Angiogenic markers, neovascularization and malignant deformation of Barrett's esophagus

P53, COX-2, iNOS Protein Expression Changes and Their Relationship with Anti-Oxidant Enzymes in Surgically and Multi-Modality Treated Esophageal Carcinoma Patients

Esophageal carcinoma has a high incidence in India but its etiology remains unknown. In the present study the correlation between apoptosis regulatory proteins and anti-oxidant enzymes in 40 esophageal carcinoma patients was examined. Patients in one group were operated by transhiatal esophagectomy and in the second group were administered cisplatin (30 mg/m2/day) and 5-fluorouracil (5-FU) (750 mg/m2/day) daily for three days followed by surgery after four weeks of neo-adjuvant therapy (NAT). Complete pathological response was achieved in 15% of patients. Results obtained by Western blot analysis showed over-expressed p53 and COX-2 protein levels in the tumor tissues as compared to the adjoining tissue and its paired normal mucosa in both groups of patients. Immunohistochemical studies showed heterogenous p53 staining pattern with sections showing both nuclear and cytoplasmic staining with 36.8% mild, 10.5% moderate and 52.6% intense p53 immunoreactivity. Both COX-2 and iNOS immunostaining revealed 25% negative and 75% mild to strongly positive immunoreactivity. Correlation studies demonstrated a positive relationship between p53 and COX-2 (P=0.030; r = +0.70) in surgically treated patients. The association of COX-2 and p53 with various anti-oxidant enzymes showed a significantly positive correlation between COX-2 expression and catalase activity and an inverse correlation between p53 expression and superoxide dismutase and catalase activity in the tumor tissue of patients given NAT. In addition, we observed a negative trend between p53 expression levels and GPx enzyme levels in both the adjoining and tumor tissue of patients having undergone surgery as main mode of treatment.

NOS-2 signaling and cancer therapy

The role of NO and cGMP signaling in tumor biology has been extensively studied during the past three decades. However, whether the pathway is beneficial or detrimental in cancer is still open to question. We suggest several reasons for this ambiguity: first, although NO participates in normal signaling (e.g., vasodilation and neurotransmission), NO is also a cytotoxic or apoptotic molecule when produced at high concentrations by inducible nitric-oxide synthase (iNOS or NOS-2). In addition, the cGMP-dependent (NO/sGC/cGMP pathway) and cGMP-independent (NO oxidative pathway) components may vary among different tissues and cell types. Furthermore, solid tumors contain two compartments: the parenchyma (neoplastic cells) and the stroma (nonmalignant supporting tissues including connective tissue, blood vessels, and inflammatory cells) with different NO biology. Thus, the NO/sGC/cGMP signaling molecules in tumors as well as the surrounding tissue must be further characterized before targeting this signaling pathway for tumor therapy. In this review, we focus on the NOS-2 expression in tumor and surrounding cells and summarized research outcome in terms of cancer therapy. We propose that a normal function of the sGC-cGMP signaling axis may be important for the prevention and/or treatment of malignant tumors. Inhibiting NOS-2 overexpression and the tumor inflammatory microenvironment, combined with normalization of the sGC/cGMP signaling may be a favorable alternative to chemotherapy and radiotherapy for malignant tumors.

Interactions between environmental factors and polymorphisms in angiogenesis pathway genes in esophageal adenocarcinoma risk: a case-only study

BACKGROUND

Gastroesophageal reflux disease (GERD), higher body mass index (BMI), smoking, and genetic variants in angiogenic pathway genes have been individually associated with increased risk of esophageal adenocarcinoma. However, how angiogenic gene polymorphisms and environmental factors jointly affect esophageal adenocarcinoma development remains unclear.

METHODS

By using a case-only design (n = 335), the authors examined interactions between 141 functional/tagging angiogenic single nucleotide polymorphisms (SNPs) and environmental factors (GERD, BMI, smoking) in modulating esophageal adenocarcinoma risk. Gene-environment interactions were assessed by a 2-step approach. First, the authors applied random forest to screen for important SNPs that had either main or interaction effects. Second, they used case-only logistic regression to assess the effects of gene-environment interactions on esophageal adenocarcinoma risk, adjusting for covariates and false-discovery rate.

