Gene modulation by the cyclooxygenase inhibitor, sulindac sulfide, in human colorectal carcinoma cells: possible link to apoptosis.

The mechanisms underlying the anti-tumorigenic properties of cyclooxygenase inhibitors are not well understood. One novel hypothesis is alterations in gene expression. To test this hypothesis sulindac sulfide, which is used to treat familial adenomatous polyposis, was selected to detect gene modulation in human colorectal cells at physiological concentrations with microarray analysis. At micromolar concentrations, sulindac sulfide stimulated apoptosis and inhibited the growth of colorectal cancer cells on soft agar. Sulindac sulfide (10 microm) altered the expression of 65 genes in SW-480 colorectal cancer cells, which express cyclooxygenase-1 but little cyclooxygenase-2. A more detailed study of 11 genes revealed that their expression was altered in a time- and dose-dependent manner as measured by real-time RT-PCR. Northern analysis confirmed the expression of 9 of these genes, and Western analysis supported the conclusion that sulindac sulfide altered the expression of these proteins. Cyclooxygenase-deficient HCT-116 cells were more responsive to sulindac sulfide-induced gene expression than SW-480 cells. However, this response was diminished in HCT-116 cells overexpressing cyclooxygenase-1 compared with normal HCT-116 cells suggesting the presence of cyclooxygenase attenuates this response. However, prostaglandin E2, the main product of cyclooxygenase, only suppressed the sulindac sulfide-induced expression of two genes, with little known biological function while it modulated the expression of two more. The most likely explanation for this finding is the metabolism of sulindac sulfide to inactive metabolites by the peroxidase activity of cyclooxygenase. In conclusion, this is the first report showing sulindac sulfide, independent of cyclooxygenase, altered the expression of several genes possibly linked to its anti-tumorigenic and pro-apoptotic activity.