Preparing Surrogate Abnormal Quality Control Samples for Platelet Function Studies and Viscoelastic Testing

In the United States, published options for clinical laboratories to perform quality control (QC) procedures less stringent than the regulatory requirements (Clinical and Laboratory Improvement Act, CLIA) based on risk assessment, although the laboratory must perform to manufacturer's minimum requirements. The US requirements for internal quality control requires at least two levels of control material every 24 h of patient testing. For some coagulation testing, the recommended quality control may be a normal sample or commercial controls that do not address all reporting components of the test. Additional circumstances and difficulties in achieving this minimum QC requirement can be due to either (1) nature of the sample type (i.e., whole blood sample requirements), (2) lack of commercial or suitable control material, or (3) unusual or rare samples. The purpose of this chapter is to provide provisional guidance for laboratory sites to prepared samples to verify the performance of reagents and testing performance of platelet function studies and viscoelastic measurements.

Nuclear factor erythroid 2-related factor 2 (NRF2) is a negative regulator of tissue plasminogen activator synthesis in cultured human vascular endothelial EA.hy926 cells

Blood coagulation and the fibrinolytic system contribute to vascular lesions. Fibrinolysis in normal circulating blood strongly depends on the balance between tissue-type plasminogen activator (t-PA) and plasminogen activator inhibitor-1 (PAI-1) secreted from vascular endothelial cells; however, the mechanisms by which endothelial fibrinolysis is regulated remain to be fully understood. In the present study, human vascular endothelial EA.hy926 cells were transfected with small interfering RNA for nuclear factor erythroid 2-related factor 2 (NRF2) and the expression of t-PA and PAI-1 and fibrinolytic activity in the conditioned medium were examined. EA.hy926 cells were also treated with sulforaphane, an NRF2 activator, and fibrinolytic activity was examined to confirm the NRF2 signaling pathway's effect. Enhanced fibrinolytic activity in the conditioned medium was observed in association with increased expression and secretion levels of t-PA in NRF2 knockdown EA.hy926 cells. However, sulforaphane inhibited fibrinolytic activity and t-PA synthesis in EA.hy926 cells without any cell damage. The expression level of PAI-1 did not change in either NRF2 knockdown or sulforaphane treated cells. These results suggest that transcription factor NRF2 may play a role in down-regulating endothelial t-PA synthesis and fibrinolytic activity.

Oriented Immobilization on Gold Nanoparticles of a Recombinant Therapeutic Zymogen

Direct immobilization of functional proteins on gold nanoparticles (AuNPs) affects their structure and function. Changes may vary widely and range from strong inhibition to the enhancement of protein function. More often though the outcome of direct protein immobilization results in protein misfolding and the loss of protein activity. Additional complications arise when the protein being immobilized is a zymogen which requires and relies on additional protein-protein interactions to exert its function. Here we describe molecular design of a glutathione-S-transferase-Staphylokinase fusion protein (GST-SAK) and its conjugation to AuNPs. The multivalent AuNP-(GST-SAK)n complexes generated show plasminogen activation activity in vitro. The methods described are transferable and could be adapted for conjugation and functional analysis of other plasminogen activators, thrombolytic preparations or other functional enzymes.

Bacterial staphylokinase as a promising third-generation drug in the treatment for vascular occlusion

Vascular occlusion is one of the major causes of mortality and morbidity. Blood vessel blockage can lead to thrombotic complications such as myocardial infarction, stroke, deep venous thrombosis, peripheral occlusive disease, and pulmonary embolism. Thrombolytic therapy currently aims to rectify this through the administration of recombinant tissue plasminogen activator. Research is underway to design an ideal thrombolytic drug with the lowest risk. Despite the potent clot lysis achievable using approved thrombolytic drugs such as alteplase, reteplase, streptokinase, tenecteplase, and some other fibrinolytic agents, there are some drawbacks, such as high production cost, systemic bleeding, intracranial hemorrhage, vessel re-occlusion by platelet-rich and retracted secondary clots, and non-fibrin specificity. In comparison, bacterial staphylokinase, is a new, small-size plasminogen activator, unlike bacterial streptokinase, it hinders the systemic degradation of fibrinogen and reduces the risk of severe hemorrhage. A fibrin-bound plasmin-staphylokinase complex shows high resistance to a₂-antiplasmin-related inhibition. Staphylokinase has the potential to be considered as a promising thrombolytic agent with properties of cost-effective production and the least side effects.

