Inhibition of proteasome function induced apoptosis in gastric cancer

• Published in: International journal of cancer 2001-08, Vol.93 (4), p.481-488
• Main Authors: Fan, Xiao Ming, Wong, Benjamin Chun Yu, Wang, Wei Ping, Zhou, Xin Min, Cho, Chi Hin, Yuen, Siu Tsan, Leung, Suet Yi, Lin, Marie Chia Mi, Kung, Hsiang Fu, Lam, Shiu Kum
• Format: Article
• Language: English
• Subjects: Adenocarcinoma - drug therapy; Adenocarcinoma - enzymology; Adenocarcinoma - pathology; Antineoplastic agents; apoptosis; Apoptosis - drug effects; Apoptosis - physiology; bax; Biological and medical sciences; Caspase 3; Caspase 7; caspases; Caspases - metabolism; Cell Cycle - drug effects; Cell Cycle Proteins - biosynthesis; Cell Cycle Proteins - genetics; Cell Division - drug effects; Cyclin-Dependent Kinase Inhibitor p21; Cyclin-Dependent Kinase Inhibitor p27; Cyclins - biosynthesis; Cyclins - genetics; Cysteine Endopeptidases - physiology; Cysteine Proteinase Inhibitors - pharmacology; Enzyme Activation - drug effects; gastric cancer; General aspects; Humans; Leupeptins - pharmacology; Medical sciences; Multienzyme Complexes - antagonists & inhibitors; Multienzyme Complexes - physiology; Pharmacology. Drug treatments; Proteasome Endopeptidase Complex; Stomach Neoplasms - drug therapy; Stomach Neoplasms - enzymology; Stomach Neoplasms - pathology; Tumor Cells, Cultured; Tumor Suppressor Protein p53 - biosynthesis; Tumor Suppressor Protein p53 - genetics; Tumor Suppressor Proteins; Ubiquitins - metabolism; ubiquitin‐proteasome; Up-Regulation - drug effects
• ISSN: 0020-7136; 1097-0215
• DOI: 10.1002/ijc.1373

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, p21waf1 and p27kip1 at 4 hr after proteasome inhibition which was identified by the accumulation of ubiquitin‐tagged proteins. This was accompanied by accumulation of cells at G1 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. © 2001 Wiley‐Liss, Inc.