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Selective apoptosis of mesothelioma cells is mediated in part by the BH3‐only protein Bim
Author(s) -
Abayasiriwardana K,
Kim K,
Lee K,
Vivo C,
Dansen T,
Hunt A,
Evan G,
Broaddus V C
Publication year - 2006
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.20.4.a1-a
Subject(s) - anisomycin , apoptosis , cancer research , phosphorylation , downregulation and upregulation , microbiology and biotechnology , flow cytometry , gene knockdown , tumor necrosis factor alpha , chemistry , biology , kinase , immunology , biochemistry , gene
Mesothelioma, like many tumors, is inherently resistant to apoptosis. However, certain stimuli can sensitize mesothelioma to apoptosis without affecting normal cells. We have previously shown that chemotherapy sensitized human mesothelioma cells, such as M28, to apoptosis induced by TRAIL (TNF‐related apoptosis inducing ligand) via stimulation of the JNK‐Stress Activated Pathway. We asked whether non‐toxic stimulators of JNK, such as anisomycin, could also sensitize M28 cells to TRAIL and, if so, by what mechanism. Anisomycin rapidly sensitized M28 to TRAIL‐induced apoptosis 8 h after treatment but did not sensitize primary human mesothelial cells. By 2 h, anisomycin induced JNK phosphorylation in M28 but not in primary mesothelial cells and also selectively upregulated Bim, a downstream BH3‐only protein target of pJNK, suggesting Bim regulation by pJNK in malignant cells. We used siRNA to knockdown Bim protein and, using timelapse video‐microscopy and flow cytometry, we demonstrated that Bim knockdown significantly delayed the onset of apoptosis induced by anisomycin and TRAIL. Although anisomycin clearly increased Bim protein, anisomycin did not increase Bim mRNA as measured by RT‐PCR but did alter Bim phosphorylation as seen on 2D gel electrophoresis and decrease Bim degradation as seen over 8 h on immunoblot. Overall, our data suggest that the sensitization by anisomycin in malignant cells is mediated in part via a JNK signaling pathway that alters Bim phosphorylation and inhibits degradation, thus priming the cells for apoptosis via the death receptor pathway. Funded by NIH NCI R01 095671