RESULTS

Random forest analyses identified 3 sets of SNPs (17 SNPs-GERD, 26 SNPs-smoking, and 34 SNPs-BMI) that had the highest importance scores. In subsequent logistic regression analyses, interactions between 2 SNPs (rs2295778 of HIF1AN, rs13337626 of TSC2) and GERD, 2 SNPs (rs2295778 of HIF1AN, rs2296188 of VEGFR1) and smoking, and 7 SNPs (rs2114039 of PDGRFA, rs2296188 of VEGFR1, rs11941492 of VEGFR1, rs17708574 of PDGFRB, rs7324547 of VEGFR1, rs17619601 of VEGFR1, and rs17625898 of VEGFR1) and BMI were significantly associated with esophageal adenocarcinoma development (all false-discovery rates ≤0.10). Moreover, these interactions tended to have SNP dose-response effects for increased esophageal adenocarcinoma risk with increasing number of combined risk genotypes.

CONCLUSIONS

These findings suggest that genetic variations in angiogenic genes may modify esophageal adenocarcinoma susceptibility through interactions with environmental factors in an SNP dose-response manner.

Immunohistochemical evaluation for P53 and VEGF (Vascular Endothelial Growth Factor) is not prognostic for long term survival in end stage esophageal adenocarcinoma

OBJECTIVES

To correlate the expression of p53 protein and VEGF with the prognosis of patients submitted to curative resection to treat esophageal adenocarcinoma.

METHODS

Forty-six patients with esophageal adenocarcinoma, submitted to curative resection, were studied. The expressions of p53 protein and VEGF were assessed by immunohistochemistry in 52.2% and 47.8% of tumors, respectively.

RESULTS

P53 protein and VEGF expressions coincided in 26% of the cases, and no correlation between these expressions was observed. None of the clinicopathological factors showed a significant correlation with p53 protein or VEGF expressions. There was no significant association between p53 protein and VEGF expressions and long-term survival.

CONCLUSION

The expression of p53 protein and VEGF did not correlate with prognosis in esophageal adenocarcinoma patients submitted to curative resection.

What is the clinical significance of stromal angiogenesis in Barrett's esophagus?

BACKGROUND

Enriched blood vessels occur in the stroma of Barrett's esophagus and are related to the ease of tumor invasion in the early stage of the cancer. Hypoxia-inducible factor (HIF) is closely related with angiogenesis through expression of vascular endothelial growth factor. The aim of the present study was to determine the predictors for angiogenesis in Barrett's esophagus and evaluate their clinical significance.

METHODS

Between December 2003 and May 2004, 209 patients with endoscopically and histologically proven Barrett's esophagus were enrolled. Before endoscopic examination, all participants answered structured questionnaires for gastroesophageal reflux symptoms and drug usage. HIF-1alpha and COX-2 protein expressions, cellular proliferation, and apoptosis were investigated immunohistochemically in biopsy samples taken from the esophagus of each patient. The degree of angiogenesis was determined by CD34 immunostaining analysis. Predictors for angiogenesis were evaluated with multivariate logistic regression analysis.

RESULTS

Sixty (28.7%) of the 209 enrolled patients with Barrett's esophagus had a high CD34 score. Factors proven as positive predictors for a high CD34 score were presence of gastroesophageal reflux symptoms, reflux esophagitis, COX-2 protein expression, and the proliferating cell nuclear antigen (PCNA) index. Administration of proton-pump inhibitors and HIF-1alpha protein expression were not predictors.

CONCLUSIONS

Reflux esophagitis and gastroesophageal reflux symptoms were positive predictors for enriched angiogenesis in the stromal portion of Barrett's esophagus, which has malignant potential because the epithelial cells express COX-2 and have accelerated cellular proliferation.