Cloning and purification of an anti-thrombotic, chimeric Staphylokinase in Pichia pastoris

There has been an increasing prevalence of cardiovascular diseases such as myocardial infarction and stroke in modern societies because of multiple lifestyle related issues like sedentariness and obesity, alcohol consumption and many more "life-style"factors. The FDA-approved thrombolytics such as Tissue Plasminogen Activator, Streptokinase etc. are used to lyse the clots in thrombotic disorders such as myocardial infarction, stroke etc. but re-occlusion and bleeding that are co-incident to their clinical usage are not addressed. Hence, there is need to develop thrombolytics having properties like increased fibrin clot specificity and thrombin inhibition capability to prevent re-occlusion. In the present work, a fusion protein construct containing two components i.e. Staphylokinase (SAK) and Epidermal Growth Factor (EGF) 4, 5, 6-like domains of human thrombomodulin (THBD) was expressed in Pichia pastoris after genetic optimization. SAK isolated from Staphylococcus aureus is a fibrin-specific plasminogen activator while EGF 4, 5, 6-like domains are reported to be responsible for imparting thrombin inhibition to human thrombomodulin, and therefore, expected could help prevent re-occlusion in the novel construct - SAK_EGF, which is a 43 kDa protein. After expression, it was purified (approx. 13-fold) using two-step purification protocol involving ion-exchange followed by Gel Filtration Chromatography (GFC). The functional characterization including plasminogen activation and thrombin inhibition showed that both the fusion partners viz. SAK and 4,5,6 EGF-like domains retained their respective activities after fusion, confirming it to be a bio-active construct. Thus, this engineered protein could be clinically promising due to the combinatorial effect of fibrin-specific thrombus lysis and prevention of re-occulusion.

Copper diethyldithiocarbamate as an inhibitor of tissue plasminogen activator synthesis in cultured human coronary endothelial cells

Recent developments have shown that organic-inorganic hybrid molecules have the potential to provide useful tools for analyzing biological systems. In the case of fibrinolysis, which is the phenomenon whereby fibrin is degraded by plasmin that has been converted from plasminogen via tissue plasminogen activator (t-PA) secreted from vascular endothelial cells, we hypothesized that there may be organic-inorganic hybrid molecules that could be used to analyze the mechanisms by which endothelial fibrinolysis is regulated. In our present study, we found that a copper complex - copper diethyldithiocarbamate (Cu10) - reduces t-PA activity in a conditioned medium of cultured human coronary endothelial cells by inhibiting the t-PA synthesis without changing the synthesis of plasminogen activator inhibitor type 1, which is a t-PA inhibitor. Copper sulfate, the Cu10 ligand, and zinc/iron complexes with the same Cu10 ligand, did not exhibit such biological activity. These results indicate that Cu10 has the potential to provide a useful tool for finding alternative pathways that downregulate endothelial t-PA synthesis.

Serpins in Venous Thrombosis and Venous Thrombus Resolution

Several serpins function as potent inhibitors of thrombolytic serine proteases. Venous thrombosis is a common and debilitating condition whose incidence is on the rise. Studies using genetically modified mice and inhibitors have shown that the plasminogen activator inhibitors (PAI), PAI-1 and PAI-2, are primary regulators of plasminogen activation and contribute to regulating the resolution of experimental venous thrombi, via inflammatory mechanisms, vascular remodeling, and inhibition of fibrinolysis. Therapies to accelerate venous thrombus resolution would be beneficial, since delayed or incomplete clot resolution frequently leads to postthrombotic syndrome, a long-term complication associated with debilitating limb swelling, pain, and recurrent skin ulceration. Here we describe a useful and reproducible mouse model for the study of venous thrombus resolution involving ligation of the inferior vena cava and elucidation of the molecular and cellular determinants of venous thrombus formation and resolution.

Can the benefits of rtPA treatment for stroke be improved?Rev Neurol (Paris). 2017;173:566-571. [PMID: 28797689 DOI: 10.1016/j.neurol.2017.07.003]

Tissue-type plasminogen activator (tPA) is a serine protease well known to promote fibrinolysis. This is why: its recombinant form (rtPA) can be used, either alone or combined with thrombectomy, to promote recanalization/reperfusion following ischemic stroke. However, its overall benefits are counteracted by some of its side-effects, including incomplete lysis of clots, an increased risk of hemorrhagic transformation and the possibility of neurotoxicity. Nevertheless, better understanding of the mechanisms by which tPA influences brain function and promotes its alteration may help in the design of new strategies to improve stroke therapy.

