Thrombin drives tumorigenesis in colitis-associated colon cancer

Genetic Susceptibility of Thrombin Measurement Levels and the Risk of Colon Adenocarcinoma: A Mendelian Randomization Study

Aims/Background: This investigation sought to establish a possible correlation between thrombin measurement levels and the risk of developing colon adenocarcinoma (COAD). Methods: Thrombin measurement levels were sourced from a study by Pietzner M (2020, PMID: 33328453) and integrated into the IEU database. Data on COAD were obtained from the FinnGen database (2021, C3_COLON_ADENO). Various analytical methods were used to assess the relationship, including inverse variance weighting (IVW), mendelian randomization-Egger (MR-Egger) regression, as well as weighted median and mode techniques. Sensitivity analyses were performed, including Cochran's Q test, MR-Egger intercept test, mendelian randomization Pleiotropy RESidual Sum and Outlier (MR-PRESSO), along with leave-one-out analysis, to ensure the robustness of the results. Results: The IVW analysis indicated a significant inverse association between elevated thrombin levels and the risk of COAD (odds ratio (OR) = 0.76, 95% CI = 0.66-0.88, p = 0.0003). These findings were supported by the weighted median analysis (OR = 0.78, 95% CI = 0.68-0.90, p = 0.0006) and the weighted mode analysis (OR = 0.78, 95% CI = 0.68-0.88, p = 0.0017). Conclusion: This research identified an inverse causal relationship between thrombin measurement levels and the incidence of COAD, suggesting that higher thrombin levels are associated with a reduced risk of developing COAD.

Prothrombin Knockdown Protects Podocytes and Reduces Proteinuria in Glomerular Disease

Chronic kidney disease (CKD) is a leading cause of death, and its progression is driven by glomerular podocyte injury and loss, manifesting as proteinuria. Proteinuria includes urinary loss of coagulation zymogens, cofactors, and inhibitors. Importantly, both CKD and proteinuria significantly increase the risk of thromboembolic disease. Prior studies demonstrated that anticoagulants reduced proteinuria in rats and that thrombin injured cultured podocytes. Herein we aimed to directly determine the influence of circulating prothrombin on glomerular pathobiology. We hypothesized that (pro)thrombin drives podocytopathy, podocytopenia, and proteinuria. Glomerular proteinuria was induced with puromycin aminonucleoside (PAN) in Wistar rats. Circulating prothrombin was either knocked down using a rat-specific antisense oligonucleotide or elevated by serial intravenous infusions of prothrombin protein, which are previously established methods to model hypo- (LoPT) and hyper-prothrombinemia (HiPT), respectively. After 10 days (peak proteinuria in this model) plasma prothrombin levels were determined, kidneys were examined for (pro)thrombin co-localization to podocytes, histology, and electron microscopy. Podocytopathy and podocytopenia were determined and proteinuria, and plasma albumin were measured. LoPT significantly reduced prothrombin colocalization to podocytes, podocytopathy, and proteinuria with improved plasma albumin. In contrast, HiPT significantly increased podocytopathy and proteinuria. Podocytopenia was significantly reduced in LoPT vs. HiPT rats. In summary, prothrombin knockdown ameliorated PAN-induced glomerular disease whereas hyper-prothrombinemia exacerbated disease. Thus, (pro)thrombin antagonism may be a viable strategy to simultaneously provide thromboprophylaxis and prevent podocytopathy-mediated CKD progression.

Macrophages and platelets in liver fibrosis and hepatocellular carcinoma

During fibrosis, (myo)fibroblasts deposit large amounts of extracellular matrix proteins, thereby replacing healthy functional tissue. In liver fibrosis, this leads to the loss of hepatocyte function, portal hypertension, variceal bleeding, and increased susceptibility to infection. At an early stage, liver fibrosis is a dynamic and reversible process, however, from the cirrhotic stage, there is significant progression to hepatocellular carcinoma. Both liver-resident macrophages (Kupffer cells) and monocyte-derived macrophages are important drivers of fibrosis progression, but can also induce its regression once triggers of chronic inflammation are eliminated. In liver cancer, they are attracted to the tumor site to become tumor-associated macrophages (TAMs) polarized towards a M2- anti-inflammatory/tumor-promoting phenotype. Besides their role in thrombosis and hemostasis, platelets can also stimulate fibrosis and tumor development by secreting profibrogenic factors and regulating the innate immune response, e.g., by interacting with monocytes and macrophages. Here, we review recent literature on the role of macrophages and platelets and their interplay in liver fibrosis and hepatocellular carcinoma.

PARs in the inflammation-cancer transformation of CRC

Colorectal cancer (CRC) is one of the common malignancies with a global trend of increasing incidence and mortality. There is an urgent need to identify new predictive markers and therapeutic targets for the treatment of CRC. Protease-activated receptors (PARs) are a class of G-protein-coupled receptors, with currently identified subtypes including PAR1, PAR2, PAR3 and PAR4. Increasingly, studies suggest that PARs play an important role in the growth and metastasis of CRC. By targeting multiple signaling pathways may contribute to the pathogenesis of CRC. In this review, we first describe recent studies on the role of PARs in CRC inflammation-cancer transformation, focusing on the important role of PARs in signaling pathways associated with inflammation-cancer transformation, and summarize the progress of research on PARs-targeted drugs.

