As tumour tissues express CCL20 at the mRNA level (Fig. 1g) and EGFR/Ras signalling upregulates CCL20 expression (Fig. 1a–c), we next performed immunohistochemical analysis of CCL20 protein expression and ERK activation in serial sections of tumour samples from breast cancer, melanoma and HNSCC patients (Fig. 2a). Here, EGFR is linked to breast carcinoma.