltransferase (AGT) has been shown to protect cells from the toxic and mutagenic effect of alkylating agents by removing lesions from the O6 position of guanine. O6-Benzylguanine (BG) is a potent inactivator of AGT, resulting in an increase in the sensitivity of cells to the toxic effects of chemotherapeutic alkylating agents. Chinese hamster ovary (CHO) cells and CHO cells transfected with wild-type AGT (CHOWTAGT) and a mutant AGT [P138 M/V139I/P140K (CHOMIK)] known to be resistant to BG were treated with BG and various alkylating agents. BG treatment alone dramatically decreased AGT activity in CHOWTAGT cells but resulted in no depletion in AGT activity in CHOMIK cells. In the absence of AGT, these cells are highly sensitive to the toxic and mutagenic effects of temozolomide and 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU), and no further sensitization occurs in the presence of BG. In contrast, CHOWTAGT cells are resistant to temozolomide and BCNU, and treatment with BG resulted in a significantly higher cell killing and mutation frequency. CHOMIK cells were completely resistant to temozolomide or BCNU in the presence and absence of BG. Both cell killing and mutation frequency of 4-hydroperoxycyclophosphamide (4-HC) in CHO, CHOWTAGT, and CHOMIK cells were increased in the presence of BG. 4-HC generates two active metabolites, phosphoramide mustard (PM) and acrolein. BG had no effect on 4hydroperoxydidechlorocyclophosphamide (which generates acrolein and a nonalkylating form of PM) in CHO cells and CHOMIK cells, but enhancement of toxicity was observed with PM in both these cell lines. Therefore, we attribute the enhancement to the PM metabolite of 4-HC. Our results demonstrate that wild-type AGT plays an important role in protecting against the toxic and mutagenic effect of O6 alkylating agents and that a mutant AGT resistant to inactivation by BG effectively prevents BG-enhanced toxicity and mutagenicity induced by these agents. Expression of the AGT protein contributes to resistance of 4-HC. BG also enhances the toxicity of 4-HC and PM by a mechanism that may not involve the AGT repair protein.

Animals↗
PubMed1976

Alkylating properties of phosphoramide mustard.

The relative alkylating activities of two of the cytotoxic metabolites of cyclophosphamide, phosphoramide mustard and nornitrogen mustard, have been studied at pH 4.6 and 7.4. The products formed on alkylation of ethanethiol by these metabolites have been identified, confirming that phosphoramide mustard undergoes alkylation reactions as an intact molecule. Deuterated analogs of the two metabolites have been synthesized, namely N,N-bis(2,2-dideutero-2-chloroethyl)-phosphorodiamidic acid and N,N-bis(2,2-dideutero-2-chloroethyl)amine and used to determine that alkylation proceeds directly via an aziridinium intermediate rather than a direct SN2 displacement of the chlorine atom.

Alkylation↗
PubMed2002

Synthesis of aromatic nitrogen mustard agents and analysis of their alkylation activity at physiological pH and temperature.

A Structure Activity Relationship (SAR) study was accomplished with six aromatic compounds which have a nitrogen mustard (N-mustard) substituent. N-mustard agents are very important for the clinical treatment of many types of cancers. All N-mustard agents synthesized alkylated a nucleophilic primary amine (p-chloroaniline) in aqueous solvent at pH 7.4 and 37 degrees C. Rate constants and rate equations were determined for the alkylation reactions by monitoring the formation of a fluorescent complex formed when fluorescamine complexes the unreacted p-chloroaniline. Fluorescamine complexation of the unreacted primary amine halts the alkylation reaction and allows the determination of remaining unreacted primary amine, which in turn permits the determination of rate constants and rate equations. The fluorescamine-amine complex shows a strong absorbance peak at a wavelength of 400 nanometers in aqueous solvent. The molar absorptivity (epsilon) was calculated to be 18.37 L/(mole x cm). First order rate constants ranged from 0.513E-2 minute(-1) to 1.32E-2 minute(-1) with second order rate constants from 2.85E-2 (M x minute)(-1) to 4.78E-2 (M x minute)(-1). The aromatic compounds included benzoic acid, m-chlorobenzoic acid, hydrocinnamic acid, m-toluic acid, and 3,4-dimethoxybenzoic acid. The synthesis procedure produced the N-mustard agents at > or = 90% yield and high purity. Partition coefficient Log(Kow)Log P values ranged from 2.66 to 4.18. The N-mustard agents consisted of greyish-yellow crystals which retained alkylation activity for more than ten weeks when stored at -10 degrees C and were soluble in water at 25 degrees C and 37 degrees C.

