Biomedical subjects

J K Field

Publications and source records attributed to J K Field.

At least 55 records · Page 3Linked to original sources

PubMed2000

The evolution of loss of heterozygosity on chromosome 17 during the progression to barrett's adenocarcinoma involves a unique combination of target sites in individual specimens.

We have previously identified thirteen common minimally deleted regions (MRs) on chromosome 17 in twelve Barrett's esophageal adenocarcinoma (BOA) specimens using 41 precisely mapped microsatellite markers (Dunn et al., Oncogene, 17: 987-993, 1999). The aim of the present study has been to identify the earliest sites of loss on this chromosome that arise and persist during the progression to BOA. This has been undertaken by the analysis of multiple carefully microdissected tissue samples from each of five esophagectomy specimens, several of which contained identifiable premalignant tissue. Our data demonstrate a stepwise accumulation of loss in each analyzed specimen, consistent with a single clonal pathway in four specimens and several coexisting pathways in one specimen. Several clonal anomalies (loss preceding heterozygosity and variable intrasample degrees of loss at different markers) were also observed. Within extensively deleted regions of the tumor (seen in three specimens), small deletions were detected in premalignant tissue, predominantly at the site of our identified MRs, and these losses were seen to expand and merge during the progression to BOA. Clonal losses at MRs were first detected in tissue showing early changes histologically, including Barrett's intestinal metaplasia and intermediate-grade dysplasia. Our results provide further support for many of the MRs we have previously identified, thereby adding to evidence for the existence of multiple novel cancer-associated genes on chromosome 17 involved in the development of BOA.

Adenocarcinoma↗

PubMed2000

K-ras point mutation detection in lung cancer: comparison of two approaches to somatic mutation detection using ARMS allele-specific amplification.

BACKGROUND: The use of sensitive molecular techniques to detect rare cells in a population is of increasing interest to the molecular pathologist, but detection limits often are poorly defined in any given molecular assay. We combined the approaches of real-time quantitative PCR with ARMS(TM) allele-specific amplification in a novel assay for detecting mutant K-ras sequences in clinical samples. METHODS: ARMS reactions were used to detect seven commonly occurring mutations in the K-ras oncogene. These mutations produce amino acid changes in codon 12 (Gly to Ala, Arg, Asp, Cys, Ser, or Val) and codon 13 (Gly to Asp). A control reaction was used to measure the total amount of amplifiable K-ras sequence in a sample so that the ratio of mutant to wild-type sequence could be measured. Quantitative data were confirmed for a selection of samples by an independent cloning and sequencing method. The assay was used to analyze 82 lung tumor DNA samples. RESULTS: The assay detected K-ras mutations in 44% of adenocarcinomas, which is equivalent to frequencies reported in the literature using ultrasensitive techniques. Forty-six percent of squamous carcinomas were also positive. The ratio of mutant sequence in the tumor DNA samples was 0.04-100%. CONCLUSIONS: The assay is homogeneous, with addition of tumor DNA sample being the only step before results are generated. The quantitative nature of the assay can potentially be used to define the analytical sensitivity necessary for any specified diagnostic application of K-ras (or other) point mutation detection.

Alleles↗

PubMed1999

Envoplakin, a possible candidate gene for focal NEPPK/esophageal cancer (TOC): the integration of genetic and physical maps of the TOC region on 17q25.

Focal nonepidermolytic palmoplantar keratoderma (NEPPK), or tylosis, is an autosomal, dominantly inherited disorder of the skin that manifests as focal thickening of the palmar and plantar surfaces. In three families studied, the skin disorder cosegregates with esophageal cancer and oral lesions. New haplotype analysis, presented here, places the tylosis esophageal cancer (TOC) locus between D17S1839 and D17S785. Envoplakin (EVPL) is a protein component of desmosomes and the cornified envelope that is expressed in epidermal and esophageal keratinocytes and has been localized to the TOC region. Mutation analysis of EVPL in the three affected families failed to show tylosis-specific mutations, and haplotype analysis of three intragenic sequence polymorphisms of the EVPL gene placed it proximal to D17S1839. Confirmation of the exclusion of EVPL as the TOC gene by location was obtained by integration of the genetic and physical mapping data using radiation hybrid, YAC, BAC, and PAC clones. This new physical map will allow further identification of candidate genes underlying NEPPK associated with esophageal cancer, which may also be implicated in the development of sporadic squamous cell esophageal carcinoma and Barrett's adenocarcinoma.

