CYSLTR1 and neoplasm: MK571, a CysLT1R antagonist, induced apoptosis and dose-dependent proliferation inhibition in two non-tumor cell lines (Int 407 and IEC-6 cells), but only led to proliferation reduction without apoptosis in the tumor intestinal cell lines (Caco-2, SW480, HCT-116 and HT-29 cells); the presence of nuclear CysLT1Rs in intestinal cancer cells, which are inaccessible to the receptor antagonist, might provide a clue to the finding [56].