A novel role for carcinoembryonic antigen-related cell adhesion molecule 6 as a determinant of gemcitabine chemoresistance in pancreatic adenocarcinoma cells.

Abstract	Most patients with pancreatic adenocarcinoma present with surgically incurable disease. Gemcitabine, the principal agent used to treat such patients, has little impact on outcome. Overexpression of carcinoembryonic antigen-related cell adhesion molecule (CEACAM) 6, a feature of this malignancy, is associated with resistance to anoikis and increased metastasis. The purpose of this study was to determine the role of CEACAM6 in cellular chemoresistance to gemcitabine. CEACAM6 was stably overexpressed in Capan2 cells, which inherently express very low levels of the protein. Suppression of CEACAM6 expression was achieved in BxPC3 cells, which inherently overexpress CEACAM6, by stable transfection of a CEACAM6 small interfering RNA-generating vector. The effects of modulating CEACAM6 expression on gemcitabine-induced cytotoxicity were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide cytotoxicity assay, flow cytometric apoptosis quantification, caspase profiling, and Western analysis of cytoplasmic cytochrome c release. The roles of Akt and c-Src kinases as downstream targets of CEACAM6 signaling were examined. Stable overexpression of CEACAM6 in Capan2 increased gemcitabine chemoresistance, whereas CEACAM6 gene silencing in BxPC3 markedly increased the sensitivity of these cells to gemcitabine. Differential expression of CEACAM6 modulates Akt activity in a c-Src-dependent manner, and CEACAM6 overexpression appears to protect cells from cytochrome c-induced caspase 3 activation and apoptosis.
Authors	Mark S Duxbury, Hiromichi Ito, Eric Benoit, Talat Waseem, Stanley W Ashley, Edward E Whang
Journal	Cancer research (Cancer Res) Vol. 64 Issue 11 Pg. 3987-93 (Jun 01 2004) ISSN: 0008-5472 [Print] United States
PMID	15173012 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)
Chemical References	Antigens, CD Antigens, Neoplasm Antimetabolites, Antineoplastic CEACAM6 protein, human Cell Adhesion Molecules GPI-Linked Proteins Proto-Oncogene Proteins Deoxycytidine Cytochromes c Protein-Tyrosine Kinases CSK Tyrosine-Protein Kinase src-Family Kinases CSK protein, human AKT1 protein, human Protein Serine-Threonine Kinases Proto-Oncogene Proteins c-akt CASP3 protein, human Caspase 3 Caspases Gemcitabine
Topics	Adenocarcinoma (drug therapy, genetics, metabolism) Antigens, CD Antigens, Neoplasm (biosynthesis, genetics) Antimetabolites, Antineoplastic (pharmacology) CSK Tyrosine-Protein Kinase Caspase 3 Caspases (metabolism) Cell Adhesion Molecules (antagonists & inhibitors, biosynthesis, genetics) Cell Line, Tumor Cytochromes c (metabolism) Deoxycytidine (analogs & derivatives, pharmacology) Drug Resistance, Viral Enzyme Activation GPI-Linked Proteins Gene Silencing Humans Pancreatic Neoplasms (drug therapy, genetics, metabolism) Protein Serine-Threonine Kinases (metabolism) Protein-Tyrosine Kinases (metabolism) Proto-Oncogene Proteins (metabolism) Proto-Oncogene Proteins c-akt Transfection src-Family Kinases Gemcitabine

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