Base Sequence↗

PubMed1999

Genetic alterations in bronchial lavage as a potential marker for individuals with a high risk of developing lung cancer.

Using 12 microsatellite markers, we have studied DNAs from the bronchial lavage of 90 individuals who were referred to an early-lung-cancer clinic in the Northwest of England with suspected lung cancer. Genetic alterations were detected in 15 (35%) of 43 patients with lung cancer but also in 11 (23%) of 47 patients with no cytological or radiological evidence of bronchial neoplasia. No significant differences were found between the referring symptoms in any of the second group of individuals with and without genetic alterations. No correlation was found between smoking exposure and loss of heterozygosity (LOH)/microsatellite alterations (MAs) in the microsatellite markers. On comparing LOH with MAs based on cytology review, we found that the prevalent type of alteration in specimens with cytological evidence of malignancy was LOH; in contrast, the individuals with no cytological evidence of malignancy showed a preponderance of MAs (P = 0.01). Our results indicate that a substantial proportion of cells in the bronchial lavage from suspected lung cancer patients carry identifiable genetic alterations. However, the presence of genetic alterations in the bronchial lavage of individuals with no clinical evidence of lung cancer raises the question whether instability is a phenomenon solely associated with cancer or represents a feature of nonneoplastic diseases. Our results suggest that microsatellite PCR-based assays can be developed as tools for the earlier identification of genetic changes in cells exfoliating in the bronchus.

Adenocarcinoma↗

PubMed1999

Multiple target sites of allelic imbalance on chromosome 17 in Barrett's oesophageal cancer.

Twelve Barrett's adenocarcinomas have been analysed for the occurrence of allelic imbalance (LOH) on chromosome 17 using 41 microsatellite markers. This study provides evidence for 13 minimal regions of LOH, six on 17p and seven on 17q. Four of these centre in the vicinity of the known tumour suppressor genes (TSGs) TP53 (17p13.1), NFI (17q11.2), BRCA1 (17q21.1), and a putative TSG (17p13.3). The tumours all displayed relatively small regions of LOH (1-10 cM), and in several tumours extensive regions of LOH were detected. One tumour displayed only two very small regions of LOH; 17p11.2 and 17p13.1. The frequency of allelic imbalance has been calculated based on the LOH encompassing only one minimal region, and based on all the LOH observations. By both evaluations the highest LOH frequencies were found for regions II (p53), III (17p13.1 centromeric to p53), IV (17p12), V (17p11.2) and VII (NF1, 17q11.2). Our data supports the existence of multiple TSGs on chromosome 17 and challenges the view that p53 is the sole target of LOH on 17p in Barrett's adenocarcinoma.

Adenocarcinoma↗

PubMed1999

LOH at the sites of the DCC, APC, and TP53 tumor suppressor genes occurs in Barrett's metaplasia and dysplasia adjacent to adenocarcinoma of the esophagus.

Barrett's esophagus carries a 30- to 100-fold increased risk of adenocarcinoma, which is thought to develop via a metaplasia-dysplasia-carcinoma progression. A common genetic abnormality detected in Barrett's adenocarcinoma is loss of heterozygosity (LOH) at the sites of known or putative tumor suppressor genes, of which there are at least 9 associated with esophageal adenocarcinoma. The aim of this study was to identify at which histological stage of carcinogenesis LOH at these sites occur. Microdissection of multiple paraffin-embedded tissue blocks from 17 esophagogastrectomy specimens of adenocarcinoma arising in Barrett's esophagus yielded areas of metaplasia, low-, intermediate- and high-grade dysplasia, and carcinoma. LOH analysis of microdissected tissues was performed using a double polymerase chain reaction technique with 11 microsatellite primers shown previously to have LOH in at least 30% of esophageal adenocarcinomas. Identical LOH was detected in premalignant and malignant tissues in 4 of 17 patients, and was located at 5q21-q22 (D5S346 primer), 17p11.1-p12 (TCF2 primer), 17p13.1 (TP53 primer), 18q21.1 (detected in colon cancer tumor suppressor gene [DCC] primer), and 18q23-qter (D18S70 primer). These results suggest that LOH at the sites of the DCC, adenomatous polyposis coli (APC), and TP53 tumor suppressor genes occur before the development of adenocarcinoma in Barrett's esophagus, and so merit further study as potential biomarkers of neoplastic progression in patients with Barrett's esophagus undergoing endoscopic and histological surveillance.

