Mechanism of the abnormal vitamin K-dependent gamma-carboxylation process in human hepatocellular carcinomas

Cancer. 1994 Sep 1;74(5):1533-41. doi: 10.1002/1097-0142(19940901)74:5<1533::aid-cncr2820740507>;2-v.


Background: An important marker for hepatocellular carcinoma is the presence of des-gamma-carboxy (abnormal) prothrombin. However, the molecular basis for the reduced carboxylation of prothrombin is unknown.

Methods: Two groups of patients were defined according to the absence (Group I, n = 7) or presence (Group II, n = 8) of des-gamma-carboxy prothrombin. The enzymatic activity of gamma-carboxylase and the total microsomal prothrombin concentration were determined in all tumors. The kinetic parameters for the synthetic peptide Phe-Leu-Glu-Glu-Leu (FLEEL) were measured in eight tumors. The gamma-carboxylase mRNA expression was evaluated by Northern blot analysis in 12 of 15 tumors. In addition, the total vitamin K content (K1, K1 epoxide, and menaquinones 4-10) in 10 tumors was investigated by high performance liquid chromatography.

Results: Concentrations of menaquinones 4-10 were normal in the nontumorous part of the liver but significantly decreased (P = 0.02) in all the tumors (Groups I and II). This decrease was more severe in Group II (P = 0.02). The tumors in Group I had normal or increased gamma-carboxylase activity and increased mRNA expression (P < 0.02) as compared with their nontumorous counterparts. The tumors in Group II were heterogeneous. Five tumors displayed low gamma-carboxylase activity, associated with low mRNA expression in two, whereas two others had high gamma-carboxylase activity and mRNA expression. The concentration of FLEEL at half-maximal velocity was normal in all the tumors examined (Groups I and II), and a relation was found between the level of expression of gamma-carboxylase and the maximal velocity for FLEEL carboxylation in the tumors in Group II (r = 0.98; P < 0.01). The microsomal content of normal prothrombin was within normal limits in all tumors (Groups I and II).

Conclusions: Tumor vitamin K content has a critical role in the synthesis of des-gamma-carboxy prothrombin. Furthermore, the gamma-carboxylase defect, which is observed in some secreting tumors, is the result of the defective gene expression of a normal enzyme and not the consequence of the presence of a competitive inhibitor. It is possible that a 75% reduction in gamma-carboxylase gene expression could take a part in the secretion of des-gamma-carboxy prothrombin, but this mechanism is not predominant.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Biomarkers*
  • Carbon-Carbon Ligases*
  • Carcinoma, Hepatocellular / blood
  • Carcinoma, Hepatocellular / genetics
  • Carcinoma, Hepatocellular / metabolism*
  • Carcinoma, Hepatocellular / pathology
  • Factor V / analysis
  • Gene Expression Regulation, Neoplastic
  • Humans
  • Ligases / analysis
  • Ligases / genetics
  • Ligases / metabolism*
  • Liver / enzymology
  • Liver / metabolism
  • Liver Neoplasms / blood
  • Liver Neoplasms / genetics
  • Liver Neoplasms / metabolism*
  • Liver Neoplasms / pathology
  • Microsomes, Liver / enzymology
  • Protein Precursors / analysis
  • Protein Precursors / genetics
  • Protein Precursors / metabolism*
  • Prothrombin / analysis
  • Prothrombin / genetics
  • Prothrombin / metabolism*
  • RNA / analysis
  • RNA / genetics
  • RNA, Neoplasm / analysis
  • RNA, Neoplasm / genetics
  • Vitamin K / analogs & derivatives
  • Vitamin K / analysis
  • Vitamin K / metabolism*
  • Vitamin K 1 / analogs & derivatives
  • Vitamin K 1 / analysis
  • Vitamin K 2 / analogs & derivatives
  • alpha-Fetoproteins / analysis


  • Biomarkers
  • Protein Precursors
  • RNA, Neoplasm
  • alpha-Fetoproteins
  • Vitamin K 2
  • Vitamin K
  • vitamin K1 oxide
  • menatetrenone
  • acarboxyprothrombin
  • RNA
  • Vitamin K 1
  • Factor V
  • Prothrombin
  • Ligases
  • Carbon-Carbon Ligases
  • glutamyl carboxylase