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Background and Aim: Recent observational studies have shown therapeutic benefits of acetylsalicylic acid (ASA) in several types of cancer. We examined whether ASA exerts antitumor activity in esophageal adenocarcinoma (EAC)., Methods: Human EAC cells (OE33) were treated with ASA (0-5 mM) to evaluate proliferation, apoptosis, and migration. In vivo model: OE33-derived tumors were subcutaneously implanted into athymic mice which were allocated to ASA (5 or 50 mg/kg/day)/vehicle (5-6 animals/group). Tumor growth was assessed every 2-3 days, and after 40 days, mice were euthanized. Plasma drug levels were determined by high-performance liquid chromatography. Histological and immunohistochemical (Ki67, activated caspase-3) analysis of tumors were performed. The effect of ASA on tumor prostaglandin E2 (PGE2) levels was also evaluated., Results: In vitro cell proliferation and migration were significantly inhibited while apoptosis increased (p < 0.05) by ASA. Although ASA did not induce tumor remission, tumor progression was significantly lower in ASA-treated mice when compared to non-treated animals (478 % in mice treated with 5 mg/kg/day ASA vs. 2696 % control; 748 % in mice treated with 50 mg/kg/day ASA vs. 2670 % control). Maximum tumor inhibition was 92 and 85 %, respectively. This effect was associated with a significant decrease of proliferation index in tumors. ASA 5 mg/kg/day did not modify tumor PGE2 levels. Whereas tumor PGE2 content in mice treated with ASA 50 mg/kg was lower than in control mice, the difference was not significant., Conclusion: Although these results need to be confirmed in other EAC cells, our data suggest a role for ASA in the treatment of this tumor.

Aspirin has been proposed in recent years as a candidate for chemoprevention of adenocarcinoma in patients with Barrett's esophagus. The aim of the present study was to evaluate the effect of acetylsalicylic acid (ASA) in an experimental model of esophageal adenocarcinoma. An animal model of gastroenteroesophageal reflux was established using Wistar rats undergoing esophagojejunostomy with gastric preservation. Following surgery, rats were divided into three groups: i) control (vehicle); ii) ASA 50 mg/kg/day; and iii) ASA 5 mg/kg/day. Four months after surgery, the surviving animals were sacrificed and the rat esophagi were assessed for histological and biochemical [prostaglandin E2 (PGE2) and lipoxin A4 (LXA4 ) levels] analysis. As in the control rats, those receiving aspirin treatment showed no decrease in inflammation grade, extent of ulcerated esophageal mucosa, length of intestinal metaplasia in continuity with anastomosis, presence of intestinal metaplasia beyond anastomosis, severity of dysplasia or incidence of adenocarcinoma. In contrast, aspirin-treated rats showed decreased esophageal tissue levels of PGE2 and increased LXA4, significantly in the high-dose aspirin group (p=0.008 and p=0.01, respectively). In this rat model of gastroesophageal reflux, the administration of aspirin modified esophageal tissue levels of PGE2 and LXA4, but was not effective in preventing the development of esophageal adenocarcinoma.

Gastrin is the main hormone responsible for the stimulation of gastric acid secretion; in addition, gastrin and its derivatives exert proliferative and antiapoptotic effects on several cell types. Gastrin synthesis and secretion are increased in certain situations, for example, when proton pump inhibitors are used. The impact of sustained hypergastrinemia is currently being investigated. In vitro experiments and animal models have shown that prolonged hypergastrinemia may be related with higher cancer rates; although, this relationship is less clear in human beings. Higher gastrin levels have been shown to cause hyperplasia of several cell types; yet, the risk for developing cancer seems to be the same in normo- and hypergastrinemic patients. Some tumors also produce their own gastrin, which can act in an autocrine manner promoting tumor growth. Certain cancers are extremely dependent on gastrin to proliferate. Initial research focused only on the effects of amidated gastrins, but there has been an interest in intermediates of gastrin in the last few decades. These intermediates aren't biologically inactive; in fact, they may exert greater effects on proliferation and apoptosis than the completely processed forms. In certain gastrin overproduction states, they are the most abundant gastrin peptides secreted. The purpose of this review is to examine the gastrin biosynthesis process and to summarize the results from different studies evaluating the production, levels, and effects of the main forms of gastrin in different overexpression states and their possible relationship with Barrett's and colorectal carcinogenesis.