Adenocarcinoma↗

PubMed1999

The tylosis esophageal cancer (TOC) locus: more than just a familial cancer gene.

Tylosis (focal non-epidermolytic palmoplantar keratoderma; NEPPK) is associated with esophageal cancer in three families, two of which contain six or seven generations. The causative locus, the tylosis esophageal cancer (TOC) gene, has been localized to a small region on chromosome 17q25. Recent loss of heterozygosity (LOH) studies have indicated a role for the TOC gene in sporadic squamous cell esophageal cancer and Barrett's adenocarcinoma. We have now integrated genetic and physical mapping data from the TOC region, based on microsatellite markers and radiation hybrid, yeast (YAC), bacterial (BAC) and P1 artificial chromosomal (PAC) clones, and formed a partial minimal contig of one non-chimeric YAC (330 kb) and one PAC. Twenty-three candidate genes, including envoplakin (EVPL), were mapped against this contig, but only one was shown to be located within the minimal region. This physical map will allow further characterization of the region and identification of a gene implicated in both familial and sporadic squamous cell esophageal carcinoma and Barrett's adenocarcinoma.

Barrett Esophagus↗

PubMed1999

Fractional allele loss indicates distinct genetic populations in the development of squamous cell carcinoma of the head and neck (SCCHN).

Loss of heterozygosity (LOH) had been widely used to assess genetic instability in tumours and a high LOH on chromosome arms 3p, 9p and 17p has been considered to be a common event in squamous cell carcinoma of the head and neck (SCCHN). We have investigated LOH in 52 SCCHN using a range of microsatellite markers. LOH was observed in 69% of individuals on 17p using seven markers, in 64% of individuals on 3p using 17 markers and in 61% of individuals on 9p using 11 markers. Fractional allele loss (FAL) has been calculated for each tumour (FAL is the number of chromosomal arms showing LOH divided by the number of informative chromosomal arms) and a median FAL value of 0.25 was obtained in the 52 SCCHN studied. The LOH data were examined on the basis of FAL scores: low FAL (LFAL), 0.00-0.19; medium FAL (MFAL), 0.20-0.32; high FAL (HFAL), 0.33-0.88. HFAL tumours demonstrated a significantly higher LOH on chromosome arms 3p, 9p and 17p, with 94% LOH on 3p, 94% on 9p and 100% on 17p compared with LFAL tumours. Six of the 16 patients in the LFAL group were found to have no LOH on 3p, 9p or 17p and of these four had LOH at other sites, on chromosomes 2p25-p24, 5q21-22, 7pter-p22, 8q13-q22.1, 11q23.3, 13q32, 17q, 18p11.21, 18q21.31 and 19q12-q13.1. These results indicate that LFAL patients form a subset of SCCHN tumours with distinct molecular initiating events which may represent a discrete genetic population.

Alleles↗

PubMed1999

Telomerase activity in non-small cell lung carcinomas correlates with smoking status.

Human telomerase is a ribonucleoprotein DNA polymerase which maintains the telomeric region of human chromosomes and has been detected in all types of human cancer tested. We used the telomeric repeat amplification protocol (TRAP) assay to examine 71 non-small cell lung carcinomas (NSCLC) and their adjacent normal tissue. Telomerase activity was detected in 61 (86%) of the 71 NSCLC examined but not in any of the matched normal lung tissues. A significant correlation was found between the presence of telomerase activity and current smoking status at the time of diagnosis (p=0. 0076). In addition, a trend was found between telomerase activity and smoking exposure (p=0.06). Our findings demonstrate that telomerase activity is a common phenomenon in NSCLC cases but not in the normal lung. However, certain cases in former smokers may follow a telomerase independent pathway.

