Stromal cell senescence augments haematopoietic cell fitness in clonal haematopoiesis.

Microenvironment remodelling impacts tumour growth and metastasis, but whether remodelling promotes pre-malignant clonal fitness remains unknown. Here, using single-cell RNA-sequencing of the bone-marrow microenvironment in a mouse model of DNMT3A-mutant clonal haematopoiesis (CH), we identify mesenchymal stromal cells (MSCs) in a molecular state of cellular senescence. Elevated bone-marrow MSC senescence is also observed in humans with CH driven by several common somatic mutations. MSC senescence is induced by mutant haematopoietic cells in a contact-independent manner through production of soluble factors including TNF-α and IL-6. These cytokines activate a Stat3-driven pathway that is necessary and sufficient for MSC senescence induction. Genetic or pharmacological depletion of senescent non-haematopoietic cells reduces the burden of CH and delays progression to myeloid neoplasia. Our findings show that microenvironment remodelling modifies pre-malignant clonal fitness and identifies disruption of the crosstalk between pre-malignant cells and their niche as a cancer prevention strategy.