Biomedical subjects

Nan Hu

Publications and source records attributed to Nan Hu.

34 records · Page 2Linked to original sources

PubMed2004

High frequency of CDKN2A alterations in esophageal squamous cell carcinoma from a high-risk Chinese population.

Because previous studies have shown that loss of heterozygosity (LOH) is common on chromosome arm 9p in esophageal squamous cell carcinoma (ESCC) and that genetic alterations in CDKN2A and CDKN2B on 9p are also common, we sought to determine whether LOH and these genetic alterations are related. We performed LOH studies on chromosome bands 9p21-p22 and searched for genetic alterations of CDKN2A and CDKN2B in 56 ESCCs from a high-risk Chinese population. Seventy-three percent of patients were found to have LOH at one or more loci on chromosome bands 9p21-p22, and LOH occurred more frequently in patients with a family history of upper gastrointestinal cancer than in those with a negative family history (P = 0.01, global permutation test). CDKN2A mutations (point mutations, deletions, insertions) were observed in 25% (14 of 56) of cases, and the LOH pattern was significantly different for individuals with and without a CDKN2A mutation (P = 0.01, global test). Three new single nucleotide polymorphisms (SNPs) and 2 previously reported SNPs were identified in this group of patients. Intragenic allelic loss at polymorphic sites in CDKN2A was detected in 32% (18 of 56) of patients. Seven of the 56 (13%) cases exhibited what is considered classic evidence (n = 4) or showed potential evidence (n = 3) of biallelic inactivation. Only one alteration was observed in CDKN2B, G171A in the 5' untranslated region. Both mutation and intragenic allelic loss in CDKN2A appear to play a role in the development of ESCC.

Alleles↗

PubMed2004

Identifying multiple changepoints in heterogeneous binary data with an application to molecular genetics.

Identifying changepoints is an important problem in molecular genetics. Our motivating example is from cancer genetics where interest focuses on identifying areas of a chromosome with an increased likelihood of a tumor suppressor gene. Loss of heterozygosity (LOH) is a binary measure of allelic loss in which abrupt changes in LOH frequency along the chromosome may identify boundaries indicative of a region containing a tumor suppressor gene. Our interest was on testing for the presence of multiple changepoints in order to identify regions of increased LOH frequency. A complicating factor is the substantial heterogeneity in LOH frequency across patients, where some patients have a very high LOH frequency while others have a low frequency. We develop a procedure for identifying multiple changepoints in heterogeneous binary data. We propose both approximate and full maximum-likelihood approaches and compare these two approaches with a naive approach in which we ignore the heterogeneity in the binary data. The methodology is used to estimate the pattern in LOH frequency on chromosome 13 in esophageal cancer patients and to isolate an area of inflated LOH frequency on chromosome 13 which may contain a tumor suppressor gene. Using simulations, we show that our approach works well and that it is robust to departures from some key modeling assumptions.

Chromosomes, Human, Pair 13↗

PubMed2004

Angiotensin-converting enzyme inhibition, body composition, and physical performance in aged rats.

This study was designed to test the effects of angiotensin-converting enzyme (ACE) inhibition on body composition and physical performance in aged rats. Male Brown Norway x F344 rats were randomized to receive daily injections of enalapril (40 mg/kg or 80 mg/kg) or saline from 24 to 30 months of age. Body composition was determined using dual-energy X-ray absorptiometry (DXA), and physical performance was assessed using the grip strength and inclined plane procedures. Performance measures were assessed at baseline and monthly thereafter. DXA was performed at baseline, 3 months, and 6 months of follow-up. Compared with the enalapril groups, the saline group experienced a greater 6-month decline in the physical performance measures. Lean body mass declined in both groups; however, the enalapril groups also experienced a significant loss of fat mass. These results suggest that ACE inhibition may prevent age-related declines in physical performance, which may be mediated by a reduction in body fat mass.

Age Factors↗

PubMed2004

Emergence of resistance to carbocyclic oxetanocin G in herpes simplex virus type 1 and genetic analysis of resistant mutants.