Aim: To evaluate the effects of indomethacin [dual cyclooxygenase (COX)-1/COX-2 inhibitor] and 3-(3,4-difluorophenyl)-4-(4-(methylsulfonyl) phenyl)-2-(5H)-furanone (MF-tricyclic) (COX-2 selective inhibitor) in a rat experimental model of Barrett's esophagus and esophageal adenocarcinoma., Methods: A total of 112 surviving post-surgery rats were randomly divided into three groups: the control group (n = 48), which did not receive any treatment; the indomethacin group (n = 32), which were given 2 mg/kg per day of the COX-1/COX-2 inhibitor; and the MF-tricyclic group (n = 32), which received 10 mg/kg per day of the selective COX-2 inhibitor. Randomly selected rats were killed either 8 wk or 16 wk after surgery. The timing of the deaths was in accordance with a previous study performed in our group. Only rats that were killed at the times designated by the protocol were included in the study. We then assessed the histology and prostaglandin E2 (PGE2) expression levels in the rat esophagi. An additional group of eight animals that did not undergo esophagojejunostomy were included in order to obtain normal esophageal tissue as a control., Results: Compared to a control group with no treatment (vehicle-treated rats), indomethacin treatment was associated with decreases in ulcerated esophageal mucosa (16% vs 35% and 14% vs 17%, 2 mo and 4 mo after surgery, respectively; P = 0.021), length of intestinal metaplasia in continuity with anastomosis (2 ± 1.17 mm vs 2.29 ± 0.75 mm and 1.25 ± 0.42 mm vs 3.5 ± 1.54 mm, 2 mo and 4 mo after surgery, respectively; P = 0.007), presence of intestinal metaplasia beyond anastomosis (20% vs 71.4% and 0% vs 60%, 2 mo and 4 mo after surgery, respectively; P = 0.009), severity of dysplasia (0% vs 71.4% and 20% vs 85.7% high-grade dysplasia, 2 mo and 4 mo after surgery, respectively; P = 0.002), and adenocarcinoma incidence (0% vs 57.1% and 0% vs 60%, 2 mo and 4 mo after surgery, respectively; P < 0.0001). Treatment with the selective COX-2 inhibitor, MF-tricyclic, did not prevent development of intestinal metaplasia or adenocarcinoma. In parallel, we observed a significant decrease in PGE2 levels in indomethacin-treated rats, but not in those treated with MF-tricyclic, at both 2 mo and 4 mo. Compared to control rats that did not undergo surgery (68 ± 8 ng/g, P = 0.0022 Kruskal-Wallis test) there was a significant increase in PGE2 levels in the esophageal tissue of the rats that underwent surgery either 2 mo (1332 ± 656 ng/g) or 4 mo (1121 ± 1015 ng/g) after esophagojejunostomy. However, no differences were found when esophageal PGE2 levels were compared 2 mo vs 4 mo post-esophagojejunostomy. At both the 2- and 4-mo timepoints, we observed a significant decrease in PGE2 levels in indomethacin-treated rat esophagi compared to those in either the control or MF-tricyclic groups (P = 0.049 and P = 0.017, respectively). No differences in PGE2 levels were found when we compared levels in rats treated with MF-tricyclic to not-treated rats., Conclusion: In this rat model of gastrointestinal reflux, indomethacin was associated with a decrease in the severity of esophagitis and reduced development of esophageal intestinal metaplasia and adenocarcinoma.

Cyclooxygenase (COX) inhibition has been shown to prevent the development of esophageal adenocarcinoma (EAC). However, the potential of this approach for treatment of established cancer has been poorly investigated. Our objective was to determine whether non-selective or selective inhibition of the COX pathway affects the growth of esophageal adenocarcinoma xenografts in nude mice. A human esophageal adenocarcinoma xenograft model was established by subcutaneous inoculation of OE33 cells in nude mice. Small tumor slices harvested from four OE33 xenografts were implanted in the flanks of new mice that were randomized to different treatments (6 animals per group): indomethacin (3 mg/kg/day), parecoxib (0.11 and 0.22 mg/kg/day) or a selective prostaglandin E₂ receptor antagonist (AH-23848B, 1 mg/kg/day). For each treatment, a control group of 6 animals (vehicle) carrying xenografts from the same OE33 tumor was included. Tumor growth was measured twice a week. After 8 weeks mice were euthanized. Tumors were assessed by histological analysis, mRNA expression of COX isoenzymes, PGE₂ receptors and PGE₂ content. All OE33 tumors were poorly differentiated esophageal adenocarcinomas. Tumors expressed COX-2, EP₁, EP₂ and EP₄ receptor mRNA. Treatment with parecoxib, higher dose or indomethacin significantly inhibited tumor growth. Furthermore, indomethacin induced tumor regression (74 vs 582% in control animals; p<0.01). However, AH-23848B or parecoxib low dose failed to affect tumor growth significantly. PGE₂ content in tumors was significantly decreased by high-dose parecoxib and indomethacin. Indomethacin and parecoxib inhibit the growth of human esophageal adenocarcinoma xenografts in nude mice, which suggests a potential role for NSAIDs or selective COX-2 inhibitors for EAC chemotherapy.

