Figure 4. CysLT₂R signaling mediates anti-tumorigenic effects.

(A) An alkaline phosphatase activity assay was used to determine the differentiation of Caco-2 cells. Cells were treated with IFN-α (500–2000 U/ml) and/or LTC₄ (40 nM) for 72 h. The alkaline phosphatase activity was determined by measuring the absorbance at 405 nm due to formation of p-nitrophenol. (B) QPCR quantification of mRNA expression of MUC2 with or without treatment with LTC₄ (40 nM), IFN-α (1000 U/ml), pretreatment for 30 min with CysLT₂R inhibitor AP-100984 (1 µM) or CysLT₁R inhibitor Montelukast (1 µM), in Caco-2 cells. (C) Caco-2 cells were incubated with LTC₄ (40 nM) and/or IFN-α (1000 U/ml) for 48 h in medium containing 1.5% serum. To determine proliferation by thymidine uptake, [methyl-³H] thymidine (0.5 µCi/well) was added to the wells during stimulation. (D) Cell migration was analyzed with Int 407 cells grown in the presence or absence of EGF (100 ng/ml) and/or LTC4 (40 nM). The cells were allowed to invade a collagen gel on top of a Boyden chamber for 18 hrs. The results are shown as means ± SD of at least three different experiments; *, P<0.05; **, P<0.01; ***, P<0.001.