Publications by authors named "Kraker A"

Introduction And Hypothesis: Vaginal mesh surgery is subject of debate due to the impact of mesh-related complications on patient's lives. Not all of these complications are symptomatic. Restoration of the anatomy and improvement of pelvic floor function as a result may counter the experienced discomfort related to adverse events.

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Pelvic organ prolapse (POP) is a common problem. There is a significant risk of recurrent POP after surgery. To reduce this risk vaginal meshes have been introduced.

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The protein kinase checkpoint kinase 1 (Chk1) has been implicated as a key regulator of cell cycle progression and DNA repair, and inhibitors of Chk1 (e.g., UCN-01 and EXEL-9844) potentiate the cytotoxic actions of chemotherapeutic drugs in tumor cells.

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Objective: To compare the short-term effects of two oral continuous combined oestrogen-progestogen treatment regimens on blood concentrations of several cardiovascular risk markers in healthy postmenopausal women.

Study Design: In a 12-week randomised controlled study, 48 healthy non-hysterectomised postmenopausal women, aged 41-58 years, received either no treatment (control group; n=16), or daily oral continuous combined treatment with 1 mg micronised 17beta-oestradiol plus 5 mg dydrogesterone (E/D group; n=18) or 0.625 mg conjugated equine oestrogens plus 5 mg medroxyprogesterone acetate (CEE/MPA group; n=14).

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Pyrrolo[3,4-c]carbazoles bearing solubilising basic side chains at the 8-position retain potent Wee1 and Chk1 inhibitory properties in isolated enzyme assays, and evidence of G2/M checkpoint abrogation in several cellular assays. Co-crystal structure studies confirm that the primary binding to the Wee1 enzyme is as described previously, with the C-8 side chains residing in an area of bulk tolerance.

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A series of N-6 substituted 9-hydroxy-4-phenylpyrrolo[3,4-c]carbazole-1,3(2H,6H)-diones were prepared from N-substituted (5-methoxyphenyl)ethenylindoles. The target compounds were tested for their ability to inhibit the G2/M cell cycle checkpoint kinases, Wee1 and Chk1. Analogues with neutral or cationic N-6 side chains were potent dual inhibitors.

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High-throughput screening has identified a novel class of inhibitors of the checkpoint kinase Wee1, which have potential for use in cancer chemotherapy. These inhibitors are based on a 4-phenylpyrrolo[3,4-c]carbazole-1,3(2H,6H)-dione template and have been shown by X-ray crystallography to bind at the ATP site of the enzyme. An extensive study of the effects of substitution around this template has been carried out, which has identified substituents which lead to improvements in potency and selectivity for Wee1.

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A series of 2-anilino-6-phenylpyrido[2,3-d]pyrimidin-7(8H)-ones were synthesized and evaluated for their inhibitory properties against the non-receptor kinase c-Src and the G2/M checkpoint kinase Wee1. Overall, the compounds were 10-100-fold more potent inhibitors of c-Src than Wee1, and variation of substituents on the 6-phenyl ring did not markedly alter this preference. Solubilizing substituents off the 2-anilino ring in many cases increased Wee1 activity, thus lowering this preference to about 10-fold.

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Purpose: To determine maximum tolerated dose of CI-994, a novel oral histone deacetylase inhibitor, in combination with carboplatin and paclitaxel in patients with advanced solid tumors.

Patients And Methods: Patients with advanced solid tumors who had received two or fewer prior chemotherapy regimens were eligible for trial. Five cohorts of patients were treated with escalating doses (4-6 mg/m2) and alternative schedules (7 days or 14 days) of CI-994.

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Objective: To compare the effects of 17 beta-oestradiol plus dydrogesterone with conjugated equine oestrogens plus medroxyprogesterone acetate on serum lipids, apolipoproteins and lipoprotein(a) in postmenopausal women.

Methods: A multi-centre, prospective, randomised, double-blind, comparative one-year study in 362 healthy postmenopausal women aged 39-74 years with an intact uterus. Fasting blood samples were taken at baseline and after 28 and 52 weeks of treatment.

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CI-994 or N-acetyldinaline [4-(acetylamino)-N-(2-amino-phenyl) benzamide] is an antitumor cytostatic agent currently undergoing clinical trial. Although several changes in cellular metabolism induced by the drug have been characterized, the primary molecular mechanism of its antitumor activity has been previously unknown. Here, we show that CI-994 is a histone deacetylase (HDAC) inhibitor that causes histone hyperacetylation in living cells.

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Inhibition of the constitutively active Bcr-abl tyrosine kinase(TK) by STI571 has proven to be a highly effective treatment for chronic myelogenous leukemia (CML). However, STI571 is only transiently effective in blast crisis, and drug resistance emerges by amplification of or development of mutational changes in Bcr-abl. We have screened a family of TK inhibitors of the pyrido [2,3-d]pyrimidine class, unrelated to STI571, and describe here a compound with substantial activity against STI-resistant mutant Bcr-abl proteins.

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Chronic myelogenous leukemia (CML) is a myeloproliferative disease characterized by the BCR-ABL genetic translocation and constitutive activation of the Abl tyrosine kinase. Among members of the Signal Transducers and Activators of Transcription (STAT) family of transcription factors, Stat5 is activated by the Bcr-Abl kinase and is implicated in the pathogenesis of CML. We recently identified PD180970 as a new and highly potent inhibitor of Bcr-Abl kinase.

