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Biomedical subjects

K D Paull

Publications and source records attributed to K D Paull.

At least 37 records · Page 2Linked to original sources
PubMed1993

Dual inhibition of topoisomerase II and tubulin polymerization by azatoxin, a novel cytotoxic agent.

Azatoxin (NSC 640737) is a synthetic molecule that was rationally designed as a topoisomerase II inhibitor (Leteurtre et al., Cancer Res 52: 4478-4483, 1992). The present study was undertaken in order to investigate the molecular pharmacology and the cytotoxic activity of azatoxin in human tumor cells. Alkaline elution experiments performed in HL-60 cells demonstrated that: (1) azatoxin induces DNA-protein cross-links and protein-linked DNA single- and double-strand breaks characteristics of topoisomerase II inhibition in HL-60 cells; and (2) the potency of azatoxin is comparable to that of etoposide (VP-16). Testing of azatoxin in 45 human cell lines in the National Cancer Institute (NCI) in vitro Drug Screening Program indicated that azatoxin was potent (mean IC50 = 0.13 microM), but that its cell line sensitivity profile was correlated with that of tubule inhibitors rather than that of topoisomerase II inhibitors. These data led us to investigate the anti-tubulin activity of azatoxin. We found that azatoxin inhibited tubulin polymerization in vitro and was a mitotic inhibitor at 1 microM and above in the human colon cancer cell line KM20L2. In these cells topoisomerase II inhibition, as detected by the induction of protein-linked DNA strand breaks, required azatoxin concentrations of at least 10 microM. In summary, azatoxin is a potent cytotoxic agent that inhibited both tubulin and topoisomerase II. At lower azatoxin concentrations the former activity prevailed whereas at higher concentrations topoisomerase II inhibition became prominent.

Cell Death↗
PubMed1993

Synthesis and cytotoxicity of 1,6,7,8-substituted 2-(4'-substituted phenyl)-4-quinolones and related compounds: identification as antimitotic agents interacting with tubulin.

A series of 1,6,7,8-substituted 2-(4'-substituted phenyl)-4-quinolones and related compounds have been synthesized and evaluated as cytotoxic compounds and as antimitotic agents interacting with tubulin. The 2-phenyl-4-quinolones (22-30) with substituents (e.g. F, Cl, and OCH3) at C-6, C-7, and C-8 show, in general, potent cytotoxicity against human lung carcinoma (A-549), ileocecal carcinoma (HCT-8), melanoma (RPMI-7951), and epidermoid carcinoma of the nasopharynx (KB) and two murine leukemia lines (P-388 and L1210). Introduction of alkyl groups at N-1 or C-4 oxygen led to inactive compounds (35-43 and 50). In addition, compounds 24, 26, and 27 were evaluated in the National Cancer Institute's 60 human tumor cell line in vitro screen. These compounds demonstrated the most marked effects in the screen on two colon carcinoma cell lines (COLO-205 and KM-20L2) and on a central nervous system tumor cell line (SF-539) with compound 26 the most potent of the three agents. Compounds 24, 26, and 27 were potent inhibitors of tubulin polymerization, with activity nearly comparable to that of the potent antimitotic natural products colchicine, podophyllotoxin, and combretastatin A-4. The three agents also inhibited the binding of radiolabeled colchicine to tubulin, but this inhibition was less potent than that obtained with the natural products.

Animals↗
PubMed1993

In vitro assessment of N-[2-(dimethylamino)ethyl]acridine-4-carboxamide, a DNA-intercalating antitumour drug with reduced sensitivity to multidrug resistance.

