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Ataxia telangiectasia and Rad3-related protein (ATR) is a critical component of the DNA damage response and a potential target in the treatment of cancers. An ATR inhibitor, BAY 1895344, was evaluated for its use in differentiated thyroid cancer (DTC) therapy. BAY 1895344 inhibited cell viability in four DTC cell lines (TPC1, K1, FTC-133, and FTC-238) in a dose-dependent manner. BAY 1895344 treatment arrested DTC cells in the G2/M phase, increased caspase-3 activity, and caused apoptosis. BAY 1895344 in combination with either sorafenib or lenvatinib showed mainly synergistic effects in four DTC cell lines. The combination of BAY 1895344 with dabrafenib plus trametinib revealed synergistic effects in K1 cells that harbor BRAFV600E. BAY 1895344 monotherapy retarded the growth of K1 and FTC-133 tumors in xenograft models. The combinations of BAY 1895344 plus lenvatinib and BAY 1895344 with dabrafenib plus trametinib were more effective than any single therapy in a K1 xenograft model. No appreciable toxicity appeared in animals treated with either a single therapy or a combination treatment. Our findings provide the rationale for the development of clinical trials of BAY 1895344 in the treatment of DTC. [ABSTRACT FROM AUTHOR]

Wee1 is a kinase that regulates the G2/M progression by the inh ibition of CDK1, which is critical for ensuring DNA damage repair before initiation of mitotic entry. Targeting Wee1 may be a potential strategy in the treatment of anaplastic thyr oid cancer, a rare but lethal disease. The therapeutic effects of adavosertib, a Wee1 inhibitor for anaplastic thyroid cancer was evaluated in this study. Adavosertib inhibited cell growth in three anaplastic thyroid cancer cell lines in a dose-dependent manner. Cell cycle analysis revealed cells were accumulated in the G2/M phase. Adavosertib induced caspase-3 activity and led to apoptosis. Adavosertib monotherapy showed significant retardation of the growth of two anaplastic thyroid cancer tumor models. The combination of adavosertib with dabrafenib and trametinib revealed strong synergism in vitro and demonstrated robust suppression of tumor growth in vivo in anaplastic thyroid cancer xenograft models with BRAFV600E mutation. The combination of adavosertib with either sorafenib or lenvatinib also demonstrated synergism in vitro and had strong inhibition of tumor growth in vivo in an anaplastic thyroid cancer xenograft model. No appreciable toxicity appeared in mice treated with either a single agent or combination treatment. Our findings suggest adavosertib holds the promise for the treatment of patients with anaplastic thyroid cancer. [ABSTRACT FROM AUTHOR]

Polo-like kinases (PLKs) are pivotal regulators of cell proliferation and cell survival; therefore, PLKs may be potential targets in the treatment of malignancy. The therapeutic effects of volasertib, a PLKs inhibitor for papillary and follicular thyroid cancer (known as well-differentiated thyroid cancer (WDTC)), were evaluated in this study. Volasertib inhibited cell proliferation in two papillary and two follicular thyroid cancer cell lines in a dose-dependent manner. Volasertib treatment reduced cells in the S phase and increased cells in the G2/M phase. Volasertib activated caspase-3 activity and induced apoptosis. Drug combinations of volasertib and sorafenib showed mostly synergism in four welldifferentiated thyroid carcinoma cell lines in vitro. Volasertib treatment in vivo retarded the growth of a papillary thyroid tumor model. Furthermore, the combination of volasertib with sorafenib was more effective than a single treatment of either in a follicular thyroid cancer xenograft model. Promising safety profiles appeared in animals treated with either volasertib alone or volasertib and sorafenib combination therapy. These findings support volasertib as a potential drug for the treatment of patients with WDTC. [ABSTRACT FROM AUTHOR]

