SLC7A11 and neoplasm: MMTV-PyMT tumour-derived cell lines express the SLC7A11 subunit (also called xCT) of the system Xc- glutamate–cystine antiporter at significantly higher levels than NMuMG cells (Supplementary Fig. 1a), suggesting that acquisition of expression of this transporter might be responsible for increased glutamate release from invasive cells.