Biomedical subjects

B W Fox

Publications and source records attributed to B W Fox.

At least 37 records · Page 2Linked to original sources

PubMed1991

Effect of verapamil on daunorubicin accumulation in lymphocytes isolated from patients undergoing chemotherapy.

Verapamil was shown to be capable of increasing intracellular daunorubicin levels in normal lymphocytes isolated from patients undergoing chemotherapy for epithelial ovarian cancer. The extent of the increase in daunorubicin accumulation was variable, occurring in the range of 0-123% as compared with intracellular daunorubicin levels attained in the absence of verapamil. No similar effect was seen in lymphocytes isolated from healthy volunteers. A tentative explanation of these data may be the induction of multidrug resistance (mdr)-like characteristics in normal lymphocytes following cytotoxic chemotherapy.

Daunorubicin↗

PubMed1991

Metallothionein levels in ovarian tumours before and after chemotherapy.

The metallothionein content of ovarian tumours is considerably higher than that found in normal ovaries (greater than 100-fold differences in mean values, P less than 0.001). There was no difference between the metallothionein content of tumours from patients who had completed chemotherapy, usually with a regimen containing a platinum drug, and tumours from untreated patients. Similarly, the level of metallothionein was not influenced by response to therapy, age, stage, histology, or tumour cell differentiation state. These data do not support the hypothesis that metallothionein content is a major determinant of tumour sensitivity in ovarian cancer.

Adult↗

PubMed1991

DNA interstrand crosslinking and sequence selectivity of dimethanesulphonates.

Members of the homologous series of alkanediol dimethanesulphonates of general formula H3C.SO2O.(CH2)n.O.SO2.CH3 have been tested for their ability to produce DNA interstrand crosslinking and DNA sequence selectivity of guanine-N7 alkylation. In a sensitive crosslinking gel assay the efficiency of DNA interstrand crosslink formation, dependent on the ability of the alkylating moiety to span critical nucleophilic distances within the DNA, was found at 6 h to be 1,6-hexanediol dimethanesulphonate (Hexa-DMS) (n = 6) greater than methylene dimethanesulphonate (MDMS) (n = 1) greater than 1,8-octanediol dimethanesulphonate (Octa-DMS) (n = 8) greater than Busulphan (n = 4). The DNA interstrand crosslinking produced by MDMS was not due to either of its hydrolysis products, formaldehyde or methanesulphonic acid (MSA). In contrast the extent of monoalkylation at guanine-N7 as determined by a modified DNA sequencing technique was found to be Busulphan much greater than Hexa-DMS = Octa-DMS, with a sequence selectivity somewhat less than that of other chemotherapeutic alkylating agents such as nitrogen mustards. MDMS at high levels induced a non-specific depurination as a result of the reduction in pH resulting from MSA release. More strikingly MDMS (and MSA) produced a single strong site of guanine reaction (depurination) in a guanine-rich 276 base pair fragment of pBR322 DNA in the sequence of 5'-ATGGTGG-3'. This was observed when non-specific depurination was negligible and was not seen with formic acid. Thus structurally similar alkylating agents can differ in their type and extent of DNA monoalkylation and interstrand crosslinking, and in some cases (e.g. MDMS/MSA) produce reactions with a high degree of selectivity.

Alkylation↗

PubMed1991

Dimethanesulphonate esters in receptor mapping studies. 1. Benzene 1,2-, 1,3- and 1,4-diol, dimethanol and diethanol dimethanesulphonates and anti-tumour activity.

The anti-tumour activities of nine aromatic dimethanesulphonate esters were examined. Their biological effects have been related to both their chemical reactivity and to the computer-modelled vectorial positions of the centres of alkylation of the compounds. One compound (19) has shown activity between sensitive and resistant Yoshida tumours in vivo and also shows the highest activity between these two cell lines in vitro. In its minimal energy form, this compound would require to interact with converging nucleophilic centres about 6 A apart, and it is tentatively suggested that this may be an appropriate dimension for a receptor which is required to be alkylated in order to show anti-tumour activity.

Animals↗

PubMed1990

Differential cytotoxicity of combretastatins A1 and A4 in two daunorubicin-resistant P388 cell lines.

Combretastatin A4, a novel anti-mitotic agent was effective against two P388 cell lines with acquired resistance to daunorubicin. In contrast, Combretastatin A1, a close structural analogue of A4, showed a high degree of cross-resistance. Combretastatin A1 was also more efficient at increasing intracellular daunorubicin concentrations in both resistant cell lines. Neither agent was capable of altering anthracycline accumulation in the parental (sensitive) cell line. We propose that the cross-resistance to Combretastatin A1 occurs, at least in part, as a result of the increased affinity of the drug-efflux process operative in these resistant cells for Combretastatin A1 vs Combretastatin A4. Hence, Combretastatin A4 may play a role in the treatment of tumours with acquired resistance to the anthracycline antibiotics.