The Clinical Study of Urokinase-Type Plasminogen Activator and Vascular Endothelial Growth Factor in Gastric Cancer

The aim of this study is to explore the expression and significance of urokinase-type plasminogen activator (u-PA) and vascular endothelial growth factor (VEGF) in gastric cancer, providing a novel insight for the diagnosis and treatment of gastric cancer. The gastric cancer specimens, which were excised from 87 patients and confirmed during July, 2012-July, 2014, were selected as observation group, and the normal tissue next to the tumor (more than 5 cm from the edge of the tumor) from 45 patients were randomly selected as control. u-PA and VEGF were detected by immunohistochemistry for the analysis of the correlation of u-PA and VEGF in two groups. The positive rates of u-PA and VEGF in gastric cancer tissue were 81.61 and 79.31 %, respectively, which were 6.67 and 8.89 % in the control group, respectively. The positive rates in the observation group were obviously higher than those in the control group, and the difference was statistically significant (P < 0.05). Among the 87 gastric cancer tissue samples from the observation group, the positive rates of u-PA and VEGF in the gastric cancer with poor differentiation, lymphatic metastasis, invasion up to serosal layer, and TNM stage III + IV were obviously higher than those in the gastric cancer with high differentiation, non-lymphatic metastasis, invasion not up to the serosal layer, and TNM stage I + II, and the difference was statistically significant (P < 0.05). Among the 87 gastric cancer tissue samples from the observation group, u-PA and VEGF were found to be positive in 60 cases and negative in 7 cases. By comparing the two groups, u-PA and VEGF were positively correlated in gastric cancer tissue (P < 0.05). u-PA and VEGF were highly expressed in gastric cancer tissue, which could be used as the molecular biological indicators to predict the invasion and metastasis potential of gastric cancer. The combination of two factors plays a guiding role in early diagnosis and treatment of gastric cancer.

Enhanced truncated-t-PA (CT-b) expression in high-cell-density fed-batch cultures of Pichia pastoris through optimization of a mixed feeding strategy by response surface methodology

Recently, Pichia pastoris has been the focal point of interest as an expression system for production of many recombinant proteins. The study and optimization of feeding strategy are of major importance to achieve maximum volumetric productivity in fed-batch cultivations. Among different feeding strategies used in P. pastoris fed-batch cultures, those trying to maintain a constant specific growth rate have usually resulted in superior productivities. The objective of the present study was to investigate and optimize the co-feeding of glycerol and methanol to attain maximum expression of t-PA in P. pastoris fed-batch cultures with constant specific growth rate. The experiments were designed by response surface methodology, considering the specific feeding rates of methanol and glycerol as independent variables. In each experiment, glycerol and methanol were fed according to a predetermined equation to maintain a constant specific growth rate. It was found that with glycerol feeding for higher specific growth rates, the inhibitory properties of glycerol are more pronounced, while the best expression level was achieved when the ratio of µ set glycerol to that of methanol was around 1.67. In all specific growth rates tested, almost a similar ratio of the specific glycerol feeding rate to that of methanol led to the maximum protein production and activity. The statistical model predicted the optimal operating conditions for µ set glycerol and that of methanol to be 0.05 and 0.03 h(-1), respectively. Applying the optimum strategy, maximum of 52 g/L biomass, 300 mg/L t-PA and 340,000 IU/mL enzyme activity were obtained.

The plasminogen activation system in neuroinflammation

The plasminogen activation (PA) system consists in a group of proteases and protease inhibitors regulating the activation of the zymogen plasminogen into its proteolytically active form, plasmin. Here, we give an update of the current knowledge about the role of the PA system on different aspects of neuroinflammation. These include modification in blood-brain barrier integrity, leukocyte diapedesis, removal of fibrin deposits in nervous tissues, microglial activation and neutrophil functions. Furthermore, we focus on the molecular mechanisms (some of them independent of plasmin generation and even of proteolysis) and target receptors responsible for these effects. The description of these mechanisms of action may help designing new therapeutic strategies targeting the expression, activity and molecular mediators of the PA system in neurological disorders involving neuroinflammatory processes. This article is part of a Special Issue entitled: Neuro Inflammation edited by Helga E. de Vries and Markus Schwaninger.

