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Biomedical subjects

Ka-Fai To

Publications and source records attributed to Ka-Fai To.

At least 55 records · Page 3Linked to original sources
PubMed2003

Rapid clearance of plasma Epstein-Barr virus DNA after surgical treatment of nasopharyngeal carcinoma.

PURPOSE: Circulating EBV DNA analysis has been shown to be valuable in the detection, prognostication, and monitoring of nasopharyngeal carcinoma (NPC) patients. A previous study has shown that, after radiotherapy, plasma EBV DNA levels of NPC patients would decline exponentially with a median half-life of 3.8 days. We postulate that this decline in plasma EBV DNA reflects the decrease in cancer cell population and, therefore, the rate of decline reflects the radiosensitivity of the tumor. However, this postulation would hold true only if EBV DNA is rapidly eliminated from the circulation. In this study, we determined the in vivo elimination rate of plasma EBV DNA in NPC patients. EXPERIMENTAL DESIGN: We monitored the level of plasma EBV DNA in NPC patients during and after surgical resection of NPC. The half-life of plasma EBV DNA was then calculated by plotting the natural logarithm of EBV DNA concentrations against time. RESULTS: The median half-life of plasma EBV DNA after surgical resection of NPC was 139 min. After a median follow-up of 6.7 days, EBV DNA was undetectable in 8 of 11 patients. One of 8 patients with undectable EBV DNA and all of the patients with detectable EBV DNA developed clinical relapse. CONCLUSIONS: The in vivo elimination of EBV DNA is very rapid after surgical resection of NPC. The failure of complete and rapid elimination of EBV DNA from the circulation predicts disease recurrence.

Biomarkers, Tumor↗
PubMed2003

Inactivation of helicase-like transcription factor by promoter hypermethylation in human gastric cancer.

Helicase-like transcription factor (HLTF), a member of the SWI/SNF (mating type switching/sucrose nonfermenting) chromatin-remodeling complex, is recently found to be inactivated by promoter hypermethylation in human colorectal cancer. However, the role of this putative tumor suppressor gene in other tumors has not been determined. We evaluated the role of HLTF promoter hypermethylation in gastric cancer. Expression of HLTF was examined by reverse-transcription (RT)-polymerase chain reaction (PCR), and promoter hypermethylation in HLTF was determined by methylation-specific PCR. Bisulfite DNA sequencing was performed to determine the detailed methylation profiles of the promoter region. HLTF expression was lost in two of five gastric cell lines and in 13 (28%) of 46 primary gastric cancers. Accordingly, promoter hypermethylation was detected in the two cell lines and in nine of 13 gastric cancer samples. Of the ten normal gastric specimens and ten paired adjacent nonneoplastic tissues, methylation was detected in only one adjacent nonneoplastic tissue. Bisulfite DNA sequencing of the promoter region of HLTF showed that the CpG island was densely methylated in cell lines and cancer samples; this also appeared to correlate with expression level. Treatment of gastric cell lines that lacked HLTF expression with the demethylating agent 5-azacytidine (5-azaDC) restored HLTF expression. These results suggest that HLTF promoter hypermethylation is frequently demonstrated in human gastric cancer, and inactivation of HLTF or the chromatin-remodeling complex may play a crucial role in gastric carcinogenesis.

Adaptor Proteins, Signal Transducing↗
PubMed2003

Enteric involvement of severe acute respiratory syndrome-associated coronavirus infection.

BACKGROUND AND AIMS: Severe acute respiratory syndrome (SARS) is a recently emerged infection from a novel coronavirus (CoV). Apart from fever and respiratory complications, gastrointestinal symptoms are frequently observed in patients with SARS but the significance remains undetermined. Herein, we describe the clinical, pathologic, and virologic features of the intestinal involvement of this new viral infection. METHODS: A retrospective analysis of the gastrointestinal symptoms and other clinical parameters of the first 138 patients with confirmed SARS admitted for a major outbreak in Hong Kong in March 2003 was performed. Intestinal specimens were obtained by colonoscopy or postmortem examination to detect the presence of coronavirus by electron microscopy, virus culture, and reverse-transcription polymerase chain reaction. RESULTS: Among these 138 patients with SARS, 28 (20.3%) presented with watery diarrhea and up to 38.4% of patients had symptoms of diarrhea during the course of illness. Diarrhea was more frequently observed during the first week of illness. The mean number of days with diarrhea was 3.7 +/- 2.7, and most diarrhea was self-limiting. Intestinal biopsy specimens obtained by colonoscopy or autopsy showed minimal architectural disruption but the presence of active viral replication within both the small and large intestine. Coronavirus was also isolated by culture from these specimens, and SARS-CoV RNA can be detected in the stool of patients for more than 10 weeks after symptom onset. CONCLUSIONS: Diarrhea is a common presenting symptom of SARS. The intestinal tropism of the SARS-CoV has major implications on clinical presentation and viral transmission.

