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K K Chan

Publications and source records attributed to K K Chan.

At least 55 records · Page 3Linked to original sources
PubMed1999

XK469, a selective topoisomerase IIbeta poison.

XK469 (NSC 697887) is a synthetic quinoxaline phenoxypropionic acid derivative that possesses unusual solid tumor selectivity and activity against multidrug-resistant cancer cells. We report here that XK469 and its S(-) and R(+)-isomers induce reversible protein-DNA crosslinks in mammalian cells. Under protein denaturing conditions, the protein-DNA crosslinks are rendered irreversible and stable to DNA banding by CsCl gradient ultracentrifugation. Several lines of evidence indicate that the primary target of XK469 is topoisomerase IIbeta. Preferential targeting of topoisomerase IIbeta may explain the solid tumor selectivity of XK469 and its analogs because solid tumors, unlike leukemias, often have large populations of cells in the G(1)/G(0) phases of the cell cycle in which topoisomerase IIbeta is high whereas topoisomerase IIalpha, the primary target of many leukemia selective drugs, is low.

Animals↗
PubMed1999

Characterization of a brain-specific nuclear LIM domain protein (FHL1B) which is an alternatively spliced variant of FHL1.

We have amplified and sequenced a novel, alternatively spliced variant of a human gene coding for the four-and-a-half LIM domain protein 1 (FHL1). This gene is located at chromosome Xq27 and the spliced variant is named FHL1B. The ORF of FHL1B cDNA codes for a LIM-only protein that possesses a zinc finger and three tandem repeats of LIM domains at the N-terminus with an active bipartite nuclear localization signal (NLS) motif and a possible RBP-J binding region at the C-terminus. FHL1B and FHL1 have the same N-terminal three-and-a-half LIM domains but different C-terminal protein sequences, due to the presence of an additional alternative exon 4b in FHL1B causing a frame-shift in the 3'coding region. RT-PCR results revealed that the expression of FHL1 is not restricted in skeletal muscle and heart, but is widely distributed in other tissues, including brain, placenta, lung, liver, kidney and pancreas, albeit as a low abundance transcript. In contrast, FHL1B is specifically expressed in brain. The C-terminal alternative region in FHL1B is sufficient to localize FHL1B in the nucleus of mammalian cell. FHL1B is probably related to neural differentiation and certain fragile X syndrome.

Alternative Splicing↗
PubMed1999

Gas chromatographic-mass spectrometric analysis of perillyl alcohol and metabolites in plasma.

Perillyl alcohol (POH), a metabolite of d-limonene and a component of the lavender oil, is currently in Phase I clinical trials both as a chemopreventative and chemotherapeutic agent. In vivo, POH is metabolized to less active perillic acid (PA) and cis- and trans-dihydroperillic acids [DHPA, 4-(1'-methylethenyl)-cyclohexane-1-carboxylic acid]. Previous pharmacokinetic studies using a GC-MS method detected POH metabolites but not POH itself; thus these studies lacked information on the parent drug. The present report describes a sensitive GC-MS method for the quantitation of POH and metabolites using stable-isotopically labeled internal standards. The residue obtained from CH2Cl2 extraction of a plasma sample was silylated. The products were separated on a capillary column and analyzed by an ion-trap GC-MS using NH3 chemical ionization. POH-d3 was used as the internal standard for POH while 13C-PA-d2 was used as the internal standards for the metabolites. The quantitation limits for POH, PA, cis- and trans-DPA were <10 ng/ml using 1-2 ml plasma. The assay was validated in rat and human plasma. The assay was linear from 2 to 2000 ng/ml for POH, 10 to 1000 ng/ml for PA and trans-DHPA, and 20 to 1000 ng/ml for cis-DHPA monitored. The within-run and between-run coefficients of variation were all <8%. Preliminary pharmacokinetic data from a rat following i.v. administration of POH at 23 mg/kg and from a patient receiving POH at 500 mg/m2 p.o. was also provided. Intact POH, PA, cis- and trans-DHPA were all detected in plasma in both cases. Two new major metabolites were found in human and one in the rat plasma.

Animals↗
PubMed1999

Use of V79 cells with stably transfected cytochrome P450 cDNAs in studying the metabolism and effects of cytotoxic drugs.

