γ-Carboxyglutamic acid content of hepatocellular carcinoma-associated des-γ-carboxy prothrombin

Abstract

Serum des-gamma-carboxy prothrombin (DCP) is a useful marker for the diagnosis of hepatocellular carcinoma (HCC), but the exact mechanism of its synthesis and its structural properties in liver diseases are unknown. DCP is measured by the monoclonal antibody MU-3. The purpose of this study was to examine the epitope of MU-3 and to characterize the differences in DCP between HCC and benign liver diseases. The epitope of MU-3 was examined by ELISA using prothrombin Gla domain polypeptides and was determined to be amino acid residues 17-27 of the prothrombin Gla domain, which has four gamma-carboxyglutamic acid residues (Gla) at positions 19, 20, 25 and 26. Peptides having a glutamic acid residue (Glu) at these positions reacted strongly to MU-3 but lost reactivity when Glu 19 or 20 was changed to Gla. In the order of gamma-carboxylation, MU-3 reacted strongly to DCP containing 0-1 Gla, weakly to 2-4 Gla and not at all to DCP containing more than five Gla. After adsorbing normal prothrombin with barium carbonate, DCP reaction to MU-3 was measured by determining the amount of DCP that was adsorbed by MU-3-coated beads. The proportion of DCP reacting to MU-3 in HCC was 41.0-76.8%, whereas in patients with benign liver diseases, only 0-42.1% reacted to MU-3. These results indicate that DCP variants preferentially synthesized in HCC have less than four Gla, which are restricted to positions 16, 25, 26 and 29, whereas DCP variants in benign liver diseases have more than five Gla.

Des-γ-Carboxy Prothrombin (DCP) as a Potential Autologous Growth Factor for the Development of Hepatocellular Carcinoma

“…These Gla residues are originally glutamic acid (Glu) residues in prothrombin precursor. The ten Glu residues are respectively at the positions of 6, 7, 14, 16, 19, 20, 25, 26, 29, and 32 in N-terminal domain [1,12]. In hepatocyte, these Glu residues must be converted into Gla residues before prothrombin obtains the coagulation activity.…”

“…DCP lacks the activity of interacting with other coagulation factors [1,2]. Since Liebman et al reported an elevated plasma DCP in patients with HCC, DCP has been considered as a specific marker for diagnosis of HCC [3,4,5,6].…”

Des-gamma-carboxy prothrombin as an important prognostic indicator in patients with small hepatocellular carcinoma

“…DCP is an abnormal prothrombin that is produced by under-carboxylation of normal prothrombin [37] . Suzuki et al [38] reported that DCP exerts a mitogenic effect on hepatocellular carcinoma cells via a Met-Janus kinase 1-STAT3 signaling pathway.…”

Vitamin K₂ Inhibits the Growth of Hepatocellular Carcinoma via Decrease of Des-Gamma-Carboxy Prothrombin

“…So far, the precise mechanism underlying DCP production is still controversial. Prothrombin is synthesized in the liver depending on the presence of vitamin K-dependent ␥ -glutamyl carboxylase in the posttranslational process [4][5][6]20] . The prothrombin precursor has 10 Glu residues in the N-terminus that are converted into ␥ -carboxy-glutamic acid (Gla) residues by ␥ -glutamyl carboxylase in the presence of vitamin K [21] .…”

“…It has been shown that recurrence and metastasis are more frequent in HCC patients with positive des-␥ -carboxy prothrombin (DCP) than in patients with negative DCP [2][3][4] . DCP (also known as protein induced by vitamin K absence or antagonist-II) is an abnormal prothrombin that is not completely carboxylated by the shortage of vitamin K [5] . Recently, DCP has been reported as a potential autologous growth factor for HCC development.…”