The successful treatment of cancer requires the identification of new drugs with novel actions. N-[2-(Dimethylamino)ethyl]acridine-4-carboxamide dihydrochloride (DACA) is a topoisomerase II-targeted antitumour drug with curative activity against murine Lewis lung carcinoma. DACA was assessed for novel patterns of growth inhibition using normal and multidrug-resistant human cell lines. Cells were cultured in 96-well microtitre trays and tested against DACA and related topoisomerase-directed drugs, including amsacrine, etoposide and doxorubicin, and drug concentrations for 50% growth inhibition (IC50 or GI50 values) were determined. In a series of Jurkat leukaemia lines characterised as exhibiting atypical multidrug resistance, DACA was to a large extent capable of overcoming multidrug resistance exhibited towards the other topoisomerase-directed agents. DACA was also tested against the National Cancer Institute 60-tumour-specific cell-line panel (GI50 values ranging from 420 to 5,400 nM; mean, 2,100 nM) and against a series of primary cultures of surgically excised melanomas (IC50 values ranging from 60 to 1,600 nM; mean, 590 nM). DELTA values (deviations of logarithmic IC50 or GI50 values from the mean) were calculated and compared by correlation analysis. The standard deviation of DELTA values was found to be lower for DACA than for the other topoisomerase II-directed drugs amsacrine, etoposide, doxorubicin and mitozantrone in both the cell lines and the primary cultures. These lower standard deviations appear to have resulted from the reduced susceptibility of DACA to both P-glycoprotein- and topoisomerase II-mediated multidrug-resistance mechanisms occurring naturally in cell lines and primary cultures.

Acridines↗
PubMed1992

Cytotoxicity of a new IMP dehydrogenase inhibitor, benzamide riboside, to human myelogenous leukemia K562 cells.

COMPARE computer program suggested that benzamide riboside, BR, 3-(1-deoxy-beta-D-ribofuranosyl)benzamide, should have a similar mechanism of action as that of tiazofurin, an inhibitor of IMP dehydrogenase (IMPDH). This hypothesis was tested in K562 cells in culture. BR was cytotoxic to K562 cells with an IC50 of 2 microM. Incubation of K562 cells with BR resulted in a significant decrease in GMP and GTP levels with a concurrent increase in IMP pools, and with a significant inhibition of IMPDH activity. However, 290-fold higher BR concentration was needed to demonstrate in vitro inhibition of IMPDH activity, suggesting that the agent may require metabolism to exert its action. These results provide evidence that BR is a new inhibitor of IMPDH. This investigation should be helpful to design new analogues having activity against IMPDH.

Antineoplastic Agents↗
PubMed1992

Identification of novel antimitotic agents acting at the tubulin level by computer-assisted evaluation of differential cytotoxicity data.

Data generated in the new National Cancer Institute drug evaluation program, which are based on inhibition of cell growth in 60 human tumor cell lines, were probed with nine known antimitotic agents using the COMPARE algorithm. Cytotoxicity data were available on approximately 7000 compounds at the time of the analysis, and, based on the criteria used, 82 compounds were selected as positive by the computer search. Nine were the probe compounds themselves, and 41 were analogues of known antimitotic agents. Among the remaining 32 compounds there were 19 distinct chemical species. Agents in ten of these groups (containing 20 compounds) were effective inhibitors of in vitro tubulin polymerization and caused the mitotic arrest of cells grown in culture. Two compounds were related natural products binding in the Vinca domain of tubulin, and the others were synthetic agents which interfered with colchicine binding. The remaining 12 agents (one natural product, the remainder synthetic) fell into several groups: two compounds were weak inhibitors of tubulin polymerization, inhibited colchicine binding, and caused mitotic arrest; one compound weakly inhibited tubulin polymerization but did not cause an increase in the number of cells arrested in mitosis; two compounds caused mitotic arrest at micromolar concentrations, but thus far no in vitro interaction with tubulin has been observed; the remainder neither inhibited tubulin polymerization nor caused a rise in the number of cultured cells arrested in mitosis. Tubulin-dependent GTP hydrolysis was stimulated or inhibited by all agents which inhibited tubulin polymerization with the exception of one compound. The analysis of differential cytotoxicity data thus appears to have great promise for the identification of new antimitotic agents with antineoplastic potential.

Algorithms↗
PubMed1992

Multidrug-resistant phenotype of disease-oriented panels of human tumor cell lines used for anticancer drug screening.

