SLC9A1 and breast cancer: Figure 6—figure supplement 1 provides plots of steady-state pHi and net acid extrusion as functions of tumor size and patient age. (E,F) Ordinal logistic regression analyses show the independent influences of patient age, tumor size, histology, malignancy grade, and expression of estrogen and HER2 receptors on protein expression levels for NHE1 (E) and NBCn1 (F) in human breast cancer tissue (n=73).