Biological Evaluation, Molecular Docking Analyses, and ADME Profiling of Certain New Quinazolinones as Anti-colorectal Agents

Colorectal carcinogenesis is a complex process, which is linked to dysregulation of human secretory phospholipases A₂ (hsPLA₂-G-IIA, hsPLA₂-G-V, and hsPLA₂-G-X), proteases (cathepsin-B, collagenase, thrombin, elastase, and trypsin), carbohydrate hydrolyzing enzymes (α-amylase and α-glucosidase), and free radical generating enzyme (xanthine oxidoreductase (XOR)). Therefore, some new quinazolinones were synthesized and evaluated as inhibitors against this array of enzymes as well as cytotoxic agents on LoVo and HCT-116 cells of colorectal cancer. Compounds 3g, 10, 8, 3c, and 1c exhibited promising cytotoxic effects with IC₅₀ values ranging from 206.07 to 459.79 μM. Nine compounds showed promising enzymatic inhibitory effects, 3b, 3d, 3f, 5, 1a, and 12 (α-amylase), 8 (thrombin, elastase and trypsin), 10 (hsPLA₂-G-IIA and hsPLA₂-G-V), and 3f (α-glucosidase and XOR). Therefore, the most active inhibitors, were subjected to validated molecular docking studies to identify their affinities and binding modes. The expected physicochemical and pharmacokinetic features of the active candidates, 1a, 1c, 3b, 3c, 3d, 3f, 3g, 5, 8, 10, and 12 were predicted using bioavailability radar charts and boiled-egg graphical representations along with the Lipinski rule of five filter. Collectively, these studies showed the significance of derivatives 1c, 3b, 3c, 3d, 8, 10, and 12 as lead scaffolds for further optimization to develop enzymes inhibitors and anti-colorectal agents.

Survival outcomes with warfarin compared with direct oral anticoagulants in cancer-associated venous thromboembolism in the United States: A population-based cohort study

BACKGROUND

Direct oral anticoagulants (DOACs) have comparable efficacy with low-molecular-weight heparin (LMWH) for the treatment of cancer-associated venous thromboembolism (VTE). Whether there is a mortality benefit of DOACs compared with warfarin in the management of VTE in cancer is not established.

METHODS AND FINDINGS

Utilizing the United States' Surveillance, Epidemiology, and End Results (SEER)-Medicare linked databases from 2012 through 2016, we analyzed overall survival in individuals diagnosed with a primary gastric, colorectal, pancreas, lung, ovarian, or brain cancer and VTE who received a prescription of DOAC or warfarin within 30 days of VTE diagnosis. Patients were matched 1:2 (DOAC to warfarin) through exact matching for cancer stage and propensity score matching for age, cancer site, cancer stage, and time interval from cancer to VTE diagnosis. The analysis identified 4,274 patients who received a DOAC or warfarin for the treatment of VTE within 30 days of cancer diagnosis (1,348 in DOAC group and 2,926 in warfarin group). Patients were of median age 75 years and 56% female. Within the DOAC group, 1,188 (88%) received rivaroxaban, and 160 (12%) received apixaban. With a median follow-up of 41 months, warfarin was associated with a statistically significantly higher overall survival compared to DOACs (median overall survival 12.0 months [95% confidence interval (CI): 10.9 to 13.5] versus 9.9 months [95% CI: 8.4 to 11.2]; hazard ratio (HR) 0.85; 95% CI: 0.78 to 0.91; p < 0.001). Observed differences in survival were consistent across subgroups of cancer sites, cancer stages, and type of VTE. The study limitations include retrospective design with potential for unaccounted confounders along with issues of generalizability beyond the cancer diagnoses studied.

CONCLUSIONS

In this analysis of a population-based registry, warfarin was associated with prolonged overall survival compared to DOACs for treatment of cancer-associated VTE.

Substrate rigidity dictates colorectal tumorigenic cell stemness and metastasis via CRAD-dependent mechanotransduction

Tumor physical microenvironment contributes greatly to the response of tumor cells. However, the mechanism of how extracellular substrate rigidity remodels colorectal cancer (CRC) cell fate and affects CRC progression remains elusive. Here, we show that F-actin regulator KIAA1211, also known as Capping protein inhibiting regulator of actin dynamics (CRAD), negatively correlates with CRC progression, stemness, and metastasis. Mechanistically, decreased CRAD in soft substrates induces Yes-associated protein (YAP) retention in the cytoplasm, restoring the repression effect on stemness markers NANOG and OCT4, thereby promoting CRC stemness and metastasis. Furthermore, CRAD deficiency promotes colorectal tumor cell softening and regulates epithelial-mesenchymal transition (EMT) states, contributing to its metastasis potential. Clinically, CRAD expression is correlated with malignant degrees and metastasis in CRC patients. Our work uncovers a role of CRAD in anticancer and mechanical signal transduction of the extracellular matrix in CRC.

