Because it has been reported that the tumour‐derived factors such as CCL2, SDF1, IL6, TNFα, VEGF, G‐CSF, TGFβ, and CXCL1 function in the pre‐metastatic phase (McAllister & Weinberg, 2014; Wang et al, 2017), we applied those factors to HepELs in the tumour‐bearing mouse liver in vitro (Fig 7C). The gene discussed is CCL2; the disease is neoplasm.