Abstract 1845: Exploring the mode of action of a highly efficacious ruthenium-based chemotherapeutic agent in triple negative breast cancer

Abstract Purpose: Triple negative breast cancer (TNBC) is an aggressive subtype of breast cancer that is defined by the absence of expression of progesterone receptor, estrogen receptor, and human epidermal growth factor receptor 2. TNBC has a higher incidence in younger women and those of African descent. Due to the inability to target a receptor, treatment is mostly limited to anthracycline and taxane-based nonspecific chemotherapy. Within the past two years more therapies have become available for later stage TNBC, such as antibody-drug conjugate sacituzumab govitecan-hziy. A potential water-soluble ruthenium-based chemotherapeutic agent was developed in our lab, showing high cytotoxicity against different cancer types in a National Cancer Institute 60-cell line panel. A preliminary in vivo study of this complex showed a pronounced 56% reduction of tumor growth with a TNBC MDA-MB-231 cell line xenograft mouse model, with little system toxicity and preferential accumulation of the complex in tumor tissue. These studies prompted us to further evaluate it in TNBC cell lines MDA-MB-231 and HCC-1806, derived from Caucasian and African ancestry patients respectively. This investigation revealed significant anti-angiogenic, anti-invasive, and anti-migratory properties for the complex, along with subcellular accumulation in the mitochondria and an apoptotic mechanism of cell death in both cell lines. Preliminary proteomic analysis was completed to understand the molecular pathway involved, which was determined to be P53-independent. Macrophage colony stimulating factor (M-CSF) showed an inhibition of protein expression, implicating the ruthenium complex as a potential inhibitor of phosphoinositide 3-kinases/protein kinase B (PI3K/Akt) pathway which acts downstream of M-CSF, and is involved with enhanced cancerous proliferation. In light of these findings, we report here on in vitro studies focused on further investigating the involvement of the PI3K/Akt molecular pathway and mechanism of action of this ruthenium complex. Experimental Design: Western blot studies directed toward key markers in the PI3K/Akt pathway will be assessed, which include Akt, c-Raf, PI3K, PTEN, and PDK1. Furthermore, mitochondrial involvement was determined through reactive oxygen species (ROS) generation and changes to mitochondrial membrane potential (MMP). Results: A significant increase of ROS generation was seen with exposure to the compound, along with slight MMP depolarization. Western blot analysis may further implicate an inhibition of the PI3K/Akt pathway. Conclusions: Our results show that the mechanistic action of the tested ruthenium complex has mitochondrial involvement, with inhibitory effects in the PI3K/Akt pathway. The very significant anti-cancer properties outlined in the preclinical evaluation of this complex will be further investigated in PDX mice models. Citation Format: Nazia Nayeem, Karen Hubbard, Maria Contel. Exploring the mode of action of a highly efficacious ruthenium-based chemotherapeutic agent in triple negative breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 1845.