Adult↗
PubMed2003

Positional mapping for amplified DNA sequences on 1q21-q22 in hepatocellular carcinoma indicates candidate genes over-expression.

BACKGROUND/AIMS: Comparative genomic hybridization analysis on hepatocellular carcinoma (HCC) indicated frequent gains of 1q and an amplicon at 1q21-q22. Current cytogenetic evidences confer much importance on 1q21-q22, where a role in drug resistance, tumor metastasis and shorter patient survival had been implicated. METHODS: Using positional mapping by interphase cytogenetics, we investigated the amplicon 1q21-q22 in five HCC cases. Three amplification maxima represented by yeast artificial chromosomes (YACs) 955E11, 876B11 and 945D5 that mapped to regions 1q21.1, 1q21.2 and 1q22, respectively, were indicated. We further investigated candidate genes expression in the mapped YACs by quantitative reverse-transcription-polymerase chain reaction. A panel of genes encoding protein transcripts involved in apoptosis, cell cycle progression, calcium binding and jumping translocation was studied. RESULTS: Among ten HCC cases with the amplicon 1q21-q22 examined, we found a significant gene expression level of JTB, SHC1, CCT3 and COPA in the tumors than the paired adjacent non-malignant liver tissues (P< or =0.04). CONCLUSIONS: Our interphase findings on 1q21-q22 pinpointed three affected loci between D1S305 and D1S2369. Up-regulation of candidate genes identified within these over-represented regions may represent targets in the progression of HCC and may carry prognostic significance.

Carcinoma, Hepatocellular↗
PubMed2003

A novel mutation (G233D) in the glycogen phosphorylase gene in a patient with hepatic glycogen storage disease and residual enzyme activity.

We identified a novel mutation in the glycogen phosphorylase gene (PGYL) in a Chinese patient with glycogen storage disease (GSD) type VI. The patient presented with gross hepatomegaly since the age of two without history of any hypoglycemic attack. Otherwise, he was largely asymptomatic. Liver tissue enzyme assays revealed a mild deficiency of total glycogen phosphorylase. Both PGYL and PHKA2 genes were sequenced. The patient was homozygous of a missense mutation G233D in PGYL. This location forms a hairpin turn secondary structure and the small glycine residue is completely conserved in all the orthologous proteins from Escherichia coli to mammals. This is the sixth reported mutation of this form of GSD.

Amino Acid Sequence↗
PubMed2003

Human metapneumovirus detection in patients with severe acute respiratory syndrome.

We used a combination approach of conventional virus isolation and molecular techniques to detect human metapneumovirus (HMPV) in patients with severe acute respiratory syndrome (SARS). Of the 48 study patients, 25 (52.1%) were infected with HMPV; 6 of these 25 patients were also infected with coronavirus, and another 5 patients (10.4%) were infected with coronavirus alone. Using this combination approach, we found that human laryngeal carcinoma (HEp-2) cells were superior to rhesus monkey kidney (LLC-MK2) cells commonly used in previous studies for isolation of HMPV. These widely available HEp-2 cells should be included in conjunction with a molecular method for cell culture followup to detect HMPV, particularly in patients with SARS.

Adult↗
PubMed2002

Promoter hypermethylation of tumor-related genes in gastric intestinal metaplasia of patients with and without gastric cancer.