Adenocarcinoma↗

PubMed1999

Heterogeneous nuclear ribonucleoprotein A2/B1 up-regulation in bronchial lavage specimens: a clinical marker of early lung cancer detection.

This study examines the use of a new epithelial marker in the detection of early lung cancer in bronchial lavage samples. The monoclonal antibody 703D4 recognizes the heterogeneous nuclear ribonucleoprotein (hnRNP) A2/B1, and its overexpression/up-regulation was assessed and compared with routine diagnostic cytology. One hundred and three individuals were recruited into a prospective study. These individuals were referred to a chest physician with a request to examine for possible lung cancer, and a full clinical work-up was undertaken, including bronchoscopy and radiological investigations. In this study, we analyzed hnRNP expression in individuals with metaplastic bronchial epithelial cells or tumor cells in the bronchial lavage specimens, in a blinded study. The results from 103 bronchial lavage specimens indicate that hnRNP overexpression was more accurate in detecting evidence of a neoplasia than routine cytological examination. Twenty-two of 23 specimens in which malignant cells were identified cytologically demonstrated overexpression of hnRNP A2/B1. However, in the 80 specimens that were reported as cytologically negative, 41 of 80 demonstrated hnRNP overexpression, and 29 of these individuals were shown to have a lung neoplasm based on radiological findings and/or the biopsy taken at the bronchoscopy. An additional 4 of these 41 patients were shown to have a lung neoplasm within 8 months of the initial bronchoscopy. In conclusion, detection of hnRNPA2/B1 in bronchial lavage specimens that contain metaplastic bronchial epithelial cells or cancer cells predicts the presence of a neoplasm with a sensitivity of 96%, 82%, specificity.

Adult↗

PubMed1998

Loss of heterozygosity in sporadic oesophageal tumors in the tylosis oesophageal cancer (TOC) gene region of chromosome 17q.

From the genotyping of UK and US tylotic families with a high risk of oesophageal cancer we have previously localized the tylosis-associated cancer susceptibility gene (TOC gene, tylosis oesophageal cancer gene) to a 1 cM region on the long arm of chromosome 17 (Kelsell et al., 1996). In the present study we investigated loss of heterozygosity (LOH) patterns of 35 sporadic squamous cell carcinomas of the oesophagus using six polymorphic microsatellite markers encompassing this locus. Twenty-four of the 35 cases (69%) revealed LOH at one or more loci. Deletion was most frequently observed with the marker D17S801 (64% LOH, informative cases), which shows significant linkage to the TOC locus. The LOH analysis in sporadic oesophageal cancer we report here is thus consistent with the hypothesis that the tylosis oesophageal cancer susceptibility gene is also involved in the pathogenesis of a proportion of sporadic squamous cell carcinomas of the oesophagus.

Carcinoma, Squamous Cell↗

PubMed1998

Synchronous oral carcinomas: independent or common clonal origin?

Second primary tumors in patients with head and neck cancer have a detrimental impact on long-term survival; at least 15% of patients develop additional tumors. Originally, it was hypothesized that multiple tumors developed independently after widespread epithelial exposure to carcinogens (the field cancerization theory), but recent molecular studies now support the alternative theory of a common clonal origin. If multiple tumors originate from the same clone, early genetic alterations in these cells should be common to all of the tumors. We have compared the pattern of allelic imbalance in paired tumors from five male patients with two synchronous oral squamous cell carcinomas and in peripheral dysplasia using microsatellite markers on chromosomes 3p, 9p, and 17p. Discordance, usually through loss of alternate alleles at the same microsatellite loci, was detected in two patients. The remaining three patients had identical alterations in their tumors. The changes identified occurred early in tumorigenesis, because, with only one exception, these were also present in the associated dysplasia. Thus, we provide evidence that synchronous oral squamous cell carcinomas are of independent origin in some patients but may be of common clonal origin in others.

