16-16-dimethylprostaglandin-e2 and Adenocarcinoma

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.

Topics: 16,16-Dimethylprostaglandin E2; Adenocarcinoma; Apoptosis; Barrett Esophagus; Blotting, Western; Butyrates; Cell Line, Tumor; Cell Proliferation; Cyclooxygenase 1; Cyclooxygenase 2; Cyclooxygenase 2 Inhibitors; Cyclooxygenase Inhibitors; Dose-Response Relationship, Drug; Esophageal Neoplasms; Humans; Pyrazoles; Receptors, Prostaglandin E; Reverse Transcriptase Polymerase Chain Reaction; Thymidine

Sulindac causes regression of and prevents recurrence of colonic adenomas in patients with familial adenomatous polyposis. Although cell cycle arrest and apoptosis have been proposed, the mechanism of action is poorly understood. In this study, we characterized the growth-inhibitory effects of active metabolites of sulindac in cultured colon adenocarcinoma cells by determining the contribution of apoptosis and cell cycle arrest and the requirement for cyclooxygenase (COX) inhibition and p53 involvement and compared the effects of sulindac metabolites with the chemotherapeutic drug, 5-fluorouracil (5-FU). Time course and dose-response experiments demonstrated that increased apoptosis paralleled the growth-inhibitory effects of the sulfide and sulfone. A relationship among a series of nonsteroidal anti-inflammatory drugs was observed between potency for growth inhibition and ability to induce apoptosis but not potency to inhibit COX. For example, the sulfone was at least 5000-fold less potent than the sulfide for inhibiting COX but only 6.5-fold less potent for inducing apoptosis. Moreover, the prostaglandin analogue, dimethyl-prostaglandin E2, failed to reverse the apoptosis-inducing effects of the sulfide. Sulindac metabolites caused G1 cell cycle arrest in proliferating cells but were comparably effective in nonproliferating cells. In contrast, 5-FU treatment was less effective in nonproliferating cells. Combined treatment with sulindac metabolites and 5-FU did not result in an additive apoptotic response. Treatment of cells with 5-FU increased p53 protein levels, whereas sulindac metabolites did not induce expression. Saos-2 cells, which lack p53, responded to sulindac metabolites but not 5-FU. These results show that apoptosis primarily contributes to growth inhibition by sulindac metabolites. The biochemical pathway does not require COX inhibition or p53 induction and appears to be fundamentally different from the apoptotic response to 5-FU.

Topics: 16,16-Dimethylprostaglandin E2; Adenocarcinoma; Anti-Inflammatory Agents, Non-Steroidal; Apoptosis; Cell Cycle; Cell Division; Cell Survival; Colonic Neoplasms; Cyclooxygenase Inhibitors; Dose-Response Relationship, Drug; Fluorouracil; Growth Inhibitors; Humans; Prostaglandin-Endoperoxide Synthases; Sulindac; Time Factors; Tumor Cells, Cultured; Tumor Suppressor Protein p53

Eicosanoids have been implicated in the pathogenesis of cancer and are known to regulate the expression of antigens of the major histocompatibility complex (MHC). In human colon cancer, we have recently observed that: (a) the expression of MHC class I and II antigens are markedly reduced; and (b) the levels of PGE2, but not of PGF2 alpha and LTB4, are elevated compared to histologically normal mucosa. Therefore, we investigated the effect of PGE2, PGF2 alpha and LTB4 on the regulation of MHC class I antigens in two human colon adenocarcinoma cell lines and in a murine model of colon cancer. None of these eicosanoids had any significant effect on the expression of MHC class I antigens in the human colonocytes or the transcription rate of class I genes, with the exception of LTB4 which only modestly suppressed the transcription rate. Similarly, 16, 16-dimethyl-PGE2 had no effect on the expression of MHC class I genes in the colonocytes of BALB/c mice treated with the carcinogen dimethylhydrazine. We conclude that PGE2, PGF2 alpha and LTB4 did not affect the expression of MHC class I antigens in cultured human colon adenocarcinoma cells, and 16, 16-dimethyl PGE2 did not affect their expression in mice, even when mice were treated with a colon carcinogen. Thus, these eicosanoids are an unlikely regulator of the observed underexpression of MHC class I antigens in human colon cancer.

