Publications by authors named "Kuo-Hsing Chen"

17 Publications

  • Page 1 of 1

Chemotherapy agents stimulate dendritic cells against human colon cancer cells through upregulation of the transporter associated with antigen processing.

Sci Rep 2021 Apr 27;11(1):9080. Epub 2021 Apr 27.

Graduate Institute of Oncology, National Taiwan University, Taipei, Taiwan, R.O.C..

Single immunotherapy fails to demonstrate efficacy in patients with microsatellite stable (MSS) metastatic colorectal cancer (mCRC). Research on immune reactions before and after systemic agents for mCRC is warranted. Our study examined cell line models to compare the expression of immune surface markers on colon cancer cells before and after chemotherapy agents. We also elucidated mechanisms underlying the effects of chemotherapy agents on immune surface markers. We used real-world clinical samples with NanoString analysis and the Perkin-Elmer Opal multiplex system. We established that chemotherapy agents, particularly 7-ethyl-10-hydroxycamptothecin (SN-38), the active metabolite of irinotecan, stimulated the expression of stimulatory MHC class I alleles through stimulation the pathway of transporters associated with antigen processing 1 and 2 (TAP1 and TAP2) in cell line models. Application of infected cell protein 47 (ICP-47), a specific inhibitor of the TAP1/TAP2, significantly inhibited expression of TAP1/TAP2 and also inhibited the expression of the downstream MHC class I. In the functional assay, SN-38 significantly promoted the phagocytosis of colon cancer cells by monocyte-derived dendritic cells (MoDCs). We confirmed that the expression of major histocompatibility complex (MHC) class I, significantly increased after first-line chemotherapy and targeted therapy in the samples of real-world patients with de novo mCRC. Our study provides new insights for novel immunotherapy combinations.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41598-021-88648-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8079421PMC
April 2021

Association between risk factors, molecular features and CpG island methylator phenotype colorectal cancer among different age groups in a Taiwanese cohort.

Br J Cancer 2021 Apr 12. Epub 2021 Apr 12.

Department of Oncology, National Taiwan University Hospital, Taipei, Taiwan.

Background: CpG island methylator phenotype (CIMP) represents a carcinogenesis pathway of colorectal cancer (CRC) and the association between CIMP CRC, molecular features and risk factors in East Asian population is less studied.

Methods: We prospectively enrolled newly diagnosed CRC patients at the National Taiwan University Hospital. Clinicopathological data and risk factors for CRC were collected during interview. The tumour samples were subjected to CIMP, RAS/BRAF mutation and microsatellite instability tests. CIMP-high was determined when ≧3 methylated loci of p16, MINT1, MINT2, MINT31 and MLH1 were identified. Multivariate logistic regression was used to evaluate the association between risk factors and CIMP-high CRC.

Results: Compared with CIMP-low/negative CRC, CIMP-high CRC was associated with more stage IV disease, BRAF V600E mutation and high body mass index (BMI ≧ 27.5 kg/m) in younger patients (age < 50 y), and more right-sided tumour, BRAF V600E mutation, MSI-high and colorectal polyp in elder patients (age ≧ 50 y). Multivariate analyses showed that BMI ≧27.5 kg/m was significantly associated with CIMP-high CRC in younger patients.

Conclusions: We identified distinct clinicopathological features for CIMP-high CRC among different age groups in Taiwan. Our data suggest the association between BMI ≧27.5 kg/m and CIMP-high CRC in patients younger than 50 years.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1038/s41416-021-01300-5DOI Listing
April 2021

An Integrative Morphomolecular Classification System of Gastric Carcinoma With Distinct Clinical Outcomes.

Am J Surg Pathol 2020 08;44(8):1017-1030

Departments of Pathology.

