Apoptosis induction and cyclooxygenase-2 regulation in human colorectal adenoma and carcinoma cell lines by the cyclooxygenase-2-selective non-steroidal anti-inflammatory drug NS-398

Identification of specific genes and pathways involved in NSAIDs-induced apoptosis of human colon cancer cells

AIM

To study whether indomethacin (IND), a nonselective cyclooxygenase (COX) inhibitor or NS-398 (NS), a COX-2-selective inhibitor, induces apoptosis in human colon cancer cells and which apoptosis-related genes and pathways are involved.

METHODS

Human colon cancer Caco-2 cells were treated with either: placebo, IND (0.05-0.5 mmol/L) or NS (0.01-0.2 mmol/L) for 1, 5 and 18 h. We then studied: (1) Cell death by the TUNEL method, (2) mRNA expression of 96 apoptosis-related genes using DNA microarray, (3) expression of selected apoptosis related proteins by Western blotting.

RESULTS

Both IND and NS induced apoptosis in 30%-50% of Caco-2 cells in a dose dependent manner. IND (0.1 mmol/L for 1 h) significantly up-regulated pro-apoptotic genes in four families: (1) TNF receptor and ligand, (2) Caspase, (3) Bcl-2 and (4) Caspase recruiting domain. NS treatment up-regulated similar pro-apoptotic genes as IND. In addition, IND also down-regulated anti-apoptotic genes of the IAP family.

CONCLUSION

(1) Both non-selective and COX-2-selective NSAIDs induce apoptosis in colon cancer cells in a dose dependent manner. (2) Both NSAIDs induce apoptosis by activating two main apoptotic pathways: the death receptor pathway (involving TNF-R) and the mitochondrial pathway. (3) IND induces apoptosis by up-regulating pro-apoptotic genes and down-regulating anti-apoptotic genes, while NS only up-regulates pro-apoptotic genes. (4) Induction of apoptosis in colon cancer cells by NSAIDs may explain in part, their inhibitory action on colon cancer growth.

Two-dimensional polyacrylamide gel electrophoresis analysis of indomethacin-treated human colon cancer cells

AIM: To establish the two-dimensional gel electrophoresis (2-DE) profiles of indomethacin (IN)-treated human colon cancer cell line HCT116, and to provide a new way to study its anti-tumor molecular mechanism through analyzing a variety of protein maps.

METHODS: Two-DE profiles of HCT116 were established in IN-treated and untreated groups. Total proteins were separated by immobilized pH gradient-based 2-DE. The gels were stained by silver, scanned by ImageScanner, and analyzed with Image Master software.

RESULTS: Clear background, well-resolved and reproducible 2-DE patterns of HCT116 cells were acquired in IN-treated and untreated group. The average deviation of spot position was 0.896±0.177 mm in IEF direction and 1.106±0.289 mm in SDS-PAGE direction respectively. In IN-treated group, 1169±36 spots were detected and 1061±32 spots were matched, the average matching rate was 90.6% in three gels. In untreated group, 1256±50 spots were detected and 1168±46 spots were matched, the average matching rate was 93.0% in three gels. Forty-five differential protein spots were displayed between IN-treated and untreated groups. Of which, 34 protein spots decreased and 9 showed higher expression in IN-treated group, and only two protein spots showed an expression in untreated cells.

CONCLUSION: Two-DE profiles of IN-treated and untreated HCT116 cells were established. Apparent 45 different protein spots were detected in IN-treated and untreated HCT116 cells. The analysis on differential protein spots may serve as a new way to study the molecule mechanism of IN-treated colon cancer.