PURPOSE: Studying the metabolism of cytotoxic drugs has become increasingly necessary to predict clinically significant drug-drug interactions and to understand the basis of interindividual variations in the pharmacokinetics of anticancer agents. The aim of this study was to determine the feasibility of using V79 Chinese hamster fibroblasts, which are stably transfected with cytochrome P450 (CYP) cDNAs, to study the metabolism of cytotoxic drugs in vitro. METHODS: The 3-[4,5-dimethylthiazol-2yl]-2,5-diphenyltetrazolium bromide (MTT) assay was used to determine cell survival after incubation with drugs. Gas chromatography/mass spectroscopy was used for the quantitation of metabolites of cyclophosphamide and ifosfamide in culture medium. The coculture technique was used to study the generation of cytotoxic metabolites in culture medium. RESULTS: After treatment with either cyclophosphamide or ifosfamide (100 microM to 1 mM) cytotoxicity was demonstrated in only cytochrome CYP2B1- and cytochrome CYP3A4-expressing cells. Treatment of parental nontransfected cells that were cocultured with CYP-expressing cells with cyclophosphamide resulted in increased sensitivity to this drug. All active and inactive metabolites of cyclophosphamide and ifosfamide were detected in the culture medium. Cyclophosphamide-induced cytotoxicity in CYP2B1- and CYP3A4-expressing cells was abrogated by metyrapone and midazolam/ troleandomycin, respectively. Paclitaxel showed greater cytotoxicity against parental V79 cells than against the CYP2BI-, 2E1-, or 3A4-expressing cells, which was also influenced by cotreatment with CYP inhibitors. CONCLUSIONS: Stable expression of CYP cDNAs by V79 cells provided an in vitro system to study cytotoxic drug metabolism. Cell viability and metabolite assays were used to determine the differential metabolism and effects in different CYP-transfected cell lines treated with cytotoxic drugs. The potential use of this V79 cell expression system is in studying enzymes involved in the metabolism of cytotoxic drugs, especially early in drug development. In addition, this system may be used to determine drug interactions that may influence the outcome of therapy in patients with cancer.

Animals↗
PubMed1999

Phase II studies with DaunoXome in patients with nonresectable hepatocellular carcinoma: clinical and pharmacokinetic outcomes.

A total of 14 Chinese patients with inoperable hepatocellular carcinoma received a liposomal formulation of daunorubicin (DaunoXome) at a dose equivalent to 100 mg/m2 of the free drug every 3 weeks. Altogether, 12 patients were assessable for response; 2 patients had stable disease for 8 weeks, but all eventually developed progressive disease and there was no responder. The drug was well tolerated, with no evidence of cardiac toxicity being observed. Deterioration of liver-function tests was attributed to progressive tumors in the terminal stage of the disease. Pharmacokinetics studies revealed a biexponential decay for daunorubicin in association with mean initial and terminal half-lives of 1.8 and 7.4 h, respectively, and a mean total clearance of 15.0+/-5.5 ml/min. The AUC ratio between the metabolite daunorubicinol and daunorubicin was 0.07. These data differ markedly from the pharmacokinetics of the free drug.

Adult↗
PubMed1999

Developmental expression of Mab21l2 during mouse embryogenesis.

mab-21 has been identified as a critical component required for sensory organ identity establishment in Caenorhabditis elegans. [Chow, K.L., Emmons, S.W., 1994. Development 120, 2579-2592; Chow, E. L., Hall, D.H., Emmons, S.W., 1995. Development 121, 3615-3625]. Human and mouse homologs of this gene have been isolated and their transcripts are predominantly detected in the eye and cerebellum [Margolis, R.L., Stine, O.C., McInnis, M.G., et al., 1996. Hum. Mol. Genet 5, 607-616; Mariani, M., Corradi, A., Baldessari, D., et al., 1998. Mech. Dev. 79, 131-135. We report here the expression profile of a second murine mab-21 homolog, Mab21l2 [Wong, R.L.Y., Wong, H.T., Chow, K.L., 1999. Cyto. Cell Genet., [in press]. Whole mount in situ hybridization data from embryonic day 8.5 to day 15 revealed that Mab21l2 expression patterns partially overlapped with that of Mab21l1. In addition, its strong expression in the mid- and hindbrain, otic vesicle, optic vesicle, maxillary and mandibular process, paraxial mesoderm, dorsal midline, limb bud and developing digits suggest that Mab21l2 has more diverse functions in vertebrate development.

Animals↗
PubMed1999

Bilateral synchronous tonsillar carcinoma.

