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The COX-2 selective inhibitor-independent COX-2 effect on colon carcinoma cells is associated with the Delta1/Notch1
Hui Zhang1, Yingjiang Ye, Zhigang Bai
1Surgical Oncology Laboratory and Department of Gastroenterological Surgery, Peking University People's Hospital, Beijing, PR China.
Background:
Cyclooxygenase-2 (COX-2) is a key factor in the development of colorectal cancer, and non-steroidal anti-inflammatory drugs (NSAIDs) have anti-colorectal cancer activity. However, the potential molecular mechanism of the COX-2 selective inhibitor effect on proliferation and apoptosis of colon cancer cells is unclear. In this study, we have demonstrated for the first time that the Delta1/Notch1 signal transduction pathway mediates the COX-2 selective inhibitor effect on colorectal cancer cells, and we reveal the mechanism of the Notch1 pathway in terms of regulating the proliferation and apoptosis of colorectal cancer cells.
Methods And Result:
Colon cancer cell lines HT-29 and SW480 were treated with NS-398 (a COX-2 selective inhibitor) and DAPT (a gamma-secretase inhibitor). The colormetric MTT cell proliferation assay and flow cytometry were used to measure cell proliferation and apoptosis. Reverse transcriptase (RT)-PCR and ELISA analyses were used to detect the levels of COX-2 mRNA expression and prostaglandin E2 (PGE2) concentration from the two cell lines, respectively. The expression of the Notch1, Delta1, ICN, Hes1 and NF-kappaB2 proteins was measured by Western blot. Immunohistochemistry results showed that Notch1 was expressed mainly in the cytoplasm and ICN mainly in the nucleus. COX-2 mRNA was highly expressed in HT-29 cells but not in SW480 cells. Both COX-2 mRNA expression and PGE2 concentration decreased in HT-29 cells treated with NS-398; however, PGE2 levels did not change in SW480 cells treated with NS-398. NS-398 and DAPT inhibited cell proliferation and induced apoptosis in a dose time-dependent manner accompanied by significantly decreased Notch1 activity (P < 0.01), and resulted in a significant down-regulation of Hes1 and NF-kappaB2 (P < 0.01).
Conclusions:
Our results show that the selective COX-2 inhibitor may inhibit the proliferation and induce apoptosis in colon cancer cells through the COX-2-dependent pathway (HT-29) by decreasing the COX-2 mRNA/PGE2 levels and the activity of the COX-2-independent pathway (SW480). The Notch1 signal pathway mediates the effects of the COX-2 inhibitor on the proliferation and apoptosis of colon cancer cells. This may be a new target of the selective COX-2 inhibitor effect on colon cancer.
Insights
Selective COX-2 inhibitors reduce colon cancer cell proliferation and induce apoptosis by modulating the Delta1/Notch1 pathway. This pathway is key to understanding how these drugs affect colorectal cancer progression.
Area of Science:
- Oncology
- Molecular Biology
- Pharmacology
Background:
- Cyclooxygenase-2 (COX-2) is implicated in colorectal cancer development.
- Non-steroidal anti-inflammatory drugs (NSAIDs) show anti-colorectal cancer activity, but the precise molecular mechanisms are not fully understood.
- The role of COX-2 selective inhibitors in colon cancer cell proliferation and apoptosis requires further elucidation.
Purpose of the Study:
- To investigate the molecular mechanism underlying the effect of COX-2 selective inhibitors on colon cancer cell proliferation and apoptosis.
- To determine if the Delta1/Notch1 signal transduction pathway mediates the effects of COX-2 inhibitors in colorectal cancer.
- To elucidate the role of the Notch1 pathway in regulating colon cancer cell proliferation and apoptosis.
Main Methods:
- Utilized colon cancer cell lines (HT-29 and SW480) treated with NS-398 (COX-2 selective inhibitor) and DAPT (gamma-secretase inhibitor).
- Assessed cell proliferation and apoptosis using MTT assays and flow cytometry.
- Quantified COX-2 mRNA, prostaglandin E2 (PGE2) levels, and protein expression (Notch1, Delta1, ICN, Hes1, NF-kappaB2) via RT-PCR, ELISA, and Western blot.
Main Results:
- NS-398 treatment decreased COX-2 mRNA and PGE2 levels in HT-29 cells, but not SW480 cells.
- Both NS-398 and DAPT inhibited cell proliferation and induced apoptosis in a dose- and time-dependent manner.
- Inhibition was associated with decreased Notch1 activity, Hes1, and NF-kappaB2 expression.
Conclusions:
- Selective COX-2 inhibitors impact colon cancer cell proliferation and apoptosis via both COX-2-dependent (HT-29) and independent (SW480) pathways.
- The Delta1/Notch1 signal pathway is identified as a key mediator of COX-2 inhibitor effects on colon cancer cells.
- The Notch1 pathway represents a potential novel therapeutic target for selective COX-2 inhibitors in colorectal cancer treatment.
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