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Vascular endothelial growth factor A (VEGF-A) regulates many aspects of vascular physiology. VEGF-A stimulates signal transduction pathways that modulate endothelial outputs such as cell migration, proliferation, tubulogenesis, and cell-cell interactions. Multiple VEGF-A isoforms exist, but the biological significance of this is unclear. Here we analyzed VEGF-A isoform-specific stimulation of VCAM-1 gene expression, which controls endothelial-leukocyte interactions, and show that this is dependent on both ERK1/2 and activating transcription factor-2 (ATF-2). VEGF-A isoforms showed differential ERK1/2 and p38 MAPK phosphorylation kinetics. A key feature of VEGF-A isoform-specific ERK1/2 activation and nuclear translocation was increased phosphorylation of ATF-2 on threonine residue 71 (T71). Using reverse genetics, we showed ATF-2 to be functionally required for VEGF-A-stimulated endothelial VCAM-1 gene expression. ATF-2 knockdown blocked VEGF-A-stimulated VCAM-1 expression and endothelial-leukocyte interactions. ATF-2 was also required for other endothelial cell outputs, such as cell migration and tubulogenesis. In contrast, VCAM-1 was essential only for promoting endothelial-leukocyte interactions. This work presents a new paradigm for understanding how soluble growth factor isoforms program complex cellular outputs and responses by modulating signal transduction pathways., (© 2014 Fearnley et al. This article is distributed by The American Society for Cell Biology under license from the author(s). Two months after publication it is available to the public under an Attribution–Noncommercial–Share Alike 3.0 Unported Creative Commons License (http://creativecommons.org/licenses/by-nc-sa/3.0).)

3-Nitrobenzanthrone (3-NBA) is a potent mutagen and a suspected human carcinogen present in particulate matter of diesel exhaust and ambient air pollution. Employing an assay with human p53 knock-in (Hupki) murine embryonic fibroblasts (HUFs), we examined p53 mutations induced by 3-NBA and its active metabolite, N-hydroxy-3-aminobenzanthrone (N-OH-3-ABA). Twenty-nine immortalized cultures (cell lines) from 89 HUF primary cultures exposed at passage 1 for 5 days to 2 microM 3-NBA harboured 22 different mutations in the human DNA-binding domain sequence of the Hupki p53 tumour suppressor gene. The most frequently observed mutation was GC to TA transversion (46%), corroborating previous mutation studies with 3-NBA, and consistent with the presence of persistent 3-NBA-guanosine adducts found in DNA of exposed rodents. Six of the transversions found solely in 3-NBA-treated HUFs have not been detected thus far in untreated HUFs, but have been found repeatedly in human lung tumours. (32)P-post-labelling adduct analysis of DNA from HUF cells treated with 2 microM 3-NBA for 5 days showed a pattern similar to that found in vivo, indicating the metabolic competence of HUF cells to metabolize 3-NBA to electrophilic intermediates. Total DNA binding was 160 +/- 56 per 10(7) normal nucleotides with N(2)-guanosine being the major adduct. In contrast, identical treatment with N-OH-3-ABA resulted in a 100-fold lower level of specific DNA adducts and no carcinogen-specific mutation pattern in the Hupki assay. This indicates that the level of DNA adduct formation by the mutagen is critical to obtain specific mutation spectra in the assay. Our results are consistent with previous experiments in Muta Mouse and are compatible with the possibility that diesel exhaust exposure contributes to mutation load in humans and to lung cancer risk.

Current methods to analyze gene expression measure steady-state levels of mRNA. To specifically analyze mRNA transcription, we have developed a technique that can be applied in vivo in intact cells and animals. Our method makes use of the cellular pyrimidine salvage pathway and is based on affinity-chromatographic isolation of thiolated mRNA. When combined with data on mRNA steady-state levels, this method is able to assess the relative contributions of mRNA synthesis and degradation/stabilization. It overcomes limitations associated with currently available methods such as mechanistic intervention that disrupts cellular physiology, or the inability to apply the techniques in vivo. Our method was first tested in serum response of cultured fibroblast cells and then applied to the study of renal ischemia reperfusion injury, demonstrating its applicability for whole organs in vivo. Combined with data on mRNA steady-state levels, this method provided a detailed analysis of regulatory mechanisms of mRNA expression and the relative contributions of RNA synthesis and turnover within distinct pathways, and identification of genes expressed at low abundance at the transcriptional level.

