CXCR4 and neoplasm: In the tumour cell-as-signal-releaser mode of interactions, we found that the receptor‒ligand pairs significantly increased in IBC tumour cell interactions were PTN‒NCL, MIF‒CD74 + CXCR4, MIF‒CD74 + CD44, and MDK‒NCL and that these receptor‒ligand pairs mediated a wide range of interactions between the tumour and other cell types (Fig. 5d).