Activation of cyclin-dependent kinase activity is frequently observed in many human cancers; therefore, cyclin-dependent kinases that promote cell cycle transition and cell proliferation may be potential targets in the treatment of malignancy. The therapeutic effects of roniciclib, a cyclin-dependent kinase inhibitor for papillary and follicular thyroid cancer (designated as well-differentiated thyroid cancer), were investigated in this study. Roniciclib inhibited cell proliferation in two papillary and two follicular thyroid cancer cell lines in a dose-dependent manner. Roniciclib activated caspase-3 activity and induced apoptosis. Cell cycle progression was arrested in the G2/M phase. Roniciclib treatment in vivo retarded the growth of two well-differentiated thyroid tumors in xenograft models in a dose-dependent fashion. Furthermore, the combination of roniciclib with sorafenib was more effective than either single treatment in a follicular thyroid cancer xenograft model. Acceptable safety profiles appeared in animals treated with either roniciclib alone or roniciclib and sorafenib combination therapy. These findings support roniciclib as a potential drug for the treatment of patients with welldifferentiated thyroid cancer. [ABSTRACT FROM AUTHOR]

Background: We assessed the utility of the dual PI3K/mTOR inhibitor NVP-BEZ235 (BEZ235) as single agent therapy and in combination with conventional chemotherapy for thyroid cancer. Methodology/Principal Findings: Eight cell lines from four types of thyroid cancer (papillary, follicular, anaplastic, medullary) were studied. The cytotoxicity of BEZ235 and five conventional chemotherapeutic agents alone and in combination was measured using LDH assay. Quantitative western blot assessed expression of proteins associated with cell cycle, apoptosis and signaling pathways. Cell cycle distribution and apoptosis were measured by flow cytometry. Murine flank anaplastic thyroid cancers (ATC) were treated with oral BEZ235 daily. We found that BEZ235 effectively inhibited cell proliferation of all cancer lines, with ATC exhibiting the greatest sensitivity. BEZ235 consistently inactivated signaling downstream of mTORC1. BEZ235 generally induced cell cycle arrest at G0/G1 phase, and also caused apoptosis in the most sensitive cell lines. Baseline levels of p-S6 ribosomal protein (Ser235/236) and p27 correlated with BEZ235 sensitivity. Growth of 8505C ATC xenograft tumors was inhibited with BEZ235, without any observed toxicity. Combination therapy of BEZ235 and paclitaxel consistently demonstrated synergistic effects against ATC in vitro. Conclusions: BEZ235 as a single therapeutic agent inhibits thyroid cancer proliferation and has synergistic effects in combination with paclitaxel in treating ATC. These findings encourage future clinical trials using BEZ235 for patients with this fatal disease. [ABSTRACT FROM AUTHOR]

We describe herein the discovery of a series of panaxytriol (PXT)-derived polyacetylene small molecules with promising cytoprotective activity. In mouse xenograft models, we have demonstrated the capacity of our synthetic analogs to mitigate a range of cancer therapeutic agent-induced toxicities, including body weight loss, lethality, neurotoxicity, and hematotoxicity. Our PXT analogs have also been found to reduce radiation-induced body weight loss and lethality in mouse models. Moreover, several PXT analogs appear to exhibit moderate in vivo antiinflammatory activity as well as in vitro immunoenhancing capabilities. These compounds appear to derive their activity through induction of cancer preventive phase 2 enzymes. The studies described herein suggest that coadministration of a PXT-derived agent with cancer chemotherapeutics or radiation therapy may serve to mitigate a range of therapy-associated toxicities. [ABSTRACT FROM AUTHOR]

Imatinib mesylate (STI571, Gleevec®) is a signal transduction inhibitor and novel anti-cancer agent. It selectively inhibits aberrantly activated tyrosine kinases in malignant cells, for example, bcr-abl in leukaemia, platelet-derived growth factor receptor and stem cell factor receptor (c-Kit) in solid cancers including malignant glioma. However, recently published clinical studies with imatinib monotherapy in patients with malignant glioma demonstrated only very modest anti-tumour activity. The aim of this study was to investigate the biological activity of imatinib, its cellular mechanisms of action and its synergism with other chemotherapeutic agents in human malignant glioma cells in culture. Expression of PDGF/R and c-Kit was analyzed by RT-PCR. Proliferation was measured by MTT assays and drug synergy was assessed by the Chou–Talalay method. Cell cycle and apoptosis were analyzed by flow cytometry and migration by monolayer migration assays. Multi-immunoblot was performed on imatinib-treated and control malignant glioma cells. Results indicate that imatinib is more effective in inhibiting cell colony formation and migration rather than proliferation. Imatinib treatment caused cell cycle arrest of glioma cells in G0–G1 or G2/M, with significant elevation of a few cyclin-dependent kinases. Furthermore, imatinib acted synergistically with chemotherapy agents, such as the DNA alkylating agent, temozolomide, and riboneucleotide reductase inhibitors, for example, hydroxyurea at varied effective dose levels. In conclusion, imatinib exerts varied biological effects on malignant glioma cells in culture. Synergistic interaction of imatinib with chemotherapy agents may be related to cell cycle control mechanisms and could be potentially important in a clinical setting. [ABSTRACT FROM AUTHOR]

