CCL2 and neoplasm: For example, KRAS-mutation status has been linked to PPARδ-CCL2 expression (involved in M2 macrophage transformation and recruitment) [83, 84], reduced NK cell cytotoxicity by increased expression of HLA-E [85] and PD-L1 [86], and epithelial-mesenchymal transition (EMT) [52], a sensitiser for tumours to NK cytotoxicity (Fig. 2).