AIM: To elucidate the potentiality of emergence of drug-resistance to carbocyclic oxetanocin G (C.OXT-G), a new effective antiviral drug for herpetic keratitis during treatment and the mechanism of this drug resistance. METHODS: A C.OXT-G resistant strain (C.OXT-Gr) was established by serially propagating the herpes simplex virus (HSV) -1 in African green monkey kidney (VERO) cells in the presence of C.OXT-G. After the drug sensitivity assay and the thymidine kinase (TK) activity assay, the molecular basis for the drug resistance was studied using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis and PCR direct sequencing technology. RESULTS: After the 10th passage in 10 microm C.OXT-G, the ED50 of the C.OXT-Gr was 17.08-fold greater than that of the original strain on the average and the TK activities of these resistant strains were extremely reduced. PCR-SSCP analysis on TK gene of the wild HSV-1 and the C.OXT-Gr showed altered migration patterns in part 3 and part 4, while PCR-SSCP analysis on DNA polymerase gene showed no difference among the viruses. Sequence analysis revealed a deletion of G at position of 430 that caused frameshift, resulting in premature termination in the TK gene. CONCLUSION: The drug resistance to C.OXT-G may appear during the treatment due to the deficiency of TK activity caused by a single mutation in the TK gene of HSV-1.

Animals↗

PubMed2004

[Loss of heterozygosity in esophageal squamous cell carcinoma and its precursor lesion].

OBJECTIVE: To detect the loss of heterozygosity (LOH) in esophageal squamous cell carcinoma and adjacent high-grade squamous dysplasia, and to evaluate possible tumor suppressor genes in the development and progression of invasive malignancy. METHODS: LOH was detected in normal esophageal mucosa, high grade squamous dysplasia and esophageal squamous cell carcinoma using microdissection and polymerase chain reaction technology. The changes of LOH at seven microsatellite markers and the relationship between LOH rate and clinicopathologic parameters were analyzed. RESULTS: In high grade squamous dysplasia, LOH was detected at D13S802 (40%), D13S267 (32%), D13S221 (31%), D9S942 (30%), D17S520 (24%) and D9S171 (33%). However, D17S1798 LOH was not detected. In invasive squamous cell carcinoma, LOH was detected as follows: D13S267 (71%), D13S802 (58%), D17S520 (55%), D13S221 (45%), D9S942 (43%), D9S171 (33%) and D17S1798 (11%). The frequency of LOH in the seven microsatellite markers, the pathologic grade, clinical stage and occurrence of lymph node metastasis did not show any statistically significant correlation (P > 0.05). CONCLUSIONS: The progression from normal squamous epithelium to high grade squamous dysplasia and subsequently to invasive squamous cell carcinoma of the esophagus was associated with accumulation of genetic errors. Possible tumor suppressor genes related to the development of esophageal squamous cell carcinoma may exist near D13S802 (13q12.12). Possible tumor suppressor genes near D13S267 (13q13.1), D17S1798 (17p13.3) and D17S520 (17p13.1) may be related to the progression of esophageal squamous cell carcinoma.

Adult↗

PubMed2003

Gene expression analysis of esophageal squamous cell carcinoma reveals consistent molecular profiles related to a family history of upper gastrointestinal cancer.

Tumor and matched normal tissue from 19 esophageal squamous cell carcinoma patients from a high-risk area of China were analyzed with 7680 gene cDNA microarrays. Forty-one genes were differentially expressed (P < 0.001; >/==" BORDER="0">2-fold change) between tumor and matched normal samples (13 overexpressed and 28 underexpressed). Hierarchical clustering showed consistent molecular profiles across patients. Multidimensional scaling plots visually distinguished cases by family history status, which was confirmed statistically using a global permutation test (P = 0.007); we then identified 152 genes of which the expression differed in tumors from family history positive versus negative cases (55 overexpressed and 97 underexpressed at P < 0.001). These data indicate that molecular profiles in esophageal squamous cell carcinoma are highly consistent and that expression patterns in familial cases differ from those in sporadic cases.

Aged↗

PubMed2003

Microsatellite alterations in esophageal dysplasia and squamous cell carcinoma from laser capture microdissected endoscopic biopsies.

