Modulation of growth in human esophageal adenocarcinoma cells by group IIa secretory phospholipase A₂

Objective

Esophageal adenocarcinoma is thought to arise from lesions produced by chronic esophageal inflammation. Secretory phospholipase A₂ is an important mediator of mucosal response to gastroesophageal reflux, but its role in the function of mature cancer cells is unclear. We sought to determine the influence of group IIa secretory phospholipase A₂ on proliferation of human esophageal adenocarcinoma cells.

Methods

FLO-1 and OE33 cells derived from human esophageal adenocarcinoma were cultured with standard techniques. Cells were treated with 1-, 5-, 10-, and 20-μmol/L doses of 5-(4-benzyloxyphenyl)-4S-(7-phenylheptanoylamino)pentanoic acid, a specific inhibitor of group IIa secretory phospholipase A₂, for 72 hours. Gene for group IIa secretory phospholipase A₂ (PLA2G2A) was overexpressed and silenced with lentiviral infection techniques. Cell proliferation and viability were measured with standard 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide and bromodeoxyuridine incorporation assays. All assays were performed in triplicate. PLA2G2A expression was measured with quantitative reverse transcriptase polymerase chain reaction; protein levels were detected with immunofluorescence microscopy. Statistical analysis was by analysis of variance with Fisher post hoc analysis.

Results

Secretory phospholipase A₂ protein was found in both malignant esophageal adenocarcinoma cell lines. Treatment with specific group IIa secretory phospholipase A₂ inhibitor resulted in dose-dependent reductions in growth and cell number in both cell lines. Overexpression of PLA2G2A resulted in enhanced cancer cell growth, whereas gene knockdown attenuated growth.

Conclusions

Group IIa secretory phospholipase A₂ appears significant in growth and proliferation of human esophageal adenocarcinoma cells. Secretory phospholipase A₂ inhibition should be studied further regarding potential chemopreventive and therapeutic properties in esophageal adenocarcinoma.

CTSNet classification: 7

Abbreviations and Acronyms: 5-LOX, 5-lipoxygenase, BrdU, bromodeoxyuridine, COX-2, cyclooxygenase-2 FBS, fetal bovine serum, GFP, transgene for green fluorescent protein, LDH, lactate dehydrogenase, LVUT, lentiviral expression vector pLVUT-tTR-KRAB, MTT, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, PBS, phosphate-buffered saline solution, PCR, polymerase chain reaction, PGE₂, prostaglandin E₂, PLA2G2A, gene for group IIa secretory phospholipase A₂, RT-PCR, reverse transcriptase polymerase chain reaction, shRNA, short hairpin RNA, sPLA₂, secretory phospholipase A₂