Impact of proteolytic enzymes in colorectal cancer development and progression

Tumor invasion and metastasis is a highly complicated, multi-step phenomenon. In the complex event of tumor progression, tumor cells interact with basement membrane and extracellular matrix components. Proteolytic enzymes (proteinases) are involved in the degradation of extracellular matrix, but also in cancer invasion and metastasis. The four categories of proteinases (cysteine-, serine-, aspartic-, and metalloproteinases) are named and classified according to the essential catalytic component in their active site. We and others have shown that proteolytic enzymes play a major role not only in colorectal cancer (CRC) invasion and metastasis, but also in malignant transformation of precancerous lesions into cancer. Tissue and serum-plasma antigen concentrations of proteinases might be of great value in identifying patients with poor prognosis in CRC. Our results, in concordance with others indicate the potential tumor marker impact of proteinases for the early diagnosis of CRC. In addition, proteinases may also serve as potential target molecules for therapeutic agents.

Markers of low activity of tissue plasminogen activator/plasmin are prevalent in schizophrenia patients

INTRODUCTION

Clot buster tissue plasminogen activator (tPA) and its end-product plasmin play a well-defined role in neurochemistry. They mediate a number of events that culminate in tolerance against excitotoxicity, hippocampal neurogenesis, synaptic remodeling, neuronal plasticity, cognitive and emotional processing. Abnormalities in these processes have been implicated in schizophrenia pathogenesis.

METHODS

Laboratory markers of low activity of tPA/plasmin were analyzed in 70 schizophrenia adults (DSM-IV), and 98 age-matched controls, consecutively selected at university hospitals.

RESULTS

All but two patients had positive markers (1-6, mean 2.1). Twenty-nine patients and 11 controls had hyperinsulinemia (44% vs. 11%) and 20 patients and 11 controls had hypertriglyceridemia (29% vs. 11%). Both insulin and triglycerides stimulate production of plasminogen activator inhibitor (PAI)-1, a major tPA inhibitor. Nineteen patients and six controls had hyperhomocysteinemia (27% vs. 6%), a condition that impairs tPA catalytic activity. Fifteen patients (22%) but no controls had free-protein S deficiency, a condition that reduces PAI-1 inhibition. Twenty-one patients (30%) but no controls had 1-3 antiphospholipid antibodies in medium or/high levels. Such antibodies are able to inhibit tPA/plasmin activity. Both PAI-1 polymorphism 4G/5G and heterozygous prothrombin G20210A were more prevalent in patients (60% vs. 48% and 2% vs. 1%, respectively), but difference lacked significance. PAI-1 polymorphism was synergistic with hyperinsulinemia. Protein C deficiency was not detected in patients or controls.

CONCLUSION

We have found a high prevalence of markers of low tPA/plasmin activity in a sample of schizophrenia patients. Our findings should be validated in large studies, preferably in medication-naïve patients.

Reduced fibrinogen, fibrinolytic biomarkers, and physical parameters after a weight-loss program in obese subjects

Background:

Obese subjects are at risk of multiple comorbidities including stroke and coronary heart disease (CHD), which is partly due to disturbances in the hemostatic system.

Aims:

The aims of the present study were to determine the effects of a weight-loss program on fibrinogen and fibrinolytic markers.

Materials and Methods:

Twenty-eight obese subjects were involved in a weight-loss program consisted of exercise and nutritional education for 12-weeks duration. Physical parameters were documented and blood specimen was tested at pre and post-intervention for fibrinogen, tissue plasminogen activator (t-PA), plasminogen activator inhibitor-1 (PAI-1), and thrombin activatable fibrinolysis inhibitor (TAFI). Paired t-test was used for statistical analysis.

Results:

There was a significant decline in the levels of t-PA, PAI-I, TAFI and fibrinogen following the weight-loss program (P < 0.01 for each). A significant positive correlation between tPA levels and body weight, body mass index (BMI), waist circumference, and fat-free mass were found. There was also a significant correlation betwen BMI and other blood parameters.