Esophageal squamous cell carcinoma (ESCC), with a 5 year survival below 15%, is one of the most common fatal cancers worldwide. Significant reduction in mortality may be achieved by detecting and treating asymptomatic precursor lesions and curable early cancers. To explore this possibility and look for potential early detection markers, we examined alterations in 16 microsatellite markers in laser capture microdissected (LCM) endoscopic biopsies from the esophagus, including 15 dysplasias and 22 ESCCs, in patients from Shanxi Province, a region in north-central China. We found a significant increase in the total frequency of allelic loss with increasing disease severity. Allelic loss was seen in 2% of the markers in patients with low grade dysplasia (LGD), 15% of the markers in patients with high grade dysplasia (HGD), and 35% of the markers in patients with ESCC. Ten different markers (D3S4513, D5S2501, D8S1106, D9S118, D9S910, D13S1493, D13S894, D13S796, D15S655, and D17S1303) showed allelic loss in one or more of the premalignant lesions tested. The frequency of microsatellite instability (MSI) also increased with histological severity, from 22% in LGD to 33% in HGD and 59% in ESCC. These results indicate that the development of ESCC is associated with genetic instability, that this instability can be detected in endoscopic biopsies of recognized precursor lesions in patients without invasive cancer, and that these markers may be useful as predictive markers in the early detection of ESCC. Finally, we also report methodologic/technical modifications that enhance the use of LCM for screening endoscopic biopsies.

Adult↗

PubMed2003

Allelic loss on chromosome 13q14 and mutation in deleted in cancer 1 gene in esophageal squamous cell carcinoma.

Previous studies have shown frequent allelic loss on chromosome 13 in esophageal squamous cell carcinoma (ESCC). We assessed the frequency of allelic loss on chromosome 13q14 and mutations of deleted in cancer 1 (DICE1) (also found on 13q14) in ESCC patients to determine if this candidate tumor suppressor gene has a role in the development of ESCC, and whether this gene was an inactivation target for allelic loss on chromosome 13q14. Initially, we examined allelic loss at five markers flanking DICE1 in 56 ESCC patients from Shanxi Province, China, and then examined the entire coding sequence of this gene for mutations using polymerase chain reaction-single-strand confirmation polymorphism (PCR-SSCP) analysis and DNA sequencing. Subsequently, we extended our evaluation to an additional 80 ESCC patients and 232 healthy individuals to confirm the germline variant found in the initial 56 ESCC patients. The frequencies of allelic loss were 71, 58, and 75% for D13S325, D13S757, and D13S887, respectively, in the initial 56 ESCC patients studied. Overall, 73% of informative patients had loss of heterozygosity (LOH) for at least one of these three markers. Somatic mutations were identified in three patients (3/56, 5%), and one novel polymorphism was identified in 3% of ESCC patients (4/136) and 3% of healthy individuals (6/232). We conclude that DICE1 mutations occur in ESCC but are infrequent. The candidate tumor suppressor gene corresponding to the frequent allelic loss on chromosome 13q14 in ESCC remains unknown.

Alleles↗

PubMed2003

Common genetic variants of TP53 and BRCA2 in esophageal cancer patients and healthy individuals from low and high risk areas of northern China.

TP53 and BRCA2 are frequently mutated in cancer and polymorphisms of these genes may modify cancer risk. We used SSCP and DNA sequencing to assess and compare frequencies of R72P (TP53) and 5'UTR203G>A, N372H, and K1132K (BRCA2) polymorphisms in healthy Chinese subjects at varying risk for esophageal squamous cell carcinoma (ESCC) and in ESCC patients. Suggestive overall differences in the distributions of genotypes by risk groups were seen for all genotypes except K1132K. Differences in R72P and N372H were most likely a reflection of lack of Hardy-Weinberg equilibrium (HWE), however, the difference in 203G>A was due to low prevalence of GG in ESCC patients (0.22 versus 0.36 in high risk group (P=0.047), and 0.22 versus 0.40 in low risk group (P=0.010)), consistent with a disease association. These data suggest that the 203G>A polymorphism in BRCA2 may be associated with risk of ESCC.

Adult↗

PubMed2003

Novel level of signalling control in the JAK/STAT pathway revealed by in situ visualisation of protein-protein interaction during Drosophila development.