Promoter hypermethylation is an alternative mechanism of gene silencing in human cancers including gastric cancer. While intestinal metaplasia (IM) is generally regarded as a precancerous lesion of the stomach, our study examines the presence of gene promoter hypermethylation in IM of patients with and without gastric cancer. We examined 31 samples of gastric cancer, 36 gastric IM (21 associated with gastric cancer and 15 from noncancer patients) and 10 normal gastric biopsies. Tissues containing foci of IM were carefully microdissected from paraffin-embedded section. Bisulfite-modified DNA was examined for gene promoter hypermethylation in DAP-kinase, E-cadherin, GSTP1, p14, p15, p16, RASSF1A and hMLH1 by methylation-specific-PCR. None of the control gastric tissues had hypermethylation detected, but gene promoter hypermethylation was frequently detected in gastric cancer and IM. The mean number of methylated genes in cancer and IM was 3.0 and 1.4, respectively (p < 0.0001). Methylation in IM from cancer patients was all associated with concurrent methylation in the corresponding tumor samples. The numbers of methylated genes were similar in IM obtained from cancer and noncancer patients. By examining the methylation patterns of these genes, 3 differential methylation patterns were recognized: hypermethylation was more frequent in cancer than in IM (DAP-kinase, p14, p15 and p16); comparable frequencies of methylation in cancer and IM (E-cadherin and hMLH1); and no methylation (GSTP1). Aberrant methylation in tumor-related genes is frequently detected in gastric IM of both cancer and noncancer patients, suggesting their early involvement in the multistep progression of gastric carcinogenesis.

Aged↗
PubMed2002

Promoter hypermethylation of the EDNRB gene in nasopharyngeal carcinoma.

To identify the epigenetic changes in nasopharyngeal carcinoma (NPC), we performed methylation-sensitive restriction fingerprinting (MSRF) analysis on NPC cell lines and xenografts. A 190 bp sequence methylated in NPC tumors was isolated and showed high homology to the 5' CpG island of the endothelin receptor B (EDNRB) gene. Since the EDNRB gene is commonly inactivated in prostate and bladder cancers, it may be a candidate target gene involved in NPC tumorigenesis. By bisulfite sequencing, we have confirmed that hypermethylation of the 5' CpG island of EDNRB occurred in both xenografts and all 4 cell lines but not in 2 normal nasopharyngeal outgrowths. RT-PCR demonstrated that only original EDNRB transcripts, but not the splicing transcripts, were expressed in normal nasopharyngeal epithelial cells. Loss of the original EDNRB expression was consistently found in 2 xenografts and 3 cell lines with dense methylation patterns. Treatment of these 3 cell lines with 5'-aza-2'-deoxycytidine led to re-expression of the EDNRB transcript and demethylation of its promoter regions. Our results demonstrate that silencing of EDNRB gene expression in NPC is associated with promoter hypermethylation. Using methylation-specific PCR, we also detected methylation of the 5' CpG island of EDNRB in 19/21 (90.5%) primary tumors, while no methylation was found in all 6 normal nasopharyngeal epithelia. The high frequencies of promoter hypermethylation suggest that repression of the EDNRB gene may play a role in the development of NPC.

Base Sequence↗
PubMed2002

Consistent chromosome 10 rearrangements in four newly established human hepatocellular carcinoma cell lines.

Cancer cell lines represent an invaluable resource for isolation of novel genes relevant to tumor pathogenesis and as in vitro models. In this study, we report on the successful establishment of four cell lines from hepatocellular carcinoma tissue. These cell lines, designated HKCI-1, HKCI-2, HKCI-3, and HKCI-4, have been growing continuously for more than 24 months and have been passaged more than 50 times. A comprehensive cytogenetic characterization on the primary tumors and the derived cell lines was achieved by the combined approach of spectral karyotyping and comparative genomic hybridization. Chromosomal imbalances from the primary tumors were also maintained in the cell lines and included gains of 1q, 6p, 7, 10p, 17q, and 20 and loss of 4q. Recurring translocations included t(X;11), t(1;10), t(4;16), i(5)(p10), t(7;21), t(8;17), t(9;22), i(10)(p10), t(14;20), t(16;22), and t(17;19). It was noteworthy that consistent chromosome 10 aberrations, in particular t(1;10)(q10;p10), were detected in all four cell lines. Furthermore, microsatellite analysis on primary tumor and derived cell lines indicated a common deleted region of 10q23-q26. The functional importance of chromosome 10 aberrations in relation to the pathogenesis of HCC is unknown; however, the high frequency with which such aberrations were maintained in the cell lines suggests proliferative advantages of 10q loss or 10p gain in the multistep development of hepatic neoplasia.