Disease-oriented panels of human tumor cell lines used by the National Cancer Institute for large-scale in vitro anticancer drug screening were evaluated for multidrug-resistant phenotype at the functional (in vitro drug sensitivity) and molecular levels. The cell line panels manifested a broad range of sensitivities to drugs typically associated with multidrug resistance (MDR) as well as to drugs not associated with MDR. Individual cell lines displayed unique and characteristic profiles of response. Patterns of correlated response were observed among, but not between, MDR and non-MDR drugs. Strong evidence of correlated response was limited to drugs sharing an intracellular mechanism of action. Several tumor cell lines exhibited a high degree of resistance to MDR drugs and relative sensitivity to non-MDR drugs, contained high levels of MDR-1 mRNA, and expressed cell surface P-glycoprotein detectable with one or more monoclonal antibodies. Parallel expression of all of these features representing the classic MDR phenotype was observed among members of the colon and renal tumor panels. Certain individual cell lines among other panels (lung, ovarian, melanoma, and central nervous system) also manifested some aspects of the MDR phenotype to various extents. Identification of MDR cell lines used for large-scale in vitro anticancer drug screening will facilitate interpretation of data in a way which may allow identification of new drug leads of potential value in treatment of MDR tumor cell populations.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1992

Preclinical antitumour activity and animal toxicology studies of rhizoxin, a novel tubulin-interacting agent.

Rhizoxin is a 16-membered antifungal macrocyclic lactone isolated from the plant pathogenic fungus Rhizopus chinensis. The compound binds to tubulin, preventing microtubule formation, and inhibiting mitosis. It possesses antitumour activity in vivo against various preclinical murine models, both leukaemias and solid tumours model, as well as in vincristine- and doxorubicin-resistant leukaemia lines. In the present study, cytotoxic activity was observed in human tumour cell lines in vitro at very low concentrations (+/- 10(-10) M) particularly against melanoma, colon, renal, non-small cell and small cell lung cancer. In vivo antitumour activity was demonstrated in murine P388 and L1210 murine leukaemias, solid tumour models B16 melanoma and M5076 sarcoma, and in 5 out of 9 human solid tumour xenografts: LOX melanoma, MX-1 breast cancer, non-small cell lung cancer A549, and small cell lung cancers LXFS 605 and LXFS 650. The absence of cross-resistance to vinca alkaloids was confirmed in vivo against the vincristine-resistant P388 leukaemia subline and the vincristine-resistant human small cell lung cancer LXFS 650. In addition, the antitumour activity of rhizoxin was improved by prolonged or repeated drug administration indicating a schedule dependency. In animal toxicology studies, transient changes in erythrocyte and leukocyte numbers, local phlebitis, diarrhea, and spermatogenic arrest were observed. The LD10 value of rhizoxin after a single intravenous injection was 2.8 mg/kg (8.4 mg/m2). One-tenth of the mouse equivalent LD10 (0.84 mg/m2), the starting dose for clinical phase I studies, was considered to be safe in rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1991

Halichondrin B and homohalichondrin B, marine natural products binding in the vinca domain of tubulin. Discovery of tubulin-based mechanism of action by analysis of differential cytotoxicity data.

Data generated in the new National Cancer Institute drug evaluation program, which is based on inhibition of cell growth in 60 human tumor cell lines, were used to compare new compounds with agents of known mechanism of action in terms of their differential cytotoxicity. Two marine natural products, halichondrin B and homohalichondrin B, appeared repeatedly when the data base was probed with known antimitotic agents. We confirmed that both compounds were highly cytotoxic (IC50 values for L1210 murine leukemia cells of 0.3 and 1 nM, respectively), with accumulation of cells arrested in mitosis at toxic concentrations, that both inhibited the polymerization of purified tubulin, and that both inhibited microtubule assembly dependent on microtubule-associated proteins. Limited amounts of homohalichondrin B, the less active agent, were available, so only halichondrin B was studied in detail. Halichondrin B did not interfere with colchicine binding to tubulin, but it was a noncompetitive inhibitor of the binding of vinblastine to tubulin (apparent Ki, 5.0 microM). Halichondrin B was therefore compared with other agents which interfere with the binding of vinca alkaloids to tubulin (vinblastine, maytansine, dolastatin 10, phomopsin A, rhizoxin) in terms of its effects on tubulin polymerization, inhibition of GTP hydrolysis, inhibition of nucleotide exchange, and stabilization of tubulin, as well as the quantitative assessment of its effects on vinca alkaloid binding and inhibition of cell growth. Since halichondrin B was originally isolated from the same organism as the phosphatase inhibitor okadaic acid, and since it is about 50-fold more effective than okadaic acid as an inhibitor of L1210 cell growth, perturbations of cellular microtubules observed following treatment with okadaic acid should be interpreted cautiously.

