Abstract 6850: Unraveling molecular factors contributing to metallomic dyshomeostasis induced by triple-negative breast cancer using single-cell RNA sequencing
Authors: Hum Nicholas R. , Rolison John M. , Leon Nicole F. , Navid Ali , Sebastian Aimy , Wimpenny Josh , Loots Gabriela 
Published: March 2024

Abstract
Triple-negative breast cancer (TNBC) comprises 20% of breast cancer cases and exhibits an aggressive phenotype with increased metastasis; these patients have limited treatment options, poorer prognosis and higher mortality than other breast cancers (BC). Metallomics is a relatively new discipline that studies the abundance of metal ions in biological samples. Metallomic analysis has identified differences in BC patients in elements such as iron (Fe) and zinc (Zn) but it is unclear if these reflect metabolic changes in the tumor. In this study, we conducted metallomic profiling to characterize 55 trace elements in the circulation and in the tumor microenvironment of orthotopic mammary fat pad tumors from two isogenic BC cell lines (highly metastatic 4T1; nonmetastatic 67NR). We complemented this analysis with single-cell RNA sequencing of the tumor to determine if complementary changes occur in molecules known to utilize metals as co-factors or transporters and identify drivers of metal metabolism in different tumors. We performed analysis on systemic metal elements by examining whole blood (including blood cells and platelets) and plasma separately. Tumor samples were assessed at the whole tissue level, and we also profiled separated immune or non-immune cells from the tumor. Li, Na, Mg, P, S, K, Ca, Fe, Cu, Zn, Rb were detectable within 100ul of input of whole blood or plasma. Metallomic analysis of the tumor and associated cell populations detected differential levels of Na, Mg, P, S, K Ca, Fe, Zn, and Rb from an average of 200mg of tissue or 2 million cells. Based on scRNAseq analysis, 67NR tumors were composed of greater proportions of cancer cells relative to the 4T1 tumors (79.1% vs 58.8% of tumor cells respectively) and endothelial cells (2.5% vs 1.8%). 4T1 tumors contained an increased abundance of cancer-associated fibroblasts (5.6% vs 2.1%) as well as immune infiltration (33.8% vs 16.3%). Fibroblasts and macrophage populations also showed elevated metal transporter expression levels based on gene expression relative to other tumor residing cell types yet minor differences induced by cancer type. Cancer cells express high levels of metal transport genes (Zn, Ca, Co, Na, Mg, Fe). 67NR cancer cells exhibited increased gene expression of many metal-transporting proteins including numerous solute carrier (SLC) group of membrane transport proteins such as Slc41a2 when compared to the more aggressive 4T1 cells. This study underscores the potential of linking metallomic profiling to tumor composition and cancer behaviors, offering a pathway for identifying novel biomarkers to differentiate aggressive and non-aggressive forms of breast cancer.
This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344.
Citation Format: Nicholas R. Hum, John M. Rolison, Nicole F. Leon, Ali Navid, Aimy Sebastian, Josh Wimpenny, Gabriela Loots. Unraveling molecular factors contributing to metallomic dyshomeostasis induced by triple-negative breast cancer using single-cell RNA sequencing [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6850.