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Biomedical subjects

J M Abraham

Publications and source records attributed to J M Abraham.

At least 37 records · Page 2Linked to original sources
PubMed1997

A transforming growth factor beta 1 receptor type II mutation in ulcerative colitis-associated neoplasms.

BACKGROUND & AIMS: Numerous gastrointestinal tumors, notably sporadic and ulcerative colitis (UC)-associated colorectal carcinomas and dysplasias, gastric cancers, and esophageal carcinomas, manifest microsatellite instability. Recently, a transforming growth factor beta 1 type II receptor (TGF-beta 1RII) mutation in a coding microsatellite was described in colorectal carcinomas showing instability. One hundred thirty-eight human neoplasms (61 UC-associated, 35 gastric, 26 esophageal, and 16 sporadic colorectal) were evaluated for this TGF-beta 1RII mutation. METHODS: Whether instability was present at other chromosomal loci in these lesions was determined. In lesions manifesting or lacking instability, the TGF-beta 1RII coding region polydeoxyadenine (poly A) microsatellite tract was polymerase chain reaction amplified with 32P-labeled deoxycytidine triphosphate. Polymerase chain reaction products were electrophoresed on denaturing gels and exposed to radiographic film. RESULTS: Three of 18 UC specimens with instability at other chromosomal loci (17%) showed TGF-beta 1RII poly A tract mutation, including 2 cancers and 1 dysplasia; moreover, 2% of UC specimens without instability (1 of 43) (1 cancer), 81% of unstable sporadic colorectal cancers (13 of 16), and none of the 61 stable or unstable gastric or esophageal cancers contained TGF-beta 1RII mutations. CONCLUSIONS: Mutational inactivation of the poly A microsatellite tract within TGF-beta 1RII occurs early and in a subset of unstable UC neoplasms and commonly in sporadic colorectal cancers but may be rare in unstable gastric and esophageal tumors.

Activin Receptors, Type I↗
PubMed1996

Infrequent DPC4 gene mutation in esophageal cancer, gastric cancer and ulcerative colitis-associated neoplasms.

Homozygously Deleted in Pancreatic Cancer 4 (DPC4), a recently identified candidate tumor suppressor gene, was previously shown to be altered in human pancreatic cancers. We examined DPC4 mutation in 30 examples of three other types of gastrointestinal malignancy: 10 esophageal cancers, 10 gastric cancers and 10 colorectal cancers occurring in the preneoplastic condition, ulcerative colitis. The entire coding region of DPC4 (including all 11 exons) was analysed by either direct sequencing of PCR product or the in vitro synthesized protein assay. No coding region mutations of DPC4 were found in any of the samples examined. Our results suggest that inactivation of DPC4 may not be important in the majority of these types of gastrointestinal cancer.

Colitis, Ulcerative↗
PubMed1996

Products of enteropathogenic E. coli inhibit lymphokine production by gastrointestinal lymphocytes.

Previously we have shown that lysates of enteropathogenic Escherichia coli (EPEC) inhibit lymphokine production by mitogen-activated peripheral blood mononuclear cells (PBMCs). The aim of the present study was to determine whether products of EPEC alter lymphokine expression by gastrointestinal mucosal lymphocytes. Lysates from EPEC clones inhibited mitogen-stimulated interleukin-2 (IL-2), IL-4, IL-5, and interferon-gamma (IFN-gamma) but not IL-8 mRNA expression by lamina propria mononuclear cells isolated from surgically resected colon specimens. Inhibitory lysates did not significantly change CD25 expression on either CD4, CD8, or CD45R0 lymphocytes by flow cytometry. Bacterial supernatants of EPEC inhibited IL-2 and IL-5 protein secretion by mitogen-stimulated PBMCs. EPEC lysates inhibited IL-2 mRNA expression induced by lysates of nonpathogenic E. coli. In conclusion, EPEC contains a novel gene(s) that encodes factors that selectively inhibit IL-2, IL-4, IL-5, and IFN-gamma expression by mucosal mononuclear cells without affecting CD25 or IL-8 expression. Thus enteric bacteria can produce factors that may regulate the function of the gastrointestinal mucosal immune system.