Animals↗

PubMed1989

The effect of ifosfamide and its metabolites on intracellular glutathione levels in vitro and in vivo.

The effect of ifosfamide and its metabolites on intracellular levels of glutathione in P388 cells in vitro has been studied. It is demonstrated that glutathione depletion occurs only in the presence of 4-hydroperoxyifosfamide and chloroacetaldehyde. In contrast isophosphoramide mustard had no effect on glutathione levels in intact cells. The concentration of 4-hydroperoxyifosfamide required to reduce glutathione levels by 50% was approximately 1 mM and this represents a concentration far in excess of that achievable in patients receiving the drug. However the concentration of chloroacetaldehyde (approximately 100 microM) required to reduce intracellular levels of glutathione to a similar extent is attained in patients receiving ifosfamide. The glutathione levels in lymphocytes isolated from a patient undergoing an eight hour infusion of ifosfamide showed a marked decrease to about 30% of their original value. We conclude that ifosfamide causes glutathione depletion in vivo and the majority of this can be accounted for by the production of chloroacetaldehyde.

Acetaldehyde↗

PubMed1989

Isolation and characterization of proteins cross-linked to DNA by the antitumor agent methylene dimethanesulfonate and its hydrolytic product formaldehyde.

This study attempted to characterize proteins cross-linked to DNA of Yoshida lymphosarcoma cells treated with methylene dimethanesulfonate (MDMS) and its hydrolytic products formaldehyde (HCHO) and methanesulfonic acid (MSA). MDMS and HCHO treatments produced a similar extent and type of DNA-protein cross-linking in Yoshida lymphosarcoma cells. All five major histones (H1, H2a, H2b, H3, and H4) were among the nuclear proteins cross-linked to DNA. Certain discrete differences were also apparent in these studies. MDMS cross-linked proteins of 29 and 48 kDa to DNA that were not observed following HCHO treatment alone, and HCHO cross-linked a 26-kDa protein to DNA that was not observed following MDMS treatment. Because semicarbazide prevented all MDMS-induced DNA-protein cross-linking, HCHO must be the component responsible for this lesion. The 26-kDa protein has been identified as an H4-H2b dimer. The formation of this dimer is particularly sensitive to MSA release on hydrolysis of MDMS because, in the presence of MSA, HCHO preferentially cross-linked an H2a-H2b dimer and a 48-kDa non-histone protein to DNA. Differences in DNA-protein cross-linking between these two agents are therefore proposed to arise from discrete changes in chromatin structure induced directly by MSA release.

Animals↗

PubMed1989

Structures of three DNA cross-linking agents, ethane-1,2-di(methylsulfonate), propane-1,3-di(methylsulfonate) and n-butane-1,4-di(methylsulfonate).

(I): C4H10O6S2, Mr = 218.25, P2(1)/c, a = 7.2611 (9), b = 5.8726 (4), c = 10.6628 (19) A, beta = 103.95 (1) degree, V = 441.3 (2) A3, Z = 2, Dm = 1.65, Dx = 1.642 Mg m-3, lambda(Cu K alpha) = 1.54184 A, mu = 5.43 mm-1, F(000) = 228, R = 0.0336 and wR = 0.0346 for 745 unique reflections with F greater than or equal to 3 sigma (F), T = 298 K. (II): C5H12O6S2, Mr = 232.28, P2(1)/c, a = 11.030 (1), b = 8.452 (1), c = 11.162 (1) A, beta = 104.65 (1) degree, V = 1006.8 (3) A3, Z = 4, Dm 1.54, Dx = 1.532 Mg m-3, lambda(Cu K alpha) = 1.54184 A, mu = 4.79 mm-1, F(000) = 488, R = 0.0418 and wR = 0.0430 for 1666 unique reflections with F greater than or equal to 3 sigma(F), T = 298 K. (III): C6H14O6S2, Mr = 246.30, P1, a = 5.6147 (9), b = 6.8343 (6), c = 7.5434 (6) A, alpha = 110.61 (1), beta = 92.08 (1), gamma = 76.15 (1) degree, V = 262.7 (3) A3, Z = 1, Dm = 1.56, Dx = 1.557 Mg m-3, lambda(Cu K alpha) = 1.54184 A, mu = 4.79 mm-1, F(000) = 130, R = 0.0397 and wR = 0.0425 for 907 unique reflections with F greater than or equal to 3 sigma(F), T = 298 K. All three compounds have a common conformation in the C.O.SO2.CH3 part of the molecules due to weak O...H interactions. Compounds (I) and (III) have a trans conformation about the central C--C bond, whereas (II) is cis.

Busulfan↗

PubMed1989

Interaction of the novel agent amphethinile with tubulin.

