In comparison, in human breast cancer (MCF-7) cells expressing both α2β1 integrins and a constitutively active receptor tyrosine kinase (ErbB2), cell surface pH is 7.05, and only an increase to 7.2 by means of NHE1 inhibition leads to optimum migration on collagen I [80]. This evidence concerns the gene NTRK1 and breast carcinoma.