Antigens, CD↗
PubMed1996

Rodent cell transformation and immediate early gene expression following 60-Hz magnetic field exposure.

Some epidemiological studies suggest that exposure to power frequency magnetic fields (MFs) may be associated with an elevated risk of human cancer, but the experimental database remains limited and controversial. We investigated the hypothesis that 60-Hz MF action at the cellular level produces changes in gene expression that can result in neoplastic transformation. Twenty-four hour 200 microT continuous MF exposure produced negative results in two standard transformation systems (Syrian hamster embryo cells and C3H/10T1/2 murine fibroblasts) with or without postexposure to a chemical promoter. This prompted a reexamination of previously reported MF-induced changes in gene expression in human HL60 cells. Extensive testing using both coded and uncoded analyses was negative for an MF effect. Using the same exposure conditions as in the transformation studies, no MF-induced changes in ornithine decarboxylase expression were observed in C3H/10T1/2 cells, casting doubt on a promotional role of MF for the tested cells and experimental conditions.

Animals↗
PubMed1996

Esophagin cDNA cloning and characterization: a tissue-specific member of the small proline-rich protein family that is not expressed in esophageal tumors.

Cancer may be understood as the net effect of differences in gene expression between normal and transformed cells. In a novel direct approach applying this principle, complete genes expressed at altered mRNA levels in malignant versus normal esophageal epithelium were identified and isolated from cDNA libraries. One clone was expressed in normal esophageal mucosae but absent in esophageal carcinomas. By in situ hybridization, Northern blotting, and immunohistochemistry, expression of this gene was restricted to normal esophageal mucosa; it is designated esophagin. Esophagin expression was greatest in the superficial, most mature layers of esophageal squamous mucosa and was restricted to this organ, being undetectable in other squamous epithelia. A genomic clone localized esophagin to chromosomal region 1q21-q22. The expressed protein contains multiple direct repeats of an 8-amino acid motif rich in proline, with significant homology to the cornifin, pig 20K, monkey MT5, and human small proline-rich genes spri and spril. Esophagin constitutes the newest and largest member of this small proline-rich gene family and is associated with differentiation and the benign phenotype of the human esophageal epithelial cell.

Amino Acid Sequence↗
PubMed1996

Alterations of transforming growth factor-beta 1 receptor type II occur in ulcerative colitis-associated carcinomas, sporadic colorectal neoplasms, and esophageal carcinomas, but not in gastric neoplasms.

BACKGROUND & AIMS: Gastric cancers, sporadic colorectal cancers, and ulcerative colitis (UC)-associated colorectal carcinomas and dysplasias manifest microsatellite instability (MI); however, esophageal carcinomas rarely exhibit MI. Recently, a transforming growth factor-beta 1 type II receptor (TGF-beta 1RII) mutation in a coding microsatellite was described in primary colorectal carcinomas demonstrating MI. No previous studies of TGF-beta 1RII have addressed mechanisms of inactivation other than MI in human tumors; furthermore, MI-negative tumors have not been examined for TGF-beta 1RII mutation. We evaluated 138 primary human neoplasms for mutation in the poly-A microsatellite tract of TGF-beta 1RII. Additionally, a group of esophageal tumors was evaluated for the expression of TGF-beta 1RII messenger RNA (mRNA). METHODS: First, we determined whether MI was present at other chromosomal loci in these lesions. The poly-deoxyadenine (poly-A) microsatellite tract within the TGF-beta 1RII coding region was then PCR-amplified. In a group of MI-negative esophageal tumors, RT-PCR was performed to determine the expression of TGF-beta 1RII mRNA. RESULTS: Among 17 MI+ UC specimens, 3 (18%) demonstrated TGF-beta 1RII poly-A tract mutation (2 cancers and 1 dysplasia), while 2 (4%) of 44 MI-negative UC specimens (1 dysplasia and 1 tumor), and 13 (81%) of 16 MI+ sporadic colorectal cancers, contained TGF-beta 1RII poly-A mutation. No gastric or esophageal tumors contained TGF-beta 1RII mutation. Among 21 MI-negative esophageal carcinomas. 6 cases (28.5%) had TGF-beta 1RII transcripts that were low or undetectable by RT-PCR. CONCLUSIONS: Mutation within the poly-A microsatellite tract of TGF-beta 1RII occurs early in a subset of UC-neoplasms and commonly in sporadic colorectal cancers, but may be rare in MI+ gastric tumors. Diminished expression of TGF-beta 1RII mRNA in esophageal tumors suggests that mechanisms of inactivation in this gene other than MI play a role in esophageal carcinogenesis.