Synchronous cancers occur in four per cent of patients with head and neck malignancies but no bilateral synchronous tonsillar carcinomas have been described in the English literature. We describe the first such case and discuss the prognostic aspect of this carcinoma. In the presence of contralateral neck nodes in patients with head and neck malignancies, a careful search should be made for a second head and neck primary.

Aged↗
PubMed1999

NB1-C16-insulin: site-specific synthesis, purification, and biological activity.

PURPOSE: To develop a simple and efficient method for the synthesis and purification of NB1-lipid-modified-insulin without the use of protecting agents. METHODS: Bovine insulin was allowed to react with cis-9-hexadecenal in an aqueous-organic medium in the presence of NaBH3CN at room temperature overnight. HPLC and ESI LC/MS coupled with dithiothreitol and trypsin treatment were employed for product identification and optimization. The product was purified by a differential C18 solid-phase extraction. The biological effects of the modified insulin were evaluated by receptor binding assay and hypoglycemic effect measurement. RESULTS: NB1-cis-9-hexadecenyl insulin was synthesized by a one-step reductive alkylation in sodium salicylate and isopropanol solution in high yield (80%). The site selectivity and yield of the reaction were found to be affected by pH, medium, and insulin-to-aldehyde ratio. After solid phase extraction, the purity was found to be approximately 98%. This derivative showed a Kd to the insulin receptor of 5.72x10(-9) M and a significantly slower glucose lowering rate than insulin. CONCLUSIONS: NB1-hexadecenyl insulin was synthesized by reductive alkylation without the use of protective agents in high yield. NB1-hexadecenyl insulin retained significant binding affinity to insulin receptor and showed a pronounced hypoglycemic effect.

Alkylation↗
PubMed1999

Phase II trial of radical surgery for locally advanced pelvic neoplasia.

BACKGROUND: Reported operative mortality and survival rates following total pelvic exenteration (TPE) for recurrent pelvic neoplasia are now as good as those for many primary treatments. The currently accepted primary treatments for these tumours are, however, still either radiotherapy alone or radiotherapy and chemotherapy. The primary aim of this study was to evaluate the safety and tolerability of TPE and secondarily to ascertain survival after TPE. METHODS: This was a phase II study of 50 patients with locally advanced pelvic tumours who underwent TPE. RESULTS: Thirty-two patients (64 per cent) underwent TPE for recurrent carcinoma of the cervix, seven (14 per cent) for rectal cancer, three (6 per cent) for vulval carcinoma, three (6 per cent) for vaginal carcinoma, two (4 per cent) for prostate cancer and three (6 per cent) for other tumours. The 30-day mortality rate was 8 per cent with an in-hospital mortality rate of 16 per cent. The crude morbidity rate was 62 per cent, with 23 patients (46 per cent) having grade III or IV toxicity. A complete response was achieved in 63 per cent and a partial response in 37 per cent of patients. The overall median survival time was 86 weeks; it was 111 weeks in patients in whom a complete response was achieved. CONCLUSION: The survival and operative mortality rates that are now attainable with TPE are comparable to those achieved with chemoradiotherapy in advanced pelvic neoplasia. TPE should no longer be reserved for salvage therapy and should perhaps be compared with chemoradiotherapy as first-line treatment in a phase III randomized trial in patients with these tumours.

Adult↗
PubMed1999

Posteromedial tibial plateau injury including avulsion fracture of the semimembranous tendon insertion site: ancillary sign of anterior cruciate ligament tear at MR imaging.

PURPOSE: To evaluate posteromedial tibial plateau injuries of or about the semimembranous tendon insertion site and their association with anterior cruciate ligament (ACL) tears on magnetic resonance (MR) images. MATERIALS AND METHODS: A retrospective study of MR images and conventional radiographs was performed in 10 patients with posteromedial tibial plateau injuries, including avulsion fractures of the semimembranous tendon insertion site. Associated abnormalities were analyzed, including ACL tears, medial meniscal tears, and other lateral femorotibial compartment injuries. Findings from the clinical history and physical examination were correlated with radiographic and MR imaging findings. Nine patients had arthroscopically or surgically documented ACL tears. RESULTS: All 10 patients had ACL tears at MR imaging. Five patients had posteromedial tibial plateau fractures: Four had avulsion fractures of the tendon insertion site, and one had a fracture lateral to the site. Five patients had posteromedial tibial plateau bruises: Two had bruises at the tendon insertion site. Five patients had tears of the posterior horn of the medial meniscus. Two patients had posterior meniscocapsular separations. Three patients showed evidence of the O'Donoghue triad. Six patients had bruises of the lateral tibial plateau and of the lateral femoral condyle. CONCLUSION: There appears to be an association between posteromedial tibial plateau injuries and ACL tears. Posteromedial tibial plateau injuries may be predictive of ACL status.

