SCN4B and breast cancer: The growth of primary mammary tumours, measured with a calliper (Supplementary Fig. 10b) or by bioluminescent imaging (Fig. 10e,f), was reduced in mice implanted with oeSCN4B cells compared with those implanted with shSCN4B. At the end of the study, primary mammary tumours from the two groups were analysed and the non-expression of SCN4B/β4 in the shSCN4B group or expression in the oeSCN4B group was confirmed by immunohistochemistry (Fig. 10g).