Colitis, Ulcerative↗
PubMed1995

Genomic DNA and messenger RNA expression alterations of the CDKN2B and CDKN2 genes in esophageal squamous carcinoma cell lines.

The genes CDKN2B (MTS2) and CDKN2 (MTS1) encoding the proteins p15 and p16 are both located on chromosomal band 9p21, a locus at which frequent homozygous and heterozygous deletions occur in many primary human tumors, including esophageal carcinoma. CDKN2 and CDKN2B belong to a family of cyclin-dependent kinase 4 inhibitors (INK41) and control cell proliferation during the G1 phase of the cell cycle. Their inactivation may contribute to uncontrolled growth in human cancers. To investigate whether CDKN2B and CDKN2 are involved in esophageal tumorigenesis, we studied homozygous deletion, intragenic mutation, and messenger RNA (mRNA) expression of CDKN2 and CDKN2B in nine esophageal squamous cancer cell lines. Polymerase chain reaction (PCR) amplification revealed that five of the nine cell lines (55%) manifested homozygous deletions of CDKN2B, CDKN2, and/or flanking loci on chromosomal band 9p21. Reverse transcriptase-PCR (RT-PCR) was used to examine CDKN2 and CDKN2B mRNA in the nine cell lines. Lack of CDKN2 and CDKN2B mRNA correlated perfectly with homozygous deletion involving these genes. No subtle intragenic mutations of CDKN2B or CDKN2 were detected by DNA sequencing of their entire coding sequences in any cell lines lacking homozygous deletion. Two of the cell lines manifested homozygous deletions excluding CDKN2; one of these two deletions also excluded CDKN2B. These results suggest that inactivation of CDKN2B and CDKN2 may contribute to the malignant phenotype in esophageal cells and that homozygous deletion may be the predominant mechanism for inactivation of CDKN2B and CDKN2. Alternatively, a gene or genes adjacent to CDKN2B/CDKN2 may constitute the target(s) of deletion at this locus.

Alleles↗
PubMed1995

Intragenic mutations of CDKN2B and CDKN2A in primary human esophageal cancers.

The CDKN2A and CDKN2B genes, encoding p16 and p15 respectively, are located on chromosome 9p21, a locus at which frequent homozygous and heterozygous deletions occur in many primary human tumors, including esophageal carcinoma. CDKN2A and CDKN2B inhibit cyclin dependent kinase 4 (CDK4) and CDK6 and control cellular proliferation by preventing entry into the S phase of the cell cycle. Their inactivation may contribute to uncontrolled growth in human cancer. We previously described CDKN2A exon 2 mutations in a pilot study of 43 esophageal cancers. In order to determine whether CDKN2A and CDKN2B are frequent targets of 9p21 deletion in esophageal carcinogenesis, we have now analyzed 60 primary esophageal cancers for mutations in both exons 1 and 2 of CDKN2A and CDKN2B by direct sequencing of PCR amplified genomic DNAs. In conjunction with our previously published data, we have identified a total of eight nucleic acid substitutions among 60 esophageal carcinomas; here, we describe one new CDKN2B nonsense mutation and one new silent CDKN2B mutation that occurred somatically. Taken together, these results suggest that intragenic mutations in CDKN2A and CDKN2B occur in esophageal cancer, but that they are infrequent events. In view of the known high frequency of loss of heterozygosity at the chromosome 9p21 locus in esophageal cancers, the current data suggest that intragenic mutation is not the predominant mode of inactivation of CDKN2A and CDKN2B or that other genes are targets of deletion at this locus in these cancers.