Conclusion:

Reduced fibrinogen, fibrinolytic, and physical parameters were demonstrated in obese subjects following the weight reduction program. These findings suggest the possible beneficial effects of this program on the hemostatic burden particularly on the fibrinolytic biomarkers.

Nitric oxide increases the invasion of pancreatic cancer cells via activation of the PI3K-AKT and RhoA pathways after carbon ion irradiation

Previous studies have shown that serine proteases and Rho-associated kinase contribute to carbon ion radiation-enhanced invasion of the human pancreatic cancer cell line PANC-1. The results presented here show that nitric oxide synthase (NOS) also plays a critical role in this process. Irradiation of PANC-1 cells promoted invasion and production of nitric oxide (NO), which activated the PI3K-AKT signaling pathway, while independently activating RhoA. Inhibition of PI3K, Rho-associated kinase, and serine protease alone or in conjunction with NOS suppressed the radiation-enhanced invasion of PANC-1 cells, suggesting that they could serve as possible targets for the management of tumor metastasis.

The PLAU P141L single nucleotide polymorphism is associated with collateral circulation in patients with coronary artery disease

INTRODUCTION AND OBJECTIVES

Urokinase-type plasminogen activator, which is encoded by the PLAU gene, plays a prominent role during collateral arterial growth. We investigated whether the PLAU P141L (C > T) polymorphism, which causes a mutation in the kringle domain of the protein, is associated with coronary collateral circulation in a cohort of 676 patients with coronary artery disease.

METHODS

The polymorphism was genotyped in blood samples using a TaqMan-based genotyping assay, and collateral circulation was assessed by the Rentrop method. Multivariate logistic regression models adjusted by clinically relevant variables to estimate odds ratios were used to examine associations of PLAU P141L allelic variants and genotypes with collateral circulation.

RESULTS

Patients with poor collateral circulation (Rentrop 0-1; n = 547) showed a higher frequency of the TT genotype than those with good collateral circulation (Rentrop 2-3; n = 129; P = .020). The T allele variant was also more common in patients with poor collateral circulation (P = .006). The odds ratio of having poorly developed collaterals in patients bearing the T allele (adjusted for clinically relevant variables) was statistically significant under the dominant model (odds ratio = 1.83 [95% confidence interval, 1.16-2.90]; P = .010) and the additive model (odds ratio = 1.73 [95% confidence interval, 1.14-2.62]; P = .009).

CONCLUSIONS

An association was found between coronary collateral circulation and the PLAU P141L polymorphism. Patients with the 141L variant are at greater risk of developing poor coronary collateral circulation.

Direct microscopic monitoring of initial and dynamic clot lysis using plasmin or rt-PA in an in vitro flow system

INTRODUCTION

Plasmin is a direct-acting thrombolytic agent with a favorable safety profile upon intra-arterial delivery in pre-clinical and phase I studies. However, the thrombolytic efficacy of plasmin, relative to that of rt-PA, remains to be established. We have compared the dynamics of clot lysis with plasmin or rt-PA in an in vitro perfusion system, in which thrombolytic agent is administered locally, allowed to induce lysis for short intervals, then washed with plasma in a re-circulation circuit.

MATERIALS AND METHODS

Whole blood human clots were prepared in observation chambers, exposed to plasmin or rt-PA at equimolar concentrations (1.2/1.0, 1.8/1.5 and 2.4/2.0 mg/ml) for measured intervals of time, followed by perfusion with human plasma. Clot size was monitored by digital analysis of sequential photographs obtained through an optical microscope.

RESULTS

Plasma perfusion after incubation with thrombolytic agent rapidly removed superficial clot fragments. This initial decrease in clot size was greater with plasmin than with rt-PA when tested at the highest concentrations of agent (0.63 ± 0.11 vs. 0.30 ± 0.11, p=0.001 for clots with non-cross-linked fibrin and 0.53 ± 0.15 vs. 0.14 ± 0.15, p=0.02, for clots with cross-linked-fibrin). Subsequent clot lysis during plasma flow was greater after prior incubation with rt-PA. Longer incubation times of plasmin resulted in larger portions of the clot being washed free. Repeated plasmin incubations and plasma perfusions of a clot successfully induced stepwise reductions in clot size.

CONCLUSIONS

Initial clot lysis is greater with direct exposure using plasmin than rt-PA. During washout and circulation with plasma, rt-PA induced continued clot lysis, while plasmin lysis was curtailed, presumably because of plasmin inhibition.

