Abstract 397: The role of heparan sulfate in enhancing the chemotherapeutic response in triple-negative breast cancer

Abstract

Abstract Among women worldwide, breast cancer has the highest incidence and is the leading cause of cancer-related death. Patients with the triple-negative breast cancer (TNBC) subtype have an inferior prognosis in comparison to other breast cancers because the current therapies do not facilitate long-lasting responses. Thus, there is a critical need for novel therapeutic strategies that induce stronger responses. In our previous research, we discovered that augmenting the concentration of extracellular ATP (eATP) greatly enhances the chemotherapeutic response of TNBC cell lines by activating purinergic receptors (P2RXs), leading to cell death through the induction of non-selective membrane permeability. However, eATP levels are limited by several classes of extracellular ATPases. One endogenous molecule of interest that can inhibit multiple classes of extracellular ATPases is heparan sulfate. Heparan sulfate itself is degraded by heparanase, an enzyme that is known to be highly expressed in various cancers, including breast cancer. Heparan sulfate has previously been shown to regulate several cancer-related processes such as fibroblast growth factor signaling, neoangiogenesis by sequestering vascular endothelial growth factors in the extracellular matrix, hedgehog signaling and cell adhesion. In this project, we identified an additional mechanism for a tumor suppressor role of heparan sulfate: inhibition of extracellular ATPases, leading to augmented levels of eATP. Several heparanase inhibitors have been previously identified, including OGT 2115, suramin, PI-88, and PG 545. We hypothesized that heparanase inhibitors would augment eATP concentrations in TNBC by increasing heparan sulfate in the tumor microenvironment, resulting in increased cell death in response to chemotherapy. We treated TNBC cell lines MDA-MB 231, Hs 578t, and MDA-MB 468 and non-tumorigenic immortal mammary epithelial MCF-10A cells with increasing concentrations of the chemotherapeutic agent paclitaxel in the presence of heparan sulfate and/or OGT 2115 with eATP content and cell viability being assessed. Moreover, to confirm that the effects of OGT 2115 are mediated through eATP, we utilized specific antagonists to the purinergic receptors P2RX4 and P2RX7. In addition, the protein expression of heparanase was compared in all the examined cell lines via Western blot analysis. We also evaluated the effects of this combination on the breast cancer-initiating cell population in the treated cells using flow cytometry and tumorsphere formation efficiency assays. These results demonstrate that inhibiting the degradation of heparan sulfate in the tumor microenvironment enhances the susceptibility of TNBC cell lines to chemotherapy by augmenting extracellular ATP concentrations. This strategy could potentially be used to induce deeper and more durable responses in triple-negative breast cancer patients. Citation Format: Jasmine M. Manouchehri, Jharna Datta, Mathew A. Cherian. The role of heparan sulfate in enhancing the chemotherapeutic response in triple-negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 397.