Identification of a new marker of hepatocellular carcinoma by serum protein profiling of patients with chronic liver diseases

Surface-enhanced laser desorption ionization time-of-flight mass spectrometry (SELDI-TOF MS) is a proteomic technique that enables the profiling of proteins present in any biological material studied. We used this approach to identify new biomarkers of hepatocellular carcinoma (HCC) in the sera of patients with cirrhosis. Sera from 82 patients with cirrhosis, either without (n = 38) or with (n = 44) HCC, were analyzed by SELDI-TOF MS, and the results of the two groups were compared. The most efficient protein peaks leading to discrimination of patients with HCC were selected (receiver operative characteristic curves). The highest-scoring peak combination was established in a first group of serum samples (multinomial regression) and was tested in an independent group. The protein corresponding to the highest discrimination was purified and characterized further. The intensity of 30 protein peaks significantly differed between cirrhotic patients with and without HCC. An algorithm including the six highest-scoring peaks allowed correct classification (presence or absence of HCC) of 92.5% of patients in the test sample set and 90% in the validation sample set. The highest discriminating peak (8,900 Da) was purified further and was characterized as the C-terminal part of the V10 fragment of vitronectin. An in vitro study suggested that the increase of the 8,900-Da fragment in the serum of patients with HCC may proceed from the cleavage of native vitronectin with metalloproteases, a family of enzymes whose activity is enhanced in HCC. In conclusion, global protein profiling is an efficient approach that enabled us to identify a catalytic fragment of vitronectin as a new serum marker of HCC in patients with chronic liver diseases.