A robust morphomolecular classification system for gastric carcinoma is required. A 4-tier morphologic classification is proposed, including diffuse, intestinal, tubular, and lymphoid types. A tissue microarray for mismatch repair immunohistochemistry and Epstein-Barr virus (EBV) in situ hybridization were performed in 329 gastric carcinomas. DNA flow cytometry was used to detect aneuploidy in formalin-fixed paraffin-embedded samples. Lymphoid histology was the third most common histologic pattern at our institute and strongly associated with EBV infection and PMS2/MLH1-deficiency (both P<0.001). HER2 overexpression and SATB2 expression more frequently occurred in intestinal histology (both P<0.001). Loss of ARID1A expression was strikingly associated with lymphoid histology (P<0.001) and negative E-cadherin expression was correlated with diffuse histology (P=0.001). Programmed death-ligand 1 expression was most frequently present in lymphoid-type gastric carcinoma than other histologic subtypes and correlated with the molecular features of PMS2/MLH1-deficiency and EBV infection (all P<0.001). Aneuploidy was detected in 53% of gastric carcinomas and was highly correlated with intestinal type and the least with the lymphoid type (P<0.001). Notably, lymphoid-type gastric carcinoma showed the best outcome, whereas tubular type showed the worst survival rate (P<0.001). We integrated aneuploidy with morphologic patterns to propose a morphomolecular classification scheme, which served as a successful and independent prognostic factor in multivariate 5-year disease-free survival analysis (P<0.001). Overall, we describe an integrated morphomolecular classification system for gastric carcinomas to effectively predict patient outcomes. This system is cost-effective and reliable and can help select target therapeutics and facilitate clinical management.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1097/PAS.0000000000001521DOI Listing
August 2020

Human Breathomics Database.

Database (Oxford) 2020 01;2020

Graduate Institute of Biomedical Electronics and Bioinformatics, National Taiwan University, No. 1, Sec. 4, Roosevelt Road, Taipei 10617, Taiwan.

Breathomics is a special branch of metabolomics that quantifies volatile organic compounds (VOCs) from collected exhaled breath samples. Understanding how breath molecules are related to diseases, mechanisms and pathways identified from experimental analytical measurements is challenging due to the lack of an organized resource describing breath molecules, related references and biomedical information embedded in the literature. To provide breath VOCs, related references and biomedical information, we aim to organize a database composed of manually curated information and automatically extracted biomedical information. First, VOCs-related disease information was manually organized from 207 literature linked to 99 VOCs and known Medical Subject Headings (MeSH) terms. Then an automated text mining algorithm was used to extract biomedical information from this literature. In the end, the manually curated information and auto-extracted biomedical information was combined to form a breath molecule database-the Human Breathomics Database (HBDB). We first manually curated and organized disease information including MeSH term from 207 literatures associated with 99 VOCs. Then, an automatic pipeline of text mining approach was used to collect 2766 literatures and extract biomedical information from breath researches. We combined curated information with automatically extracted biomedical information to assemble a breath molecule database, the HBDB. The HBDB is a database that includes references, VOCs and diseases associated with human breathomics. Most of these VOCs were detected in human breath samples or exhaled breath condensate samples. So far, the database contains a total of 913 VOCs in relation to human exhaled breath researches reported in 2766 publications. The HBDB is the most comprehensive HBDB of VOCs in human exhaled breath to date. It is a useful and organized resource for researchers and clinicians to identify and further investigate potential biomarkers from the breath of patients. Database URL: https://hbdb.cmdm.tw.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1093/database/baz139DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6978997PMC
January 2020

CpG Island Methylator Phenotype May Predict Poor Overall Survival of Patients with Stage IV Colorectal Cancer.

Oncology 2019 12;96(3):156-163. Epub 2018 Dec 12.

Department of Oncology, National Taiwan University Hospital, Taipei City, Taiwan,

Objective: We aimed to study the prognostic role of CpG island methylator phenotype (CIMP) in patients with different stages of colorectal cancer (CRC).

Material And Methods: We analyzed CIMP in stage I-IV CRC specimens from patients who were diagnosed between 2005 and 2013. CIMP status was determined using a 5-gene MethyLight-based assay. The clinicopathologic characteristics were reviewed and the overall survival (OS) was compared between patients with CIMP-high CRC and those with CIMP-low/negative CRC.