Alkylation↗
PubMed2003

An intron splice acceptor polymorphism in hMSH2 and risk of leukemia after treatment with chemotherapeutic alkylating agents.

PURPOSE: We sought to determine whether the -6 exon 13 T>C polymorphism in the DNA mismatch repair gene hMSH2 modulates susceptibility to acute myeloid leukemia after therapy and particularly after O(6)-guanine alkylating chemotherapy. We also determined the extent of microsatellite instability (MSI) in therapy-related acute myeloid leukemia (t-AML) as a marker of dysfunctional DNA mismatch repair. EXPERIMENTAL DESIGN: Using a novel restriction fragment length polymorphism, verified by direct sequencing, we have genotyped 91 t-AML cases, 420 de novo acute myeloid leukemia cases, and 837 controls for the hMSH2 -6 exon 13 polymorphism. MSI was evaluated in presentation bone marrow from 34 cases using the mononucleotide microsatellite markers BAT16, BAT25, and BAT26. RESULTS: Distribution of the hMSH2 -6 exon 13 polymorphism was not significantly different between de novo acute myeloid leukemia cases and controls, with heterozygotes and homozygotes for the variant (C) allele representing 12.2 and 1.6%, respectively, of the control population. However, the variant (C) hMSH2 allele was significantly overrepresented in t-AML cases that had previously been treated with O(6)-guanine alkylating agents, including cyclophosphamide and procarbazine, compared with controls (odds ratio, 4.02; 95% confidence interval, 1.40-11.37). Thirteen of 34 (38%) t-AML cases were MSI positive, and 2 of these 13 cases were homozygous for the variant (C) allele, a frequency substantially higher than in the control population. CONCLUSIONS: Association of the hMSH2 -6 exon 13 variant (C) allele with leukemia after O(6)-guanine alkylating agents implicates this allele in conferring a nondisabling DNA mismatch repair defect with concomitant moderate alkylation tolerance, which predisposes to the development of t-AML via the induction of DNA mismatch repair-disabling mutations and high-grade MSI. Homozygosity for the hMSH2 variant in 2 of 13 MSI-positive t-AML cases provides some support for this model.

Adolescent↗
PubMed2003

Enhancing alkylating agent resistance through ERCC2 gene transfection in human glioma cell line.

OBJECTIVE: To confirm the enhancing effect of excision repair cross complementing rodent repair deficiency gene 2 (ERCC2) on alkylating agents resistance. METHODS: The authors constructed a pcDNA3-ERCC2 plasmid. The pcDNA3-ERCC2 was transfected into a selected ERCC2 negative human glioma cell line, SKMG-4, using liposome-mediated transfection. After G418 selection, a stable transfected cell line was obtained and tested for cytotoxicity of several alkylating agents. RESULTS: The stable transfectant was obtained and confirmed by RT-PCR as well as Western blot analysis to be strongly expressing ERCC2 at both mRNA and protein levels. The IC(90) ( micro mol/L) of two alkylating agents, cisplatin and melphalan, increased from 1.0 to 1.75 (75%) and 5.6 to 9.0 (61%), respectively, compared with control cell line. CONCLUSION: The present data provided evidences and confirmed the authors' previous results that ERCC2 contributes, at least partially, to alkylating agent resistance in human glioma cell line.

Antineoplastic Agents, Alkylating↗
PubMed1976

The glomerular deposition of soluble immune complexes prepared with reduced and alkylated antibodies and with intact antibodies in mice.

