We carried out three independent biological repeats of the orthotopic breast tumour model shown in Fig. 1a, implanting either 5 × 105 4T1 or 4T07 cells into the mammary fat pad of the αSMA-RFP BALB/c mice, analysing a total of 128 tumours and 12 healthy mammary fad pads. Here, ACTA1 is linked to neoplasm.