Leptin Stimulates Proliferation and Inhibits Apoptosis in Barrett’s Esophageal Adenocarcinoma Cells by Cyclooxygenase-2-Dependent, Prostaglandin-E2-Mediated Transactivation of the Epidermal Growth Factor Receptor and c-Jun NH2-Terminal Kinase Activation

Abstract

Obesity is an important risk factor for esophageal adenocarcinoma (EAC), and elevated serum leptin is characteristic of obesity. We hypothesized that leptin may have biological effects in promoting esophageal adenocarcinoma and examined the effects of leptin on the OE33 Barrett's-derived EAC line. Proliferation was assessed by dimethylthiazoldiphenyltetra-zoliumbromide and 5-bromo-2'-deoxyuridine incorporation assays and apoptosis by ELISA of intracellular nucleosomes. Intracellular signaling was examined using specific pharmacological inhibitors and direct detection of phosphorylated active kinases. Expression of the long and short leptin receptors by OE33 cells was confirmed by RT-PCR, Western blotting and immunocytochemistry. Leptin stimulated OE33 cell proliferation in a dose-dependent manner and inhibited apoptosis. These effects were dependent on cyclooxygenase (COX)-2 and replicated by adding prostaglandin E2 (PGE2). The effects of PGE2 and leptin were abolished by the EP-4 antagonist AH23848. ERK, p38 MAPK, phosphatidylinositol 3'-kinase/Akt, and Janus tyrosine kinase (JAK)-2 were activated upstream of COX-2 induction, whereas the epidermal growth factor receptor and c-Jun NH2-terminal kinase (JNK) were downstream of COX-2. The activation of ERK and Akt but not p38 MAPK was JAK2 dependent. PGE2 stimulated phosphorylation of JNK in an EGF receptor-dependent manner, and activation of the epidermal growth factor receptor required protein kinase C, src, and matrix metalloproteinase activities. We conclude that leptin stimulates cell proliferation and inhibits apoptosis in OAC cells via ERK, p38 MAPK, phosphatidylinositol 3'-kinase/Akt, and JAK2-dependent activation of COX-2 and PGE2 production. Subsequent PGE2-mediated transactivation of the epidermal growth factor receptor and JNK activation are essential to the leptin effects. These effects may contribute to the greatly increased risk of esophageal adenocarcinoma in obesity.

Effect of adrenotensin on cell proliferation is mediated by angiotensin II in cultured rat mesangial cells

“…In co-treatment experiments, losartan was added 30 min prior to adrenotensin. After 48 h, cell proliferation was assessed by bromodeoxyuridine (BrdU) incorporation assays as described previously [14] . Briefly, 10 µmol/L BrdU labeling solution was added to the medium.…”

Reduced Risk of Barrett’s Esophagus in Statin Users: Case–Control Study and Meta-Analysis

“…Thus it is possible that statin and aspirin impair survival of the Barrett's clone at a very early stage and so impair establishment of a mature Barrett's segment. There are several putative mechanisms that could also be involved: aspirin reduced NF-kB signalling (38), which may in turn alter the nuclear transcription factor milieu that seems to be important in driving the development of Barrett's (39) and statins may influence the secretion of adipokines (such as adiponectin and leptin) which in term seem to influence the behaviour of metaplastic Barrett's epithelial cells (40)(41)(42)(43)(44)). …”

Gastroesophageal Reflux Disease: Molecular Predictors in Neoplastic Progression of Barrett's Esophagus

“…The EP-4 receptor then causes activation of PKC, src, and MMPs, which increase cleavage and extracellular shedding of EGFR ligands, HB-EGF and TGFα. These transactivate an epidermal growth factor receptor (EGFR) (Beales and Ogunwobi, 2007;Ogunwobi et al, 2006;Ogunwobi and Beales, 2008b). Ultimately, C-jun NH 2 terminal kinase (JNK) is then activated which leads to the inhibition of apoptosis and increased proliferation.…”

“…Ultimately, C-jun NH 2 terminal kinase (JNK) is then activated which leads to the inhibition of apoptosis and increased proliferation. It is by this pathway which leptin may predispose obese patients to an increased risk of EAC (Beales and Ogunwobi, 2007;Ogunwobi et al, 2006). Adiponectin is produced solely by white adipose tissue and has been shown to have antiatherogenic, anti-inflammatory, and anti-diabetic actions (Housa et al, 2006;Nishida et al, 2007).…”