Upregulation of CCL2 around HER2+ early cancer cells was also observed at the protein levels as confirmed by quantifying soluble CCL2 in the conditioned media of the early cancer cells by enzyme-linked immunosorbent assay (ELISA) and by IF analysis (Fig. 6c, d, Supplementary Table 6 and Supplementary Fig. 5G–H, Supplementary Table 7). Here, CCL2 is linked to cancer.