Animals↗
PubMed1990

Comparison of in vitro anticancer-drug-screening data generated with a tetrazolium assay versus a protein assay against a diverse panel of human tumor cell lines.

The National Cancer Institute (NCI) is implementing a large-scale in vitro drug-screening program that requires a very efficient automated assay of drug effects on tumor cell viability or growth. Many laboratories worldwide have adopted a microculture assay based on metabolic reduction of 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). However, because of certain technical advantages to use of the protein-binding dye sulforhodamine B (SRB) in a large-scale screening application, a detailed comparison of data generated by each type of assay was undertaken. The MTT and SRB assays were each used to test 197 compounds, on simultaneous days, against up to 38 human tumor cell lines representing seven major tumor categories. On subsequent days, 38 compounds were retested with the SRB assay and 25 compounds were retested with the MTT assay. For each of these three comparisons, we tabulated the differences between the two assays in the ratios of test group values to control values (T/C) for cell survival; calculated correlation coefficients for various T/C ratios; and estimated the bivariate distribution of the values for IC50 (concentration of drug resulting in T/C values of 50%, or 50% growth inhibition) for the two assays. The results indicate that under the experimental conditions used and within the limits of the data analyses, the assays perform similarly. Because the SRB assay has practical advantages for large-scale screening, however, it has been adopted for routine use in the NCI in vitro antitumor screen.

Antineoplastic Agents↗
PubMed1989

Display and analysis of patterns of differential activity of drugs against human tumor cell lines: development of mean graph and COMPARE algorithm.

The objective of this study was to develop and investigate an approach to optimally detect, rank, display, and analyze patterns of differential growth inhibition among cultured cell lines. Such patterns of cellular responsiveness are produced by substances tested in vitro against disease-oriented panels of human tumor cell lines in a new anticancer screening model under development by the National Cancer Institute. In the first phase of the study, we developed a key methodological tool, the mean graph, which allowed the transformation of the numerical cell line response data into graphic patterns. These patterns were particularly expressive of differential cell growth inhibition and were conveniently amenable to further analyses by an algorithm we devised and implemented in the COMPARE computer program.

Antineoplastic Agents↗
PubMed1989

Preclinical antitumor activity of an alpha-picoline derivative, penclomedine (NSC 338720), on human and murine tumors.

Penclomedine, a synthetic alpha-picoline derivative, was identified as a potential antitumor agent in the P388 leukemia prescreen of the National Cancer Institute. Upon further evaluation in the National Cancer Institute in vivo tumor panel, the compound demonstrated good activity against two breast tumors. A single i.p. dose or five daily doses caused partial regressions of advanced-stage s.c. implanted mouse CD8F1 mammary adenocarcinomas. Also, penclomedine administered i.p. on Days 1,5, and 9 caused regression of the human MX-1 mammary carcinoma implanted under the renal capsule of athymic mice. In contrast, penclomedine demonstrated only marginal to moderate activity against the i.p. implanted L1210 leukemia and M5076 sarcoma and was inactive in three additional non-breast tumor models (i.p. B16 melanoma, i.v. Lewis lung carcinoma, and s.c. colon adenocarcinoma 38). Penclomedine administered p.o. and i.p. was equally effective against the subrenal capsule MX-1. Doses given p.o. every fourth day caused complete regression of 39 of 40 advanced-stage s.c. implanted MX-1 tumors but were much less effective against human H82 small cell lung carcinomas (13 of 80 complete regressions). Penclomedine p.o. also inhibited growth of the human MCF-7 and mouse 16/C breast adenocarcinomas. Further studies to support the development of penclomedine to clinical trial are in progress.

Animals↗
PubMed1988

Evaluation of a soluble tetrazolium/formazan assay for cell growth and drug sensitivity in culture using human and other tumor cell lines.

