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

Mol Ther. 2004 Mar;9(3):355-67. doi: 10.1016/j.ymthe.2003.11.014.

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.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • 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
  • 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

Substances

  • Antigens, Differentiation
  • Cell Cycle Proteins
  • Cytokines
  • 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
  • molecular chaperone GRP78