Base Sequence↗
PubMed1995

Products of enteropathogenic Escherichia coli inhibit lymphocyte activation and lymphokine production.

The aim of this study was to determine whether products of enteric bacteria are able to regulate lymphocyte activation and cytokine production. Whole bacteria and bacterial lysates from different strains of Escherichia coli were tested for their ability to inhibit cytokine production by peripheral blood mononuclear cells as determined by reverse transcription-PCR, Northern (RNA) blotting of cellular RNA, or enzyme-linked immunosorbent assay for cytokine protein. Lysates from two pathogenic strains of E. coli, enteropathogenic E. coli (EPEC) and enterohemorrhagic E. coli, inhibited mitogen-stimulated expression of interleukin-2 (IL-2), IL-4, IL-5, and gamma interferon. IL-1 beta, IL-6, IL-8, IL-10, IL-12, and Rantes mRNA expression was not affected. The inhibitory activity was dose dependent, protease and heat sensitive, nondialyzable, and not due to cellular toxicity. The inhibitory activity remained in EPEC strains having mutations in known virulence factors. Nonpathogenic E. coli HB101 transformed with a 22-kb cosmid clone derived from EPEC chromosomal DNA expressed the inhibitory activity. Thus, certain strains of pathogenic E. coli express a protein or proteins encoded by chromosomal genes that selectively inhibit lymphocyte activation and lymphokine production. Therefore, immunosuppressive factors produced by pathogenic bacteria could be important in modifying gastrointestinal immune responses in enteric bacterial infections or gastrointestinal autoimmune diseases.

Bacterial Proteins↗
PubMed1995

p53 mutational status and survival of human breast cancer MCF-7 cell variants after exposure to X rays or fission neutrons.

We assessed cytotoxicity of X rays or fission neutrons and the status of the p53 tumor suppressor gene in irradiated and unirradiated actively growing cultures of human breast cancer MCF-7 cells. One parental or wild-type (WT) and the other resistant to adriamycin (ADRR) were studied within the same experiment. We found that, relative to MCF-7 WT cells, MCF-7 ADRR cells exhibited a small but significant resistance to X rays, but not to fission neutrons. Single-strand conformation polymorphism analysis followed by DNA sequencing and immunohistochemical staining with a p53 protein-specific antibody performed on pooled polyclonal or monoclonal populations of MCF-7 WT or ADRR cells confirmed that wild-type cells have two normal copies of the p53 gene. We discovered p53 loss of heterozygosity and a point mutation in the remaining allele of the p53 gene in adriamycin-resistant cells. This mutation is a splice acceptor site change on the upstream border of exon 5 and results in p53 protein overexpression. No new p53 mutations were observed in MCF-7 WT or ADRR cells surviving either X or fission-neutron irradiations. Our results suggest that the mutant p53 allele affects cytotoxic outcomes of DNA damage from X rays but not from neutrons.

Base Sequence↗
PubMed1994

Frequent loss of heterozygosity on chromosome 9 in adenocarcinoma and squamous cell carcinoma of the esophagus.