The novel agent amphethinile is shown to inhibit tubulin assembly in vitro. This agent is capable of displacing colchicine but not vinblastine from tubulin and causes a stimulation in GTPase activity in vitro. The affinity constant for the association of this drug with tubulin has been determined (Ka = 1.3 x 10(6) M-1). It is concluded that amphethinile belongs to the class of agents which share a common binding site with colchicine on the tubulin molecule.

Animals↗

PubMed1989

Structural and biochemical comparison of the anti-mitotic agents colchicine, combretastatin A4 and amphethinile.

The novel agents amphethinile and combretastatin A4 are shown to be very similar to colchicine in their interactions with purified tubulin. All three agents can inhibit tubulin assembly at similar treatment levels and have comparable affinity constants for tubulin. Amphethinile and combretastatin A4 are capable of displacing colchicine but not vinblastine from tubulin. A comparison of the structures of these agents shows that whereas colchicine and combretastatin A4 contain a trimethoxybenzene group (a moiety also found in other colchicine-like agents such as podophyllotoxins and steganacin) no obvious similarity is seen for amphethinile. The three-dimensional structures of these agents, determined from either crystallographic data or by energy minimization procedures, show, however, that all three agents consist of two planar, or almost planar, ring systems which are tilted with respect to each other. Using computer graphic techniques it can be shown that their ring systems are superimposable and that the planar sections of each molecule are at an angle of 50-60 degrees to each other. It is proposed that the angular bicyclic structure of these agents is one determining factor for their efficient binding to tubulin.

Animals↗

PubMed1988

An autoradiographic study of the intrarenal localisation and retention of cisplatin, iproplatin and paraplatin.

The intrarenal localisation of platinum following the intravenous administration of platinum-195m-labelled cisplatin, iproplatin and paraplatin was studied using autoradiography. Following injection of cisplatin, platinum was distributed throughout the kidney even up to 14 days after treatment. In the case of iproplatin and paraplatin rapid platinum clearance was noted from the glomeruli, blood vessels and renal medulla within 2 h of administration. Relative cortical and medullary platinum radionuclide concentrations for all three agents were determined by Chalkley grid analysis. This showed greater relative concentrations of platinum in the cortex at increasing times following iproplatin and paraplatin compared with cisplatin. It is suggested that the lower renal toxicity of iproplatin and paraplatin than of cisplatin may be due to reduced platinum retention within the pars recta.

Animals↗

PubMed1988

A phase I and pharmacokinetic study of amphethinile.

Amphethinile is a new spindle poison with a novel structure that has shown activity in the L1210, ADJ/PC6 and Walker carcinoma rodent tumours. In addition the agent appeared to have an improved therapeutic ratio compared to existing spindle poisons and is well absorbed when administered orally. The starting dose for the phase I study was 40 mg m-2 (1/10th mouse LD10) and further patients were studied at 200, 400, 800 and 1200 mg m-2, dose escalation being based on pharmacological monitoring. Significant toxic effects were seen only at 800 and 1200 mg m-2. At these doses patients experienced nausea and vomiting, light headedness during the infusion and varying degrees of lethargy following therapy. Two of six patients at 800 mg m-2 developed severe pain in the tumour bearing area 1-2 h after treatment and one experienced colicky abdominal pain. At 1200 mg m-2 two patients died within 48 h of treatment from what appeared to be vascular causes. Following these episodes the trial was discontinued. Neutropenia and alopecia occurred in two patients, one at 800 and one at 1200 mg m-2. These patients achieved the highest drug exposure in terms of area under the concentration x time curve. It was not possible to achieve an AUC consistently high enough to produce cytotoxic effects due to the occurrence of dose limiting toxicities thus amphethinile cannot at present be recommended for phase II testing by the i.v. route. The dose escalation scheme based on pharmacological monitoring resulted in a considerable saving in the duration of the trial. Further evaluation of this methodology is recommended.

Adult↗

PubMed1988

Pre-clinical studies of a novel anti-mitotic agent, amphethinile.

A new antitumour agent is described, which has been shown to induce a G2/M block in murine leukaemia cells in vitro. In addition this agent has been shown to be equally toxic toward parental and daunorubicin-resistant P388 cells in vitro. These resistant cells are highly cross-resistant to the established anti-mitotic agents vincristine and vinblastine. Drug accumulation studies in cells have shown that whereas resistance in this cell line is associated with decreased drug accumulation in the case of daunorubicin, vincristine and vinblastine, this effect is much less pronounced for amphethinile. It is proposed that amphethinile is a poor substrate for the drug efflux process associated with the pleiotropic resistance mechanism operating in these cells. The data suggest that cell sensitivity towards amphethinile differs qualitatively from that of the vinca alkaloids and anthracycline. Pharmacokinetic studies in male mice were undertaken. Area under the curve values (AUC), show that levels of approximately 313 micrograms l-1 h-1 were attained at doses equivalent to the LD10. The alpha half life is approximately 8 min after a bolus intravenous injection. The beta half life was approximately 100 min and relatively independent of dose level.