Platelet and Cancer-Cell Interactions Modulate Cancer-Associated Thrombosis Risk in Different Cancer Types

The first cause of death in cancer patients, after tumoral progression itself, is thrombo-embolic disease. This cancer-associated hypercoagulability state is known as Trousseau's syndrome, and the risk for developing thrombotic events differs according to cancer type and stage, as well as within patients. Massive platelet activation by tumor cells is the key mediator of thrombus formation in Trousseau's syndrome. In this literature review, we aimed to compare the interactions between cancer cells and platelets in three different cancer types, with low, medium and high thrombotic risk. We chose oral squamous cell carcinoma for the low-thrombotic-risk, colorectal adenocarcinoma for the medium-thrombotic-risk, and pancreatic carcinoma for the high-thrombotic-risk cancer type. We showcase that understanding these interactions is of the highest importance to find new biomarkers and therapeutic targets for cancer-associated thrombosis.

Coagulome and the tumor microenvironment: an actionable interplay

Human tumors often trigger a hypercoagulable state that promotes hemostatic complications, including venous thromboembolism. The recent application of systems biology to the study of the coagulome highlighted its link to shaping the tumor microenvironment (TME), both within and outside of the vascular space. Addressing this link provides the opportunity to revisit the significance of biomarkers of hemostasis and assess the communication between vasculature and tumor parenchyma, an important topic considering the advent of immune checkpoint inhibitors and vascular normalization strategies. Understanding how the coagulome and TME influence each other offers exciting new prospects for predicting hemostatic complications and boosting the effectiveness of cancer treatment.

Overall survival with warfarin vs. low-molecular-weight heparin in cancer-associated thrombosis

BACKGROUND

When compared with warfarin, low-molecular-weight heparin (LMWH) reduces the incidence of recurrent venous thromboembolism (VTE) in cancer. However, a survival benefit of LMWH over warfarin for the treatment of cancer-associated VTE has not been established.

METHODS

Using the Surveillance, Epidemiology and End Results and Medicare linked database from 2007 through 2016, we identified Medicare beneficiaries (aged ≥66 years) who were: (1) diagnosed with primary gastric, colorectal, pancreatic, lung, ovarian, or brain cancer; (2) diagnosed with cancer-associated VTE; and (3) prescribed LMWH or warfarin within 30 days. The primary outcome was overall survival (OS). Patients were matched 1:1 using exact matching for cancer stage and propensity score matching for cancer diagnosis, age, year of VTE, and time from cancer diagnosis to index VTE. Cox proportional-hazards regression was performed to estimate hazard ratios (HR) and 95% confidence intervals (95% CI).

RESULTS

A total of 9706 patients were included. Warfarin was associated with a significant improvement in OS compared with LMWH (median OS, 9.8 months [95% CI, 9.1-10.4] vs. 7.2 months [95% CI, 6.8-7.8]; HR, 0.86; 95% CI 0.83-0.90; p < .001). The survival advantage was most pronounced in pancreatic (HR 0.82 [95% CI, 0.74-0.90], p < .001) and gastric cancers (HR 0.82 [95% CI, 0.68-0.98], p = .03). The observed differences in survival were consistent across subgroups including cancer stage, age, comorbidity burden, and year of VTE.

CONCLUSIONS

In this population-based study, warfarin was associated with improved OS compared with LMWH for the treatment of cancer-associated VTE.

Cancer animal models in thrombosis research

The cancer-thrombosis relationship has been established for decades, in both cancer biology and in the clinical signs and symptoms seen in cancer patients (thrombosis in cancer patients has been associated with a worse prognosis and survival). As the link between the pathologies becomes clearer, so does the need to develop models that enable researchers to study them simultaneously in vivo. Mouse models have often been used, and they have helped determine molecular pathways between cancer spread and thrombosis in humans. This review is a summary of the current literature that describes the use of cancer mouse models in thrombosis research. We included cancer models that are not yet used in thrombosis research, but that can positively impact this area of research in the near future. We describe the most commonly used techniques to generate thrombosis as well as the mouse strains and cancer cell types that are commonly used along with inoculation techniques. We endeavoured to create a compendium of the different mouse models that are beneficial for cancer-thrombosis research, as understanding these mechanisms is crucial for creating better and more effective treatments for thrombosis in cancer patients.

The Activation of Prothrombin Seems to Play an Earlier Role than the Complement System in the Progression of Colorectal Cancer: A Mass Spectrometry Evaluation

Colorectal cancer (CRC) is the second cause of death in men and the third in women. This work deals with the study of the low molecular weight protein fraction of sera from patients who underwent surgery for CRC and who were followed for several years thereafter. MALDI-TOF MS was used to identify serum peptidome profiles of healthy controls, non-metastatic CRC patients and metastatic CRC patients. A multiple regression model was applied to signals preliminarily selected by SAM analysis to take into account the age and gender differences between the groups. We found that, while a signal m/z 2021.08, corresponding to the C3f fragment of the complement system, appears significantly increased only in serum from metastatic CRC patients, a m/z 1561.72 signal, identified as a prothrombin fragment, has a significantly increased abundance in serum from non-metastatic patients as well. The findings were also validated by a bootstrap resampling procedure. The present results provide the basis for further studies on large cohorts of patients in order to confirm C3f and prothrombin as potential serum biomarkers. Thus, new and non-invasive tests might be developed to improve the classification of colorectal cancer.