It is commonly accepted that activation of most signalling pathways is induced by ligand receptor dimerisation. This belief has been challenged for some vertebrate cytokine receptors of the JAK/STAT pathway. Here we study whether DOME, the Drosophila receptor of the JAK/STAT pathway, can dimerise and if the dimerisation is ligand-dependent. To analyse DOME homo-dimerisation, we have applied a beta-gal complementation technique that allows the detection of protein interactions in situ. This technique has been used previously in cell culture but this is the first time that it has been applied to whole embryos. We show that this technique, which we rename betalue-betalau technique, can be used to detect DOME homo-dimerisation in Drosophila developing embryos. Despite DOME being ubiquitously expressed, dimerisation is developmentally regulated. We investigate the state of DOME dimerisation in the presence or absence of ligand and show that DOME dimerisation is not ligand-induced, indicating that ligand independent cytokine receptor dimerisation is a conserved feature across phyla. We have further analysed the functional significance of ligand-independent receptor dimerisation by comparing the effects of ectopic ligand expression in cells in which the receptor is, or is not, dimerised. We show that ligand expression can only activate STAT downstream targets or affect embryo development in cells in which the receptor is dimerised. These results suggest a model in which ligand-independent dimerisation of the JAK/STAT receptor confers cells with competence to activate the pathway prior to ligand reception. Thus, competence to induce the JAK/STAT signalling pathway in Drosophila can be regulated by controlling receptor dimerisation prior to ligand binding. These results reveal a novel level of JAK/STAT signalling regulation that could also apply to vertebrates.

Alleles↗

PubMed2003

[Early intravenous thrombolysis with recombinant tissue plasminogen activator for acute cerebral infarction].

OBJECTIVE: To evaluate the efficacy and safety of recombinant tissue plasminogen activator (rt-PA) and to explore the most suitable dosage of rt-PA in the early treatment of the Chinese patients with acute cerebral infarction (ACI). METHODS: The patients who suited for the standard were divided into three groups. Group A received rt-PA at 0.9 mg/kg, group B received rt-PA at 0.7 mg/kg, and group C did not receive any thrombolytic therapy. In thrombolytic groups, rt-PA at 8 mg was injected intravenously in a bolus at first and then the rest was given over 60 minutes. The maximal dosage was 90 mg. The Chinese stroke scale (CSS) and Barthel Index (BI) were used to evaluate the recovery of neurological functions after rt-PA treatment for 24 hours and 90 days. The hemorrhagic rate and 30 days mortality rate were also analysed. RESULTS: In group A the CSS significant effective rate was 41.18 percent at 24 hours and 76.47 percent at 90 days after thrombolysis. At 90 days BI significant effective rate was 58.82 percent. At 30 days hemorrhagic rate was 8.82 percent and mortality rate was 5.88 percent. In group B, the CSS significant effective rate was 39.39 percent at 24 hours and 69.70 percent at 90 days. At 90 days, BI significant effective rate was 54.55 percent, and at 30 days, hemorrhagic rate was 9.09 percent and mortality rate was 9.09 percent. In group C, the CSS significant effective rate was 21.21 percent, at 24 hours and 30.30 percent at 90 days (P>0.05). At 90 days, BI was 21.21 percent the mortality rate was 9.09 percent. At 30 days the mortality rate was no significant difference within three groups At 90 days, significant effective rate was 73.13 percent vs. 30.30 percent in thrombolytic and control groups (P=0.001 7). The significant disability rate was 13.43 percent vs. 24.24 percent. CONCLUSION: For Chinese individuals, with ACI, rt-PA thrombolysis was effective and safe. The dosage of 0.9 mg/kg for foreign people also fitted for Chinese individuals.

Acute Disease↗

PubMed2003

Evidence for a familial esophageal cancer susceptibility gene on chromosome 13.

Previous segregation analyses of pedigrees from areas of China where esophageal squamous cell carcinoma (ESCC) rates are extraordinarily high suggested a Mendelian mode of transmission. We initiated a search for a major ESCC gene by conducting a genome-wide scan in ESCC tumors. Chromosome 13 showed loss of heterozygosity (LOH) in 95% of microsatellite markers, the highest frequency of LOH on any chromosome. In the current study, we established a high-resolution deletion map using 107 markers on 13q and compared LOH frequency by family history of upper gastrointestinal cancer. Overall allelic loss was significantly higher in those with a positive (versus negative) family history, suggesting the presence of an inherited tumor suppressor gene on 13q in ESCC.

