title: Claudin-7 increases chemosensitivity to cisplatin through the upregulation of caspase pathway in human NCI-H522 lung cancer cells.
abstract: Claudins are a family of tight junction (TJ) integral membrane proteins that play a crucial role in maintaining cell polarity, adhesion, and paracellular permeability. Changes in expression levels of claudin proteins have been associated with human lung cancer. Previously, we have reported that claudin-7 expression is significantly downregulated in human lung carcinomas. To investigate the role of claudin-7 in lung cancer cells after anti-cancer drug treatments, we transfected claudin-7 cDNA into human NCI-H522 lung cancer cells, which have no detectable expression of claudin-7 protein. Flow cytometry analysis demonstrated that cells transfected with claudin-7 had a significantly higher percentage of cell apoptosis when compared to that of vector transfected cell population. The cell viability assayed by MTT and Annexin V was significantly decreased and cell apoptosis was dramatically increased in claudin-7 transfected cells compared to that of vector transfected cells after cisplatin treatment. Cisplatin is an anti-cancer drug clinically used to treat tumors in several tissues including lung tumors. Most importantly, after cisplatin treatment, the expression levels of cleaved caspase-3, -8, and poly adenosine 5'-diphosphate ribose polymerase (PARP) were much higher in claudin-7 transfected cells than in control cells. Furthermore, using the site-directed mutagenesis approach, we identified that claudin-7 was phosphorylated at serine 204 by protein kinase C. Non-phosphorylated claudin-7 mutant showed increased cell viability, suggesting that phosphorylation increases chemosensitivity to cisplatin treatment. We concluded that claudin-7 expression in H522 lung cancer cells increases chemosensitivity to cisplatin through the increased activation of caspase pathway.
authors: Department of Anatomy and Cell Biology, East Carolina University, Greenville, NC, USA.
authors: John
authors: J
authors: Hoggard
authors: Junming
authors: J
authors: Fan
authors: Zhe
authors: Z
authors: Lu
authors: Qun
authors: Q
authors: Lu
authors: Leonard
authors: L
authors: Sutton
authors: Yan-Hua
authors: YH
authors: Chen
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy / Q000235:genetics / Q000378:metabolism / Q000628:therapy; D000970:Antineoplastic Agents / Q000494:pharmacology*; D017209:Apoptosis / Q000187:drug effects / Q000235:genetics; D053148:Caspase 3 / Q000235:genetics* / Q000378:metabolism; D053181:Caspase 8 / Q000235:genetics / Q000378:metabolism*; D045744:Cell Line, Tumor; D002470:Cell Survival / Q000187:drug effects / Q000235:genetics; D002945:Cisplatin / Q000494:pharmacology*; D057167:Claudins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008175:Lung Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000378:metabolism / Q000628:therapy*; D010766:Phosphorylation / Q000187:drug effects; D011065:Poly(ADP-ribose) Polymerases / Q000235:genetics / Q000378:metabolism; D011493:Protein Kinase C / Q000235:genetics / Q000378:metabolism; D014162:Transfection / Q000379:methods; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D000970:Antineoplastic Agents; C473255:CLDN7 protein, human; D057167:Claudins; D011065:Poly(ADP-ribose) Polymerases; D011493:Protein Kinase C; D053148:Caspase 3; D053181:Caspase 8; D002945:Cisplatin