Aged↗
PubMed2002

Case report: human herpesvirus 7 associated fatal encephalitis in a peripheral blood stem cell transplant recipient.

Previous studies have suggested a neuroinvasive and neuropersistent potential of human herpesvirus 7 (HHV-7). In this report, a case of fatal encephalitis is described and its association with HHV-7 infection is discussed. An 8-year-old girl received a peripheral blood stem cell transplant for relapsed acute lymphoblastic leukaemia. The post-transplant period was uneventful and a course of intrathecal chemotherapy was given on Day-30. On Day-41, she developed acute encephalopathy with diplopia and nystagmus. She ran a rapid downhill course and succumbed despite antiviral treatment. The only positive pathological finding was the multiple microscopic foci of haemorrhage associated with neuronal degeneration detected in the brain stem. All microbiological investigations were negative, except for the presence of HHV-7 DNA in cerebrospinal fluid and brain stem tissue samples.

Brain Stem↗
PubMed2002

Mutational and haplotype analysis of AGL in patients with glycogen storage disease type III.

Glycogen storage disease type III (GSD III) is a rare autosomal recessive inherited disorder caused by a deficiency of the glycogen-debranching enzyme (AGL). We investigated two GSD III patients and identified four different mutations. Nucleotide sequence analysis revealed patient 1 of Chinese descent to be a compound heterozygote for a novel nonsense mutation, R34X, and the splicing mutation (IVS32-12A > G) reported in a Japanese patient. Patient 2 of Japanese origin was found to be compound heterozygous for a novel nonsense mutation, Y1148X, and the splicing mutation (IVS14+1G > T) that we had described previously. To determine whether splicing mutations occurred independently, we performed intense AGL haplotype analysis using 21 intragenic polymorphic markers plus a novel polymorphism IVS32-97 A/G in the vicinity of the IVS32 splicing mutation. Patient 1 of Chinese origin and the Japanese patient homozygous for the IVS32-12A > G were found to have different haplotypes, indicating the IVS32-12A > G mutation to be a recurrent mutation. This is the first recurrent mutation established by intense haplotyping in the AGL gene.

Adult↗
PubMed2002

Frequent loss of chromosome 3p and hypermethylation of RASSF1A in cholangiocarcinoma.

BACKGROUND/AIMS: Cholangiocarcinoma comprises 5-20% of all primary malignant tumors of the liver. However, the lack of information about the genetic basis of cholangiocarcinoma has impeded characterization and understanding of its biological behavior. METHODS: In this study, genome-wide aberrations in 13 cases of cholangiocarcinoma were examined by the molecular cytogenetic technique, comparative genomic hybridization. RESULTS: Frequent gains of 1q, 3q, 8q, 15q and 17q, and common losses on 3p, 4q, 6q, 9p, 17p and 18q were found. The finding of common chromosome 3p loss (approximately 40%) with a minimal deleted region of 3p13-p21 has prompted our further investigation on the tumor suppressor gene RASSF1A, located at 3p21.3. Using bisulphite modification followed by methyl-specific PCR, a high incidence of methylated RASSF1A promoter region was detected in our current series (9/13 cases; 69%). Further expression analysis on the nine cases with promoter hypermethylation indicated much reduced RASSF1A expression compared to normal livers. CONCLUSIONS: Our current molecular cytogenetic investigation on primary cholangiocarcinoma provided overall karyotypic information and represents the first report on the methylation status of RASSF1A in cholangiocarcinoma. The high incidence of 3p loss and RASSF1A promoter hypermethylation detected may have implications for this tumor suppressor gene in the malignant progression of cholangiocarcinoma.

Adult↗
PubMed2002

Identification of four distinct regions of allelic imbalances on chromosome 1 by the combined comparative genomic hybridization and microsatellite analysis on hepatocellular carcinoma.

