Growth inhibitory actions of prothrombin on normal hepatocytes: Influence of matrix

Abstract

Most hepatomas have a defect in prothrombin carboxylation, and can secrete under-carboxylated prothrombin or des-γ-carboxy-prothrombin (DCP), the function of which is unknown. We considered that prothrombin-DCP axis might also be involved in growth control. Hepatocytes and hepatoma cells were treated with prothrombin, and DNA synthesis and cytoskeleton were studied. Prothrombin inhibited DNA synthesis in hepatocytes on fibronectin, but not collagen matrix. Hepatoma cell lines were not inhibited. We found that hepatoma cell matrix conferred resistance to hepatocytes. Prothrombin decreased fibronectin but not collagen amounts, but only in the presence of hepatocytes and not hepatoma cells, indicating that it has a differential action on matrix proteins. It also caused changes in cell shape and actin depolymerization. In vivo, there was a decrease in plasma prothrombin activity after a partial hepatectomy (PH) concomitant with a peak of DNA synthesis by the hepatocyte at 24 h after PH. Injection of warfarin at the time of PH, further inhibited PT activity and enhanced this 24 h peak of DNA synthesis. Furthermore, repeated injection of prothrombin lowered the peak DNA synthesis after PH. The data support the hypothesis that prothrombin can act as a hepatocyte growth inhibitor, likely at the level of fibronectin loss and result in cytoskeletal changes. Hepatomas resist this action, possibly due to their different matrix proteins. This represents a novel mechanism for growth regulation and provides a possible biological significance for the tumor marker DCP.

Integrin α5‐induced EGFR activation by prothrombin triggers hepatocyte apoptosis via the JNK signaling pathway

“…Since K vitamins have been shown to have growth inhibitory activities (Wang et al, 1995; Nishikawa et al, 1995; Hitomi et al, 2005) and prothrombin is a major vitamin K dependent blood coagulation factor, we hypothesized that prothrombin might also be a cell growth regulator. Our previous investigation showed that prothrombin significantly inhibited normal hepatocyte DNA synthesis in fibronectin‐coated culture dishes, confirming that prothrombin is a cell growth inhibitor and this growth inhibitory effect is mediated by cell–matrix interactions (Carr et al, 2007).…”

“…Since our previous data showed that PT inhibits hepatocyte DNA synthesis on fibronectin matrix, and causes fibronectin degradation (Carr et al, 2007), we reasoned that the effects of prothrombin on DNA synthesis inhibition might be related to fibronectiin receptor integrin α5 signaling. We first examined the integrin α5 phosphorylation status.…”

“…We previously showed that prothrombin inhibits normal rat hepatocyte DNA synthesis and induces cell shape changes in fibronectin‐coated dishes (Carr et al, 2007). To examine whether these cell shape changes might be due to apoptosis, we used an end‐labeling TUNEL (TdT‐mediated dUTP nick‐end labeling) assay system to label apoptotic hepatocytes.…”

“…The fact that prothrombin inhibited rat hepatocyte DNA synthesis on fibronectin matrix, suggested to us that fibronectin, or it's receptor integrin α5 might be involved in its signaling mechanisms. Our previous work had shown that prothrombin is able to degrade fibronectin (Carr et al, 2007). The current study shows that prothrombin can also induce prolonged tyrosine phosphorylation of integrin α5, the fibronectin binding protein.…”

Detecting Phenotype-Specific Interactions between Biological Processes from Microarray Data and Annotations

“…Abnormally prolonged prothrombin time, an indication of reduced coagulation function, has been discovered to be associated with aggravated stage in cases of gastric and lung cancer [58], [59]. Moreover, data of [60] supported that prothrombin is involved in cell cycle regulation as a DNA synthesis inhibitor, possibly through an induction of cytoskeleton deorganization. This inhibition was only observed in hepatocytes but not in hepatoma cells likely due to different extracellular matrix (ECM) protein interactions in normal versus cancer condition.…”