Abstract P3-06-07: Glutathione peroxidase 8 (GPX8) as a novel therapeutic target in triple negative breast cancer

Abstract

Abstract Negative Breast Cancer (TNBC) accounts about 15% of the breast cancer incidence worldwide. While molecular subtypes which express estrogen and progesterone receptors (ER, PR) and the human epidermal growth factor receptor 2 (HER2, ERBB2) are favorable, TNBC is more associated with patient poor prognosis. GPX8 is a poorly characterized enzyme that resides in the endoplasmic reticulum, is an essential regulator of tumor aggressiveness. We found that GPX8 expression was induced by the epithelial-mesenchymal transition (EMT) program. Moreover, in breast cancer patients, GPX8 expression significantly correlated with known mesenchymal markers and poor prognosis. Strikingly, GPX8 knockout in TNBC mesenchymal-like cells (MDA-MB-231) resulted in an epithelial-like morphology, down-regulation of EMT characteristics, and loss of cancer stemness features. In addition, GPX8 knockout significantly delayed tumor initiation and decreased its growth rate in mice. We found that these GPX8 loss-dependent phenotypes were accompanied by the repression of crucial autocrine factors, in particular, interleukin-6 (IL-6). In these cells, IL-6 bound to the soluble receptor (sIL6R), stimulating the JAK/STAT3 signaling pathway by IL-6 trans-signaling mechanisms, so promoting cancer aggressiveness. We observed that in GPX8 knockout cells, this signaling mechanism was impaired as sIL6R failed to activate the JAK/STAT3 signaling pathway. Altogether, we present the GPX8/IL-6/STAT3 axis as a metabolic-inflammatory pathway that acts as a robust regulator of breast cancer cell aggressiveness. These findings motivated us to suggest GPX8 as a novel therapeutic target in TNBC. Citation Format: Anees Khatib. Glutathione peroxidase 8 (GPX8) as a novel therapeutic target in triple negative breast cancer [abstract]. In: Proceedings of the 2021 San Antonio Breast Cancer Symposium; 2021 Dec 7-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2022;82(4 Suppl):Abstract nr P3-06-07.