Alleles↗

PubMed1998

Alterations of the p16-pRb pathway and the chromosome locus 9p21-22 in non-small-cell lung carcinomas: relationship with p53 and MDM2 protein expression.

The p16-pRb and p53-MDM2 pathways represent vital cell cycle checkpoints. Recent studies provide evidence that these pathways are directly linked via MDM2-pRb interaction and p53 suppression of the RB1 gene. In the present study we investigated the alterations of this G1 phase protein network using immunohistochemical and molecular methods in a series of 68 non-small-cell lung carcinomas (NSCLCs) and correlated the findings with clinicopathological features and prognosis of the patients. Aberrant expression (Ab) of p16 and pRb was observed in 33 (49%) and 27 (40%) of the carcinomas, respectively. Analysis of the region that encodes for p16 by deletion mapping, a polymerase chain reaction (PCR)-based methylation assay and PCR single-strand conformation polymorphism (SSCP) analysis revealed that deletions and transcriptional silencing by methylation might represent the main mechanisms of CDKN2/p16ink4a inactivation in NSCLCs. The results of deletion mapping also suggest that other tumor suppressor genes may reside at the 9p21-22 region, which encodes for CDKN2/MTS1/p16ink4a, p14ARF, and MTS2/p15ink4b. In addition, microsatellite instability was observed with a frequency of 16% in the 9p21-22 chromosome area. Overexpression (P) of p53 and MDM2 proteins was found in 39 (58%) and 47 (70%) of the cases, respectively. A highly significant association was observed between p53 overexpression and p53 mutations (P = 0.006). Statistical analysis of the expression patterns of the biologically relevant molecules (p16/pRb, p53/MDM2, MDM2/pRb, and p53/pRb) showed coincident overexpression of p53 and MDM2 (P = 0.04) and that abnormal pRb was correlated with elevated levels of MDM2 (P = 0.013) and p53 (P = 0.01), respectively. We suggest that deregulated expression of these molecules may act synergistically. An important finding of the study was that multiple impairments (three and four molecules affected) of the p16/pRb/p53/MDM2 network occurred in a large proportion (43%) of the carcinomas. This finding in addition to the absence of correlation with clinical stage of the tumors suggests that multiple hits of this network may be a relatively early event in the development of a subset of NSCLCs. The relationship between the factors examined in the present study, clinicopathological features, and survival of the patients did not reveal any significant correlations with the exception of smoking, which was associated with microsatellite alterations (loss of heterozygosity and microsatellite instability) at the 9p21-22 locus (P = 0.04) and the immunophenotypes p53(P)/MDM2(P) (P = 0.04) and p16(Ab)/pRb(Ab)/p53(P)/MDM2(P) (P = 0.03), respectively. We suggest that in a subset of NSCLCs, simultaneous deregulation of the members of this network may represent one way of initiating the oncogenic procedure whereas in other NSCLC subgroups alternative pathways may play this role.

Adult↗

PubMed1998

Allelotype analysis of oesophageal adenocarcinoma: loss of heterozygosity occurs at multiple sites.

Deletions of tumour-suppressor genes can be detected by loss of heterozygosity (LOH) studies, which were performed on 23 cases of adenocarcinoma of the oesophagus, using 120 microsatellite primers covering all non-acrocentric autosomal chromosome arms. The chromosomal arms most frequently demonstrating LOH were 3p (64% of tumours), 5q (45%), 9p (52%), 11p (61%), 13q (50%), 17p (96%), 17q (55%) and 18q (70%). LOH on 3p, 9p, 13q, 17p and 18q occurred mainly within the loci of the VHL, CDKN2, Rb, TP53 and DCC tumour-suppressor genes respectively. LOH on 5q occurred at the sites of the MSH3 mismatch repair gene and the APC tumour-suppressor gene. 11p15.5 and 17q25-qter represented areas of greatest LOH on chromosomes 11p and 17q, and are putative sites of novel tumour-suppressor genes. LOH on 9p was significantly associated with LOH on 5q, and tumours demonstrating LOH at both the CDKN2 (9p21) and MSH3 (5q11-q12) genes had a significantly higher fractional allele loss than those retaining heterozygosity at these sites. Six of nine carcinomas displaying microsatellite alterations also demonstrated LOH at CDKN2, which may be associated with widespread genomic instability. Overall, there are nine sites of LOH associated with oesophageal adenocarcinoma.