The kidney localization and glomerular deposition of soluble immune complexes in mice were greater and more persistent following the intravenous administration of complexes prepared with reduced and alkylated antibodies than following the administration of complexes prepared with intact antibodies. The increased glomerular deposition following the administration of complexes prepared with reduced and alkylated antibodies was associated with the persistence of circulating complexes composed of more than two antigen and two antibody molecules (Haakenstad AO, Mannik M:Lab Invest 35:283, 1976). The deposition of immune complexes in glomeruli, as detected by immunofluorescence, appeared to precede the detection of mouse C3 in glomerular deposits following the administration of both preparations of complexes. The deposition of mouse C3 was more intense and persisted longer in mice receiving complexes containing reduced and alkylated antibodies than in mice receiving complexes containing intact antibodies. The ultrastructural studies indicated that both preparations of complexes initially localized as electron-dense material in endothelial cell fenestrae and in the subendothelial space of the glomerular capillary loops and subsequently accumulated in the mesangial matrix between mesangial cells. The material persisted in the mesangium of mice receiving complexes with reduced and alkylated antibodies, whereas it was removed from the mesangium of mice receiving complexes with intact antibodies. The mechanism for removal of complexes from the mesangial matrix was not defined, but it did not appear to occur through phagocytosis by the mesangial cell.

Alkylation↗
PubMed1992

Lethality, DNA alkylation, and cell cycle effects of adozelesin (U-73975) on rodent and human cells.

Adozelesin (U-73975) is an extremely potent cytotoxic agent which causes 90% lethality, after 2 h exposure in vitro, of Chinese hamster ovary and lung (CHO and V79), mouse melanoma (B16), and human ovarian carcinoma (A2780) cells at 0.33, 0.19, 0.2, and 0.025 ng/ml, respectively. Under similar conditions, Adriamycin and cisplatin had 90% lethality values in CHO cells of 150 ng/ml (= 249 nM) and 6800 ng/ml (= 2266 nM), respectively. The relative drug sensitivity of the cell lines (A2780 > V79, B16, CHO) was correlated to the relative amounts of [3H]adozelesin alkylated to DNA. The greater sensitivity of A2780 was due to (a) greater DNA alkylation at different drug doses and (b) greater intrinsic sensitivity of A2780 which resulted in greater cell kill at comparable DNA alkylation. Phase specific toxicity studies show that adozelesin was least lethal to CHO cells in mitosis and very early G1. Lethality increased as cells progressed through G1 and was maximal in late G1 and early S. Mitotic cells had lower drug uptake and correspondingly less drug binding to DNA than G1 or S-phase cells. However, based on the amount of drug alkylated per micrograms of DNA, cells in M, G1, and S were equally sensitive. Therefore, the lower sensitivity of M-phase cells was due to lower drug uptake. Adozelesin had three different effects on progression of CHO, V79, B16, and A2780 through the cell cycle: (a) slowed progression through S which resulted in significantly increasing the percentage of S-phase cells. This effect was transient; (b) cell progression was blocked in G2 for a long time period; (c) the response of the cell lines to the G2 block differed. CHO and V79 cells escaped G2 block by dividing and entered the diploid DNA cycle or did not undergo cytokinesis and became tetraploid. On the contrary, B16 and A2780 cells remained blocked in G2 and did not become tetraploid. Cell progression was inhibited in a similar manner when a synchronized population of M, G1, or S-phase cells were exposed to adozelesin.

Alkylation↗
PubMed1992

Prolonged D2 antidopaminergic activity of alkylating and nonalkylating derivatives of spiperone in rat brain.