C5aR1 is a master regulator in Colorectal Tumorigenesis via Immune modulation

Numerous factors have been claimed to play important roles in colorectal cancer (CRC) tumorigenesis, including myeloid-derived suppressor cells (MDSCs) and other immune cells, cytokines, and chemokines; however, the precise mechanisms of colorectal tumorigenesis remain elusive, and there is a lack of effective preventive treatments. Here, we investigated the role of complement system, a key regulator of immune surveillance and homeostasis, in colorectal tumorigenesis.

Methods: The prototypical CRC model was induced by combined administration of azoxymethane (AOM)/ dextran sulfate sodium (DSS) in Wild-type (WT), C3-, C5-, C5ar1-, and C5ar2-deficient mice. Using flow cytometry, immunohistochemical staining and multiplex bead assay, we profiled the immune cells, cytokines and chemokines. Bone marrow transplantation was employed to determine the contribution of immune cells in colorectal tumorigenesis. Further, we used C5aR1 antagonist PMX205 to investigate the protective role in colorectal tumorigenesis.

Results: Complement was extensively activated in inflamed tissues of AOM/DSS-induced murine CRC model, leading to multifaceted consequences. The deficiency of complement C5 or especially C5ar1, but not C3 almost completely prevented CRC tumorigenesis. C5a/C5aR1 signaling recruited MDSCs into the inflamed colorectum to impair CD8⁺ T cells, and modulated the production of critical cytokines and chemokines, thus initiating CRC. Moreover, the C5aR1 antagonist PMX205 strongly impeded colorectal tumorigenesis. Bone marrow transplantation further revealed that C5aR1 expression by immune cells was critical for colorectal tumorigenesis.

Conclusion: Our study identifies C5a/C5aR1 signaling as a vital immunomodulatory program in CRC tumorigenesis and suggests a feasible preventive strategy.

The Immune Microenvironment and Cancer Metastasis

The dynamic interplay between neoplastic cells and the immune microenvironment regulates every step of the metastatic process. Immune cells contribute to invasion by secreting a cornucopia of inflammatory factors that promote epithelial-to-mesenchymal transition and remodeling of the stroma. Cancer cells then intravasate to the circulatory system assisted by macrophages and use several pathways to avoid recognition by cytotoxtic lymphocytes and phagocytes. Circulating tumor cells that manage to adhere to the vasculature and encounter premetastic niches are able to use the associated myeloid cells to extravasate into ectopic organs and establish a dormant microscopic colony. If successful at avoiding repetitive immune attack, dormant cells can subsequently grow into overt, clinically detectable metastatic lesions, which ultimately account to most cancer-related deaths. Understanding how disseminated tumor cells evade and corrupt the immune system during the final stages of metastasis will be pivotal in developing new therapeutic modalities that combat metastasis.

Cell type-specific mechanisms coupling protease-activated receptor-1 to infectious colitis pathogenesis

BACKGROUND

Protease-activated receptor-1 (PAR-1) plays a major role in multiple disease processes, including colitis. Understanding the mechanisms coupling PAR-1 to disease pathogenesis is complicated by the fact that PAR-1 is broadly expressed across multiple cell types.

OBJECTIVE

Determine the specific contributions of PAR-1 expressed by macrophages and colonic enterocytes to infectious colitis.

METHODS

Mice carrying a conditional PAR-1 allele were generated and bred to mice expressing Cre recombinase in a myeloid- (PAR-1ΔM ) or enterocyte-specific (PAR-1ΔEPI ) fashion. Citrobacter rodentium colitis pathogenesis was analyzed in mice with global PAR-1 deletion (PAR-1-/- ) and cell type-specific deletions.

RESULTS

Constitutive deletion of PAR-1 had no significant impact on weight loss, crypt hypertrophy, crypt abscess formation, or leukocyte infiltration in Citrobacter colitis. However, colonic shortening was significantly blunted in infected PAR-1-/- mice, and these animals exhibited decreased local levels of IL-1β, IL-22, IL-6, and IL-17A. In contrast, infected PAR-1ΔM mice lost less weight and had fewer crypt abscesses relative to controls. PAR-1ΔM mice had diminished CD3+ T cell infiltration into colonic tissue, but macrophage and CD4+ T cell infiltration were similar to controls. Also contrasting results in global knockouts, PAR-1ΔM mice exhibited lower levels of IL-1β, but not Th17-related cytokines (ie, IL-22, IL-6, IL-17A). Infected PAR-1ΔEPI mice exhibited increased crypt hypertrophy and crypt abscess formation, but local cytokine elaboration was similar to controls.

CONCLUSIONS

These studies reveal complex, cell type-specific roles for PAR-1 in modulating the immune response to Citrobacter colitis that are not readily apparent in analyses limited to mice with global PAR-1 deficiency.

[Effect of natural hirudin on angiogenesis of human microvascular endothelial cells]

Objective

To explore the effect of natural hirudin on proliferation of human microvascular endothelial cells (HMVECs) and its preliminary mechanism of promoting angiogenesis.