The epothilones represent a promising class of natural product-based antitumor drug candidates. Although these compounds operate through a microtubule stabilization mechanism similar to that of taxol, the epothilones offer a major potential therapeutic advantage in that they retain their activity against multidrug-resistant cell lines. We have been systematically synthesizing and evaluating synthetic epothilone congeners that are not accessible through modification of the natural product itself. We report herein the results of biological investigations directed at two epothilone congeners: iso-fludelone and iso-dehydelone. Iso-fludelone, in particular, exhibits a number of properties that render it an excellent candidate for preclinical development, including biological stability, excellent solubility in water, and remarkable potency relative to other epothilones. In nude mouse xenograft settings, iso-fludelone was able to achieve therapeutic cures against a number of human cancer cell lines, including mammarian-MX-1, ovarian-SK-OV-3, and the fast-growing, refractory, sub- cutaneous neuroblastoma-SK-NAS. Strong therapeutic effect was observed against drug-resistant lung-A549/taxol and mammary-MCF-7/Adr xenografts. In addition, iso-fludelone was shown to exhibit a significant therapeutic effect against an intracranially implanted SK-NAS tumor. [ABSTRACT FROM AUTHOR]

Purpose: Multidrug resistance (MDR) continues to be a major obstacle for successful anticancer therapy. One of the principal factors implicated in MDR is the over expression of P-glycoprotein (Pgp), the product of the MDR1 gene. Methods: Here we explore the possibility of using the transcription inhibitor tetra- O-methyl nordihydroguaiaretic acid (M4N) to inhibit Sp1-regulated MDR1 gene expression and restore doxorubicin and paclitaxel sensitivity to multidrug resistant human cancer cells in vitro and in vivo. Results: We found that M4N acted synergistically with doxorubicin and paclitaxel in inhibiting the growth of the cells in culture allowing significant dose reductions of both drugs. We observed no such synergism when M4N was used in combination with cisplatin, another chemotherapeutic agent, but not a Pgp substrate, as analyzed by the combination index and isobologram methods. Analysis of MDR1 mRNA and Pgp levels revealed that at sublethal doses, M4N inhibited MDR1 gene expression in the multidrug resistant NCI/ADR-RES cells and reversed the MDR phenotype as measured by Rhodamine-123 retention. In addition, M4N was found to inhibit doxorubicin-induced MDR1 gene expression in drug sensitive MCF-7 breast cancer cells. Conclusions: M4N and maltose-tri- O-methyl nordihydroguaiaretic acid (maltose-M3N), a water-soluble derivative of NDGA, were also able to reverse the MDR phenotype of the tumor cells in a xenograft model system and combination therapy with M4N or maltose-M3N and paclitaxel was effective at inhibiting growth of these tumors in nude mice. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the pharmacological properties and the possible therapeutic applications of a series of synthetic marine natural product analogs, ningalins (N1–N6), in terms of cytotoxicity, MDR-reversing activity, and enhancement of drug combinations with antitumor agents in vitro and in vivo. Methods: XTT assays, [3H]azidopine binding to P-glycoprotein (Pgp), cellular accumulation and efflux of labeled drugs were carried out in vitro. Drug combinations using combination index, dose-reduction index, and isobologram were performed in vitro and enhancement of efficacy in drug combinations against human colon carcinoma HCT-116 xenografts were conducted with nude mice. Results: N3 at sub-IC50 cytotoxic concentration (10 μM) was capable of enhancing vinblastine (VBL) cytotoxicity toward human leukemic CCRF-CEM cells about 50,000-fold as measured by the decrease of IC50 of VBL. For CCRF-CEM/VBL1000 (1,500-fold resistant to VBL and overexpressing Pgp), N3 and N5 enhanced VBL cytotoxicity as much as 6.2 million-fold and 210,000-fold, respectively. Moreover, N3 and N5 collaterally made CCRF-CEM/VBL1000 cells 4,000-fold and 130-fold, respectively, more susceptible to VBL than the parent CCRF-CEM cells. In human mammary carcinoma cells MX-1/paclitaxel which were 170-fold resistant to taxol and 38-fold resistant to VBL, N3 was capable of enhancing VBL effect as much as 6,000-fold. Combination therapy on murine P388/doxorubicin (DX) leukemia with DX + N3 or taxol + N3 achieved greater efficacy than the therapy with each drug alone. Impressively, nude mice, bearing human colon carcinoma HCT-116 cells, treated with a suboptimal dosage of taxol in combination with N3, N5 or N6 led to shrinkage of established tumor and achieved total tumor remission, while taxol alone had no tumor disappearance in this xenograft model. Furthermore, the enhancement of antitumor effect by ningalins, at least in parts, are due to inhibiting Pgp which was supported by the observation that the ningalins compete for [3H]azidopine binding to Pgp, increase the cellular accumulation of VBL or taxol, and inhibit drug efflux from the tumor cells. Conclusion: The profound enhancement of antitumor cytotoxicity of vinblastine and taxol in vitro by ningalins may have multiple mechanisms including the MDR-reversing effects. The mechanisms for collateral sensitivity by ningalins against sensitive (parent) cells are not yet clear. The marked enhancement of therapeutic effect of taxol by ningalins against xenograft tumors in nude mice suggests potential applications of therapeutic use of ningalins. [ABSTRACT FROM AUTHOR]

