Abstract B221: Clopidogrel augments cisplatin cytotoxicity by enhancing delivery and direct receptor mediated effects.

Abstract

Abstract Clopidogrel, a well known P2Y12 (purinergic receptor) inhibitor is widely used for its role in preventing thrombosis by platelet aggregation inhibition. Tumor vasculature is critically dependent on platelet mediated hemostasis and disruption of the same can promote its leakiness. This can increase the intra-tumoral delivery of chemotherapeutic nanoformulations, which depend on the Endothelial permeability and retention (EPR) effect. Also, Expression of P2Y12 receptors has been documented in some cancer cell lines like C6 glioma, kidney carcinoma and colon carcinoma. However, its direct role in altering response to chemotherapeutics has not been studied. In this project we evaluated the role of P2Y12 receptor inhibitors (Clopidogrel and 2-Methylthioadenosine 5-Monophosphate) in potentiating the tumor cytotoxicity of cisplatin based chemotherapeutics in vitro and in vivo. Western blot studies in 4T1 breast cancer cell lines showed a low basal expression of P2Y12 receptors with significant up regulation by cisplatin treatment in a time and dose dependent fashion. Co-administration of P2Y12 inhibitor (MeSAMP) with cisplatin resulted in significantly increased upregulation of caspase dependent apoptotic pathway when compared to cisplatin alone. This was mediated by downstream inhibition of PI3K-pAKT-mTOR pathway by the P2Y12 inhibitor. In-vitro cell proliferation assay showed that co-administration of 2-MeSAMP significantly reduced the IC-50 of cisplatin from 3.9 μM to 1.8μM. In-vivo studies in murine syngenic 4T1 breast cancer model showed significantly decreased tumour growth and increased survival in treatment groups using combination of clopidogrel and cisplatin (free and nanoformulation forms). This was more pronounced with cisplatin nano-formulation combination therapy. Further analysis of tumour tissue using Inductive Coupled Plasma-spectrophotometry confirmed that co-treatment with clopidogrel increased the delivery of free and nanoformulation form of cisplatin to tumor tissue by 1.8 and 4 folds respectively. Taken together our study findings suggest that clopidogrel can enhance therapeutic efficiency of cytotoxic agents by increasing delivery and by direct receptor level effects. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B221.