Intratumour oxidative hotspots provide a niche for cancer cell dissemination

Intratumour heterogeneity represents the hierarchical integration of genetic, phenotypic and microenvironmental heterogeneity. Although single-cell sequencing has clarified genetic and phenotypic variability, the heterogeneity of nongenetic, microenvironmental factors remains elusive. Here, we developed T-AP1, a tumour-targeted probe tracking extracellular H₂O₂, which allows the visualization and characterization of tumour cells exposed to oxidative stress, a hallmark of cancer. T-AP1 identified actively budding intratumour regions as H₂O₂-rich microenvironments (H₂O₂ hotspots), which were primarily established by neutrophils. Mechanistically, tumour cells exposed to H₂O₂ underwent partial epithelial-mesenchymal transition through p38-MYC axis activation and migrated away from H₂O₂ hotspots. This escape mechanism was absent in normal epithelial cells but prevalent in most cancers except NRF2-hyperactivated tumours, which exhibited abrogated p38 responses and enhanced antioxidant programmes, thus revealing an intrinsic stress defence programme in cancers. Together, T-AP1 enabled the identification of H₂O₂ hotspots that provide a niche for cancer cell dissemination, offering insights into metastasis initiation.