Unconventional approaches to the prevention of cancer associated thrombosis

Targeting thiol isomerase activity with zafirlukast to treat ovarian cancer from the bench to clinic

Thiol isomerases, including PDI, ERp57, ERp5, and ERp72, play important and distinct roles in cancer progression, cancer cell signaling, and metastasis. We recently discovered that zafirlukast, an FDA-approved medication for asthma, is a pan-thiol isomerase inhibitor. Zafirlukast inhibited the growth of multiple cancer cell lines with an IC50 in the low micromolar range, while also inhibiting cellular thiol isomerase activity, EGFR activation, and downstream phosphorylation of Gab1. Zafirlukast also blocked the procoagulant activity of OVCAR8 cells by inhibiting tissue factor-dependent Factor Xa generation. In an ovarian cancer xenograft model, statistically significant differences in tumor size between control vs treated groups were observed by Day 18. Zafirlukast also significantly reduced the number and size of metastatic tumors found within the lungs of the mock-treated controls. When added to a chemotherapeutic regimen, zafirlukast significantly reduced growth, by 38% compared with the mice receiving only the chemotherapeutic treatment, and by 83% over untreated controls. Finally, we conducted a pilot clinical trial in women with tumor marker-only (CA-125) relapsed ovarian cancer, where the rate of rise of CA-125 was significantly reduced following treatment with zafirlukast, while no severe adverse events were reported. Thiol isomerase inhibition with zafirlukast represents a novel, well-tolerated therapeutic in the treatment of ovarian cancer.

Statin Therapy and the Incidence of Thromboembolism and Vascular Events Following Liver Transplantation

Statin therapy may reduce the risk of venous thromboembolism (VTE), which may impact solid organ transplant outcomes. We evaluated the incidence of VTE and other complications after liver transplantation stratified by hyperlipidemia status and statin use using a retrospective cohort study approach. We reviewed all primary orthotopic liver transplantation (OLT) records from January 2014 to December 2019 from our center. Intraoperative deaths were excluded. Recipient, donor clinical and demographic data were collected. We developed risk-adjusted models to assess the effect of statin use on the occurrence of VTE, hepatic artery complications (HACs), graft failure, and death, accounting for clinical covariates and competing risks. A total of 672 OLT recipients were included in the analysis. Of this cohort, 11.9% (n = 80) received statin therapy. A total of 47 patients (7.0%) had VTE events. HACs occurred in 40 patients (6.0%). A total of 42 (6.1%) patients experienced graft loss, whereas 9.1% (n = 61) of the cohort died during the study interval. Eighty OLT recipients (29.8%) were treated with statins. In the statin treated group, 0% of patients had VTE versus 7.9% of those not on statins (P = 0.02). HACs were identified in 1.2% of the statin group and 6.8% of the nonstatin group. Untreated hyperlipidemia was associated with a 2.1-fold higher risk of HACs versus patients with no hyperlipidemia status (P = 0.05). Statin therapy was associated with significantly better risk-adjusted thromboembolic event-free survival (absence of VTE, cerebrovascular accident, myocardial infarction, HACs, and death); hazard ratio, 2.7; P = 0.01. These data indicate that statin therapy is correlated with a lower rate of VTE and HACs after liver transplantation.

The intersection of protein disulfide isomerase and cancer associated thrombosis

The mechanisms underlying the hypercoagulability of cancer are complex and include the upregulation coagulation factors or procoagulant proteins, shedding of microparticles, and direct activation of vascular cells. Protein disulfide isomerase (PDI) is a thiol isomerase secreted from activated platelets and endothelial cells and plays a critical role in both platelet aggregation and fibrin generation. A number of potential intravascular targets of PDI have been identified including cell surface receptors (e.g. β-integrins and glycoprotein Ib), receptor ligands (e.g. fibrinogen and von Willebrand factor), serine proteases (e.g. cathepsin G and kallekrein-14), and coagulation factors (e.g. factor XI and factor V). Recent clinical studies demonstrated that a small molecule inhibitor of PDI, isoquercetin, decreases platelet-dependent thrombin generation and PDI activity in plasma following oral administration. This review explores the mechanistic overlap between the molecular drivers of cancer associated thrombosis and the potential roles PDI plays in mediating thrombosis. These molecular insights provide rationale for clinical trials targeting PDI to prevent thrombosis in cancer patients.

Statins as a preventative therapy for venous thromboembolism

The anti-inflammatory effects of statins have likely not been used to their fullest extent, particularly in reducing venous thromboembolic events. Current therapy for thrombotic events hinges on anticoagulation via heparin, warfarin or new oral anticoagulants. Interventional procedures with thrombectomy may also play a critical role. Unfortunately, thrombotic events can occur and recur despite meticulous anticoagulation therapy. Venous thromboembolism (VTE) includes both deep vein thrombosis (DVT) and pulmonary embolism (PE), two complicated and prevalent diseases that can cause chronic disease states such as post-thrombotic syndrome (PTS). In 2009 the JUPITER trial demonstrated that rosuvastatin may be effective when dealing with vascular inflammation by providing an anti-inflammatory effect. Multiple subsequent studies have looked at this association with some promising findings. The mechanism of action for statins is not entirely understood but there has been a variety of proposals and subsequent testing of inflammatory biomarkers. Additional prospective trials are needed to confirm the possible benefit of VTE reduction through an anti-inflammatory effect, but if this can be shown then statins may become a safe adjunctive therapy for VTE prevention.