Loss of heterozygosity (LOH) affecting chromosome 9p has been shown to occur frequently in head and neck cancer, glioma, mesothelioma, melanoma, lung cancer, and numerous other tumor types. Chromosome 9p is therefore presumed to contain a tumor suppressor gene or genes. Since esophageal cancer shares characteristics with some of the above tumor types, we performed a detailed examination of 60 patients with squamous cell carcinoma or adenocarcinoma of the esophagus for LOH at loci D9S162, IFNA, D9S171, D9S126, D9S104, D9S165, and D9S163. Multiplex polymerase chain reactions were performed with the inclusion of one radiolabeled nucleotide, and products were electrophoresed on denaturing polyacrylamide gels. Thirty-six of the 60 patients (60%) exhibited LOH at one or more loci on chromosome 9p. Eight of 17 patients (47%) with adenocarcinoma manifested LOH, while 28 of 43 (65%) with squamous cell carcinoma showed LOH. LOH was most frequent at loci D9S171 (19 of 23, or 83%) and D9S165 (24 of 32, or 75%). These data support the hypothesis that a tumor suppressor gene or genes located on this portion of chromosome 9p exert(s) an effect on esophageal cancer development.

Adenocarcinoma↗
PubMed1994

Microsatellite instability in ulcerative colitis-associated colorectal dysplasias and cancers.

Microsatellites are short nucleotide repeat sequences present throughout the human genome. Alterations of microsatellites, comprising extra or missing copies of these sequences, have been termed microsatellite instability. This abnormality occurs in sporadic and hereditary adenocarcinomas of the proximal colon, as well as in many other tumor types. We determined whether microsatellite instability occurred in ulcerative colitis-associated cancers or precancerous dysplasias. Sixty-three patients were evaluated, consisting of 188 samples of genomic DNA (63 normal controls, 68 cancers, 52 dysplasias, and 5 adjacent tissues) at loci D2S119, D2S123, D2S147, D10S197, and D11S904. Multiplex polymerase chain reaction was performed using one radiolabeled nucleotide, and the products were electrophoresed on denaturing polyacrylamide gels. Seventeen of the 63 patients (27%) possessed lesions showing instability at 1 or more loci. Fourteen of 68 tumor samples (21%) and ten of 52 dysplasias (19%) displayed instability. There was no tendency for a greater number of loci to manifest instability in more advanced lesions. Neither anatomic location nor loss of heterozygosity at the p53 locus were associated with microsatellite instability by 2-way table analysis. These data support a role for defective DNA repair in the generation of a subset of both early and advanced ulcerative colitis-associated colorectal neoplastic lesions.

Colitis, Ulcerative↗
PubMed1994

Microsatellite instability occurs frequently and in both diploid and aneuploid cell populations of Barrett's-associated esophageal adenocarcinomas.

Alterations of microsatellites consisting of extra or missing copies of these sequences occur at relatively high frequencies in sporadic and hereditary colorectal adenocarcinomas, gastric and pancreatic cancers, and at lower frequencies in endometrial, bladder, ovarian, and other carcinomas. We determined the prevalence of microsatellite instability in esophageal adenocarcinoma, Barrett's esophagus, and squamous cell carcinoma of the esophagus. Assays were performed on 105 patients, including 28 subjects with Barrett's metaplasia, 36 with Barrett's-associated adenocarcinoma, and 42 with primary esophageal squamous cell carcinoma. Flow cytometric nuclear sorting based on DNA content was performed on 25 of the adenocarcinomas prior to DNA extraction. Specimens from 11 of the 106 patients (10%) showed instability at 1 or more chromosomal loci. Instability was seen in 2 of 28 patients (7%) with Barrett's metaplasia alone, in 8 of 36 (22%) with adenocarcinoma, and in 1 of 42 (2%) with squamous cell carcinoma. Among the 25 flow cytometrically sorted adenocarcinomas, instability occurred in 8 (32%); sorted diploid nuclei from these tumors showed instability in 4 of 8 cases (50%). These data indicate that microsatellite instability occurs frequently in Barrett's-associated esophageal adenocarcinoma. They also suggest that in esophageal adenocarcinomas, microsatellite instability can develop as an early event in metaplasia and in diploid tumor cells, before aneuploidy occurs.

Adenocarcinoma↗
PubMed1994

17p allelic losses in diploid cells of patients with Barrett's esophagus who develop aneuploidy.

