Spatial Metallomics in Colorectal Cancer: Copper-Immune and Iron-EMT Pathways

What the study examined

Colorectal cancer (CRC) is one of the most common malignancies worldwide, and its tumor microenvironment (TME) is shaped not only by cells and signaling molecules but by the local distribution of trace metals. Essential transition metals such as copper and iron are cofactors for enzymes that drive proliferation, angiogenesis, redox balance, and immune signaling, yet conventional bulk assays average metal content across an entire specimen and lose the spatial context that determines where metal-dependent biology actually occurs.

Srivastava and colleagues, working across Dartmouth's Geisel School of Medicine, Weill Cornell Medicine, and the Biomedical National Elemental Imaging Resource (BNEIR), set out to test whether elemental maps and gene-expression maps could be brought into a shared coordinate system so that metal accumulation could be interpreted alongside the transcriptional programs of the surrounding tissue. The work is explicitly framed as proof-of-concept: it analyzes a single, well-characterized CRC specimen from a patient with a left-colon, microsatellite-stable tumor (pathologic T3, node-positive, with liver metastasis) to demonstrate that a metals-based spatial pathway analysis is feasible and biologically informative before scaling to larger cohorts.

Methods: pairing elemental imaging with spatial transcriptomics

Serial sections of a single formalin-fixed, paraffin-embedded (FFPE) tumor block were split across complementary platforms. Metal distributions were imaged by laser-ablation inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-TOF-MS) at roughly 5-micron resolution, capturing copper, iron, zinc, manganese, magnesium, potassium, and calcium simultaneously across the tissue. An adjacent section was profiled with the 10x Genomics Visium (CytAssist) spatial transcriptomics assay, which measures expression of on the order of 18,000 genes within 55-micron spots laid out across the same tissue architecture.

The central technical contribution is co-registration: the team developed a workflow (referred to as TRACE, Tissue Region Analysis through Co-registration of Elemental maps) to warp the elemental images and transcriptomic spots into alignment, so that a metal value and a gene-expression profile could be read out at the same physical location. Downstream analysis combined cell-type deconvolution (Cell2Location), spatial hotspot detection (Getis-Ord Gi*), factor analysis (MEFISTO), and predictive modeling (MISTy) to relate metal abundance to genes, inferred cell types, and histological structures. Predictive models reconstructed several metals from transcriptomic and cellular features with high fidelity (reported R-squared above ~75% for potassium, copper, manganese, magnesium, calcium, and iron), supporting the idea that these metal distributions are coupled to identifiable molecular programs rather than random.

Key findings: copper with immunity, iron with EMT

Copper accumulated in regions of active tumor growth and co-localized with increased expression of immune-response genes. The elevated-copper zones were enriched for interferon-gamma response signaling (reported p = 1.09e-12) and IL-6/JAK/STAT3 signaling, and copper abundance tracked with inferred dendritic cells, endothelial cells, and macrophage populations. This positions copper not simply as a proliferation cofactor but as a marker of immunologically active tumor territory.

Iron told a different spatial story. Elevated iron correlated with mesenchymal phenotypes concentrated at the tumor's proliferative, invasive front and with genes for epithelial-to-mesenchymal transition (EMT) and extracellular-matrix (ECM) remodeling. The EMT program was strongly enriched in iron-high regions (reported p = 4.38e-21), with individual correlations to fibronectin (FN1) and matrix metalloproteinase-9 (MMP9). Because EMT and ECM remodeling are hallmarks of local invasion and metastatic dissemination, iron's spatial signature aligns with the biology of a tumor edge preparing to spread.

Mechanistic interpretation

The two metal signatures map onto two distinct, biologically coherent compartments of the tumor. Copper is a required cofactor for enzymes in mitochondrial respiration, angiogenesis, and redox signaling, and 'cuproplasticity' has emerged as a theme in cancer where copper availability tunes proliferative and inflammatory signaling. Finding copper concentrated where interferon-gamma and IL-6/JAK/STAT3 programs are active is consistent with copper-dependent modulation of immune and stromal signaling in zones of active growth.

Iron participates in Fenton chemistry, oxygen sensing, and numerous metalloenzymes, and labile iron can promote the oxidative and signaling conditions that favor EMT. Its enrichment at the mesenchymal, matrix-remodeling front dovetails with a large literature linking iron dysregulation to invasion and metastasis. Importantly, the study is correlative and single-case: it establishes spatial co-occurrence and predictive coupling between metals and pathways, not causation. The authors present it as a template for hypothesis generation and for designing metal-targeted therapeutic and biomarker studies in larger CRC cohorts.

Relevance to the metal-microbiome-disease axis

This study sits at the metal-and-disease end of the metal-microbiome-disease axis: it shows, with spatial precision, that where metals accumulate inside a colorectal tumor predicts which disease-driving programs are switched on. That is the mechanistic payoff the axis points to, metal distribution shaping immune and invasive biology in situ.

The colon is also where host, diet, metals, and microbiota meet most directly. Dietary and environmental metal exposure, luminal iron in particular, is a well-studied modifier of the gut microbiome, and microbial competition for iron and other transition metals (nutritional immunity, siderophores, and metallophores) shapes which taxa thrive at the mucosal surface. A dysbiotic, metal-stressed microbiome is in turn linked to colorectal carcinogenesis. This paper does not measure the microbiome, so any microbiome connection is contextual rather than demonstrated here; its contribution is to sharpen the tumor-side half of the axis by resolving copper-immune and iron-EMT geography at micron scale. Spatial metallomics is a promising bridge for future work that would layer microbial spatial data onto the same elemental maps.