Topics: 16,16-Dimethylprostaglandin E2; Adenocarcinoma; Animals; Colon; Colonic Neoplasms; Dinoprost; Dinoprostone; Eicosanoids; Gene Expression Regulation, Neoplastic; Genes, MHC Class I; Histocompatibility Antigens Class I; Humans; Leukotriene B4; Male; Mice; Mice, Inbred BALB C; Tumor Cells, Cultured

The effect of 16,16'-dimethyl prostaglandin E2 (dmPGE2) on the human colonic adenocarcinoma derived mucus-secreting goblet cell line HT29-18N2 was investigated. The proliferation rate of HT29-18N2 was increased by exposure to 10 or 100 microM dmPGE2. Exposure to 10 or 100 microM dmPGE2 caused a significant decrease in the rate of radiolabeled glucosamine incorporation into newly synthesized glycoproteins during an 8 or 24 h exposure. At concentrations as low as 1 microM, dmPGE2 accelerated the secretion of mucin glycoproteins as assessed by the release of newly synthesized radiolabeled glycoproteins, a mucin-specific enzyme-linked immunoassay and a whole-mount immunofluorescence assay. A 1 h exposure to dmPGE2 did not, however, result in a morphometrically detectable decrease in intracellular mucous granule stores or elicit any other readily detectable morphological change. The experimental results suggest elevated levels of PGs may contribute to the previously recognized decreases in intracellular mucin stores and shifts in the types of mucins species present at sites of mucosal inflammation in ulcerative colitis patients.

Topics: 16,16-Dimethylprostaglandin E2; Adenocarcinoma; Cell Division; Colonic Neoplasms; Dose-Response Relationship, Drug; Enzyme-Linked Immunosorbent Assay; Glucosamine; Glycoproteins; Humans; Immunohistochemistry; Mucins; Tumor Cells, Cultured

The effect of an exogenous synthetic prostaglandin analogue, 16,16-dimethyl prostaglandin E2 (16,16-dm-PGE2), as well as the effect of endogenous prostaglandin synthesis inhibition by a cyclooxygenase inhibitor, flurbiprofen, on chemically induced gastric carcinogenesis has been investigated in rats. Carcinogenesis was induced by N-methyl-N'-nitro-N-nitrosoguanidine (MNNG; CAS:70-25-7). Animals were divided into six groups: Group I, treatment with MNNG alone; Group II, treatment with 16,16-dm-PGE2 plus MNNG; Group III, treatment with flurbiprofen plus MNNG; Group IV, treatment with 16,16-dm-PGE2 alone; Group V, treatment with flurbiprofen alone; and Group VI, controls. Treatment with high doses of MNNG resulted in rapid development of malignant tumors originating from the glandular epithelium of the stomach and duodenum in animals of all groups receiving the carcinogen. The first gastric adenocarcinoma infiltrating the muscularis proper was detected after 139 days in an animal treated with a combination of MNNG and flurbiprofen. The incidence of infiltrating adenocarcinoma and the incidence of all neoplastic lesions of the glandular stomach were both significantly higher in animals treated with a combination of MNNG and flurbiprofen compared with treatment by MNNG alone or in combination with 16,16-dm-PGE2 (P less than 0.05 and P less than 0.001). The difference in tumor incidence between the last two groups was not significant. The first duodenal adenocarcinoma was detected on Day 114 in another animal of the group treated with MNNG plus flurbiprofen. When compared with the group treated with MNNG plus 16,16-dm-PGE2, significantly more animals developed duodenal adenocarcinoma when treated with MNNG plus flurbiprofen (P less than 0.005) or with MNNG alone (P less than 0.05). Results of this study indicate that inhibition of endogenous prostaglandin synthesis favors development of adenocarcinoma in the glandular stomach of rats. Vice versa, the addition of an exogenous prostaglandin analogue inhibits the development of duodenal adenocarcinoma. This protective effect of prostaglandins may be due to an increase of the thickness of the mucus gel covering the glandular epithelium, thereby preventing access of carcinogen to the mucosa.

Topics: 16,16-Dimethylprostaglandin E2; Adenocarcinoma; Animals; Body Weight; Duodenal Neoplasms; Female; Flurbiprofen; Gastric Mucosa; Methylnitronitrosoguanidine; Prostaglandins; Prostaglandins E, Synthetic; Rats; Rats, Inbred Strains; Stomach Neoplasms