Hypoxia-induced des-γ-carboxy prothrombin production in hepatocellular carcinoma

Abstract

Abstract. Des-Á-carboxy prothrombin (DCP) is an established HCC tumor marker, but the precise mechanism of its production is still unclear. Recently, we demonstrated that cytoskeletal changes during epithelial-to-fibroblastoid conversion (EFC) or epithelial mesenchymal transition (EMT) induced by chemicals plays a critical mechanistic role in DCP production via impairment in vitamin K uptake. Our proposed mechanism of DCP production is consistent with substantial clinical evidence. Supplementary vitamin K2 analogues reduced serum DCP levels in hepatocellular carcinoma (HCC) patients. HCC patients with high serum DCP are associated with vascular invasion, metastasis and tumor recurrence. On the other hand, hypoxia has been reported to induce EMT or cytoskeletal changes. Therefore, we examined whether hypoxia induced DCP production during EFC or EMT in HCC cells. Indeed, hypoxic stimulation induced hepatoma cell lines (HepG2 or PLC/PRF/5 cells) to undergo EFC or EMT and these cells produced DCP. Immunofluorescence study demonstrated that hypoxic stimulation impaired labeled low-density lipoprotein uptake, which was a surrogate for vitamin K uptake. In addition, fine filamentous actin network, which has crucial role for clathrin-mediated endocytosis of vitamin K, was disrupted in DCP producing cells by hypoxic stimulation. Thus, hypoxic stimulation induced HCC cells to produce DCP in the same mechanism as chemicals. Furthermore, immunohistochemical study using surgically resected HCC samples showed that a positive staining of nuclear hypoxia inducible factor (HIF)-1· was more frequently observed in HCC cells with stronger staining intensity of DCP. Importantly, clinical observations that DCP as an HCC tumor marker was more useful in larger tumors, which is likely to be exposed with hypoxia during tumor development, support our results.

Epithelial-mesenchymal transitions and hepatocarcinogenesis

“…Second, various events that enhance the efficiency of cancer cell EMT predict cancer invasion, metastasis, and reduced survival in HCC patients. Third, circulating EMT markers are most elevated in HCC patients with metastatic cancer (29,30). The present study by Chen et al advances this field by demonstrating that CDH1L-ARHGEF9-Cdc42 signaling plays an important role in regulating liver cell EMT (4).…”

HIF-1a Plays a Role in the Chemotactic Migration of Hepatocarcinoma Cells Through the Modulation of CXCL6 Expression

“…However, several molecules mediate the effect of HIF-1α in different cancers and its specific tumor-promoting mechanisms in HCC remain unclear. Murata et al showed that HIF-1α overexpression is associated with the production of an abnormal prothrombin, des-γ-carboxyl prothrombin or DCP, a known tumor marker in HCC [22], and HIF-1α promotes angiogenesis and metastasis via the upregulation of vascular endothelial growth factor (VEGF) and matrix metalloproteinases [23,24]. The effect of hypoxia on chemokines and their ligands was examined by Muller et al, who showed that the role of hypoxia in metastasis is mediated by its effect on the chemokine receptor CXCR4, which controls the metastatic homing of tumor cells to organs expressing high levels of its ligand SDF1 [25].…”

Tumor initiation and progression in hepatocellular carcinoma: risk factors, classification, and therapeutic targets

“…Hypoxia is involved in neo-angiogenesis and the formation of new blood vessels, induction of gene expression through the transcription factor Hif1α that regulates more than 50 targets genes and also hypoxia stimulates EMT in HCC [120] involving PI3 kinase/AKT signaling [121][122][123] .…”