Frequent chromosome 1 abnormalities detected in human hepatocellular carcinoma have been implicated in early genetic events of liver carcinogenesis. Recurrent loss of 1p with a common deleted region 1p36-p34 has been reported from microsatellite analysis, whereas common gain of the whole chromosome q-arm was described from several comparative genomic hybridization studies. The relationships between copy number changes and allelic status however remains unclear. In this study, we have conducted a simultaneous comparative genomic hybridization and microsatellite analysis study on chromosome 1 in 31 hepatocellular carcinoma cases. Microsatellite analysis revealed frequent loss of heterozygosity on 1p at loci D1S468 (74%), D1S450 (67%), D1S2667 (65%), D1S2697 (75%), D1S199 (52%), and D1S234 (67%) corresponded to the distal 1p36 region and coincided with 12 cases (86%) that presented losses on 1p by comparative genomic hybridization analysis. Although comparative genomic hybridization indicated a common deleted region of 1p36-p35 in the current series, microsatellite analysis has refined the smallest overlapping region (SOR) to 1p36.13-p36.22. Gain of 1q as revealed by comparative genomic hybridization suggested low and high-level gains, and cases that displayed an amplicon below the heterochromatic region 1q21-q25. Common allelic imbalances of polymorphic markers D1S2635 (64%), D1S484 (67%), D1S2878 (65%), D1S196 (70%), D1S249 (64%) D1S2785 (75%), D1S2842 (73%) and D1S2836 (74%) that corresponded to the regions 1q23.1-q24.2, 1q32.1 and 1q43-q44 were detected. Three distinct regions of allelic imbalances were thus suggested on recurring 1q gain found in hepatocellular carcinoma. Furthermore, microsatellite analysis has enabled a mapping of common overrepresented regions and suggested SOR on 1q23.1-q23.3 (D1S2635-D1S2878), 1q25.1-q31.1 (D1S452-D1S238), and 1q43 (D1S2785-D1S2842). Our current study has refined chromosome 1 aberrations in hepatocellular carcinoma to four regions of allelic imbalances. The SORs delineated should provide basis for further molecular investigation in hepatocarcinogenesis on genes residing on these chromosomal regions.

Adult↗
PubMed2002

Promoter hypermethylation of multiple genes in nasopharyngeal carcinoma.

PURPOSE: The methylation profile of nasopharyngeal carcinoma (NPC) has been investigated by a candidate gene approach. EXPERIMENTAL DESIGN: Four NPC cell lines, 4 NPC xenografts, 33 NPC primary tumors, and 6 samples of normal nasopharyngeal epithelium were subjected to methylation-specific PCR for analysis of promoter methylation of eight cancer-related genes. These eight genes were RASSF1A, RARbeta2, DAP-kinase, p16, p15, p14, MGMT, and GSTP1. The correlation between methylation status of these genes and clinical features such as stage, local-regional recurrence, distant metastasis, and survival has been analyzed. RESULTS: The incidence of promoter methylation in NPC samples was 84% for RASSF1A, 80% for RARbeta2, 76% for DAP-kinase, 46% for p16, 17% for p15, 20% for p14, 20% for MGMT, and 3% for GSTP1. No methylation of these genes was detected in the six normal nasopharyngeal epithelium samples. All NPC tumor samples in this study displayed aberrant methylation in at least one of these eight genes. No significant correlation between methylation status of these genes and clinical parameters of the patients was found. CONCLUSIONS: A high frequency of aberrant methylation of the 5' CpG island of the RASSF1A, RARbeta2, DAP-kinase, and p16 genes in the present study was noted. Our findings suggest that methylation of the genes in the critical pathways is common in NPC.

Apoptosis Regulatory Proteins↗
PubMed2002

Genome wide detection of oncogene amplifications in nasopharyngeal carcinoma by array based comparative genomic hybridization.

We have applied the method of genomic microarray to investigate amplification of oncogenes throughout the genome of nasopharyngeal carcinoma (NPC). Array based comparative genomic hybridization (array CGH) allows simultaneous examination of 58 oncogenes commonly amplified in various human cancers. In the present study, we have examined 15 NPC samples including five cell lines, two xenografts and eight primary tumours with array CGH to reveal the particular oncogenes associated with this cancer. This is the first genome wide survey of multiple oncogene amplifications involved in the development of NPC. Non-random gene amplifications were identified for the first time in NPC on MYCL1 in 1p34.3 and on TERC and PIK3CA at 3q26.3. Other high level amplified oncogenes included NRAS, RAF1, MYB, EGFR, FGF4, EMS1, and D17S167. Highest frequencies of gain of novel oncogenes were detected on MYCL1 (66.7%), TERC (46.7%), ESR (46.7%), PIK3CA (40%), LAMC2 (33.3%), and CSE1L (33.3%).

Carcinoma↗