title: Glucose-regulated protein 78 mediates the therapeutic efficacy of 17-DMAG in colon cancer cells.
abstract: Glucose-regulated protein 78 (GRP78) is expressed as part of the molecular response to endoplasmic reticulum (ER) stress and mediates protein folding within the cell. GRP78 is also an important biomarker of cancer progression and the therapeutic response of patients with different cancer types. However, the role of GRP78 in the cytotoxic effect of 17-DMAG in colon cancer cells remains unclear. GRP78 expression was knocked down by small interfering RNA (siRNA). The anticancer effects of 17-DMAG were assessed by an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, a flow cytometric cell-cycle analysis, and an Annexin V-propidium iodide (PI) apoptotic assay. We found that HT-29 cells expressed a lower level of GRP78 compared with DLD-1 cells. The MTT assay revealed that HT-29 cells were more sensitive to 17-DMAG treatment than DLD-1 cells. GRP78 knock down (GRP78KD) cells demonstrated an increased sensitivity to 17-DMAG treatment compared with the scrambled control cells. Based on the cell-cycle analysis and Annexin V-PI apoptotic assay, apoptosis dramatically increased in GRP78KD cells compared with scrambled control DLD-1 cells after these cells were treated with 17-DMAG. Finally, we observed a decrease in the level of Bcl-2 and an increase in the levels of Bad and Bax in GRP78KD cells treated with 17-DMAG. These results are consistent with an increased sensitivity to 17-DMAG after knock down of GRP78. The level of GRP78 expression may determine the therapeutic efficacy of 17-DMAG against colon cancer cells.
authors.affiliation: Graduate Institute of Clinical Medicine, College of Medicine, Taipei Medical University, Taipei, Taiwan.
authors.forename: Yu-Jia
authors.initials: YJ
authors.lastname: Chang
authors.forename: Chien-Yu
authors.initials: CY
authors.lastname: Huang
authors.forename: Chin-Sheng
authors.initials: CS
authors.lastname: Hung
authors.forename: Hui-Hsiung
authors.initials: HH
authors.lastname: Liu
authors.forename: Po-Li
authors.initials: PL
authors.lastname: Wei
mesh_terms: D017209:Apoptosis / Q000187:drug effects; D016227:Benzoquinones / Q000008:administration & dosage*; D002453:Cell Cycle / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D003110:Colonic Neoplasms / Q000188:drug therapy* / Q000235:genetics* / Q000473:pathology; D000091342:Endoplasmic Reticulum Chaperone BiP; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D055785:Gene Knockdown Techniques; D020868:Gene Silencing; D018841:HSP90 Heat-Shock Proteins / Q000096:biosynthesis; D019073:HT29 Cells; D006360:Heat-Shock Proteins / Q000235:genetics* / Q000378:metabolism; D006801:Humans; D047029:Lactams, Macrocyclic / Q000008:administration & dosage*; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis; D051028:bcl-2-Associated X Protein / Q000096:biosynthesis; D051025:bcl-Associated Death Protein / Q000096:biosynthesis
chemical_list: C494819:BAD protein, human; C494826:BAX protein, human; D016227:Benzoquinones; D000091342:Endoplasmic Reticulum Chaperone BiP; D018841:HSP90 Heat-Shock Proteins; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D047029:Lactams, Macrocyclic; D019253:Proto-Oncogene Proteins c-bcl-2; D051028:bcl-2-Associated X Protein; D051025:bcl-Associated Death Protein; C448659:17-(dimethylaminoethylamino)-17-demethoxygeldanamycin