Inactivation of the p53 gene, located on chromosome 17p, leads to genetic instability and aneuploidy in vitro. Aneuploid cell populations from Barrett's adenocarcinomas have a high prevalence of 17p allelic losses, and there is substantial evidence that the target of these losses is the p53 gene. If 17p allelic losses lead to aneuploidy in Barrett's esophagus, then they should be present in diploid cells from patients who develop aneuploidy. We detected 17p allelic losses in diploid cells from 10 of 11 patients (91%) with Barrett's esophagus who developed aneuploid cell populations. Our data strongly suggest that 17p allelic losses precede the development of aneuploidy during neoplastic progression in Barrett's esophagus in vivo and, therefore, support in vitro evidence for the role of p53 in genetic instability.

Adenocarcinoma↗
PubMed1994

p53 protein expression in ulcerative colitis-associated colorectal dysplasia and carcinoma.

The frequency and timing of p53 inactivation in ulcerative colitis (UC)-associated tumorigenesis were investigated using immunohistochemistry (IHC) to detect p53 protein overexpression in 56 carcinomas and 40 dysplastic epithelia derived from 58 patients with UC undergoing colectomy for neoplasia. p53 DNA in 25 of the carcinomas also was evaluated by single-strand conformation polymorphism analysis (SSCP) to detect point mutations in exons 5-8 and by loss of heterozygosity analysis to detect allelic deletions. Point mutations were detected in 20 of the 25 carcinomas (80.0%) undergoing both IHC and DNA analysis. One carcinoma contained an allelic deletion but no mutations of the corresponding allele within the region tested. p53 overexpression occurred in 16 (76.2%) of the 21 carcinomas with point mutations and/or allelic deletions but not in any of those with wild type DNA. Of the 56 carcinomas evaluated by IHC, p53 overexpression occurred in 34 carcinomas (60.7%). The proportion of positive tumors was independent of stage, anatomic location, differentiation, and histological subtype. Overexpression was observed in nine of 20 dysplastic masses devoid of and situated remote from carcinoma (45.0%) and correlated positively with increasing grade of dysplasia (P < .025). In contrast, overexpression occurred in 16 of 20 dysplastic epithelia situated adjacent to carcinoma (80.0%) and correlated with overexpression by the corresponding carcinomas but not with the grade of dysplasia present (P = .013). It is concluded that p53 overexpression can be detected by IHC in most, although not all, UC-associated carcinomas with p53 mutations and/or allelic deletions. Based on this method, p53 overexpression occurs frequently in UC-associated carcinomas regardless of stage and pathological characteristics, in noncancerous dysplastic masses with high grade dysplasia, and in dysplasias of all grades situated adjacent to carcinomas. These findings implicate p53 inactivation in the progression from dysplasia to carcinoma in UC and suggest that its occurrence in dysplastic epithelium may be an independent marker of malignant potential.

Carcinoma↗
PubMed1994

The MTS1 gene is frequently mutated in primary human esophageal tumors.

Homozygous and heterozygous deletions involving chromosome 9p21 have been reported in a variety of primary human tumors in vivo, and point mutations have been reported in melanoma cell lines in vitro within a probable tumor suppressor gene, MTS1, located at chromosome 9p21. We describe six sequence alterations occurring among twenty-four primary esophageal squamous carcinomas and nineteen primary esophageal adenocarcinomas analyzed by DNA sequencing of MTS1 exon 2. Nucleotide substitutions were observed in five squamous cell carcinomas and in one adenocarcinoma. Two occurred in the germline, while four were somatic alterations. All six nucleotide changes resulted in marked alterations in amino acid sequence. Four were nonsense mutations leading to premature termination codons; nucleotide substitutions identical to two of these stop codons were previously reported in other tumor types. Loss of heterozygosity occurred in all five informative (constitutionally heterozygous) cases in which a sequence alteration was present. Esophageal cancer is one primary human tumor in which MTS1 constitutes an apparent target of heterozygous or homozygous deletions occurring at chromosome 9p21.

Base Sequence↗