Results: Among 450 CRC specimens with successfully determined CIMP statuses, 74 (16.4%) were CIMP-high CRC. Although there was no difference in OS between patients with CIMP-high and CIMP-low/negative CRC across all stages (p = 0.4526), intriguingly, patients with stage IV CIMP-high CRC had significantly worse OS than those with stage IV CIMP-low/negative CRC (p = 0.0047). In a multivariate analysis, CIMP status remained an independent prognostic factor for overall mortality (HR = 5.60, 95% CI: 2.12-14.79, p = 0.0005) in metastatic CRC after adjusting for clinicopathologic variables and anti-cancer therapies.

Conclusion: Our results revealed that the presence of CIMP independently predicts poor OS in patients with stage IV CRC.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1159/000493387DOI Listing
March 2019

Primary tumor site is a useful predictor of cetuximab efficacy in the third-line or salvage treatment of KRAS wild-type (exon 2 non-mutant) metastatic colorectal cancer: a nationwide cohort study.

BMC Cancer 2016 05 24;16:327. Epub 2016 May 24.

Department of Oncology, National Taiwan University Hospital, 7, Chun-Shan S Rd, Taipei, 10002, Taiwan.

Background: Previous studies have shown left-sided colorectal cancer (LCRC) and right-sided colorectal cancer (RCRC) exhibit different molecular and clinicopathological features. We explored the association between the primary tumor site and cetuximab efficacy in KRAS wild-type colorectal cancer (CRC).

Methods: This study enrolled a cohort of patients, who had received cetuximab treatment after two or more lines of chemotherapy for KRAS wild-type (exon 2 nonmutant) metastatic CRC, from the databases of Taiwan Cancer Registry (2004-2010) and National Health Insurance (2004-2011). Survival data were obtained from the National Death Registry. Time to treatment discontinuation (TTD) and overall survival (OS) after the start of cetuximab treatment were compared between patients with LCRC (splenic flexure to rectum) and RCRC (cecum to hepatic flexure).

Results: A total of 969 CRC patients were enrolled. Among them, 765 (78.9 %) and 136 (14.0 %) patients had LCRC and RCRC, respectively. Patients with LCRC, compared to patients with RCRC, had longer TTD (median, 4.59 vs. 2.75 months, P = .0005) and OS (median, 12.62 vs. 8.07 months, P < .0001) after the start of cetuximab treatment. Multivariate analysis revealed a right-sided primary tumor site was an independent predictor of shorter TTD (adjusted hazard ratio [HR] = 1.32, using the LCRC group as a reference, 95 % confidence interval: 1.08-1.61, P = .0072) and OS (adjusted HR = 1.45, 95 % CI: 1.18-1.78, P = .0003).

Conclusion: Our findings demonstrate that a left-sided primary tumor site is a useful predictor of improved cetuximab efficacy in the third-line or salvage treatment of KRAS wild-type (exon 2 nonmutant) metastatic CRC.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s12885-016-2358-2DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4879738PMC
May 2016

BRAF mutation may have different prognostic implications in early- and late-stage colorectal cancer.

Med Oncol 2016 May 31;33(5):39. Epub 2016 Mar 31.

Department of Oncology, National Taiwan University Hospital, No 7, Chung-Shan South Rd, Taipei, 10002, Taiwan.

