Nature Medicine single-cell atlas maps distinct tumor microenvironments in 189 colorectal cancers across age groups

Researchers at Dana-Farber profiled tumors from patients aged 20-90 using single-cell RNA sequencing and spatial transcriptomics. They quantified epithelial, immune, and fibroblast populations while controlling for stage, sidedness, and treatment history. Early-onset tumors showed higher proportions of exhausted CD8 T cells and cancer-associated fibroblasts expressing SPP1, patterns linked to poorer response to checkpoint blockade in prior cohorts. The study design improves on earlier bulk RNA analyses by resolving cell-type proportions that previously confounded age comparisons. Absolute differences reached 1.8-fold enrichment for SPP1+ fibroblasts in patients under 50. No randomized intervention was tested; the atlas remains observational. Contextualizing with SEER incidence data and two prior bulk sequencing cohorts from 2019-2022, the atlas supports the hypothesis that tumor microenvironment differences contribute to aggressive behavior beyond germline variants. Limitations include single-institution sampling and lack of longitudinal outcome linkage. Next steps require prospective validation in multi-center cohorts with paired clinical response data to test whether the identified cell states predict progression-free survival.