Overexpression of glucose-regulated protein 78 in colon cancer.
BACKGROUND
The 78 kDa glucose-regulated protein (GRP78) has been implicated in the development of tumorigenicity, drug resistance, and cytotoxic immunology. We investigated the expression pattern of GRP78 at the protein and mRNA level in human colon carcinoma, colon adenoma and normal colon mucosa.


METHODS
Two-dimensional (2-D) gel electrophoresis, electrospray ionization tandem mass spectrometry, immunoblot analysis, reverse-transcriptase PCR and immunohistochemistry were used on colon normal and cancer tissues.


RESULTS
Comparative 2-D gel electrophoresis of individual-matched colon normal and cancer tissues revealed 15 protein spots with concordantly increased and 20 protein spots with concordantly decreased intensity in tumor tissue. Fourteen of these proteins were identified by tandem mass spectrometry. One of the identified proteins, GRP78, exhibited a marked up-regulation in colon cancer tissue. This result was further confirmed by Western blot and immunohistochemical analysis. Immunohistochemistry also revealed increased cytoplasmic GRP78 expression with progression along the normal tissue-adenoma-carcinoma sequence. However, to our surprise, there was essentially no difference in the relative mRNA expression levels of GRP78 between normal and colon tumors.


CONCLUSIONS
Our findings indicate that overexpression of GRP78 protein may be an important biomarker for malignant transformation, and increased expression might be related with the posttranscriptional regulation of GRP78 in tumor tissues.
Xing
Xiaoming
X
Department of Pathology and Pathophysiology, Center for Environmental Genomics, School of Medicine, Zhejiang University, Hangzhou 310031, PR China.
Lai
Maode
M
Wang
Yinghong
Y
Xu
Enping
E
Huang
Qiong
Q
D015153:Blotting, Western; D003106:Colon / Q000737:chemistry / Q000378:metabolism / Q000473:pathology; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism*; D018450:Disease Progression; D015180:Electrophoresis, Gel, Two-Dimensional; D000091342:Endoplasmic Reticulum Chaperone BiP; D015972:Gene Expression Regulation, Neoplastic; D006360:Heat-Shock Proteins / Q000032:analysis* / Q000235:genetics; D006801:Humans; D007150:Immunohistochemistry; D007413:Intestinal Mucosa / Q000737:chemistry / Q000378:metabolism / Q000473:pathology; D018832:Molecular Chaperones / Q000032:analysis* / Q000235:genetics; D020543:Proteome / Q000032:analysis / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D021241:Spectrometry, Mass, Electrospray Ionization
D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D006360:Heat-Shock Proteins; D018832:Molecular Chaperones; D020543:Proteome; D012333:RNA, Messenger