SLC9A1 and breast cancer: In summary, the experiments suggesting that NHE1 facilitates metastatic breast cancer are: 1, knockout of NHE1 reduced the in vivo tumor-promoting capability of MDA-MB-231 cells; 2, NHE1 deletion in MDA-MB-231 cells reduced their invasive capacity; and 3, specific inhibition of NHE1 potentiated the effect of paclitaxel, reducing cell viability, invasion and migration.