Methods

Three-dimensional culture models of HMVECs were established in vitro and observed by inverted phase contrast microscopy after 24 hours of culturing. Then, the three-dimensional culture models of HMVECs were treated with different concentrations (1, 4, and 7 ATU/mL) of the natural hirudin, respectively, and Dulbecco's modified Eagle's medium containing 10% fetal bovine serum as control. The cell proliferations of 4 groups were detected by cell counting kit 8 (CCK-8) method at 24, 48, and 72 hours; the angiogenesis of 4 groups were observed by tube formation assay at 24 hours; the expressions of vascular endothelial growth factor (VEGF) and Notch1 of HMVECs in 4 groups were observed by immunofluorescence staining at 24 hours.

Results

The observation of cells in three-dimensional culture models showed that HMVECs attached to Matrigel well, and the cells formed tube structure completely after 24 hours. The results of CCK-8 test showed that the absorbance ( A) value of 1 and 4 ATU/mL groups were higher than that of control group at each time point ( P<0.05), and A value of 4 ATU/mL group was the highest. The A value of 7 ATU/mL group was significantly lower than those of 1 and 4 ATU/mL groups and control group ( P<0.05). The tube formation assay showed that the tube structure was more in 1 and 4 ATU/mL groups than in 7 ATU/mL group and control group, and in 4 ATU/mL group than in 1 ATU/mL group, showing significant differences ( P<0.05). There was no significant difference between 7 ATU/mL group and control group ( P>0.05). The results of immunofluorescence staining showed that compared with control group, the Notch1 expression was higher in 1 and 4 ATU/mL groups and lower in 7 ATU/mL group; and there was significant difference between 4 and 7 ATU/mL groups and control group ( P<0.05). The VEGF expression was higher in 1, 4, and 7 ATU/mL groups than in control group, in 4 ATU/mL group than in 1 and 7 ATU/mL groups, showing significant differences ( P<0.05).

Conclusion

Natural hirudin can promote angiogenesis at low and medium concentrations, but suppress angiogenesis at high concentrations. Its mechanism may be related to the VEGF-Notch signal pathway.

Soft fibrin matrix downregulates DAB2IP to promote Nanog-dependent growth of colon tumor-repopulating cells

Colon cancer stem cells (CSCs) have been shown to be responsible for the recurrence and metastasis of colorectal cancer (CRC). As a crucial microenvironmental factor, extracellular matrix (ECM) stiffness is known to affect the stemness of CSCs. Recently, fibrin deposition in the stroma of CRC was demonstrated to be responsible for tumor development. In this study, we used salmon fibrin gel to provide a 3D ECM for colon cancer cells and investigated its effects on cell growth as well as the underlying mechanisms. Compared with stiff 420 Pascal (Pa) and 1 050 Pa gels, 90 Pa soft fibrin gel was most efficient at isolating and enriching tumor colonies. The size and number of colony formation negatively correlated with gel stiffness. Specifically, these tumor colonies exhibited efficient tumorigenicity, upregulated stem cell markers, and had anti-chemotherapeutic properties and were thus named tumor-repopulating cells (TRCs). More importantly, the self-renewal molecule Nanog was sharply induced in 3D-cultured colon TRCs; further, Nanog siRNA significantly inhibited colony formation, suggesting the indispensable role of Nanog in TRC growth. A subsequent mechanistic study illustrated that Nanog expression could be modulated through fibrin gel stiffness-induced DAB2IP/PI3K/FOXA1 signaling in colon TRCs.

Thrombin Generation and Cancer: Contributors and Consequences

The high occurrence of cancer-associated thrombosis is associated with elevated thrombin generation. Tumour cells increase the potential for thrombin generation both directly, through the expression and release of procoagulant factors, and indirectly, through signals that activate other cell types (including platelets, leukocytes and erythrocytes). Furthermore, cancer treatments can worsen these effects. Coagulation factors, including tissue factor, and inhibitors of coagulation are altered and extracellular vesicles (EVs), which can promote and support thrombin generation, are released by tumour and other cells. Some phosphatidylserine-expressing platelet subsets and platelet-derived EVs provide the surface required for the assembly of coagulation factors essential for thrombin generation in vivo. This review will explore the causes of increased thrombin production in cancer, and the availability and utility of tests and biomarkers. Increased thrombin production not only increases blood coagulation, but also promotes tumour growth and metastasis and as a consequence, thrombin and its contributors present opportunities for treatment of cancer-associated thrombosis and cancer itself.

Protease-Activated Receptors in the Intestine: Focus on Inflammation and Cancer

Protease-activated receptors (PARs) belong to the G protein-coupled receptor (GPCR) family. Compared to other GPCRs, the specificity of the four PARs is the lack of physiologically soluble ligands able to induce their activation. Indeed, PARs are physiologically activated after proteolytic cleavage of their N-terminal domain by proteases. The resulting N-terminal end becomes a tethered activation ligand that interact with the extracellular loop 2 domain and thus induce PAR signal. PARs expression is ubiquitous and these receptors have been largely described in chronic inflammatory diseases and cancer. In this review, after describing their discovery, structure, mechanisms of activation, we then focus on the roles of PARs in the intestine and the two main diseases affecting the organ, namely inflammatory bowel diseases and cancer.

