Oncogene induced senescence (OIS) is a tumour suppressive response to oncogene activation that can be transmitted to neighbouring cells through secreted factors of the senescence associated secretory phenotype (SASP). Using single-cell transcriptomics we observed two distinct endpoints, a primary marked by Ras and a secondary by Notch. We find that secondary senescence in vitro and in vivo requires Notch, rather than SASP alone as previously thought. Currently, primary and secondary senescent

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... lls are not thought of as functionally distinct endpoints. A blunted SASP response and the induction of fibrillar collagens in secondary senescence compared to OIS point towards a functional diversification.