Carcinoma, Squamous Cell↗

PubMed2003

[Development of impact acceleration measurement facility in return-cabin of spacecraft].

OBJECTIVE: To provide the basis for medical evaluation of spacecraft, and to measure the impact acceleration of return-cabin of spacecraft. METHOD: A facility to measure the impact acceleration of "SZ-3" and "SZ-4" during landing was developed and the acquired test data were analyzed. RESULT: The data of impact acceleration of return-cabins of "SZ-3" and "SZ-4" were accurately recorded during landing. Most reliable and scientific data were gotten. CONCLUSION: This facility could validate and evaluate the specifications of relevant systems of spacecraft, and provided the scientific basis for the decision if "SZ-5", the manned spacecraft, could be launched.

Acceleration↗

PubMed2002

Identification of somatic mutations of the RNF6 gene in human esophageal squamous cell carcinoma.

We mapped a tumor suppressor gene locus to an 800-kb interval on human chromosome 13q12.11 for esophageal squamous cell carcinoma (ESCC). Two genes, ML-1 and RNF6, are located within this 800-kb interval. We analyzed both genes for the presence of mutations in 24 ESCC primary tumors and 16 tumor cell lines by directly sequencing the PCR products that were amplified from each exon. No mutation was detected in ML-1. In contrast, three somatic mutations in the RNF6 gene were detected in the ESCC primary tumors, and one mutation was also found in a tumor cell line. Identification of multiple somatic mutations in RNF6 suggests that RNF6 is a potential tumor suppressor gene involved in the pathogenesis of ESCC.

Carcinoma, Squamous Cell↗

PubMed2002

2D differential in-gel electrophoresis for the identification of esophageal scans cell cancer-specific protein markers.

The reproducibility of conventional two-dimensional (2D) gel electrophoresis can be improved using differential in-gel electrophoresis (DIGE), a new emerging technology for proteomic analysis. In DIGE, two pools of proteins are labeled with 1-(5-carboxypentyl)-1'-propylindocarbocyanine halide (Cy3) N-hydroxy-succinimidyl ester and 1-(5-carboxypentyl)-1'-methylindodi-carbocyanine halide (Cy5) N-hydroxysuccinimidyl ester fluorescent dyes, respectively. The labeled proteins are mixed and separated in the same 2D gel. 2D DIGE was applied to quantify the differences in protein expression between laser capture microdissection-procured esophageal carcinoma cells and normal epithelial cells and to define cancer-specific and normal-specific protein markers. Analysis of the 2D images from protein lysates of approximately 250,000 cancer cells and normal cells identified 1038 protein spots in cancer cell lysates and 1088 protein spots in normal cell lysates. Of the detected proteins, 58 spots were up-regulated by >3-fold and 107 were down-regulated by >3-fold in cancer cells. In addition to previously identified down-regulated protein annexin I, tumor rejection antigen (gp96) was found up-regulated in esophageal squamous cell cancer. Global quantification of protein expression between laser capture-microdissected patient-matched cancer cells and normal cells using 2D DIGE in combination with mass spectrometry is a powerful tool for the molecular characterization of cancer progression and identification of cancer-specific protein markers.

Biomarkers, Tumor↗

PubMed2002

Infrequent mutation in the BRCA2 gene in esophageal squamous cell carcinoma.

PURPOSE: Previous studies have shown a high rate of allelic loss in esophageal squamous cell carcinoma (ESCC) in the vicinity of the BRCA2 gene. We aimed to assess whether the tumor suppressor gene BRCA2 was the inactivation target for allelic loss observed on chromosome 13q in ESCC. EXPERIMENTAL DESIGN: We examined the entire coding sequence of the BRCA2 gene for mutations using single-strand conformation polymorphism analysis and DNA sequencing in 56 ESCC patients from Shanxi, China. RESULTS: Eight mutations were identified in 5 patients (9%), including 3 with germ-line mutations and 2 with only somatic mutations. However, all but 1 of the mutations were missense or silent changes and of unknown significance. Evidence for potential biallelic inactivation was seen in only 4 (7%) cases. CONCLUSIONS: BRCA2 mutations occur in ESCC but are infrequent and of unknown consequence. The putative target tumor suppressor gene corresponding to the high rate of chromosome 13q allelic loss remains unknown.

Alleles↗