We have previously described the application of an automated microculture tetrazolium assay (MTA) involving dimethyl sulfoxide solubilization of cellular-generated 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT)-formazan to the in vitro assessment of drug effects on cell growth (M.C. Alley et al., Proc. Am. Assoc. Cancer Res., 27:389, 1986; M.C. Alley et al., Cancer Res. 48:589-601, 1988). There are several inherent disadvantages of this assay, including the safety hazard of personnel exposure to large quantities of dimethyl sulfoxide, the deleterious effects of this solvent on laboratory equipment, and the inefficient metabolism of MTT by some human cell lines. Recognition of these limitations prompted development of possible alternative MTAs utilizing a different tetrazolium reagent, 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)-5-[(phenylamino)carbonyl] -2H- tetrazolium hydroxide (XTT), which is metabolically reduced in viable cells to a water-soluble formazan product. This reagent allows direct absorbance readings, therefore eliminating a solubilization step and shortening the microculture growth assay procedure. Most human tumor cell lines examined metabolized XTT less efficiently than MTT; however, the addition of phenazine methosulfate (PMS) markedly enhanced cellular reduction of XTT. In the presence of PMS, the XTT reagent yielded usable absorbance values for growth and drug sensitivity evaluations with a variety of cell lines. Depending on the metabolic reductive capacity of a given cell line, the optimal conditions for a 4-h XTT incubation assay were 50 micrograms of XTT and 0.15 to 0.4 microgram of PMS per well. Drug profiles obtained with representative human tumor cell lines for several standard compounds utilizing the XTT-PMS methodology were similar to the profiles obtained with MTT. Addition of PMS appeared to have little effect on the metabolism of MTT. The new XTT reagent thus provides for a simplified, in vitro cell growth assay with possible applicability to a variety of problems in cellular pharmacology and biology. However, the MTA using the XTT reagent still shares many of the limitations and potential pitfalls of MTT or other tetrazolium-based assays.

Azo Compounds↗
PubMed1988

Preclinical antitumor activity of batracylin (NSC 320846).

Batracylin (NSC 320846, BAY H 2049), given ip on days 2 and 9 at a dose 400 mg/kg, inhibited tumor growth completely in 80-100% of mice with early-stage colon adenocarcinoma 38. Therapeutic efficacy against this subcutaneously implanted tumor was retained upon oral administration of Batracylin although, compared to ip treatment, larger doses were required. Batracylin also caused regression of advanced (400 mg) colon 38 tumors. Only modest activity was observed for this compound against P388 leukemia, but P388 sublines with acquired resistance to either adriamycin or cisplatin demonstrated collateral sensitivity. Batracylin currently is undergoing toxicological evaluation by NCI prior to clinical trials.

Adenocarcinoma↗
PubMed1987

In vivo antitumor activity of 6-benzyl-1,3-benzodioxole derivatives against the P388, L1210, B16, and M5076 murine models.

A series of 6-benzyl-1,3-benzodioxoles have been synthesized and evaluated against the in vivo ip P388 murine lymphocytic leukemia. Selected activities against this system were tested against the additional in vivo systems L1210, B16, M5076, and MX1. The most active of the 6-benzyl-1,3-benzodioxoles tested were as effective as podophyllotoxin as experimental antitumor agents in vivo, but larger doses were required. Three of the P388-active series members were active against the in vitro astrocytoma assay, which detects compounds that interfere with or bind to tubulin.

Animals↗
PubMed1986

Flavone acetic acid: a novel agent with preclinical antitumor activity against colon adenocarcinoma 38 in mice.

Flavone acetic acid, given on Days 2 and 9 at a dose of 267 mg/kg, inhibited tumor growth completely in 60%-80% of mice with early-stage Colon Adenocarcinoma 38. The therapeutic efficacy of the flavone against this tumor was retained when the sites of tumor implantation and drug administration were separated. Flavone acetic acid also caused regression of advanced (500-mg) Colon 38 tumors, with greatest efficacy observed following administration of high individual dose rather than high total dose. Unlike many previous potential anticancer agents, only modest activity was observed for this compound against either P388 or L1210 leukemia.

Adenocarcinoma↗