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Candidate biomarkers for liver cancer
or aid in the development of sandwich ELISAs, he adds. To quantitate and compare the levels of From an inventory of >70 potential fucosylated proteins in HCC, cirrhosis, and biomarkers, researchers have identified control subjects, the researchers developed 2 that are highly specific and sensitive a lectin fluorophore-linked immunosorfor hepatocellular carcinoma (HCC), or bent assay (FLISA). With this assay, an anliver cancer. In JPR (DOI 10.1021/ tibody directed against the protein of inpr800752c), Anand Mehta and colterest is immobilized on the bottom of a leagues at the Drexel Institute for Bio96-well plate. Sample is added, and the technology and Virology target protein binds to the Research, Immunotope, antibody. If the target protein the Pennsylvania Comis fucosylated, it binds to a monwealth Institute, and biotin-conjugated lectin that the St. Louis University is added to the well. The School of Medicine report lectin-fucose interaction is their findings. detected with a fluorophoreLiver cancer is a quiet, conjugated streptavidin that deadly disease. By the binds to the biotin. time symptoms appear, Of the proteins tested by the prognosis is grim: lectin FLISA, two stood out. most patients die within a Hemopexin and fetuin A few months to a year of were more fucosylated in being diagnosed. Current HCC serum than in cirrhosis diagnostics include a or control serum. To validate blood test for the level of these findings, the researchR-fetoprotein (AFP) and ers analyzed serum samples ultrasound imaging. But Lectin FLISA. (a) A schematic of the lectin FLISA. (b) Fucosylated hemopexin from a separate set of 332 AFP levels are increased and fucosylated fetuin A are elevated in the serum of HCC patients compared subjects with the lectin in only ∼40-60% of pawith levels in subjects with cirrhosis or controls. FLISA. The subjects had tients with liver cancer; HCC, HBV or HCV without thus, many cases are not cirrhosis, a nonviral liver disMehta. To identify proteins that might caught with this assay. Ultrasound is ease, or no liver disease. Again, hemopexin have been missed in the previous effort, expensive and can detect only large and fetuin A were more fucosylated in the investigators used a commercially masses, which typically indicate late HCC samples than in the other samples. available microbead system to remove stages of cancer. According to the analysis, fucosythe 12 most abundant serum proteins, Therefore, Mehta and colleagues lated hemopexin was 92% sensitive which account for ∼95% of the serum have made it their mission to discover and 92% specific for HCC. Fucosylated protein mass. With abundant proteins biomarkers that could be incorporated fetuin A was 72% sensitive and 85% out of the picture, those present at lower into a diagnostic test for early HCC. specific for HCC. Mehta says that these levels could be analyzed more easily. Such a test would be administered to values are much higher than those reAn N-glycan analysis revealed a higher high-risk patients up to three times a ported for AFP, the conventional HCC level of fucosylation in HCC samples year. For example, most cases of liver marker. “We’ve done further studies than in samples from patients with circancer are associated with hepatitis B with these proteins now and combined rhosis or from controls. Next, pooled viral (HBV) or hepatitis C viral (HCV) them with AFP,” explains Mehta. In HCC serum was further fractionated infections, so patients with these infecthis case, the specificity was 100%, and with a lectin that was specific for core tions would be closely monitored. the sensitivity was 75% when cirrhosis fucosylation, and the bound proteins In a previous study (J. Proteome Res. samples were compared with samples were identified by LC/MS/MS. Although 2006, DOI 10.1021/pr050328x), the scienfrom patients with early (stage 1 or 2) some of the proteins were identified in tists found that the levels of fucosylated liver cancer. Much more needs to be the previous study, most of the >50 proproteins were higher in HBV-infected done, however, before these putative teins were new. Surprisingly, a few of the patients who had HCC than in controls markers can be considered bona fide newly isolated proteins weren’t glycoproor HBV-infected patients who did not biomarkers, says Mehta. “We’re still teins, says Mehta. “I think we’re identifyhave liver cancer. To discover biomarktrying to understand the biology of this ing complexes,” he explains. Such binders, the team depleted immunoglobulins change,” he points out. ers could help researchers pull out from serum samples and analyzed the —Katie Cottingham fucosylated proteins for additional study fucosylated proteomes of various sub-
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jects. With this strategy, they identified 19 possible HCC biomarkers and validated a few of these with western blots. Instead of continuing the analysis of these candidates, in the new paper, the researchers took advantage of new developments in protein-depletion technology and started over. One “goal was to dramatically increase the list of potential biomarkers for liver cancer,” explains
Journal of Proteome Research • Vol. 8, No. 2, 2009
10.1021/pr801039y
© 2009 American Chemical Society