The prognostic implication of BRAF mutant colorectal cancer remains paradoxical. Records of BRAF mutant and wild-type colorectal cancer patients at all stages were reviewed. Clinicopathologic features, including microsatellite instability, CpG islands methylator phenotype, and overall survival, of these patients were analyzed. Between 2005 and 2013, 428 colorectal cancer patients were enrolled in this study. The overall survival between BRAF mutant and wild-type patients with early-stage (stages I and II) colorectal cancer differed nonsignificantly (P = 0.99). By contrast, in late-stage (stages III and IV) patients, the median overall survival of BRAF mutant patients (N = 25) was significantly poorer than that of BRAF wild-type (N = 207) patients (BRAF mutant: 21.3 months (95% confidence interval [CI] 7.1-35.5); BRAF wild-type: 53.5 months (95% CI 37.5-69.5), P < 0.0001). In early-stage patients, we found that BRAF mutation was significantly associated with CpG island methylator phenotype-positive (P < 0.001), and microsatellite instability-high status (P = 0.0013). Conversely, in late-stage patients, BRAF mutation was significantly associated with CpG island methylator phenotype-positive (P = 0.0015) and the right-side colon (P = 0.014). BRAF mutation may have different prognostic implications in early- and late-stage colorectal cancer.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1007/s12032-016-0756-6DOI Listing
May 2016

Case report: mismatch repair proficiency and microsatellite stability in gastric cancer may not predict programmed death-1 blockade resistance.

J Hematol Oncol 2016 Mar 24;9:29. Epub 2016 Mar 24.

Department of Oncology, National Taiwan University Hospital, 7, Chun-Shan S Rd, Taipei, 10002, Taiwan.

Background: Anti-programmed death-1 therapy has poor efficacy in mismatch repair-proficient (pMMR) colorectal cancers; however, its efficacy in pMMR gastric cancers remains undetermined. Here, we report the case of a patient with pMMR and microsatellite-stable gastric cancer who exhibited a partial response to salvage anti-programmed death-1 therapy with pembrolizumab.

Case Presentation: Initially, the patient underwent subtotal gastrectomy 4 years ago for early-stage gastric cancer (pT1bN2M0, stage IIA). Immunohistochemical analysis of the tumor revealed strongly positive for HER2/neu. He had received trastuzumab plus pertuzumab, cisplatin, and capecitabine for recurrent tumors since September 2014 for 15 cycles. Disease progression of gastric cancer was found in August 2015. Since September 2015, the patient has received pembrolizumab monotherapy (200 mg as a fixed dose, every 3 weeks) for 3 months and the repeat computed tomography demonstrated a confirmed partial response. The plasma carcinoembryonic antigen also decreased dramatically. Both immunohistochemistry and a polymerase chain reaction-based method revealed that the patient had pMMR gastric cancer.

Conclusions: This case report provides the first report that mismatch repair-proficient and microsatellite-stable gastric cancers can respond well to anti-PD-1 monotherapy and indicates both markers may not sufficiently be predictive of anti-PD-1 therapy resistance in gastric cancer.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1186/s13045-016-0259-0DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4806434PMC
March 2016

Organic anxiety in a woman with breast cancer receiving denosumab.

Gen Hosp Psychiatry 2015 Mar-Apr;37(2):192.e7-8. Epub 2015 Feb 2.

Department of Psychiatry, National Taiwan University Hospital, Yun-Lin Branch, Douliu City, Yunlin County, Taiwan; Department of Psychiatry, National Taiwan University Hospital and College of Medicine, Taipei City, Taiwan. Electronic address:

Hypocalcemia can induce heterogeneous psychiatric manifestations, and its etiology can be multifactorial. Herein, we describe a patient who had previously undergone resection of parathyroid glands, who presented with extreme anxiety and hypocalcemia after denosumab treatment for cancer-related bone metastasis. The anxiety subsided soon after correction of her serum calcium level. When denosumab is prescribed for patients with predisposing factors of hypocalcemia, such as hypoparathyroidism, clinicians should be aware of symptomatic hypocalcemia.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.genhosppsych.2015.01.007DOI Listing
December 2015

Comparative effectiveness of first-line platinum-based chemotherapy regimens for advanced lung squamous cell carcinoma.

Clin Lung Cancer 2015 Mar 30;16(2):137-43. Epub 2014 Sep 30.

