The tumor suppressor activity of MDA-7/IL-24 is mediated by intracellular protein expression in NSCLC cells.

Abstract

mda-7/IL-24 (HGMW-approved symbol IL24) is a tumor suppressor gene whose expression is lost during tumor progression. Gene transfer using adenoviral mda-7/IL-24 (Ad-mda7) exhibits minimal toxicity on normal cells while inducing potent apoptosis in a variety of cancer cell lines. Ad-mda7-transduced cells express high levels of MDA-7 protein intracellularly and also secrete a soluble form of MDA-7 protein. In this study, we sought to determine whether the intracellular or secreted MDA-7 protein was responsible for anti-tumor activity in H1299 lung tumor cells. Ad-mda7 transduction of lung tumor cells increased expression of stress-related proteins, including BiP, GADD34, PP2A, caspases 7 and 12, and XBP-1, consistent with activation of the UPR pathway, a key sensor of endoplasmic reticulum (ER)-mediated stress. Blocking secretion of MDA-7 did not inhibit apoptosis, demonstrating that intracellular MDA-7 was responsible for cytotoxicity. Consistent with this result, when applied directly to lung cancer cells, soluble MDA-7 protein exhibited minimal cytotoxic effect. We then generated mda-7 expression constructs using vectors that target the expressed protein to various subcellular compartments, including cytoplasm, nucleus, and ER. Only full-length and ER-targeted MDA-7 elicited cell death in tumor cells. Thus in lung cancer cells, Ad-mda7 activates the UPR stress pathway and induces apoptosis via intracellular MDA-7 expression in the secretory pathway.

• Authors: Kerry A Sieger, Abner M Mhashilkar, Alexis Stewart, R Bryan Sutton, Randall W Strube, Si Yi Chen, Abujiang Pataer, Stephen G Swisher, Elizabeth A Grimm, Rajagopal Ramesh, Sunil Chada
• Journal: Molecular therapy : the journal of the American Society of Gene Therapy (Mol Ther) Vol. 9 Issue 3 Pg. 355-67 (Mar 2004) ISSN: 1525-0016 [Print] United States
• PMID: 15006602 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, P.H.S.)

Chemical References

• Antigens, Differentiation
• Cell Cycle Proteins
• Cytokines
• Endoplasmic Reticulum Chaperone BiP
• Heat-Shock Proteins
• Il24 protein, mouse
• Interleukins
• Molecular Chaperones
• PPP2R1B protein, human
• Proteins
• interleukin-24
• Tunicamycin
• Brefeldin A
• PPP1R15A protein, human
• Phosphoprotein Phosphatases
• Ppp1r15a protein, mouse
• Protein Phosphatase 1
• Protein Phosphatase 2
• CASP12 protein, human
• CASP7 protein, human
• Casp12 protein, mouse
• Casp7 protein, mouse
• Caspase 12
• Caspase 7
• Caspases

Topics

• Adenoviridae (genetics)
• Antigens, Differentiation
• Apoptosis
• Blotting, Western
• Brefeldin A (pharmacology)
• Carcinoma, Non-Small-Cell Lung (genetics)
• Caspase 12
• Caspase 7
• Caspases (metabolism)
• Cell Cycle Proteins
• Cell Line
• Cell Line, Tumor
• Cell Separation
• Cell Survival
• Cytokines (genetics)
• Disease Progression
• Dose-Response Relationship, Drug
• Endoplasmic Reticulum (metabolism)
• Endoplasmic Reticulum Chaperone BiP
• Flow Cytometry
• Gene Transfer Techniques
• Genes, Tumor Suppressor
• Genetic Therapy (methods)
• Genetic Vectors
• Heat-Shock Proteins (metabolism)
• Humans
• Interleukins (genetics)
• Lung Neoplasms (genetics)
• Microscopy, Fluorescence
• Models, Genetic
• Molecular Chaperones (metabolism)
• Oligonucleotide Array Sequence Analysis
• Phosphoprotein Phosphatases (metabolism)
• Plasmids (metabolism)
• Protein Folding
• Protein Phosphatase 1
• Protein Phosphatase 2
• Proteins (metabolism)
• Tunicamycin (pharmacology)