In this model, it was shown that CAFs provide aspartate to cancer cells, which is taken up via the transporter SLC1A3 (also known as the excitatory amino acid transporter 1 [EAAT1]) to support nucleotide biosynthesis, while tumour cells reciprocate with glutamine-derived glutamate taken up by the CAFs through the same transporter.23 The nature of the transport(s) responsible for efflux of these two amino acids from cancer and stromal cells is not yet clear. Here, SLC1A3 is linked to cancer.