ERBB2 and breast carcinoma: Interestingly, perfusion of 0Na+/NMDG had no effect on [Ca2+]i in the ER+ breast cancer cell line MCF‐7 (Figure 1c), but induced a [Ca2+]i transient in the Her2+ breast cancer cell line SKBR3 (Figure 1d); nevertheless, both MCF‐7 and SKBR3 cells exhibited depletion of [Na+]i upon perfusion with 0Na+/NMDG (Supplementary Figure S1b,c).