A mutation in codon 249 of the TP53 gene (249(Ser)), related to aflatoxin B(1) exposure, has previously been associated with hepatocellular carcinoma risk. Using a novel internal standard plasmid, plasma concentrations of 249(Ser)-mutated DNA were quantified by electrospray ionization mass spectrometry in 89 hepatocellular carcinoma cases, 42 cirrhotic patients, and 131 nonliver diseased control subjects, all from highly aflatoxin-exposed regions of The Gambia. The hepatocellular carcinoma cases had higher median plasma concentrations of 249(Ser) (2,800 copies/mL; interquartile range: 500-11,000) compared with either cirrhotic (500 copies/mL; interquartile range: 500-2,600) or control subjects (500 copies/mL; interquartile range: 500-2,000; P < 0.05). About half (52%) of the hepatocellular carcinoma cases had >2,500 copies of 249(Ser)/mL plasma, corresponding to the prevalence of this mutation in liver tumors in The Gambia. In comparison, only 15% of control group and 26% of cirrhotic participants exceeded this level (P < 0.05). Further subset analysis revealed a statistically significant, quantitative relation between diagnosis of hepatocellular carcinoma and levels of 249(Ser) detected at 2,501 to 10,000 copies/mL plasma (odds ratio, 3.8; 95% confidence interval, 1.3-10.9) and at >10,000 copies/mL plasma (odds ratio, 62; 95% confidence interval, 4.7-820) when compared with control subjects and after adjusting for age, gender, recruitment site, hepatitis B and C serologic status, and total DNA concentration. Levels of >10,000 copies of 249(Ser)/mL plasma were also significantly associated with the diagnosis of hepatocellular carcinoma (odds ratio, 15; 95% confidence interval, 1.6-140) when compared with cirrhotic patients. Potential applications for the quantification of 249(Ser) DNA in plasma include estimation of long-term, cumulative aflatoxin exposure and selection of appropriate high-risk individuals for targeted intervention.

Human p53 mutation spectra differ significantly from one cancer type to another. One possible reason is that carcinogenic risk factors differ, and these factors elicit distinct mutation patterns. There has been no mammalian assay, however, with which to generate mutation patterns in human p53 sequences experimentally, hampering interpretation of the human tumor spectra. We have designed a new mammalian cell assay using gene targeting technology that selects and scores human p53 gene sequence mutations in human-p53 knock-in (Hupki) murine embryonic fibroblasts (HUF) that have undergone immortalization. With the Hupki assay we examined here whether benzo(a)pyrene (BaP), a major tobacco smoke carcinogen could elicit p53 mutation patterns characterizing the human lung tumor p53 mutation spectrum. We found that, in contrast to unexposed HUFs or HUFs exposed to other carcinogenic agents, HUFs exposed to BaP acquire mutations that display major features of the human lung tumor p53 mutation spectrum: (a) predominance of G-to-T mutations, (b) unequivocal strand bias of the transversions, and (c) a mutation hotspot at codons 157 to 158. These data are consistent with the hypothesis that BaP has a direct role in causing smokers' lung tumor p53 mutations. The assay can be used to examine various hypotheses on the endogenous or exogenous factors responsible for the p53 mutations in human tumors arising in other tissues.

