Abstract 398: The inhibition of sulfation of heparan sulfate augments the chemotherapeutic response in triple-negative breast cancer

Abstract

Abstract The leading cause of cancer-related death among women worldwide is breast cancer. The triple-negative breast cancer (TNBC) subtype has limited therapeutic options that produce durable responses. As a result, it is associated with an especially poor prognosis compared to other breast cancer subtypes. Hence, the development of innovative therapeutic strategies that produce deeper and more durable responses is critically needed. We found that increasing extracellular ATP (eATP) can enhance the susceptibility of TNBC cell lines to chemotherapy through the activation of purinergic receptors (P2RXs) P2RX4 and P2RX7. However, eATP levels are limited by several different classes of eATPases, making the design of a single molecule that effectively inhibits all classes of eATPase complicated. Heparan sulfate, a carbohydrate moiety that is covalently linked to several cell surface and extracellular matrix proteins has previously been identified as an endogenous inhibitor of several classes of eATPases. Heparan sulfate is desulfated by sulfatases 1 and 2 at the 6-O-hydroxyl groups of glucosamine residues in heparan sulfate. Sulfatase 2 has been determined to be highly expressed in a variety of cancers including breast cancer, whereas sulfatase 1 is not. Several sulfatase inhibitors have been previously developed, such as OKN-007, which is a specific inhibitor of sulfatase 2. We hypothesized that OKN-007 would augment eATP levels in TNBC cell lines exposed to chemotherapy by increasing levels of heparan sulfate in the tumor microenvironment, leading to intensified cell death. TNBC cell lines MDA-MB 231, Hs 578t, and MDA-MB 468 and non-tumorigenic immortal mammary epithelial MCF-10A cells were treated with increasing concentrations of the chemotherapeutic agent paclitaxel in the presence of heparan sulfate and/or OKN-007, and eATP content and cell viability were evaluated. Inhibitors to the purinergic receptors P2RX4 and P2RX7 were used to further confirm that the mechanism of enhanced cell death induced by OKN-007 was through these receptors. In addition, basal protein and cell surface expression of sulfatases 1 and 2 were determined in all the examined cell lines via ELISA, Western blot, and flow cytometry analysis. To assess the effects on cancer-initiating cell properties, TNBC cell lines were treated with paclitaxel in the presence of heparan sulfate and/or OKN-007, and the tumorsphere formation efficiency assay used to assess for cancer-initiating cells. In parallel, we assessed for effects on cancer-initiating cells in treated cells using flow cytometry. Our results showed that inhibiting the 6-O desulfation of heparan sulfate increases eATP accumulation, thereby, enhancing TNBC cell lines’ response to chemotherapy. These findings may lead to therapies for TNBC based on sulfatase 2 inhibition that results in more effective responses with fewer side effects. Citation Format: Jasmine M. Manouchehri, Jharna Datta, Mathew A. Cherian. The inhibition of sulfation of heparan sulfate augments 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 398.