Center for Comparative Effectiveness Research, National Center of Excellence for Clinical Trial and Research, National Taiwan University Hospital, Taipei, Taiwan; Taiwan Cancer Registry, Taipei, Taiwan; Institute of Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan.

Background: Platinum-based chemotherapy is the standard first-line therapy for patients with advanced lung squamous cell carcinoma (SCC). We compared the effectiveness of first-line chemotherapy regimens.

Methods: We searched the database of the Taiwan Cancer Registry for patients with newly diagnosed advanced lung SCC from 2004 to 2007. Medication prescription data were retrieved from the database of National Health Insurance, Taiwan. We identified patients who received standard first-line platinum-based chemotherapy, which was defined as chemotherapy with a platinum (P) compound (cisplatin or carboplatin) in addition to 1 of the 4 chemotherapy agents, including gemcitabine (G), docetaxel (D), paclitaxel (T), and vinorelbine (V). Deaths were identified by searching the National Death Registry. Overall survival (OS) was compared between patients who underwent different therapies.

Results: In total, 2790 patients were identified; 983 patients (35.2%) received standard first-line chemotherapy with P and G (58.1%), D (14.5%), T (11.6%), or V (15.8%). Older patients (age ≥ 70 years) were less likely to receive P + D than P + G, P + T, or P + V (P = .018). Patients who received P + G, P + D, P + T, or P + V had similar OS (median, 8.9, 7.9, 9.5, and 8.2 months; P = .816). In multivariate analyses adjusting for age, sex, and stage, the first-line chemotherapy regimen was not a predictor for OS. With P + G as the reference group, the adjusted hazard ratios of P + D, P + T, and P + V were 1.03, 0.90, and 1.02, respectively (P = .710).

Conclusions: In patients with advanced lung SCC, various regimens did not have a significant effect on survival outcomes.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.cllc.2014.09.004DOI Listing
March 2015

Type 2 diabetes mellitus is associated with increased mortality in Chinese patients receiving curative surgery for colon cancer.

Oncologist 2014 Sep 24;19(9):951-8. Epub 2014 Jul 24.

Department of Oncology, National Taiwan University Hospital, Yun-Lin Branch, Yunlin, Taiwan, Republic of China; Department of Oncology and Center for Comparative Effectiveness Research, National Center of Excellence for Clinical Trial and Research, National Taiwan University Hospital, Taipei, Taiwan, Republic of China; Graduate Institutes of Oncology and Clinical Medicine and Department of Internal Medicine, National Taiwan University College of Medicine, Taipei, Taiwan, Republic of China; Institutes of Health Policy and Management and Epidemiology and Preventive Medicine, College of Public Health, National Taiwan University, Taipei, Taiwan, Republic of China

Background: We investigated the association between diabetes mellitus (DM) and the prognosis of patients with early colon cancer who had undergone curative surgery.

Methods: From three national databases of patients in Taiwan, we selected a cohort of colon cancer patients who had been newly diagnosed with stage I or stage II colon cancer between January 1, 2004 and December 31, 2008 and had undergone curative surgery. We collected information regarding DM (type 2 DM only), the use of antidiabetic medications, other comorbidities, and survival outcomes. The colon cancer-specific survival (CSS) and the overall survival (OS) were compared between patients with and without DM.

Results: We selected 6,937 colon cancer patients, among whom 1,371 (19.8%) had DM. The colon cancer patients with DM were older and less likely to receive adjuvant chemotherapy but had a similar tumor stage and grade, compared with colon cancer patients without DM. Compared with colon cancer patients without DM, patients with DM had significantly shorter OS (5-year OS: 71.0% vs. 81.7%) and CSS (5-year CSS: 86.7% vs. 89.2%). After adjusting for age, sex, stage, adjuvant chemotherapy, and comorbidities in our multivariate analysis, DM remained an independent prognostic factor for overall mortality (adjusted hazards ratio: 1.32, 95% confidence interval: 1.18-1.49), but not for cancer-specific mortality. Among the colon cancer patients who had received antidiabetic drug therapy, patients who had used insulin had significantly shorter CSS and OS than patients who had not.