It has been demonstrated recently that certain repetitive sequences and even expressed single-copy genes are capable of retrotransposition, but little is known about the endogenous or exogenous modifiers of this process in human cells. Retrotransposition may contribute to gene inactivation and genetic instability in cancer development. We have used the human cell line MCF-7 to generate a method for investigating de novo retrotransposition in breast cancer cells. The strategy employs a reporter construct transfected into MCF-7 cells that encodes neomycin phosphotransferase gene (neoR) sequences interrupted by an intron derived from the gamma-globin gene and sandwiched between two promoters in opposite orientation; the phosphotransferase is not produced in transfected cells expressing the plasmid until transposition via a spliced antisense neoR RNA intermediate has occurred, conferring a functional gene product and thereby resistance to G418. A stable transfectant line that showed presence of reporter plasmid DNA and expression of reporter antisense neoR was obtained and used to demonstrate spontaneous retrotransposition of neoR sequences: tester cells were subjected to selection in G418 medium, and neomycin-resistant clones were isolated at a frequency of 10(-7). A simple PCR-based prescreening of colonies fixed and stained in Petri dishes can be used to verify intronless neoR DNA. Expanded populations of G418-resistant colonies were determined to be derived from reporter sequences that had transposed via an RNA intermediate by Southern blot genotyping. This experimental assay may be used for exploring endogenous and environmental factors that influence host cell-mediated retrotransposition of unbiased cellular sequences in breast tumor cells. Genes Chromosomes Cancer 26:84-91, 1999., (Copyright 1999 Wiley-Liss, Inc.)

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.

Background & Aims: We previously discovered anti-p53 antibodies predating a cancer diagnosis in subjects at increased risk for liver, lung, breast, and prostate cancer. Recently, we reported a significant correlation (P < 0.017) between p53 antibodies and p53 mutations in patients with late-stage esophageal carcinoma. Because others have reported p53 mutations and overexpression of p53 protein in Barrett's esophagus, we studied p53 antibodies in plasma of 88 serially endoscoped patients: 36 with Barrett's metaplasia, 23 with esophageal squamous cell carcinoma, 10 with esophageal adenocarcinoma, and 19 with esophagitis or normal esophagus., Methods: We used enzyme immunoassay, immunoblotting, and immunoprecipitation assays for p53 antibodies; polymerase chain reaction, denaturant gradient gel electrophoresis, and sequencing for p53 mutations; and immunohistochemistry for p53 protein., Results: p53 antibodies were detected in 4 patients with Barrett's esophagus, including 1 with dysplasia that later progressed to adenocarcinoma, and in 10 cancer patients (P = 0.002) (8 squamous and 2 adenocarcinoma), 2 of whom (1 squamous, 1 adenocarcinoma) had antibodies before cancer was diagnosed. Other patient groups were too small for informative statistical analysis. Six antibody-positive cancer patients had p53 mutations, whereas 2 patients with cancer and 1 with Barrett's esophagus with antibodies had p53 protein overexpressed in esophageal tissues., Conclusions: Patients with Barrett's esophagus and esophageal cancer can develop p53 antibodies that may predate the clinical diagnosis of malignancy.

Esophageal tumors from 29 patients residing in Guangzhou, China were examined for mutations in exons 5-8 of the p53 tumor suppressor gene and for p53 protein accumulation in tumor cell nuclei. Anamnestic data for each patient, which included information on family history of cancer, tobacco smoking, drinking of alcoholic beverages, and dietary habits such as consumption of pickled vegetables, were recorded. Screening of DNA from tumor cells microdissected from biopsies was performed by PCR amplification of p53 gene exons 5-8, denaturing gradient gel electrophoresis analysis, and DNA sequencing. Mutations were identified in 20 of 29 tumors (69%). All tumors harboring a missense mutation in the p53 gene also showed nuclear accumulation of the tumor suppressor protein by immunohistochemistry. The most common p53 mutations in these tumors were guanine to adenine (G-->A) transitions (10 of 20 tumors; 50%). We did not find multiple mutations at codon 176, in contrast to Lung et al. in their recent study of esophageal cancer patients from Guangzhou (M. L. Lung et al., Cancer Epidemiol. Biomark. Prev., 5: 277-284, 1996). The mutation prevalence was high both in smokers (13 mutations in 20 smokers; 65%) and in nonsmokers (7 of 9 tumors with mutations; 78%), an observation that differs from that of studies in European and North American patients, which demonstrate a much higher prevalence of p53 mutations in smokers than in nonsmokers (reviewed in R. Montesano et al., Int. J. Cancer Predict. Oncol., 69: 225-235, 1996.). Our findings in this pilot study of tumor suppressor gene mutations in patients from Guangzhou support a large body of epidemiological observations pointing to dietary mutagenic carcinogens peculiar to populations in China at high risk of esophageal cancer.