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Article Synopsis
  • Src is a non-receptor protein tyrosine kinase that is overactive in over 80% of colon cancers, playing a role in tumor growth and survival by helping cells resist a form of programmed cell death called anoikis.
  • The study found that higher levels of Src activity in colon cancer cells correlate with greater resistance to anoikis, while reducing Src expression increased their susceptibility to this type of cell death.
  • Treatment with a specific Src inhibitor enhanced the effectiveness of inducing anoikis in cancer cells and showed that Src activation influences the phosphorylation of Akt, a key player in cell survival pathways, suggesting Src's role in cancer progression and metastasis.
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Activation of protein tyrosine kinases is prevalent in human cancers and previous studies have demonstrated that Stat3 signaling is a point of convergence for many of these tyrosine kinases. Moreover, a critical role for constitutive activation of Stat3 in tumor cell proliferation and survival has been established in diverse cancers. However, the oncogenic signaling pathways in melanoma cells remain to be fully defined.

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Bcr-Abl tyrosine kinase has been validated as a molecular target for the treatment of chronic myelogenous leukemia (CML). More recently, it has been reported that CML patients could develop resistance to the Bcr-Abl tyrosine kinase inhibitor, imatinib (STI571, Gleevec), pointing to the need for development of additional Bcr-Abl tyrosine kinase inhibitors or other therapeutic strategies. It was also found that a significant proportion of patients who received the Bcr-Abl inhibitor did not achieve complete cytogenetic response.

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Protein kinase C delta (PKC delta) is tyrosine-phosphorylated and catalytically inactive in mouse keratinocytes transformed by a ras oncogene. In several other model systems, Src kinases are upstream regulators of PKC delta. To examine this relationship in epidermal carcinogenesis, v-ras transformed mouse keratinocytes were treated with a selective Src kinase inhibitor (PD 173958).

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The lack of functional p53 in many cancer cells offers a therapeutic target for treatment. Cells lacking p53 would not be anticipated to demonstrate a G(1) checkpoint and would depend on the G(2) checkpoint to permit DNA repair prior to undergoing mitosis. We hypothesized that the G(2) checkpoint abrogator could preferentially kill p53-inactive cancer cells by removing the only checkpoint that protects these cells from premature mitosis in response to DNA damage.

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Constitutive activation of signal transducer and activator of transcription (STAT) proteins has been detected in a wide variety of human primary tumor specimens and tumor cell lines including blood malignancies, head and neck cancer, and breast cancer. We have previously demonstrated a high frequency of Stat3 DNA-binding activity that is constitutively-induced by an unknown mechanism in human breast cancer cell lines possessing elevated EGF receptor (EGF-R) and c-Src kinase activities. Using tyrosine kinase selective inhibitors, we show here that Src and JAK family tyrosine kinases cooperate to mediate constitutive Stat3 activation in the absence of EGF stimulation in model human breast cancer cell lines.

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In continuing our search for medicinal agents to treat proliferative diseases, we have discovered 2-substituted aminopyrido[2,3-d]pyrimidin-7-yl ureas as a novel class of soluble, potent, broadly active tyrosine kinase (TK) inhibitors. An efficient route was developed that enabled the synthesis of a wide variety of analogues with substitution on several positions of the template. From the lead structure 1, several series of analogues were made that examined the C-6 aryl substituent, a variety of water solublizing substitutents at the C-2 position, and urea or other acyl functionality at the N-7 position.

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A series of 3-aryl-1,6-naphthyridine-2,7-diamines and related 2-ureas were prepared and evaluated as inhibitors of the FGF receptor-1 tyrosine kinase. Condensation of 4,6-diaminonicotinaldehyde and substituted phenylacetonitriles gave intermediate naphthyridine-2,7-diamines, and direct reaction of the monoanion of these (NaH/DMF) with alkyl or aryl isocyanates selectively gave the 2-ureas in varying yields (23-93%). For the preparation of more soluble 7-alkylamino-2-ureas, a number of protecting groups for the 2-amine were evaluated (phthaloyl, 4-methoxybenzyl) following selective blocking of the 7-amine (trityl), but these were not superior to the (required) 2-tert-Bu-urea group itself.

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Increased expression or activity of c-Src tyrosine kinase has been associated with the transformed phenotype in tumor cells and with progression of neoplastic disease. A number of pyrido[2, 3-d]pyrimidines have been characterized biochemically and in cells as part of an assessment of their potential as anti-tumor agents. The compounds were ATP-competitive inhibitors of c-Src kinase with IC(50) values < 10 nM and from 6 to >100-fold selectivity for c-Src tyrosine kinase relative to basic fibroblast growth factor receptor (bFGFr) tyrosine kinase, platelet-derived growth factor receptor (PDGFr) tyrosine kinase, and epidermal growth factor receptor (EGFr) tyrosine kinase.

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7-substituted 3-(2,6-dichlorophenyl)-1,6-naphthyridin-2(1H)-ones are potent inhibitors of protein tyrosine kinases, with some selectivity for c-Src. The compounds were prepared by condensing 4, 6-diaminonicotinaldehyde with 2,6-dichlorophenylacetonitrile and selectively converting the 2- and 7-amino groups of the product to hydroxy and fluoro groups, respectively, by prolonged diazotization in 50% aqueous fluoboric acid. N-Methylation, followed by treatment with aliphatic diamines, aromatic amines, or their derived lithium anions, gave the desired compounds.

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PD180970 is a novel pyrido[2,3-d]pyrimidine class of ATP-competitive inhibitor of protein tyrosine kinases. We found that PD180970 inhibited in vivo tyrosine phosphorylation of p210Bcr-Abl (IC50 = 170 nM) and the p210BcrAbl substrates Gab2 and CrkL (IC50 = 80 nM) in human K562 chronic myelogenous leukemic cells. In vitro, PD180970 potently inhibited autophosphorylation of p210Bcr-Abl (IC50 = 5 nM) and the kinase activity of purified recombinant Abl tyrosine kinase (IC50 = 2.

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