Conclusion: Among patients who receive curative surgery for early colon cancer, DM is a predictor of increased overall mortality.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1634/theoncologist.2013-0423DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4153450PMC
September 2014

Primary squamous cell carcinoma of the thyroid with cardiac metastases and right ventricle outflow tract obstruction.

J Clin Oncol 2012 Sep 29;30(26):e260-3. Epub 2012 May 29.

National Taiwan University Hospital, Taipei, Taiwan.

View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1200/JCO.2011.39.9808DOI Listing
September 2012

Macrophage activation increases the invasive properties of hepatoma cells by destabilization of the adherens junction.

FEBS Lett 2006 May 27;580(13):3042-50. Epub 2006 Apr 27.

Department of Anatomy and Cell Biology, College of Medicine, National Taiwan University, 1-1 Jen-Ai Road, Taipei 10051, Taiwan.

Tumor-associated macrophages play an important role in tumor progression, but whether they exert a tumor-progressive effect remains controversial. Here, we demonstrated that activated macrophage-conditioned medium (AMCM) obtained from RAW macrophages (RAW/AMCM) induced epithelial-mesenchymal transition (EMT) and stimulated the migratory and invasive activities of HepG2 cells, whereas control conditioned media had no effect. Epithelial-cadherin (E-cadherin) and beta-catenin staining patterns were altered at the adherens junctions by RAW/AMCM treatment, with an approximately 50% decrease in E-cadherin and beta-catenin in the cell membrane. Importantly, levels of beta-catenin-associated E-cadherin were also decreased. Following RAW/AMCM treatment, enhanced activation of c-Src was seen prior to increased tyrosine phosphorylation of beta-catenin, and this led to the destabilization of adherens junctions. Pretreatment of HepG2 cells with the Src kinase inhibitor, PP2, completely abolished the effects of RAW/AMCM on the EMT, migration, invasion, and expression and association of E-cadherin and beta-catenin. AMCMs obtained from human THP-1 monocytes and mouse peritoneal macrophages also caused disassembly of the adherens junctions and migration of HepG2 cells. Furthermore, inhibition of the epidermal growth factor receptor (EGFR) with gefitinib partially prevented the downregulation of E-cadherin and beta-catenin at the adherens junctions and migration behavior induced by RAW/AMCM. Our results suggest that activated macrophages have a tumor-progressive effect on HepG2 cells which involves the c-Src- and EGFR-dependent signaling cascades.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/j.febslet.2006.04.049DOI Listing
May 2006

Influence of pH on electrophoretic behavior of phenothiazines and determination of pKa values by capillary zone electrophoresis.

Electrophoresis 2003 Sep;24(18):3154-9

Department of Chemistry, National Taiwan University, Taipei, Taiwan.

The influence of buffer pH on the electrophoretic behavior of 13 structurally related phenothiazines and determination of pK(a) values by capillary zone electrophoresis (CZE) were investigated. The results indicate that phenothiazines with a piperazine substituent behave quite differently from those with substituents having an aliphatic side chain or a piperidine moiety over the pH range studied. To separate these phenothiazines, it is preferable to select buffer pH in the range of 2.5-3.5. The pK(a) values of phenothiazines with three different types of substituents attached at the 10-position of the phenothiazine ring were determined. The determination of pK(a) values of phenothiazines allows us to rationalize the influence of buffer pH on the migration behavior of these compounds in CZE.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/elps.200305559DOI Listing
September 2003

Enantioseparation of phenothiazines in cyclodextrin-modified capillary zone electrophoresis: reversal of migration order.

Electrophoresis 2003 Sep;24(18):3139-46

Department of Chemistry, National Taiwan University, Taipei, Taiwan.