Serum antibodies reacting with the tumor suppressor protein p53 have been detected previously in cancer patients with a variety of neoplasms. Two initial (although insufficient) prerequisites for a B-cell response to occur have been proposed: p53 protein accumulation in the tumor or a mutant p53 gene, or both. We have examined 65 esophageal cancer cases (42 from Guangzhou and Shenyang, People's Republic of China, and 23 from Paris, France) to obtain a prevalence estimate of anti-p53 antibodies for this type of cancer and to define the relationship of p53 tumor status to B-cell immune response. Sera were analyzed in a triplicate assay (enzyme-linked immunoassay, immunoprecipitation, and immunoblot) for anti-p53 antibodies. Tumor DNA was screened for mutations in exons 5-8, and tumor tissue was examined by immunohistochemistry for abnormal p53 protein accumulation. p53 mutations were found in 36 (58%) of 62 cases analyzed. Sixteen patients (25%) had circulating antibodies to the tumor suppressor protein. All but two (88%) of the tumors from seropositive cases had a mutation in the DNA binding region of the p53 gene, and with one exception, these tumors also showed nuclear accumulation of the p53 protein. In contrast, tumor mutations were found in just 22 (46%) of the 48 individuals in whom we did not detect anti-p53 antibodies. Among the 22 seronegative cases for which we found no tumor mutations, 11 revealed p53 protein accumulation by immunohistochemical analysis. Thus, circulating anti-p53 antibodies may be present in one-fourth of esophageal cancer patients, most of whom also would be expected to have a p53 gene mutation in their tumors. Patients without such mutations appear considerably less likely to mount a B-cell response to the p53 tumor suppressor protein than those that do (P < 0.01).

We have examined DNA from four human esophageal carcinoma cell lines and 50 primary esophageal carcinomas obtained from China, Italy, and France for amplification of the cyclin D1 gene. We also examined 36 of these 50 carcinomas for expression of the cyclin D1 and retinoblastoma (RB) proteins by immunohistochemistry. We found a 3- to 10-fold amplification of the cyclin D1 gene in 16 of the 50 (32%) tumors and in two of the four cell lines. Cyclin D1 protein was overexpressed in 12 of 13 tumors and the two cell lines that showed gene amplification when compared to normal controls. Studies on RB protein expression indicated that 6 of the 36 (17%) tumor samples examined and one cell line did not show detectable expression of this protein. The tumors and cell lines that had cyclin D1 gene amplification and overexpression exhibited normal levels of expression of RB protein. By contrast, the tumors and cell line that did not appear to express the RB protein did not show amplification of the cyclin D1 gene and expressed only low levels of the cyclin D1 protein (P = 0.03). These results suggest that the inhibitory effect of RB on cell cycle progression can be abrogated during tumor development either by loss of expression of the RB gene or by increased expression of the cyclin D1 gene.

The prevalence and type of mutations in the p53 tumour-suppressor gene have been determined in 15 hepatocellular carcinomas (HCC) originating from Thailand. Direct sequencing of exons 5-8 revealed 2 mutations, an AGG to AGT (Arg-->Ser) transversion at codon 249, and an ATC-->AAC (Ile-->Asn) transversion at codon 254. Samples from the Thai patients were analyzed for the presence of aflatoxin-liver DNA and aflatoxin-serum albumin adducts, and all but one were found negative. All the patients were genotyped for glutathione-S-transferase (GST) mu, an enzyme possibly involved in the detoxification of AFB1, and 12 out of 15 had the null genotype. In general, the level of aflatoxin-albumin adducts in sera and the prevalence of p53 mutation at codon 249 in HCC were lower than in other areas at high risk of HCC, including southern China and parts of Africa.

