An in vitro study on mouse melanoma cells found that triphenylphosphine oxide (TPPO), a selective TRPM5 blocker, dose-dependently inhibited acidic pHe-induced matrix metalloproteinase-9 (MMP-9) production (IC50: 41 mM after 24 h), but did not reduce cell viability. This evidence concerns the gene TRPM5 and melanoma.