Mechanisms coupling thrombin to metastasis and tumorigenesis

The association of malignancy and thrombophilia is bidirectional, as evidenced by four decades of studies in animal models showing that hemostatic system components support cancer progression. Consistent with this view, clinical studies have suggested that anticoagulants not only limit thromboembolic complications associated with cancer, but also improve survival by impeding cancer progression, and may even prevent the development of cancer. In order to fully capitalize on this association, a detailed understanding of the mechanisms coupling hemostatic factors to cancer pathogenesis is required. Multiple studies have shown that thrombin-mediated procoagulant functions strongly promote metastatic potential. In particular, the platelet/fibrin(ogen) axis has been shown to protect newly formed micrometastases from innate immune surveillance, contribute to creation of a metastatic niche by recruitment of prometastatic inflammatory cells, and promote the epithelial to mesenchymal transition of metastatic cells. Thrombin-mediated functions have also been shown to support tumor growth in some contexts, and have even been linked to tumorigenesis in the setting of inflammation-driven colon cancer. Here, local thrombin-mediated extravascular fibrin deposition, and specifically fibrin-α_Mβ₂ integrin interaction, push intestinal inflammatory cells toward a pro-tumorigenic phenotype, resulting in the elaboration of key cytokines and growth factors that support the proliferation and survival of transformed intestinal epithelial cells. These studies reveal that hemostatic factors can serve as a bridge between pathological inflammation and the development of cancer. As a large proportion of cancers are caused by pathological inflammation, these studies suggest that therapies targeting the nexus between hemostasis and inflammation could be used to prevent cancer development.

Thrombin-unique coagulation system protein with multifaceted impacts on cancer and metastasis

The association between blood coagulation and cancer development is well recognized. Thrombin, the pleiotropic enzyme best known for its contribution to fibrin formation and platelet aggregation during vascular hemostasis, may also trigger cellular events through protease-activated receptors, PAR-1 and PAR-4, leading to cancer progression. Our pioneering findings provided evidence that thrombin contributes to cancer metastasis by increasing adhesive potential of malignant cells. However, there is evidence that thrombin regulates every step of cancer dissemination: (1) cancer cell invasion, detachment from primary tumor, migration; (2) entering the blood vessel; (3) surviving in vasculature; (4) extravasation; (5) implantation in host organs. Recent studies have provided new molecular data about thrombin generation in cancer patients and the mechanisms by which thrombin contributes to transendothelial migration, platelet/tumor cell interactions, angiogenesis, and other processes. Though a great deal is known regarding the role of thrombin in cancer dissemination, there are new data for multiple thrombin-mediated events that justify devoting focus to this topic with a comprehensive approach.

Hypercoagulation and complement: Connected players in tumor development and metastases

Hypercoagulation is a common feature of several tumors to the extent that individuals with coagulation defects often present with occult visceral cancers. Recent evidence has shown that hypercoagulation is not just a mere secondary effect due to the presence of the tumor, rather it actively contributes to tumor development and dissemination. Among the numerous mechanisms that can contribute to cancer-associated hypercoagulation, the ones involving immune-mediated processes are gaining increasing attention. In particular, complement cascade and hypercoagulation are one inducing the other in a vicious circle that involves neutrophil extracellular traps (NETs) formation. Together, in this feedback loop, they can promote the protumorigenic phenotype of immune cells and the protection of tumor cells from immune attack, ultimately favouring tumor development, progression and metastases formation. In this review, we summarize the role of these processes in cancer development and highlight new possible intervention strategies based on anticoagulants that can arrest this vicious circle.

Thrombin inhibition and cyclophosphamide synergistically block tumor progression and metastasis

Cancer is often associated with an increased risk of thrombotic events which are exacerbated by treatment with chemotherapeutics such as cyclosphosphamide (CP). Evidence suggests that thrombin can stimulate tumor progression via formation of fibrin and activation of protease-activated receptors (PARs) and platelets. We examined the effect of co-treatment with CP and dabigatran etexilate, a direct inhibitor of thrombin, using the murine orthotopic 4T1 tumor model. Mice receiving co-treatment with both low dose CP and dabigatran etexilate had significantly smaller mammary tumors and fewer lung metastases than mice treated with CP or dabigratran etexilate alone. Co-treatment with dabigatran etexilate and low dose CP also significantly decreased the number of arginase(+)Gr-1(+)CD11b(+) myeloid derived suppressor cells as well as levels of TGF-β in spleens from tumor bearing mice. 4T1 tumors express procoagulant tissue factor (TF) and spontaneously release TF(+) microparticles which are potent procoagulant factors that promote thrombin generation. Treatment with dabigatran etexilate alone prevented tumor-induced increases in circulating TF(+) microparticles and also decreased the numbers of tumor-induced activated platelets by 40%. These results show that co-treatment with dabigatran etexilate and CP synergistically inhibits growth and metastasis of mammary tumors, suggesting that oral administration of the thrombin inhibitor dabigatran etexilate may be beneficial in not only preventing thrombotic events in cancer patients but also in treating malignant tumors themselves.