Enantioseparations of phenothiazines with gamma-cyclodextrin (gamma-CD) as a chiral selector were investigated using citrate and phosphate buffer electrolytes at pH 3.0. Reversal of the enantiomer migration order of promethazine, ethopropazine, and trimeprazine was observed by varying gamma-CD concentration in the range of 5-9 mM, 2.5-4.5 mM and 1.5-2.8 mM, respectively, using 100 mM citrate buffer at pH 3.0. As in the case of beta-CD, the (+)-enantiomers of phenothiazines possess greater binding strength to gamma-CD than the (-)-enantiomers. The evaluation of the binding constants and limiting mobility of the complexes formed between the enantiomers of phenothiazines and gamma-CD reveals that the binding strength of phenothiazines to gamma-CD and the differences in the binding constants and limiting mobility of the complexes are responsible for the enantiomer migration reversal. Both the binding constants and limiting mobility of the complexes between the (+)-enantiomers of phenothiazine and gamma-CD are greater than those of the corresponding (-)-enantiomers in a citrate buffer, while the binding constants of the complexes primarily determined the migration order of the enantiomers in a phosphate buffer. Compared with the results obtained using a phosphate buffer, we may conclude that citrate buffer which involves competitive complexation with chiral selector plays a significant role in the enantiomer migration reversal.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1002/elps.200305558DOI Listing
September 2003

Separation and migration behavior of structurally related phenothiazines in cyclodextrin-modified capillary zone electrophoresis.

J Chromatogr A 2002 Dec;979(1-2):399-408

Department of Chemistry, National Taiwan University, P.O. Box 23-34, 1 Roosevelt Road Section 4, Taipei 10674, Taiwan.

The influences of buffer pH and the concentration of beta-cyclodextrins (beta-CDs) on the separation and migration behavior of 13 structurally related phenothiazines in CD-modified capillary zone electrophoresis (CD-CZE) using a phosphate background electrolyte at low pH were investigated. We focused on the separation of these phenothiazines, including the enantiomers of chiral analytes, with the use of beta-CD and hydroxypropyl-beta-CD (HP-beta-CD) as electrolyte modifiers or chiral selectors at concentrations less than 8 mM. The results indicate that the interactions of phenothiazines with beta-CDs are very strong and that effective separations of 13 analytes can be achieved with addition of 0.3 mM beta-CD or 0.5 mM HP-beta-CD in a phosphate buffer at pH 3.0. Binding constants of phenothiazines to beta-CDs were evaluated for a better understanding of the interactions of phenothiazines with beta-CDs.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/s0021-9673(02)01501-7DOI Listing
December 2002

Enantioseparation of phenothiazines in cyclodextrin-modified micellar electrokinetic chromatography.

J Chromatogr A 2002 Sep;971(1-2):261-6

Department of Chemistry, National Taiwan University, Taipei.

In this study, enantioseparations of five phenothiazines in cyclodextrin (CD)-modified micellar electrokinetic chromatography (MEKC) were investigated using a citrate buffer containing tetradecyltrimethylammonium bromide (TTAB) as a cationic surfactant at low pH. Beta-cyclodextrin (beta-CD) and hydroxylpropyl-beta-CD (HP-beta-CD) were selected as chiral selectors. The results indicate that the separation window is greatly enlarged by beta-CD concentration and that the separability and selectivity of phenothiazines are remarkably influenced by the concentrations of both beta-CD and TTAB, as well as buffer pH. The interaction of thioridazine with beta-CDs is considerably reduced in the presence of TTAB micelles due to competitive complexation of thioridazine with TTAB micelles, which is pH-dependent. As a result, effective enantioseparation of thioridazine is simultaneously achievable with that of trimeprazine and promethazine or ethopropazine in MEKC with addition of either beta-CD or HP-beta-CD, respectively, to a micellar citrate buffer containing TTAB at pH 3.5. Better enantioresolution of thioridazine in MEKC than in capillary zone electrophoresis can be obtained.
View Article and Find Full Text PDF

Download full-text PDF

Source
http://dx.doi.org/10.1016/s0021-9673(02)01044-0DOI Listing
September 2002