title: 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.affiliation: Department of Surgery, Brigham and Women's Hospital, Harvard Medical School, Boston, Massachusetts 02115, USA.
authors.forename: Mark S
authors.initials: MS
authors.lastname: Duxbury
authors.forename: Hiromichi
authors.initials: H
authors.lastname: Ito
authors.forename: Eric
authors.initials: E
authors.lastname: Benoit
authors.forename: Talat
authors.initials: T
authors.lastname: Waseem
authors.forename: Stanley W
authors.initials: SW
authors.lastname: Ashley
authors.forename: Edward E
authors.initials: EE
authors.lastname: Whang
mesh_terms: D000230:Adenocarcinoma / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D015703:Antigens, CD; D000951:Antigens, Neoplasm / Q000096:biosynthesis* / Q000235:genetics; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology*; D000081247:CSK Tyrosine-Protein Kinase; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D015815:Cell Adhesion Molecules / Q000037:antagonists & inhibitors / Q000096:biosynthesis* / Q000235:genetics; D045744:Cell Line, Tumor; D045304:Cytochromes c / Q000378:metabolism; D003841:Deoxycytidine / Q000031:analogs & derivatives* / Q000494:pharmacology*; D024882:Drug Resistance, Viral; D004789:Enzyme Activation; D058851:GPI-Linked Proteins; D020868:Gene Silencing; D006801:Humans; D010190:Pancreatic Neoplasms / Q000188:drug therapy* / Q000235:genetics / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D014162:Transfection; D019061:src-Family Kinases; D000093542:Gemcitabine
chemical_list: D015703:Antigens, CD; D000951:Antigens, Neoplasm; D000964:Antimetabolites, Antineoplastic; C504117:CEACAM6 protein, human; D015815:Cell Adhesion Molecules; D058851:GPI-Linked Proteins; D011518:Proto-Oncogene Proteins; D003841:Deoxycytidine; D045304:Cytochromes c; D011505:Protein-Tyrosine Kinases; D000081247:CSK Tyrosine-Protein Kinase; D019061:src-Family Kinases; C000631346:CSK protein, human; C494918:AKT1 protein, human; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D000093542:Gemcitabine