Alkyl and arylalkyl derivatives of the dopamine (DA) D2 antagonist spiperone were prepared and characterized chemically and pharmacologically. They included the N-methyl, N-phenethyl (NPS), and N-p-aminophenethyl (NAPS) derivatives, as well as the alkylating isothiocyanato (NIPS), bromacetamido, and ethylfumaramido p-substituted N-phenethylspiperones. These compounds showed high lipophilicity (log P up to 6.0 with NIPS), as well as very high in vitro D2 affinity (Ki = 35-280 pM) and D2 versus D1 selectivity (540-9000-fold) in radioreceptor assays with corpus striatum of rat brain. Of the alkylating series, NIPS showed the highest D2 affinity (57 pM) and D2 versus D1 selectivity (2040-fold) and so was selected for further evaluation. NPS, NAPS, and NIPS showed little or no affinity for 34 non-DA binding sites defined by radioligand assays for monoamine, amino acid, and peptide neurotransmitters, ion channels, peptide growth factors, and transmission mediators but did show low alpha 2 and moderate alpha 1 and 5-hydroxytryptamine (5-HT2) affinity with rat forebrain tissue in vitro; NIPS showed a marked gain in D2 versus 5-HT2 selectivity, compared with spiperone (1520- versus 26-fold). Systemic injections of NIPS induced marked decreases in rat striatal D2 binding sites 24 hr later, with little effect on D1, 5-HT2, or alpha 1 sites; NIPS and NAPS lowered apparent Bmax values at D2 receptors with little change in ligand affinity, ex vivo as well as in vitro. NPS, NAPS, and NIPS all induced dose-dependent lowering of D2 binding ex vivo (ID50 = 1-9 mumol/kg, intraperitoneally) and blocked the behavioral effects of the DA agonist apomorphine (0.9 mumol/kg) potently (ID50 = 0.3-0.5 mumol/kg) at 24 hr. Recovery from these anti-DA actions required about 1 week after equimolar (15 mumol/kg) and similarly effective doses of NPS and NAPS, as well as NIPS. Thus, highly selective and avidly bound lipophilic D2 affinity ligands with similarly avid in vitro and prolonged in vivo anti-DA activities can be derived from N-phenethylspiperones with or without an alkylating moiety present. Such affinity ligands may represent useful additions to previously used, generally less selective, D2 affinity ligands.

Alkylating Agents↗
PubMedDate not supplied

[Inhibition of yeast pyruvate decarboxylase by alkyl phosphates].

It is found that yeast pyruvate decarboxylase is inhibited by alkyl phosphates. Inhibition is competitive with respect to a substrate. The inhibition constants with n-butyl and n-heptyl esters of phosphoric acid are the values of the same order of magnitude. With an increase in the length of the alkyl phosphates hydrocarbon chain from 7 to 10 carbon atoms inhibition constants change drastically. For n-heptyl phosphate and n-decyl phosphate values KI are equal to 1.6 x 10(-4) M and 1.7 x 10(-6) M, respectively. A further increase in the number of carbon atoms in the alkyl substituent of phosphoric acid ester induces no reduction of the inhibition constant. Multiple-inhibitor experiments of pyruvate decarboxylase show that inorganic phosphate and n-decyl ester of phosphoric acid are mutually exclusive. It is suggested that the inhibition mechanism with alkyl phosphates includes the competition of the phosphoric acid residue with alpha-ketocarboxyl group of pyruvate as well as the interaction between a hydrocarbon radical and hydrophobic parts on the enzyme surface, one of them being outside the substrate binding site.

Alkylation↗
PubMed2004

Development of novel alkylating drugs as anticancer agents.

Although conventional alkylating drugs have proven efficacy in the treatment of malignancies, the agents themselves are not selective. Therefore, non-specific alkylation of cellular nucleophilic targets may contribute to many of the observed toxic effects. Novel approaches to drug discovery have resulted in candidate agents that are focused on 'soft alkylation'--alkylators with greater target selectivity. This review highlights the discovery of small molecule drugs that bind to DNA with higher selectivity, act in a unique hypoxic tumor environment, or covalently bind specific protein targets overexpressed in cancer, such as topoisomerase II, glutathione transferase pi1, beta-tubulin and histone deacetylase.

Animals↗
PubMed2006

Targeting the endothelin axis in human melanoma: combination of endothelin receptor antagonism and alkylating agents.