Phenotypic differences between esophageal and gastric intestinal metaplasia

Intestinal metaplasia is a cancer precursor in the esophagus and the stomach. Marked differences exist between the carcinogenic processes in the two locations in terms of natural history and clinical significance. We investigated biopsies from 52 patients with Barrett's esophagus and from 50 patients with gastric intestinal metaplasia in an attempt to throw light on their pathogenic processes. Morphologic characteristics, presence of Helicobacter pylori (H. pylori), and markers of differentiation, inflammation, and proliferation were evaluated by histochemical and immunohistochemical techniques. The area covered by incomplete type of intestinal metaplasia and the proportion of sulfomucins were significantly higher in the esophagus than in the stomach. Immunoreactivity with MUC1, MUC2, MUC5AC, Das-1, cytokeratins 7 and 20, inducible nitric oxide synthase and cyclooxygenase-2 antibodies was also significantly greater in Barrett's esophagus than in gastric intestinal metaplasia. In gastric intestinal metaplasia, the presence of MUC1, MUC5AC, Das-1 and cytokeratin 7 was restricted to areas with the incomplete type of metaplasia. Cell proliferation (Ki-67) was significantly higher in Barrett's esophagus than in gastric intestinal metaplasia. H. pylori was absent in all of the patients with Barrett's esophagus, while it was present in 70% of the patients with gastric intestinal metaplasia. Our observations made clear that Barrett's esophagus shares some phenotypic characteristics with gastric intestinal metaplasia, leading us to suggest that both could arise in response to injuries with eventual carcinogenic potential. However, the progression to more advanced lesions could be modulated by the nature of the carcinogenic insult.

Selective cyclooxygenase-2 inhibition suppresses basic fibroblast growth factor expression in human esophageal adenocarcinoma

Inhibition of cyclooxygenase (COX)-2 is reported to suppress growth and induce apoptosis in human esophageal adenocarcinoma (EADC) cells, although the precise biologic mechanism is unclear. In this study we tested the hypothesis that the antitumor activity of COX-2 inhibitors may involve modulation of basic fibroblast growth factor (FGF-2), which is overexpressed in EADC. We evaluated the effects of NS-398, a selective COX-2 inhibitor, on FGF-2 expression and proliferation of EADC cell lines that express COX-2 and those that do not. We also correlated COX-2 and FGF-2 expression with clinico-pathologic findings and outcome in a well-characterized series of surgically resected EADC tissues. Seg-1 cells robustly expressed COX-2 and FGF-2, whereas Bic-1 cells expressed neither transcript. FGF-2 was reduced to undetectable levels in Seg-1 cells following NS-398 treatment, but increased within 4 h of drug removal. NS-398 significantly inhibited the growth of Seg-1 cells, and this effect was ameliorated by addition of exogenous FGF-2. In contrast, NS-398 had no effect on Bic-1 cell proliferation and FGF-2 alone had no effect on proliferation of either cell line. NS-398, or a neutralizing anti-FGF-2 antibody, induced apoptosis in Seg-1 cells, and these effects were inhibited by addition of exogenous FGF-2. COX-2 protein was strongly expressed in 46% (10/22) of EADCs, and was associated with a trend towards reduced disease-free survival. These findings indicate that the antitumor effects of COX-2 inhibition in EADC cells may be mediated via suppression of FGF-2, and that COX-2 may be a clinically relevant molecular marker in the management of human EADC.

Proteomic Modification by Nitric Oxide

The role of nitric oxide (NO) in cellular signaling has become one of the most rapidly growing areas in biology during the past two decades. As a gas and free radical with an unshared electron, nitric oxide participates in various biological processes. The interaction between NO and proteins may be roughly divided into two categories. In many instances, NO mediates its biological effects by activating guanylyl cyclase and elevates intracellular cyclic GMP synthesis from GTP. However, the list of cGMP-independent effects of NO is also growing at a rapid rate. In this review, the importance and relevance of nitrotyrosine formation are stressed. The utilization of intact cell cultures, tissues, and cell-free preparations along with the use of pharmacological, biochemical, and molecular biological approaches to characterize, purify, and reconstitute these NO regulatory pathways could lead to the development of new therapies for various pathological conditions that are characterized by unbalanced production of NO.

COX-2 inhibition in cancer therapeutics: a field of controversy or a magic bullet?

Carcinogenesis is a multistep process of long-term accumulation of genetic and epigenetic aberrations at the molecular level. Understanding the mechanisms underlying carcinogenesis could further provide insights for rationally designed new therapeutic strategies for cancer prevention and treatment. Epidemiological and experimental evidence supports the preventative effect of non-steroidal anti-inflammatory drugs (NSAIDs) regarding cancer development. NSAIDs inhibit cyclooxygenase (COX) activity, thus blocking the endogenous prostaglandin production. COX-2 is a key isoenzyme in this biochemical cascade and is inducible by various oncogenic stimuli. A large volume of research data has shown that COX-2 is often upregulated in many malignant tumours, rendering it an attractive candidate target for cancer therapeutics. Various possible direct mechanisms for COX-2 implication in carcinogenesis have been suggested, whilst intense interest has recently been focused on COX-2-independent effects of NSAIDs. Several COX-2-selective inhibitors are currently under evaluation in preclinical and clinical studies, either as single agents or in combination with conventional chemotherapy, radiotherapy and other new molecularly-targeted compounds, with promising results. This article critically reviews already published data on COX-2-selective inhibitors that have been tested in cancer clinical trials, highlights ongoing research and considers the future perspectives of this novel class of agents.

