LAUSR

Simple Summary Kirsten rat sarcoma virus (KRAS)-mutant cancers are frequent, metastatic, lethal, and largely undruggable. The aim of this study was to investigate the pathways through which KRAS-mutant cancers foster their growth, thereby unravelling novel therapeutic targets. We show that KRAS-mutant tumors secrete the protein versican, which then drives the activation of NF-κB kinase (IKK) β in a type of host immune cells called macrophages. Following this activation, macrophages fuel the tumor with interleukin (IL)-1β, to close an inflammatory loop through which KRAS-mutant cancers attract host immune cells to the tumor site to accelerate tumor growth and aggressiveness. Importantly, we show that targeting IL-1β and/or versican can be an effective treatment for KRAS-mutant cancers, holding great promise for cancer patients. Abstract Kirsten rat sarcoma virus (KRAS)-mutant cancers are frequent, metastatic, lethal, and largely undruggable. While interleukin (IL)-1β and nuclear factor (NF)-κB inhibition hold promise against cancer, untargeted treatments are not effective. Here, we show that human KRAS-mutant cancers are addicted to IL-1β via inflammatory versican signaling to macrophage inhibitor of NF-κB kinase (IKK) β. Human pan-cancer and experimental NF-κB reporter, transcriptome, and proteome screens reveal that KRAS-mutant tumors trigger macrophage IKKβ activation and IL-1β release via secretory versican. Tumor-specific versican silencing and macrophage-restricted IKKβ deletion prevents myeloid NF-κB activation and metastasis. Versican and IKKβ are mutually addicted and/or overexpressed in human cancers and possess diagnostic and prognostic power. Non-oncogene KRAS/IL-1β addiction is abolished by IL-1β and TLR1/2 inhibition, indicating cardinal and actionable roles for versican and IKKβ in metastasis.