Consistent with evidence that intracellular acidification in response to digitoxin plus MEK inhibitor was at least partially mediated by reduced NHE function (Fig. 4d,g), the increase in mitochondrial Ca2+ levels in melanoma cells in response to digitoxin plus MEK inhibitor was also partially rescued by increased NHE1 expression (Fig. 5j,k). The gene discussed is SLC9A1; the disease is melanoma.