LAUSR

Simple Summary Cancer patients, particularly with glioblastoma (GBM), are at increased risk for thrombosis. This risk is further increased upon treatment with chemotherapy. Tissue factor (TF) is the initiator of the extrinsic coagulation pathway and expressed by GBM cells. Chemotherapy is known to affect TF expression and activity in several cancer types, but the effect of the commonly used chemotherapeutic agents Temozolomide and Lomustine on TF in GBM is unknown. In this study, we describe a promoting role for these agents on TF procoagulant activity and TF gene and protein expression in three GBM cell lines. This may explain the increased risk of thrombosis in GBM patients undergoing chemotherapy. Our findings may have implications for future GBM treatment since patients with high TF levels may benefit from anticoagulant treatment by decreasing the risk of chemotherapy-induced thrombosis in GBM. Abstract Glioblastoma (GBM) patients have one of the highest risks of venous thromboembolism (VTE), which is even further increased upon treatment with chemotherapy. Tissue factor (TF) is the initiator of the extrinsic coagulation pathway and expressed by GBM cells. In this study, we aimed to examine the effect of routinely used chemotherapeutic agents Temozolomide (TMZ) and Lomustine (LOM) on TF procoagulant activity and expression in GBM cells in vitro. Three human GBM cell lines (U-251, U-87, U-118) were exposed to 100 µM TMZ or 30 µM LOM for 72 h. TF procoagulant activity was assessed via an FXa generation assay and TF gene and protein expression through qPCR and Western blotting. The externalization of phosphatidylserine (PS) was studied using Annexin V flow cytometry. Treatment with TMZ and LOM resulted in increased procoagulant activity in all cell lines. Furthermore, both agents induced procoagulant activity in the supernatant and tumor-cell-secreted extracellular vesicles. In line, TF gene and protein expression were increased upon TMZ and LOM treatment. Additionally, PS externalization and induction of inflammatory-associated genes were observed. Overall, the chemotherapeutic modalities TMZ and LOM induced procoagulant activity and increased TF gene and protein expression in all GBM cell lines tested, which may contribute to the increased VTE risk observed in GBM patients undergoing chemotherapy.