This report presents a quantitative analysis of the synergistic interaction of arabinosylcytosine (araC) and cladribine (CdA) in human H9-lymphoid cell lines sensitive and resistant to araC (H9-araC cells). H9-araC cells obtained by cultivation of H9 cells in the presence of 0.5 μM arabinosylcytosine (araC) had lower deoxycytidine kinase (dCK) than the parental cell line. The IC50 values of araC and CdA calculated by using median-effect analysis and CalcuSyn software were: 0.55 μM and 1.16 μM for CdA and 0.0058 μM and 3.5 μM for araC in H9 and H9-araC cells, respectively. These values were reduced to 0.10 μM and 0.38 μM for CdA and to 0.004 μM and to 0.77 μM for araC when the drugs were used in combination. Computerized simulation of dose reduction index (DRI) indicated that at 50–99% growth inhibition levels, the doses of araC could be reduced by 2.0 to 11.9-fold and 2.9 to 5.3-fold and the doses of CdA by 5.9 and 183.7-fold and 3.1 to 164.8-fold in H9 and H9-araC cells, respectively, when the drugs are used in combination. Assessment by combination index (CI) analysis showed that the combination exhibited moderate to strong synergistic lympho-cytotoxic effects. CdA metabolic studies (influx and activation) in the presence of deoxyadenosine, deoxycytidine, or araC suggested that CdA enters cells by a deoxyadenosine-inhibitable transport system, which is different than that of araC and deoxycytidine transport system. Thus, in addition to the known mechanisms, other mechanisms might be involved in the metabolism of CdA. The demonstration that araC and CdA combinations exert synergistic cytotoxicity even in the resistant cells raises hope that such a combination may be useful in tumors that were found resistant to these drugs. [ABSTRACT FROM AUTHOR]

Background: Despite the increasing number of antiretroviral compounds, the number of useful drug regimens is limited owing to the high frequency of cross-resistance.Patients and methods: We studied in vitro two-drug combinations using three protease inhibitors (PIs), tipranavir, amprenavir and lopinavir, on isolates (003 and 004) derived from patients with resistance to multiple PIs compared with the drug-susceptible isolate 14aPre in peripheral blood mononuclear cells. Drug interactions were determined by median dose-effect analysis, with the combination index calculated at several inhibitory concentrations (IC).Results: In 14aPre experiments, the combination tipranavir + lopinavir demonstrated synergy at low concentrations (IC50), an additive effect at IC75 and antagonism at IC90IC95; tipranavir + amprenavir were antagonistic at all concentrations except IC95, where they were synergic; and the lopinavir + amprenavir combination was always antagonistic. In 003 and 004 infections, tipranavir + lopinavir and tipranavir + amprenavir combinations were antagonistic, and lopinavir + amprenavir were synergic, at all concentrations, with the exception of being additive at IC95.Conclusions: Our in vitro experiments did not show any advantage in combining second generation PIs as a therapeutic strategy in naive or multi-treatment failure subjects, with the exception of tipranavir + amprenavir at IC95 in infections by a wild-type isolate. [ABSTRACT FROM AUTHOR]

Studies the potent cross-group neutralization of primary human immunodeficiency virus (HIV) isolates with monoclonal antibodies and its implications for acquired immunodeficiency syndrome vaccine. Phylogenetic classification of HIV type 1 (HIV-1); Neutralization capability of human neutralizing monoclonal antibodies (nMAb); Potential of nMAb against divergent virus variants.