Adenocarcinoma↗

PubMed1998

The Knights of the Round Table hypothesis of tumour suppressor gene function--noble sacrifice or sexual dalliance: genes, including p53, BRCA1/2 and RB have evolved by horizontal and vertical transmission of mating factor genes and are involved in gametogenesis, implantation, development and tumourigenesis.

The genes involved in negative cell cycle regulation and familial tumour susceptibility including APC, BRCA, p53, RB, WT1 are unique and have no homologies with other genes. Our hypothesis suggests they originated from mating factor genes, which halted cell division in response to stress to generate genetic diversity by sexual mechanisms. Some have evolved principally by vertical transmission (mismatch repair), others by horizontal transmission via mobile elements, predominantly in oocytes. We demonstrate amplification in human extra-embryonic tissues in fetus and mother in implantation; in the developing fetus, differing tissue-specific patterns are seen, especially between testis and ovary. We suggest that the fetus is susceptible to maternal transmission of infections including CMV, malaria, trypanosomes, whose sequences occur within these genes. In head and neck cancers, we demonstrate specific patterns of loss or instability involving up to seven different TSG. We suggest mechanisms of tumourigenesis involve transposable elements and episome formation, leading to loss of negative cell cycle regulation and exit from G0.

Animals↗

PubMed1997

p53 mutations in squamous cell carcinoma of the head and neck predominate in a subgroup of former and present smokers with a low frequency of genetic instability.

We examined the p53 mutational profile of 65 squamous cell carcinomas of the head and neck (SCCHNs) from patients living in northwest England. Twenty-three p53 mutations were detected in 20 samples (31%). GC-->AT transitions were the predominant type of mutation. The p53 mutational profile of SCCHN tumors was similar to that of non-small cell lung tumors from patients within the same geographical area, supporting the idea of a common model for carcinogenesis in the upper respiratory tract. Statistical analysis showed that the incidence of p53 mutations among present and former smokers was significantly higher than that in nonsmokers (P < 0.02). In addition, p53 mutations were found to predominate in a group of SCCHN patients with low genetic damage, as indicated by the fractional allelic loss value. The above findings suggest an early initiating role for p53 and imply that at least two separate carcinogenic pathways may be involved in the development of SCCHN.

Alcohol Drinking↗

PubMed1997

p53 mutations in relation to human papillomavirus type 16 infection in squamous cell carcinomas of the head and neck.

The relationship between human papillomavirus (HPV) type 16 infection and p53 gene mutations was investigated in squamous cell carcinomas of the head and neck (SCCHN). HPV was detected by general primer-mediated and type-specific PCR. Alterations in the p53 gene were investigated using single-strand conformation polymorphism and sequence analysis in 27 SCCHN, of which 12 were HPV 16-positive and 15 were HPV-negative. Mutations were detected in 2/12 (16.7%) HPV 16-positive and 7/15 (46.7%) HPV-negative tumours; this difference was not statistically significant. The predominant mutations were deletions and C --> T transitions; G --> T transversions were found in only 2 tumours. Our results indicate that the presence of HPV 16 and p53 mutations is not mutually exclusive and detection of a p53 mutation does not exclude a potential role for HPV 16 in the pathogenesis of a subset of SCCHN.

Carcinoma, Squamous Cell↗

PubMed1997

Oral tylosis: a re-appraisal.

The oral lesions in patients with tylosis (palmoplantar keratoderma) associated with oesophageal cancer, are evaluated, based on their clinical presentation, histological features and long term follow-up. The terminology of these lesions is discussed, together with a proposed reclassification of some forms of palmoplantar keratoderma.

Adolescent↗