IKBKB and cancer: Constitutive activity of NFκB is normally restricted to cells from the hematopoietic lineage.25 In other cell types, basal NFκB activity is negligible and induced only after stimulation.26 However, high levels of constitutively active NFkB are found in cancer cells, induced by paracrine secretion of cytokines and other factors from the tumour.27 Therefore, it is possible that secreted factors present in the lung microenvironment allow for temporal‐specific activation of the IKKβ/NFκB pathway in the developing pulmonary endothelium.