To develop immunoprophylaxis regimens against mother-to-child human immunodeficiency virus type 1 (HIV-1) transmission, we established a simian -- human immunodeficiency virus (SHIV) model in neonatal macaques that mimics intrapartum mucosal virus exposure (T.W. Baba, J. Koch, E.S. Mittler et al.: AIDS Res Hum Retroviruses 10:351-357, 1994). We protected four neonates from oral SHIV-vpu[SUP+] challenge by ante- and postpartum treatment with a synergistic triple combination of immunoglobulin (Ig) G1 human anti-HIV-1 neutralizing monoclonal antibodies (mAbs) (T.W. Baba, V. Liska, R. Hofmann-Lehmann et al.: Nature Med 6:200-206, 2000), which recognize the CD4-binding site of Env, a glycosylation-dependent gp 120, or a linear gp41 epitope. Two neonates that received only postpartum mAbs were also protected from oral SHIV-vpu[SUP+] challenge, indicating that postpartum treatment alone in sufficient. Next, we evaluated a similar mAb combination against SHIV89.6P, which encodes env of primary HIV89.6. One of four mAb-treated neonates was protected from infection and two maintained normal CD4[SUP+] T-cell counts. We conclude that the epitopes recognized by the three mAbs are important determinants for achieving protection. Combination immunoprophylaxis with synergistic mAbs seems promising to prevent maternal HIV-1 transmission in humans. [ABSTRACT FROM AUTHOR]

Examines the curative effect of desoxyepothilones B (dEpoB) and F (dEpoF) against human tumor xenografts in mice. Synthesis of microtubule stabilizing agents; Pharmacologic properties of dEopB; Production of nonmultiple drug-resistant human lung carcinoma A549 cells.

Background: A bacterial enzyme, Escherichia coli cytosine deaminase, which converts the prodrug 5-fluorocytosine into the toxic drug 5-fluorouracil, and a viral enzyme, herpes simplex virus thymidine kinase, which converts ganciclovir from an inactive prodrug to a cytotoxic agent by phosphorylation, are being actively investigated for use in gene therapy for cancer. The purpose of this study was to determine whether combining these prodrug-activating gene therapies might result in enhanced anticancer effects.Methods: Rat 9L gliosarcoma cells were transfected with plasmids containing the E. coli cytosine deaminase gene (9L/CD cells), with plasmids containing the herpes simplex virus thymidine kinase gene (9L/TK cells), or with both expression plasmids (9L/CD-TK cells). The drug sensitivities of the cell lines were evaluated; in addition, the sensitivities of 9L and 9L/CD-TK cells mixed in varied proportions were measured. The effects of prodrug treatment on 9L/CD-TK tumor growth (i.e., size and volume) in nude mice were monitored. The isobologram method of Loewe and the multiple drug-effect analysis method of Chou-Talalay were used to measure the interaction between the two prodrug-activating gene therapies. To elucidate the mechanism of interaction, the phosphorylation of ganciclovir in 9L/CD-TK cells after varying prodrug treatments was studied.Results and Conclusions: The presence of transfected cytosine deaminase and thymidine kinase genes in 9L gliosarcoma cells reduced cell survival, both in vitro and in vivo, following treatment with the relevant prodrugs; the effects of the two components appeared to be synergistic and related mechanistically to the enhancement of ganciclovir phosphorylation by thymidine kinase following 5-fluorouracil treatment. [ABSTRACT FROM AUTHOR]

Focuses on a study which examined the therapeutic application of mitomycin C in gastric cancer. Influence of mitomycin C on DNA repair gene GADD34; Role of mitomycin in tumor cells viral production; Link between GADD34 expression inhibition and viral proliferation.