Abstract A002: Ifetroban blocks the metastatic intravascular niches by blocking the platelet activation through thromboxane A2 cascade.
Authors: Toragall Veeresh , Thomas UNIVERSITY OF Werfel  
Published: October 2024

Experimental data indicates that platelets play a crucial role in tumor metastasis, with multiple mechanisms promoting platelet activation and aggregation during tumor evolution. The coagulation and platelet activation systems, particularly Thromboxane A2 (TXA2), a prostanoid product of COX-1, are vital for cancer development and metastasis. Platelet activation aids in immune clearance, cell arrest on the endothelium, and the formation of new lesions. Therefore, we are interested examine a TXA2 antagonist (Ifetroban) efficacy against triple-negative breast cancer (TNBC) metastasis in both in vitro and in vivo models. In vitro interactions of isolated and labeled (cell tracker green) human platelets with MDA-MB-231 RFP cells showed higher activation in the control (100%) group, with a 160% increase in platelet activation observed in U44619 (platelet agonist) pretreated platelets. However, platelet activation was significantly (80%) lower (p&lt;0.05) in Ifetroban pretreated platelets compared to the control, indicating possible blockage of the TXA2 receptor. Flow cytometry analysis of CD-62p marker expression confirmed significantly lower (p&lt;0.05) expression in Ifetroban pretreated platelets compared to U44619 and no-treatment groups. In vivo studies using the 4T1 subcutaneous tumor model (1x10^6 cells) showed higher lung and liver metastatic foci in control animals, while Ifetroban treatment (50 mg/kg BW, oral dosing, pretreatment for 2 weeks before tumor induction and continued until the end) resulted in significantly lower (p&lt;0.05) numbers of lung and liver metastases. Histopathological analysis of lungs and liver confirmed these findings. Additionally, a decrease in tumor volume and weight was observed in Ifetroban-treated animals, although Ifetroban (up to 500 µM) did not show any direct toxic effects on tumor cell lines (MDA-MB-231 and 4T1), indicating its indirect anticancer efficacy by modulating the immune system. Further confirmation came from a xenograft model using Athymic nude mice induced with MDA-MB-231 RFP cells (1x10^6 cells, subcutaneous injection). The treatment regime was similar (50 mg/kg BW, oral dosing, pretreatment for 2 weeks before tumor induction and continued until the end), and results from in vivo imaging system (IVIS) studies showed a significant (p&lt;0.05) reduction in MDA-MB-231 cell metastasis to the liver and lungs compared to the control. Tumor weight and volume reductions were consistent with previous animal studies, demonstrating Ifetroban's therapeutic efficacy in different TNBC models. These results were further confirmed by the H&E staining of liver and lungs. Our findings highlight that inhibition of platelet derived TXA2 by Ifetroban plays a crucial role in inhibiting the intravascular metastatic niche that promotes tumor cell seeding in TNBC models. We strongly suggest that Ifetroban can be used as neoadjuvant therapy for breast cancer treatment.

Citation Format: Veeresh Toragall, Thomas UNIVERSITY OF Werfel. Ifetroban blocks the metastatic intravascular niches by blocking the platelet activation through thromboxane A2 cascade [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Tumor Immunology and Immunotherapy; 2024 Oct 18-21; Boston, MA. Philadelphia (PA): AACR; Cancer Immunol Res 2024;12(10 Suppl):Abstract nr A002.