NF-κB non-cell-autonomously regulates cancer stem cell populations in the basal-like breast cancer subtype.

Patients with triple-negative breast cancer display the highest rates of early relapse of all patients with breast cancer. The basal-like subtype, a subgroup of triple-negative breast cancer, exhibits high levels of constitutively active NF-κB signalling. Here we show that NF-κB activation, induced by inflammatory cytokines or by epigenetically dysregulated NIK expression, cell-autonomously upregulates JAG1 expression in non-cancer stem cells. This upregulation stimulates NOTCH signalling in cancer stem cells in trans, leading to an expansion of cancer stem cell populations. Among breast cancers, the NF-κB-dependent induction of JAG1 and the NOTCH-dependent expansion of the cancer stem cell population occur only in the basal-like subtype. Collectively, our results indicate that NF-κB has a non-cell-autonomous role in regulating cancer stem cell populations by forming intratumoural microenvironments composed of JAG1-expressing non-cancer stem cells with a basal-like subtype.