Preinvasive lesions of squamous cell carcinoma are well defined morphologically and provide a model for multistage carcinogenesis. Since alterations in the p53 tumor suppressor gene occur frequently in invasive esophageal squamous cell carcinoma, we examined a set of preinvasive lesions to investigate the timing of p53 mutation. Surgically resected tissues from nine patients with esophageal squamous cell carcinoma contained precursor lesions which had not yet invaded normal tissues. Immunohistochemistry showed high levels of p53 protein in both preinvasive lesions and invasive carcinomas in six cases; sequence analysis of all invasive tumors identified p53 missense mutations in two cases. Preinvasive lesions from both tumors with mutations plus one wild-type tumor were microdissected and sequenced. In one patient there were different mutations in the invasive carcinoma (codon 282, CGGarg > TGGtrp) and a preinvasive lesion (codon 272, GTGval > T/GTGleu/val). In a second case, an invasive carcinoma had a mutation in codon 175 (CGCarg > CAChis), and adjacent preinvasive lesions contained a wild-type sequence. A carcinoma and preinvasive lesion from the third case contained high levels of protein and a wild-type DNA sequence. Therefore, p53 mutation may precede invasion in esophageal carcinogenesis, and multifocal esophageal neoplasms may arise from independent clones of transformed cells. The timing of p53 protein accumulation is favorable for an intermediate biomarker in multistage esophageal carcinogenesis.

A strategy and methods for archival analysis of genetic and protein alterations in the p53 tumor-suppressor gene are presented. The tumor series includes 43 paraffin-embedded esophageal carcinomas from two high-incidence regions in the People's Republic of China. More than half contained elevated p53 protein levels which were detected by a high-titer polyclonal antiserum and a sensitive immunohistochemical method. To estimate the frequency of underlying mutations, DNA was isolated from conventional paraffin sections, amplified by the polymerase chain reaction, and examined by dideoxy termination sequencing. Analysis of exons 5-8 in a subset of 10 tumors revealed mis-sense point mutations in 4 out of 5 immunostain-positive tumors and a mutation encoding a stop codon in 1 of 5 immunostain-negative tumors. In this report of archival material, we conclude that detectable levels of p53 protein correlate closely with the occurrence of mis-sense mutations. Furthermore, these methods render large repositories of paraffin-embedded tumor and non-tumor tissues accessible to analysis. Immunohistochemical screening for elevated protein levels followed by sequence analysis represents an efficient strategy for the evaluation of the p53 mutational spectrum.

Esophageal squamous cell carcinoma (ESC) samples from patients residing in Uruguay and in Normandy, France, where alcoholic beverages and tobacco smoke are major risk factors, were analyzed for point mutations in the p53 tumor suppressor gene. Among 34 tumors (15 from Normandy and 19 from Uruguay) 15 point mutations in the p53 gene that result in amino acid substitutions or chain termination were identified by polymerase chain reaction amplification of exons 5-8 and direct DNA sequencing. Base substitutions in ESC from these high-incidence areas are dispersed over the midregion of the p53 gene. There are differences between ESC and other types of gastrointestinal cancer in the nature of frequent base substitutions. CpG to TpG transitions were far less prevalent in these ESC than in colorectal tumors, whereas G to T transversions, rarely found in colon cancers, were found in one-fourth of the ESC samples. Base substitutions at A:T pairs constitute an important fraction of ESC p53 mutations, in contrast to mutation patterns in most other types of solid tumors. In contrast to the frequent mutation of the p53 gene in these samples, no mutations in the H-, K-, or N-ras genes were found in 16 tumors from Uruguay by direct sequencing of exons in which transforming mutations are known to occur. A previous study on ras mutations in ESC from France was also negative (M. C. Hollstein et al., Cancer Res., 48: 5119-5123, 1988). The role of distinct etiological factors in generating these differences and the potential for linking patient exposure histories with patterns of p53 mutations in high risk populations are considered.