Limiting prothrombin activation to meizothrombin is compatible with survival but significantly alters hemostasis in mice

Thrombin-mediated proteolysis is central to hemostatic function but also plays a prominent role in multiple disease processes. The proteolytic conversion of fII to α-thrombin (fIIa) by the prothrombinase complex occurs through 2 parallel pathways: (1) the inactive intermediate, prethrombin; or (2) the proteolytically active intermediate, meizothrombin (fIIa(MZ)). FIIa(MZ) has distinct catalytic properties relative to fIIa, including diminished fibrinogen cleavage and increased protein C activation. Thus, fII activation may differentially influence hemostasis and disease depending on the pathway of activation. To determine the in vivo physiologic and pathologic consequences of restricting thrombin generation to fIIa(MZ), mutations were introduced into the endogenous fII gene, resulting in expression of prothrombin carrying 3 amino acid substitutions (R157A, R268A, and K281A) to limit activation events to yield only fIIa(MZ) Homozygous fII(MZ) mice are viable, express fII levels comparable with fII(WT) mice, and have reproductive success. Although in vitro studies revealed delayed generation of fIIa(MZ) enzyme activity, platelet aggregation by fII(MZ) is similar to fII(WT) Consistent with prior analyses of human fIIa(MZ), significant prolongation of clotting times was observed for fII(MZ) plasma. Adult fII(MZ) animals displayed significantly compromised hemostasis in tail bleeding assays, but did not demonstrate overt bleeding. More notably, fII(MZ) mice had 2 significant phenotypic advantages over fII(WT) animals: protection from occlusive thrombosis after arterial injury and markedly diminished metastatic potential in a setting of experimental tumor metastasis to the lung. Thus, these novel animals will provide a valuable tool to assess the role of both fIIa and fIIa(MZ) in vivo.

Coagulation induced by C3aR-dependent NETosis drives protumorigenic neutrophils during small intestinal tumorigenesis

Excessive activation of blood coagulation and neutrophil accumulation have been described in several human cancers. However, whether hypercoagulation and neutrophilia are linked and involved in cancer development is currently unknown. Here we show that spontaneous intestinal tumorigenesis correlates with the accumulation of low-density neutrophils with a pro-tumorigenic N2 phenotype and unprompted neutrophil extracellular traps (NET) formation. We find that increased circulating lipopolysaccharide induces upregulation of complement C3a receptor on neutrophils and activation of the complement cascade. This leads to NETosis, induction of coagulation and N2 polarization, which prompts tumorigenesis, showing a novel link between coagulation, neutrophilia and complement activation. Finally, in a cohort of patients with small but not large intestinal cancer, we find a correlation between neutrophilia and hypercoagulation. This study provides a mechanistic explanation for the tumour-promoting effects of hypercoagulation, which could be used as a new biomarker or as a therapeutic target.

It is unclear whether cancer-related hypercoagulation and neutrophilia contribute to tumorigenesis. In this study, the authors find that activation of the complement cascade causes hypercoagulation that leads to polarization of neutrophils in a mouse model of intestinal cancer, and show that blocking complement activation can reduce tumour formation.

Mechanistic roles of epithelial and immune cell signaling during the development of colitis-associated cancer

To date, substantial evidence has shown a significant association between inflammatory bowel diseases (IBD) and development of colitis-associated cancer (CAC). The incidence/prevalence of IBD is higher in western countries including the US, Australia, and the UK. Although CAC development is generally characterized by stepwise accumulation of genetic as well as epigenetic changes, precise mechanisms of how chronic inflammation leads to the development of CAC are largely unknown. Preceding intestinal inflammation is one of the major influential factors for CAC tumorigenesis. Mucosal immune responses including activation of aberrant signaling pathways both in innate and adaptive immune cells play a pivotal role in CAC. Tumor progression and metastasis are shaped by a tightly controlled tumor microenvironment which is orchestrated by several immune cells and stromal cells including macrophages, neutrophils, dendritic cells, myeloid derived suppressor cells, T cells, and myofibroblasts. In this article, we will discuss the contributing factors of epithelial as well as immune cell signaling in initiation of CAC tumorigenesis and mucosal immune regulatory factors in the colonic tumor microenvironment. In depth understanding of these factors is necessary to develop novel anti-inflammatory and anti-cancer therapies for CAC in the near future.

Genetic diminution of circulating prothrombin ameliorates multiorgan pathologies in sickle cell disease mice

