Cleavage of endoplasmic reticulum proteins in hepatocellular carcinoma: Detection of generated fragments in patient sera.
OBJECTIVE
In the past decade, there has been a rising incidence of hepatocellular carcinoma (HCC) and a progressive increase in HCC-related mortality in the United States and Western Europe. The poor survival of patients with HCC is largely related to the lack of reliable tools for early diagnosis.


METHODS
We have applied proteomics tools to the comparative analysis of protein profiles between HCC and adjacent nontumor tissues as a means for discovering novel molecular markers.


RESULTS
Forty-seven protein spots that showed reproducible variation were identified by mass spectrometry, corresponding to 23 distinct genes. A positive correlation between transcript and protein level variations was observed for only 7 out of the 23 genes. Proteolytic cleavage accounted for the discrepancies between messenger RNA and protein level changes for 7 genes including calreticulin, PDIA3, PDI, and GRP78. We detected a fragment of each of these 4 endoplasmic reticulum proteins in the culture supernatant of the PLC-PRF5 hepatoma cell line, suggesting that their cleavage leads to release of selected cleaved products in the extracellular compartment. We also detected calreticulin and PDIA3 cleavage products in sera of patients with HCC. A statistically highly significant difference in calreticulin and PDIA3 fragment serum levels between patients with HCC and healthy individuals was observed. Amounts of calreticulin and PDIA3 fragments were also significantly different between patients with HCC and at-risk patients (patients with chronic hepatitis or cirrhosis).


CONCLUSIONS
Specific isoforms in general and cleavage products in particular should therefore be further evaluated as new markers for HCC.
Chignard
Nicolas
N
Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, Michigan, USA.
Shang
Sufen
S
Wang
Hong
H
Marrero
Jorge
J
Bréchot
Christian
C
Hanash
Samir
S
Beretta
Laura
L
D014408:Biomarkers, Tumor / Q000097:blood* / Q000378:metabolism*; D006528:Carcinoma, Hepatocellular / Q000235:genetics / Q000378:metabolism; D015180:Electrophoresis, Gel, Two-Dimensional; D004721:Endoplasmic Reticulum / Q000235:genetics / Q000378:metabolism; D000091342:Endoplasmic Reticulum Chaperone BiP; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006801:Humans; D015151:Immunoblotting; D008113:Liver Neoplasms / Q000378:metabolism / Q000473:pathology; D008297:Male; D013058:Mass Spectrometry; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism; D040901:Proteomics; D012016:Reference Values; D012494:Sampling Studies; D012680:Sensitivity and Specificity; D014407:Tumor Cells, Cultured; D039221:mRNA Cleavage and Polyadenylation Factors / Q000235:genetics* / Q000378:metabolism
D014408:Biomarkers, Tumor; D000091342:Endoplasmic Reticulum Chaperone BiP; C000717247:HSPA5 protein, human; D009363:Neoplasm Proteins; D039221:mRNA Cleavage and Polyadenylation Factors