Endothelin (ET)-1 is an autocrine/paracrine growth factor or an antiapoptotic factor in human cancers, and blockade of ET-1 receptors can sensitize human tumor cells to apoptosis. The role of the ET-1 axis in the proliferation and/or apoptosis of melanoma cells and in their response to the alkylating agent, dacarbazine (DTIC), used in clinical treatment of human melanoma were investigated in five human melanoma cell lines obtained form surgical resection specimens. Melanoma cells expressed the messenger RNAs (mRNAs) for the components of the ET-1 axis. ET-1 binding was mediated by ET(B) but was inhomogeneous among melanoma cells. Exogenous ET-1 did not induce human melanoma cell proliferation. Bosentan, a dual ET(A/B)-receptor antagonist, decreased melanoma cell viability and DNA synthesis and induced melanoma cell apoptosis in defined human melanoma cells. Bosentan potentiated Fas ligand-induced apoptosis only in one melanoma cell line. Variants of ET(B)were determined using reverse transcriptase (RT) polymerase chain reaction (PCR) and primers spanning the whole sequence of the ET(B)gene. ET(B)variants were demonstrated only in one of the five cell lines, corresponding to the absence of ET-1 binding by these cells. Bosentan did not inhibit the effects of alkylating agents, and the effects of bosentan and alkylating agents were additive in melanoma cells. In conclusion, exogenous ET-1 is not a growth factor for human melanoma cells, but blockade of ET receptors decreases proliferation, induces apoptosis, and potentiates the effects of anticancer agents in defined melanoma cells, suggesting that combination therapy of ET-receptor antagonists with alkylating agents may improve their efficacy.

Alkylating Agents↗
PubMed1990

Affinity labeling of mu opioid receptors by sulfhydryl alkylating derivatives of morphine and morphinone.

After reduction of a disulfide bond at or near the mu opioid binding site in rat brain membranes, incubating membranes with 14 beta-bromoacetamido derivatives of either morphine, dihydromorphine, morphinone, or dihydromorphinone resulted in the irreversible inhibition of mu opioid binding to rat brain membranes. Without the addition of the disulfide bond-reducing reagent dithiothreitol, these affinity ligands bound reversibly to opioid binding sites. Binding to either delta or kappa opioid binding sites was not altered by alkylation of the membranes with the affinity ligands. The percentage of irreversible inhibition of mu opioid binding was dependent on the time and temperature of the incubation of membranes with the affinity ligands and on the concentrations of dithiothreitol and the affinity ligands. Incubating membranes with morphine afforded almost complete protection from alkylation of the mu opioid binding site. Naloxone and the l-isomer levorphanol also protected the site from alkylation, whereas the d-isomer dextrorphan and the kappa-selective opioid U50,488H did not protect the site. The mu-selective peptide [D-Ala2, (Me)Phe4,Gly(ol)5]enkephalin was the peptide that afforded the greatest protection. These studies have shown that, after the reduction of a disulfide bond at or near the mu opioid binding site, this sulfhydryl group can be specifically alkylated, resulting in the affinity labeling of the mu opioid binding site.

Affinity Labels↗
PubMed2006

Potentiation of alkylating agents by NLCQ-1 or TPZ in vitro and in vivo.

PURPOSE: To investigate potential synergistic interactions between bioreductive agents, either NLCQ-1 or tirapazamine (TPZ) and two alkylating chemotherapeutic drugs, and how such interactions compare in vitro and in vivo. MATERIALS AND METHODS: V79 cells (in vitro studies) and the SCCVII/C3H murine tumor model (in vivo studies) were used. The alkylating chemotherapeutic agents examined were cisplatin (cisDDP) and melphalan (L-PAM). In vivo, all agents were administered by i.p. injection wherein NLCQ-1 and TPZ were given at equitoxic doses of 10 and 23 mg/kg, respectively. Optimal administration schedules and dose modification factors (DMF) were determined in vivo for the antitumor effect or bone marrow toxicity by using the in vivo-in vitro clonogenic assay as the endpoint. RESULTS: A schedule-dependent synergistic interaction was observed between NLCQ-1/TPZ and each alkylating agent, both in vitro and in vivo, and an optimal potentiation was obtained when each bioreductive agent was administered prior to each chemotherapeutic drug. However, significant DMF values and an in vivo therapeutic index (TI) was obtained only with NLCQ-1. Limited mechanistic studies in V79 cells by using the alkaline comet assay demonstrated that hypoxic preincubation with NLCQ-1 increases the cross-links induced by subsequent aerobic exposure to cisDDP. CONCLUSIONS: These results verify our previous observations in EMT6 tumors and suggest a potential clinical use of NLCQ-1 as a synergistic adjuvant to chemotherapy with alkylating agents against solid tumors possessing hypoxic regions.

Animals↗