Western blot analysis was performed as described (Izumchenko et al, 2009 (link)). Anti-Abcc10 antibody was used at a concentration of 1 : 500 (Hopper-Borge et al, 2011 (link)). ABCB1, ABCG2 (Santa Cruz Biotechnology, Dallas, TX, USA), β-actin (Abcam, Cambridge, MA, USA), HER2 and ERα (Cell Signalling Technology, Danvers, MA, USA) antibodies were used according to the manufacturer's instructions.