Abstract

Abstract Funding Acknowledgements Type of funding sources: Foundation. Main funding source(s): IEO-Monzino Foundation Background Cardiac metastasis is considered a relatively rare malignancy, although an increasing prevalence is expected in the future due to the increasing life expectancy. Several cases of cardiac metastases remain untreatable, given the anatomical location that often hampers both surgical eradication and bioptic collection for biological characterization. Here, we use spatial transcriptomics to provide an unbiased molecular characterization of cardiac metastases, and identify novel targets for their treatment. Material and methods We performed spatial transcriptomics on samples of primary tumor, cardiac, and extra-cardiac metastasis from three different patients. First, we checked RNA integrity by means of DV200 analysis. Spatial transcriptomic analysis was performed by using the GeoMX technology (Nanostring), which provides whole-transcriptome data along with spatial distribution information of the preselected samples from the candidate regions of interest (ROIs). ROIs were selected on the formalin-fixed paraffin-embedded sections by means of geometric shapes in combination with cell markers specific for tumor cells, cardiomyocytes and endothelial cells, respectively. Differential gene expression analysis and Gene Set Enrichment Analysis (GSEA) were performed on the entire transcriptome. Cell-cell interactions between cardiac cells and cancer cells were then evaluated by means of InterCellaR. Results Differential expression analysis between cardiac metastases and extra-cardiac tumors (primary tumors + extra-cardiac metastases) identified 92 differentially expressed genes (DEGs). Of these, 53 genes were significantly overexpressed in cardiac metastases, while 39 genes were overexpressed in the extra-cardiac samples, regardless of the site of origin of the tumor. Unsupervised hierarchical clustering of protein-coding genes clearly separated the samples according to their anatomical location, in particular cardiac metastasis from extra-cardiac tumors. GSEA identified several pathways enriched in cardiac metastases compared to the extra-cardiac tumors, including mechanotransduction (e.g. keratinization and cell-matrix interaction) and triglyceride metabolism, suggesting a potential role of these signaling pathways in the development of cardiac metastasis. Interactome analysis revealed a rich plethora of receptor-ligand interactions in cardiac metastasis, especially between tumor cells and cardiomyocytes. Conclusions These results start shedding light on the mechanisms that allow cancer cell growth in the heart and pave the way to the development of novel therapies to treat this malignancy.