Related Experiment Videos
Inhibition of proteasome function induced apoptosis in gastric cancer
Abstract:
The ubiquitin-proteasome pathway plays a critical role in the degradation of cellular proteins and cell cycle control. Dysregulating the degradation of such proteins should have profound effects on tumor growth and causes cells to undergo apoptosis. The aims of this study are to evaluate the ubiquitin-proteasome pathway in gastric cancer and the potential role of pharmacological inhibition of proteasome on induction of apoptosis in gastric cancer cells. Gastric cancer cell lines AGS (p53 wild-type) and MKN-28 (p53 mutant) were treated with proteasome inhibitor MG132. The results showed that MG132 inhibited cell proliferation in AGS and MKN-28 cells in a time- and dose-dependent manner. The inhibition of cell proliferation was caused by apoptosis which was also time- and dose-dependent. AGS cells were more responsive to MG132 than MKN-28 cells. Induction of apoptosis was preceded by the activation of caspase-3, as measured by a colorimetric caspase-3 cellular activity and Western blotting of the cleavage of caspase-3 and its substrate PARP. Activation of caspase-7 was also exhibited. In addition, z-VAD-fmk, a broad spectrum caspase inhibitor, reversed apoptosis induced by MG132 in AGS and MKN28 cells. Although z-DEVD-fmk, a specific caspase-3 inhibitor, suppressed MG132-induced apoptosis in MKN28 cells, it only partially rescued the apoptotic effect in AGS cells. Caspase-3 activation was the result of release of cytochrome c from mitochondria into the cytosol, as a consequence of upregulation of bax. There were overexpressions of all the proteasome-related proteins p53, p21(waf1) and p27(kip1) at 4 hr after proteasome inhibition which was identified by the accumulation of ubiquitin-tagged proteins. This was accompanied by accumulation of cells at G(1) phase. Our present study suggests that inhibition of proteasome function in gastric cancer cells induces apoptosis and proteasomal inhibitors have potential use as novel anticancer drugs in gastric cancer.
Insights
Proteasome inhibition with MG132 triggers apoptosis in gastric cancer cells, offering potential for new cancer therapies. AGS cells showed greater sensitivity to this proteasome inhibitor than MKN-28 cells.
Area of Science:
- Oncology
- Molecular Biology
- Cell Biology
Background:
- The ubiquitin-proteasome pathway is crucial for protein degradation and cell cycle regulation.
- Dysregulation of this pathway significantly impacts tumor growth and apoptosis.
- Understanding its role in gastric cancer is vital for developing targeted therapies.
Purpose of the Study:
- To investigate the ubiquitin-proteasome pathway in gastric cancer.
- To assess the efficacy of proteasome inhibition in inducing apoptosis in gastric cancer cells.
- To explore the potential of proteasome inhibitors as anticancer drugs for gastric cancer.
Main Methods:
- Gastric cancer cell lines (AGS and MKN-28) were treated with the proteasome inhibitor MG132.
- Cell proliferation, apoptosis, caspase activation (caspase-3, caspase-7), and cytochrome c release were analyzed.
- Western blotting was used to detect protein expression (p53, p21(waf1), p27(kip1), PARP) and ubiquitin-tagged proteins.
Main Results:
- MG132 inhibited gastric cancer cell proliferation in a time- and dose-dependent manner, inducing apoptosis.
- AGS cells (p53 wild-type) were more sensitive to MG132 than MKN-28 cells (p53 mutant).
- Apoptosis was mediated by caspase-3 and caspase-7 activation, cytochrome c release, and bax upregulation, leading to G1 cell cycle arrest.
Conclusions:
- Proteasome inhibition effectively induces apoptosis in gastric cancer cells.
- Proteasome inhibitors demonstrate potential as novel therapeutic agents for gastric cancer treatment.
- The study highlights the importance of the ubiquitin-proteasome pathway in gastric cancer progression and therapeutic targeting.