Adolescent↗
PubMed1999

Superior labral anteroposterior lesions: MR arthrography with arm traction.

OBJECTIVE: The purpose of this study was to investigate the efficacy of arm traction combined with MR arthrography in the evaluation of superior labral anteroposterior (SLAP) lesions. MATERIALS AND METHODS: Cadaveric shoulders were studied with a 1.5-T MR imaging unit with the arm externally rotated. Fifteen milliliters of a gadolinium-containing contrast agent were injected into the glenohumeral joint. Twenty-four sets of images of cadaveric joints were evaluated independently by two observers. These sets consisted of MR arthrographic images obtained with traction (applied to the wrist using 1- to 3-kg weights) and without traction in five shoulders in which SLAP lesions had been excluded arthroscopically or by cadaveric sectioning; and MR arthrographic images obtained with and without traction in seven shoulders in which various types of SLAP lesions had been created arthroscopically and later confirmed by cadaveric sectioning. RESULTS: Analysis of the data indicated that MR arthrography in combination with arm traction and external rotation improved diagnostic accuracy with regard to identification and categorization of SLAP lesions when compared with studies made without traction. CONCLUSION: The combination of MR arthrography and arm traction with the shoulder in external rotation provides a more effective approach for detection of SLAP lesions than does similar MR arthrography performed without arm traction.

Aged↗
PubMed1998

Chromosomal mapping, tissue distribution and cDNA sequence of four-and-a-half LIM domain protein 1 (FHL1).

We have isolated and sequenced a human heart cDNA clone encoding a novel LIM-only protein. This full-length cDNA clone has a predicted open reading frame (ORF) encoding 280 amino acids. The ORF of this cDNA codes for a LIM-only protein that possesses four repeats of LIM domain and an extra zinc finger and this putative protein is named four-and-a-half LIM domain protein 1 (FHL1). FHL1 is unique when compared with other LIM-only proteins because it possesses an odd number of zinc fingers. When the FHL1 cDNA probe was used to hybridize with poly-(A) RNA of various human tissues, a very strong signal was detected in skeletal muscle, a moderate one in the heart; only weak signals were associated with the placenta, ovary, prostate, testis, small intestine, colon and spleen, and virtually no signal could be detected in brain, lung, liver, kidney, pancreas, thymus and peripheral blood leukocytes. The FHL1 gene was located to human chromosome at Xq27.2 by somatic cell hybrid mapping, fluorescent in situ hybridization (FISH) and radiation hybrid mapping.

Amino Acid Sequence↗
PubMed1998

Molecular cloning and characterization of FHL2, a novel LIM domain protein preferentially expressed in human heart.

A full-length cDNA clone encoding a novel LIM-only protein was isolated and sequenced from a human fetal heart cDNA library. This full-length clone consists of 1416 base pairs and has a predicted open reading frame (ORF) encoding 279 amino acids. The ORF of this polypeptide codes for the human heart-specific four and a half LIM-only protein 2 (FHL2). It possesses an extra zinc finger that is a half LIM domain and four repeats of LIM domain. When the human FHL2 cDNA probe was used to hybridize with poly-A RNA of various human tissues, a very strong signal could be seen in heart tissues, and only moderately low signals could be detected in placenta, skeletal muscle and ovary. Virtually no signal could be detected in brain, lung, liver, kidney, pancreas, spleen, thymus, prostate, testis, small intestine, colon or peripheral blood leukocyte. FHL2 was mapped to chromosome 2q12-q13 by fluorescent in-situ hybridization (FISH).

Amino Acid Sequence↗
PubMed1998

Developmental regulation of 14-3-3 epsilon isoform in rat heart.

Human heart cDNA sequencing yielded a cDNA clone that is similar in DNA and amino acid sequences to that of mouse 14-3-3 epsilon isoform. The 6xHis-tagged H1433 epsilon recombinant protein was expressed in Escherichia coli and its size was approximately 30 kDa. From Northern blot results with human multiple tissues, human skeletal muscle was found to have the highest level of h1433 epsilon mRNA expression, whereas Northern blots of human cancer cell lines detected the highest mRNA level of h1433 epsilon in colorectal adenocarcinoma SW480. The protein expression level of h1433 epsilon and Raf-1 is found to be regulated coordinately during rat heart development, and their protein expression was highest from 14.5 to 16.5 days postcoitum.