Animals↗

PubMed1987

Comparative studies of DNA cross-linking reactions following methylene dimethanesulphonate and its hydrolytic product, formaldehyde.

The technique of alkaline elution was employed to study the interactions of methylene dimethane sulphonate (MDMS) and formaldehyde (HCHO) with DNA from Yoshida lymphosarcoma cells treated with these agents. MDMS and HCHO produced a proteinase sensitive filter retention which indicated the presence of DNA-protein cross-links. MDMS also produced some proteinase K-resistant filter retention which was believed to indicate DNA-interstrand cross-linking, whilst only single-strand breaks could be detected following treatment with HCHO. Co-incubation with semicarbazide prevented all DNA-protein cross-links induced by MDMS and HCHO as well as single-strand breaks, most obvious following HCHO treatment. Semicarbazide also reduced HCHO-induced cytotoxicity in the Yoshida lymphosarcoma cell line, while no significant alteration in MDMS-induced cytotoxicity was observed. These results suggest that HCHO-induced DNA-protein cross-links and single-strand breaks do not contribute to MDMS-induced cytotoxicity, and therefore the small but significant level of MDMS-induced DNA-interstrand cross-links is the most likely cytotoxic lesion of this agent.

Animals↗

PubMed1987

Comparison of daunorubicin and anthrapyrazolone sensitivity and transport in resistant cell lines.

Two P388 cell lines with acquired resistance to daunorubicin have been shown to exhibit cross-resistance to anthrapyrazolone (NSC 357885). The degree of cross-resistance observed in these cell lines (58 and 150 fold) is similar to those observed towards daunorubicin (34 and 142 fold). However the decreased drug accumulation observed for daunorubicin in the resistant cell lines (4-6 fold) is not observed for anthrapyrazolone. Similarly, verapamil can increase daunorubicin accumulation in resistant cells but has no effect on anthrapyrazolone accumulation. It is concluded that in contrast to daunorubicin, decreased anthrapyrazolone accumulation is not the resistance mechanism operative in daunorubicin resistant cell lines towards anthrapyrazolone.

Animals↗

PubMed1987

Phase I clinical trial of methylene dimethane sulfonate.

Methylene dimethane sulfonate is the first member of the homologous series of straight-chain diol sulfonates. It was selected for phase I testing because of high activity in the rat Yoshida sarcoma system and a possible novel site of alkylation due to its small molecular size. Methylene dimethane sulfonate was administered as a rapid iv bolus infusion to 39 patients at doses ranging from 14 to 225 mg/m2. Nausea and vomiting were not severe but total alopecia occurred in the majority of patients at doses greater than 100 mg/m2. The dose-limiting toxic effect was thrombocytopenia, which was cumulative with lower, more prolonged nadirs following successive courses. The median time to platelet count nadir was 21 days, with recovery by 35 days. A minor response was seen in one patient with an adenocarcinoma of the lung. The recommended dose for phase II studies is 125 mg/m2 for patients who have received prior chemotherapy and 150 mg/m2 for those who have not, in an every 35-day schedule.

Adult↗

PubMed1986

A proposed mechanism of resistance to cyclophosphamide and phosphoramide mustard in a Yoshida cell line in vitro.

A Yoshida sarcoma cell line (YR/cyclo) showing decreased sensitivity to metabolically activated cyclophosphamide in vitro has been shown to be cross-resistant to phosphoramide mustard, the ultimate alkylating agent formed from cyclophosphamide. Resistance to these alkylating agents has been shown to be associated with increased activity of the glutathione S-transferase group of enzymes, and with elevated levels of glutathione, the cosubstrate of the enzyme. The resistant cell line shows lower levels of cellular damage, as measured by alkaline elution following treatment with phosphoramide mustard, than the parental (YS) line. The mechanism of resistance is ascribed to increased deactivation of potentially damaging metabolites of cyclophosphamide by the glutathione S-transferase enzymes, resulting in decreased cellular damage in the resistant cell line.

Animals↗

PubMed1986

Cross-linking between histones and DNA following treatment with a series of dimethane sulphonate esters.

The cross-linking of the nucleohistone to the associated DNA by a series of methanesulphonates of the busulphan series (CH3SO2O(CH2)nOSO2CH3) from n = 4-9 has been studied by gel electrophoresis, by the use of 35S labelling and by pyrenemaleimide competition. It has been shown that all the dimethanesulphonates react with the Cys 114 of histone H3, and that octamethylene dimethanesulphonate (n = 8) cross-links histone H3 with DNA via the sulphydryl group, as well as forming H3-H3 dimers.

Animals↗