Cloning and expression of hybrid streptokinase towards clot-specific activity

Streptokinase (SK) is a thrombolytic agent that is widely used to treat myocardial infarction and pulmonary embolism. The lack of fibrin specificity of SK for the clot lysis is one of the limitations of SK. In this study, we have incorporated the finger and Kringle 2 domains from the human tissue type plasminogen activator gene (t-PA) at the 5' end of the SK gene. These domains are responsible for specific binding to fibrin. We have used the pRSETB vector in an attempt to express the hybrid streptokinase possessing specificity for fibrin. On this regard, three hybrid streptokinase were constructed and expressed in Escherichia coli BL21 (DE3): the finger domain with SK (FSK), the Kringle 2 domain with SK (KSK) and the finger domain+Kringle 2 with SK (FKSK). The activities of the hybrid SKs were assessed by caseinolytic assay and clot lysis assay. All hybrid SKs were found to activate plasminogen in the caseinolytic plate assay. In the clot lysis assay, KSK and FSK were able to dissolute human blood and artificial clots in a fibrin-dependent manner unlike the SK and FKSK proteins.

Tissue-type plasminogen activator is not necessary for platelet-derived growth factor-c activation

Platelet-derived growth factors (PDGFs) are critical for development; their over-expression is associated with fibrogenesis. Full-length PDGF-C is secreted as an inactive dimer, requiring cleavage to allow receptor binding. Previous studies indicate that tissue-type plasminogen activator (tPA) is the specific protease that performs this cleavage; in vivo confirmation is lacking. We demonstrate that primary hepatocytes from tpa KO mice produce less cleaved active PDGF-CC than do wild type hepatocytes, suggesting that tPA is critical for in vitro activation of this growth factor. We developed mice that over-express full-length human PDGF-C in the liver; these mice develop progressive liver fibrosis. To test whether tPA is important for cleavage and activation of PDGF-C in vivo, we intercrossed PDGF-C transgenic (Tg) and tpa knock-out (KO) mice, anticipating that lack of tPA would result in decreased fibrosis due to lack of hPDGF-C cleavage. To measure levels of cleaved, dimerized PDGF-CC in sera, we developed an ELISA that specifically detects cleaved PDGF-CC. We report that the absence of tpa does not affect the phenotype of `PDGF-C Tg mice. PDGF-C Tg mice lacking tPA have high serum levels of cleaved growth factor, significant liver fibrosis, and gene expression alterations similar to those of PDGF-C Tg mice with intact tPA. Furthermore, urokinase plasminogen activator and plasminogen activator inhibitor-1 expression are increased in PDGF-C Tg; tpa KO mice. Our ELISA data suggest a difference between in vitro and in vivo activation of this growth factor, and our mouse model confirms that multiple proteases cleave and activate PDGF-C in vivo.

Expression, purification and characterization of recombinant plasminogen activator from Gloydius brevicaudus venom in Escherichia coli

The plasminogen activator (PA) in snake venom, a serine protease, can convert plasminogen to active plasmin, indirectly causing the degradation of fibrin. It is difficult to purify sufficient snake venom PA (SV-PA) for clinical applications due to the low SV-PA content in venom. The gene encoding PA was obtained from the venom gland of Gloydius brevicaudus using RT-PCR with primers designed according to the N-terminal amino acids of G. brevicaudus venom PA (GBV-PA), was cloned into the prokaryotic expression vector pET-42a, and recombinant GBV-PA (rGBV-PA) was expressed via Isopropyl-β-d-1-Thiogalactopyranoside (IPTG) induction. Like human tissue PA, the purified renatured rGBV-PA could significantly reduce the rabbit plasma euglobulin lysis time (ELT) and prevent thrombus formation in the inferior vena cava of rats. Within the dosage range, the dosage and effects were positively correlated.

Proteinases and their inhibitors in liver cancer

Proteinases are known to be involved in many cancer-related processes, particularly in the breakdown of extracellular matrix barriers in the course of tumor invasion and metastasis. In this review we summarize the current knowledge about the role of the most important matrix-degrading proteinases (cathepsins, matrix metalloproteinases, plasmin/plasminogen activators) and their respective inhibitors in liver cancer progression and metastasis.