Differential requirement of signal pathways for benzo[ a ]pyrene (B[ a ]P)-induced nitric oxide synthase (iNOS) in rat esophageal epithelial cells

Overexpression of inducible nitric oxide synthase (iNOS) has been reported in several human cancers, including esophageal squamous cell carcinoma (SCC). Benzo[a]pyrene (B[a]P), a polycyclic hydrocarbon carcinogen found in tobacco smoke and in the environment, induces cancer in multiple organ sites in animals and may be a causative agent for certain human cancers, such as esophageal cancer. In the present study, the effects of B[a]P on the induction of iNOS and the signaling pathways that lead to the induction were investigated in cultured rat esophageal epithelial (RE-149) cells. Treatment of RE-149 cells with B[a]P led to a marked increase in the expression of iNOS. The induction of iNOS by B[a]P was found to occur through an extracellular signal-regulated protein kinases (ERKs)-dependent pathway, since inhibition of ERKs by either pretreatment of RE-149 cells with PD98059, an inhibitor of ERKs upstream kinase MEK1/2, or overexpression of DN-ERK2, blocked the induction of iNOS by B[a]P. Furthermore, impairing nuclear factor-kappaB (NFkappaB) activation by either NEMO-BDBP, an NFkappaB specific inhibitor, or overexpression of DN-IkappaBalpha or IKK-KM markedly inhibited the expression of B[a]P-induced iNOS, suggesting that the NFkappaB pathway is also required for the induction of iNOS by B[a]P. In addition, treatment of RE-149 cells with either SB202190, a p38 kinase inhibitor, or c-JunN-terminal kinase inhibitor II, resulted in an increased induction of iNOS. Pretreatment of RE-149 cells with wortmannin, a PI-3K inhibitor, or with rapamycin, an mTOR/p70S6K pathway inhibitor, had no effect on the expression of iNOS. These results suggest that B[a]P initiates the signaling pathways leading to the induction of iNOS in cultured rat esophageal epithelial cells. In view of the potential role of iNOS in the development of esophageal SCC in humans, we speculate that the induction of iNOS by B[a]P may be one mechanism by which B[a]P could produce carcinogenic effects in the human esophagus.

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Biomarkers of esophageal adenocarcinoma and Barrett's esophagus

The rising incidence and poor prognosis of esophageal adenocarcinoma in the Western world have intensified research efforts into earlier methods of detection of this disease and its relationship to Barrett's esophagus. The progression of Barrett's esophagus to adenocarcinoma has been the focus of particular scrutiny, and a number of potential tissue and serum-based disease biomarkers have emerged. The epidemiology and pathogenesis of esophageal adenocarcinoma are outlined. Tissue biomarkers allowing risk stratification of Barrett's are reviewed as well as strategies currently being used to discover novel biomarkers that will facilitate the early detection of esophageal adenocarcinoma. Finally, the uses of biomarkers as predictive tests for targeted treatments and as surrogate endpoints in chemoprevention trials are considered.

Molecular findings in Barrett's epithelium

Barrett's metaplasia is a premalignant condition and remains the number one risk factor for developing adenocarcinoma. The histologic changes leading to adenocarcinoma are accompanied by genetic disturbances of the epithelial cells itself as well as the surrounding stroma. Genetic and epigenetic events affect the cell cycle, leading to growth self-sufficiency and ignoration of antigrowth signals. The balance of cell turnover is instable by avoidance of apoptosis and a general limitless of the replicative potential of the (mutated) stem cells. Sustained angiogenesis, not only a consequence of chronic inflammation, may precede invasion of genetically instable (aneuploid) cells. The principal genetic changes in Barrett's carcinogenesis are comparable to those known from other epithelial malignancies. Loss of p16 gene expression (by deletion or hypermethylation), the loss of p53 expression (by mutation and deletion), the increase in cyclin expression, and the losses of Rb, APC as well as various chromosomal loci have been reported. Since these genetic or epigenetic alterations are neither tumor nor stage specific, they could not gain diagnostic significance as biomarkers until now.