title: Mechanism study of peptide GMBP1 and its receptor GRP78 in modulating gastric cancer MDR by iTRAQ-based proteomic analysis.
abstract: BACKGROUND
  Multidrug resistance (MDR) is a major obstacle to the treatment of gastric cancer (GC). Using a phage display approach, we previously obtained the peptide GMBP1, which specifically binds to the surface of MDR gastric cancer cells and is subsequently internalized. Furthermore, GMBP1 was shown to have the potential to reverse the MDR phenotype of gastric cancer cells, and GRP78 was identified as the receptor for this peptide. The present study aimed to investigate the mechanism of peptide GMBP1 and its receptor GRP78 in modulating gastric cancer MDR.
  
  
  METHODS
  Fluorescence-activated cell sorting (FACS) and immunofluorescence staining were used to investigate the subcellular location and mechanism of GMBP1 internalization. iTRAQ was used to identify the MDR-associated downstream targets of GMBP1. Differentially expressed proteins were identified in GMBP1-treated compared to untreated SGC7901/ADR and SGC7901/VCR cells. GO and KEGG pathway analyses of the differentially expressed proteins revealed the interconnection of these proteins, the majority of which are involved in MDR. Two differentially expressed proteins were selected and validated by western blotting.
  
  
  RESULTS
  GMBP1 and its receptor GRP78 were found to be localized in the cytoplasm of GC cells, and GRP78 can mediate the internalization of GMBP1 into MDR cells through the transferrin-related pathway. In total, 3,752 and 3,749 proteins were affected in GMBP1-treated SGC7901/ADR and SGC7901/VCR cells, respectively, involving 38 and 79 KEGG pathways. Two differentially expressed proteins, CTBP2 and EIF4E, were selected and validated by western blotting.
  
  
  CONCLUSIONS
  This study explored the role and downstream mechanism of GMBP1 in GC MDR, providing insight into the role of endoplasmic reticulum stress protein GRP78 in the MDR of cancer cells.
authors.affiliation: State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, 127 Changle Western Road, Xi'an, 710032, China. xiaojuan318318@163.com.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, 127 Changle Western Road, Xi'an, 710032, China. lyn810828@163.com.
authors.forename: Yani
authors.initials: Y
authors.lastname: Li
authors.affiliation: State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, 127 Changle Western Road, Xi'an, 710032, China. 471845102@qq.com.
authors.forename: Guanghui
authors.initials: G
authors.lastname: Xu
authors.affiliation: State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, 127 Changle Western Road, Xi'an, 710032, China. olorin183795@gmail.com.
authors.forename: Muhan
authors.initials: M
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, 127 Changle Western Road, Xi'an, 710032, China. xuelin214209@126.com.
authors.forename: Lin
authors.initials: L
authors.lastname: Xue
authors.affiliation: State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, 127 Changle Western Road, Xi'an, 710032, China. fmmullj@126.com.
authors.forename: Lijuan
authors.initials: L
authors.lastname: Liu
authors.affiliation: State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, 127 Changle Western Road, Xi'an, 710032, China. husijun211@aliyun.com.
authors.forename: Sijun
authors.initials: S
authors.lastname: Hu
authors.affiliation: State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, 127 Changle Western Road, Xi'an, 710032, China. yingzhcindy@126.com.
authors.forename: Ying
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, 127 Changle Western Road, Xi'an, 710032, China. yongznie@fmmu.edu.cn.
authors.forename: Yongzhan
authors.initials: Y
authors.lastname: Nie
authors.affiliation: State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, 127 Changle Western Road, Xi'an, 710032, China. liangsh@fmmu.edu.cn.
authors.forename: Shuhui
authors.initials: S
authors.lastname: Liang
authors.affiliation: State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, 127 Changle Western Road, Xi'an, 710032, China. wangbiaoluodoc@163.com.
authors.forename: Biaoluo
authors.initials: B
authors.lastname: Wang
authors.affiliation: State Key Laboratory of Cancer Biology and Xijing Hospital of Digestive Diseases, Xijing Hospital, Fourth Military Medical University, 127 Changle Western Road, Xi'an, 710032, China. dingjie@fmmu.edu.cn.
authors.forename: Jie
authors.initials: J
authors.lastname: Ding
mesh_terms: D000969:Antinematodal Agents / Q000494:pharmacology*; D004317:Doxorubicin / Q000494:pharmacology; D018432:Drug Resistance, Multiple; D019008:Drug Resistance, Neoplasm; D004354:Drug Screening Assays, Antitumor; D004357:Drug Synergism; D000091342:Endoplasmic Reticulum Chaperone BiP; D006360:Heat-Shock Proteins / Q000378:metabolism*; D006801:Humans; D009842:Oligopeptides / Q000494:pharmacology*; D021381:Protein Transport; D020543:Proteome / Q000378:metabolism; D013274:Stomach Neoplasms; D014750:Vincristine / Q000494:pharmacology
chemical_list: D000969:Antinematodal Agents; D000091342:Endoplasmic Reticulum Chaperone BiP; C000604907:GMBP1 peptide; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D009842:Oligopeptides; D020543:Proteome; D014750:Vincristine; D004317:Doxorubicin