Sickle cell disease (SCD) results in vascular occlusions, chronic hemolytic anemia, and cumulative organ damage. A conspicuous feature of SCD is chronic inflammation and coagulation system activation. Thrombin (factor IIa [FIIa]) is both a central protease in hemostasis and a key modifier of inflammatory processes. To explore the hypothesis that reduced prothrombin (factor II [FII]) levels in SCD will limit vaso-occlusion, vasculopathy, and inflammation, we used 2 strategies to suppress FII in SCD mice. Weekly administration of FII antisense oligonucleotide "gapmer" to Berkeley SCD mice to selectively reduce circulating FII levels to ∼10% of normal for 15 weeks significantly diminished early mortality. More comprehensive, long-term comparative studies were done using mice with genetic diminution of circulating FII. Here, cohorts of FII(lox/-) mice (constitutively carrying ∼10% normal FII) and FII(WT) mice were tracked in parallel for a year following the imposition of SCD via hematopoietic stem cell transplantation. This genetically imposed suppression of FII levels resulted in an impressive reduction in inflammation (reduction in leukocytosis, thrombocytosis, and circulating interleukin-6 levels), reduced endothelial cell dysfunction (reduced endothelial activation and circulating soluble vascular cell adhesion molecule), and a significant improvement in SCD-associated end-organ damage (nephropathy, pulmonary hypertension, pulmonary inflammation, liver function, inflammatory infiltration, and microinfarctions). Notably, all of these benefits were achieved with a relatively modest 1.25-fold increase in prothrombin times, and in the absence of hemorrhagic complications. Taken together, these data establish that prothrombin is a powerful modifier of SCD-induced end-organ damage, and present a novel therapeutic target to ameliorate SCD pathologies.

Colon Cancer Growth and Dissemination Relies upon Thrombin, Stromal PAR-1, and Fibrinogen

Thrombin-mediated proteolysis is a major determinant of metastasis, but is not universally important for primary tumor growth. Here, we report that colorectal adenocarcinoma represents one important exception whereby thrombin-mediated functions support both primary tumor growth and metastasis. In contrast with studies of multiple nongastrointestinal cancers, we found that the growth of primary tumors formed by murine and human colon cancer cells was reduced in mice by genetic or pharmacologic reduction of circulating prothrombin. Reduced prothrombin expression was associated with lower mitotic indices and invasion of surrounding tissue. Mechanistic investigations revealed that thrombin-driven colonic adenocarcinoma growth relied upon at least two targets of thrombin-mediated proteolysis, protease-activated receptor-1 (PAR-1) expressed by stromal cells and the extracellular matrix protein, fibrinogen. Colonic adenocarcinoma growth was reduced in PAR-1-deficient mice, implicating stromal cell-associated PAR-1 as one thrombin target important for tumor outgrowth. Furthermore, tumor growth was dramatically impeded in fibrinogen-deficient mice, offering the first direct evidence of a critical functional role for fibrinogen in malignant tumor growth. Tumors harvested from fibrinogen-deficient mice displayed a relative reduction in cell proliferative indices, as well as increased tumor necrosis and decreased tumor vascular density. Collectively, our findings established a functional role for thrombin and its targets PAR-1 and fibrinogen in the pathogenesis of colonic adenocarcinoma, supporting tumor growth as well as local invasion and metastasis.

Evasion and interactions of the humoral innate immune response in pathogen invasion, autoimmune disease, and cancer

The humoral innate immune system is composed of three major branches, complement, coagulation, and natural antibodies. To persist in the host, pathogens, such as bacteria, viruses, and cancers must evade parts of the innate humoral immune system. Disruptions in the humoral innate immune system also play a role in the development of autoimmune diseases. This review will examine how Gram positive bacteria, viruses, cancer, and the autoimmune conditions systemic lupus erythematosus and anti-phospholipid syndrome, interact with these immune system components. Through examining evasion techniques it becomes clear that an interplay between these three systems exists. By exploring the interplay and the evasion/disruption of the humoral innate immune system, we can develop a better understanding of pathogenic infections, cancer, and autoimmune disease development.

Factor XIII Transglutaminase Supports the Resolution of Mucosal Damage in Experimental Colitis

The thrombin-activated transglutaminase factor XIII (FXIII) that covalently crosslinks and stablizes provisional fibrin matrices is also thought to support endothelial and epithelial barrier function and to control inflammatory processes. Here, gene-targeted mice lacking the FXIII catalytic A subunit were employed to directly test the hypothesis that FXIII limits colonic pathologies associated with experimental colitis. Wildtype (WT) and FXIII^-/- mice were found to be comparable in their initial development of mucosal damage following exposure to dextran sulfate sodium (DSS) challenge. However, unlike FXIII-sufficient mice, FXIII-deficient cohorts failed to efficiently resolve colonic inflammatory pathologies and mucosal damage following withdrawal of DSS. Consistent with prior evidence of ongoing coagulation factor activation and consumption in individuals with active colitis, plasma FXIII levels were markedly decreased in colitis-challenged WT mice. Treatment of colitis-challenged mice with recombinant human FXIII-A zymogen significantly mitigated weight loss, intestinal bleeding, and diarrhea, regardless of whether cohorts were FXIII-sufficient or were genetically devoid of FXIII. Similarly, both qualitative and quantitative microscopic analyses of colonic tissues revealed that exogenous FXIII improved the resolution of multiple colitis disease parameters in both FXIII^-/- and WT mice. The most striking differences were seen in the resolution of mucosal ulceration, the most severe histopathological manifestation of DSS-induced colitis. These findings directly demonstrate that FXIII is a significant determinant of mucosal healing and clinical outcome following inflammatory colitis induced mucosal injury and provide a proof-of-principle that clinical interventions supporting FXIII activity may be a means to limit colitis pathology and improve resolution of mucosal damage.