Spatial transcriptomics reveals atorvastatin modulates the tumor microenvironment to suppress breast cancer liver metastatic outgrowth

Abstract

Metastatic breast cancer remains incurable, underscoring the need for novel therapeutic strategies. Epidemiological and preclinical evidence suggests statins suppress metastatic outgrowth, however the underlying mechanisms remain unclear. We employed high-resolution spatial transcriptomics (ST) to explore the cellular composition and differentially expressed genes (DEGs) in the metastatic microenvironment following atorvastatin treatment. Formalin-fixed, paraffin-embedded breast cancer liver metastases from control and atorvastatin-treated mice were analyzed by Nanostring CosMx Spatial Molecular Imager (SMI)/Bruker using a 973-gene panel, profiling 212 and 207 tumor-adjacent field of views (FOVs) (TAFs) respectively, which identified eight cell clusters, while non-tumor FOVs (NTFs) were sparse. Preferential depletion of LRRC15⁺ myofibroblastic cancer associated fibroblasts (CAFs), CXCL8⁺ inflammatory CAFs, and C1QC⁺/SPP1⁺ tumor associated macrophages (TAMs) subsets were revealed by harmony-assisted cell annotation and Seurat label transfer, which further separated CAFs and TAMs into discrete functional subpopulations. Immunohistochemistry (IHC) was also performed to validate cell types in both the tissues. Wilcoxon-based DEG analysis identified metastasis-associated gene expression changes between groups. Atorvastatin treatment reduced CAFs, Hepatic stellate cells (HSCs) (significantly), and macrophages (trending) in TAFs, with no changes in NTFs. These findings were supported by IHC ( n = 4), which confirmed prominent reductions in these cell types while hepatocyte and endothelial markers remained unchanged. DEG analysis revealed coordinated downregulation of metastasis and extracellular matrix- associated transcripts in atorvastatin-treated TAFs. Our findings suggest that atorvastatin alters the cellular milieu in the disseminated microenvironment towards one in which pro-tumorigenic CAF and HSC populations are reduced, to create a microenvironmental niche favorable for maintaining metastatic dormancy and preventing relapse.