Sequence alterations in the p53 gene have been detected in human tumors of the brain, breast, lung, and colon, and it has been proposed that p53 mutations spanning a major portion of the coding region inactivate the tumor suppressor function of this gene. To our knowledge, neither transforming mutations in oncogenes nor mutations in tumor suppressor genes have been reported in human esophageal tumors. We examined four human esophageal carcinoma cell lines and 14 human esophageal squamous cell carcinomas by polymerase chain reaction amplification and direct sequencing for the presence of p53 mutations in exons 5, 6, 7, 8, and 9. Two cell lines and five of the tumor specimens contained a mutated allele (one frameshift and six missense mutations). All missense mutations detected occurred at G.C base pairs in codons at or adjacent to mutations previously reported in other cancers. The identification of aberrant p53 gene alleles in one-third of the tumors we tested suggests that mutations at this locus are common genetic events in the pathogenesis of squamous cell carcinomas of the esophagus.

An activity has been purified 350-fold from extracts of mouse plasmacytoma cells that forms 5-hydroxymethyluracil (alpha-hydroxythymine) and apyrimidinic sites with phage SPO1 DNA, which contains this base in place of thymine. This DNA glycosylase presumably functions to eliminate hydroxymethyluracil, a major thymine-derived DNA lesion produced by ionizing radiation and oxidative damage. The enzyme has no cofactor requirement and is active in EDTA. Neither intermediate formation nor hydrolysis of hydroxymethyl-deoxyuridine or hydroxymethyldeoxyuridine monophosphate was detected. The enzyme does not cleave apyrimidinic sites in DNA. It does release uracil from the uracil-containing DNA of phage PBS2, but this activity is less than 2% of the predominant uracil DNA glycosylase activity of the cell, which is separated by phosphocellulose chromatography. The major uracil DNA glycosylase does not release hydroxymethyluracil from SPO1 DNA. The hydroxymethyluracil glycosylase is also separated upon phosphocelluose chromatography from a thymine glycol DNA glycosylase activity that is accompanied by an apyrimidinic endonuclease activity.

Strains of Salmonella typhimurium that carry a nonsense mutation at the site of reversion detect a variety of naturally occurring and synthetic carbonyl compounds as direct-acting mutagens. TA104 is reverted efficiently by formaldehyde, alpha, beta-unsaturated aldehydes (enals), and dicarbonyl compounds, such as diacetyl and glutaraldehyde. This strain is much more sensitive to carbonyl mutagenesis than is TA100, a strain previously reported to detect aldehydes as mutagens, or any other characterized strains of Salmonella. Long-chain enals are very toxic to TA104, but addition of a reduced glutathione chase following an incubation period decreases this toxicity, thus enabling the detection of 4-hydroxy-pentenal, a homolog of the lipid peroxidation product, 4-hydroxy-nonenal, as a mutagen. This is the first report of the mutagenicity of a hydroxy-enal, a class of enals produced by lipid peroxidation. Testing conducted with strains that carry the nonsense mutation in different repair backgrounds indicates that the presence of pKM101 and the deletion of the uvrB gene facilitate the detection of enals and dicarbonyls, but not malondialdehyde, as mutagens. Since carbonyl compounds are widely distributed in foods, are generated during cellular metabolism, and are present in body fluids, they may make a significant contribution to the risk of human cancer.

Primary esophageal squamous cell carcinomas from 41 patients were analyzed for the presence of proto-oncogene alterations associated with this malignancy. The occurrence of activating ras gene mutations in 25 tumors was determined using oligomer hybridization of target sequences amplified by polymerase chain reaction. We found no evidence for mutations in codons 12 and 61 of the H-ras, K-ras, and N-ras genes, nor in codon 13 of the K-ras and N-ras loci in any of these tumors. The apparent absence of activated ras oncogene in esophageal cancers represents a possible exception to the presence of these mutations found consistently in numerous other types of human malignancies, and is in striking contrast to the 40% prevalence of ras mutations in human colorectal cancers. Southern blot hybridization experiments with DNAs from tumors demonstrated amplification of the epidermal growth factor receptor gene (c-erbB) in two of 25 carcinomas. No amplification of the structurally related c-erbB2 (neu) gene was detected. In three out of 12 carcinomas, the level of epidermal growth factor receptor RNA was significantly higher than in normal esophageal mucosal tissue. Our results suggest that enhanced transcription of the epidermal growth factor receptor gene is associated with the development of some esophageal cancers.