Epidemiological studies have shown that the regular use of nonsteroidal anti-inflammatory drugs (NSAIDs) is associated with a reduction of gastrointestinal cancer risk. Since up-regulation of COX-2 has been reported in different stages of the esophageal and gastric carcinogenic sequence, the cyclooxygenase-2 selective inhibitors (COXIBs) were considered a good alternative to traditional NSAIDs since they cause less injury to the gastrointestinal mucosa. However, recent chemoprevention trial data reporting an increased risk of cardiovascular events have raised serious concerns on the safety of COXIBs in chemoprevention strategies. Moreover, low expression of COX-2 has been reported in a subset of gastrointestinal cancers due to COX-2 methylation, indicating that these patients could be less responsive to treatment by specific COX-2 inhibitors. Furthermore, the COX-1 isoform may have a potential role in the angiogenic process associated with esophageal adenocarcinoma, which suggests that inhibition of COX-1 may be another effective therapeutic target in upper gastrointestinal cancer. Finally, lipoxygenase-derived products may be increased following COX-inhibition due to shunting of the arachidonic acid metabolism. Specifically, the 5-LOX pathway seems to be relevant in gastrointestinal cancer development. Taken together, these data indicate that a re-evaluation of potential chemoprevention strategies for cancers of the upper gastrointestinal tract needs to be considered.

Accumulating evidence suggests that COX-2-derived prostaglandin E(2) (PGE(2)) plays an important role in esophageal adenocarcinogenesis. Recently, PGE(2) receptors (EP) have been shown to be involved in colon cancer development. Since it is not known which receptors regulate PGE(2) signals in esophageal adenocarcinoma, we investigated the role of EP receptors using a human Barrett's-derived esophageal adenocarcinoma cell line (OE33). OE33 cells expressed COX-1, COX-2, EP(1), EP(2) and EP(4) but not EP(3) receptors as determined by real time RT-PCR and Western-blot. Treatment with 5-aza-dC restored expression, suggesting that hypermethylation is involved in EP(3) downregulation. Endogenous PGE(2) production was mainly due to COX-2, since this was significantly suppressed with COX-2 inhibitors (NS-398 and SC-58125), but not COX-1 inhibitors (SC-560). Cell proliferation ((3)H-thymidine uptake) was significantly inhibited by NS-398 and SC-58125, the EP(1) antagonist SC-51322, AH6809 (EP(1)/EP(2) antagonist), and the EP(4) antagonist AH23848B, but was not affected by exogenous PGE(2). However, treatment with the selective EP(2) agonist Butaprost or 16,16-dimethylPGE(2) significantly inhibited butyrate-induced apoptosis and stimulated OE33 cell migration. The effect of exogenous PGE(2) on migration was attenuated when cells were first treated with EP(1) and EP(4) antagonists. These findings suggest a potential role for EP selective antagonists in the treatment of esophageal adenocarcinoma.

Aim: To test whether antioxidant treatment could prevent the progression of Barrett's esophagus to adenocarcinoma., Methods: In a rat model of gastroduodenoesophageal reflux by esophagojejunal anastomosis with gastric preservation, groups of 6-10 rats were randomized to receive treatment with superoxide dismutase (SOD) or vehicle and followed up for 4 mo. Rat's esophagus was assessed by histological analysis, superoxide anion and peroxinitrite generation, SOD levels and DNA oxidative damage., Results: All rats undergoing esophagojejunostomy developed extensive esophageal mucosal ulceration and inflammation by mo 4. The process was associated with a progressive presence of intestinal metaplasia beyond the anastomotic area (9% 1st mo and 50% 4th mo) (94% at the anastomotic level) and adenocarcinoma (11% 1st mo and 60% 4th mo). These changes were associated with superoxide anion and peroxinitrite mucosal generation, an early and significant increase of DNA oxidative damage and a significant decrease in SOD levels (P<0.05). Exogenous administration of SOD decreased mucosal superoxide levels, increased mucosal SOD levels and reduced the risk of developing intestinal metaplasia beyond the anastomotic area (odds ratio = 0.326; 95%CI: 0.108-0.981; P = 0.046), and esophageal adenocarcinoma (odds ratio = 0.243; 95%CI: 0.073-0.804; P = 0.021)., Conclusion: Superoxide dismutase prevents the progression of esophagitis to Barrett's esophagus and adenocarcinoma in this rat model of gastrointestinal reflux, supporting a role of antioxidants in the chemoprevention of esophageal adenocarcinoma.