14-3-3 Proteins↗
PubMed1998

Pharmacokinetics of d-limonene in the rat by GC-MS assay.

The naturally occurring monoterpene d-limonene has been found to inhibit various stages of tumorigenesis in a number of animal models and is now being evaluated as a chemopreventive agent in humans. To date, there are little or no preclinical pharmacokinetics available nor is there a sensitive assay methodology. In this study, d-limonene and its dideuterium-labeled internal standard, limonene-d2, in whole rat blood were extracted with n-pentane which was then concentrated on a Kuderna-Danish concentrator. The residue was analyzed by an ion-trap GC -MS under ammonia chemical ionization. The detection limit of d-limonene was 1.0 ng if injected in pure form; however, due to the presence of endogenous d-limonene levels (probably from diet), the routine quantitation limit was set at 1.0 microgram ml-1. The monitored assay linearity range from 1.0 to 30 micrograms ml-1 within-day CV values of 8.0%, 2.4%, and 2.0% at 1.0, 3.0 and 10.0 micrograms ml-1, respectively (all at n = 8), and corresponding accuracy of 100%, 100%, and 101%. The between-day CV values were 12.3, 8.0, and 7.5% at 1, 6, and 20 micrograms ml-1, respectively (all at n = 8). Using this assay, pharmacokinetics of d-limonene were studied in Sprague-Dawley rats following intravenous and oral administration at 200 mg kg-1 each. Blood concentration-time profiles after intravenous administration showed a biphasic decline with a mean initial t1/2 of 12.4 min and a terminal t1/2 of 280 min. The plasma:red blood cell partition was found to be 0.84. Plasma protein binding of d-limonene was found to be 55.3% at 20 microgram ml-1. The mean total clearance was 49.6 ml min-1 kg-1, the volume of distribution at steady-state 11.7 1 kg-1, and median residence time 263 min. The blood concentration-time decline following oral administration also showed a biphasic decline with a mean initial t1/2 of 34 min and terminal t1/2 of 337 min. The oral bioavailability of d-limonene was 43.0%.

Animals↗
PubMed1998

Effects of a novel antitumor depsipeptide, FR901228, on human breast cancer cells.

Human breast cancer MCF7 and MDA-MB231 cells were used to investigate the biological and molecular activities of a novel naturally occurring agent, FR901228 (FR), that possesses a potent antitumor activity against human and murine tumor cells. Investigation of the cytotoxicity of FR and induction of internucleosomal DNA degradation in FR-treated cultures revealed that FR induced apoptotic-like cell death of MCF7 and MDA-MB231 cells. In FR-treated apoptotic cultures, flow cytometry revealed that there was a significant decrease of cells in S phase of the cell cycle. In FR-treated cells there was an increased expression of p21Cip1 and phosphorylation of Bcl-2 as determined by Western immunoblotting, and a novel cytoplasmic kinase of 33 kDa, p33 kinase, as determined by the in-gel kinase assay using myelin basic protein (MBP) as a substrate. Increased expression of p21CiP1, phosphorylation of Bcl-2, and activation of p33 MBP kinase may play part of the key mechanism for FR-induced apoptosis.

Anti-Bacterial Agents↗
PubMed1998

Chromosomal mapping of a skeletal muscle specific LIM-only protein FHL3 to the distal end of the short arm of human chromosome 1.

Four-and-a-half LIM domain proteins (FHL) possess four tandem repeats of LIM domain and an extra zinc finger. FHL family LIM proteins are unique when compared with other LIM-only proteins because they possess an odd number of zinc fingers. In this study, the tissue distribution and chromosomal mapping of skeletal muscle LIM protein FHL3 were reported. When the FHL3 cDNA probe was used to hybridize with poly-(A) RNA of various human tissues, a very strong signal was detected in skeletal muscle, and virtually no signal could be detected in heart, brain, placenta, lung, liver, kidney and pancreas. Using radiation hybrid technique, FHL3 gene was mapped to the distal end of the short arm of chromosome 1 (123.26 cR from the top of the Chr1 linkage group) and this region (near 1p34) is related to several human malignancies.

Animals↗