title: mda-7 (IL-24) Inhibits growth and enhances radiosensitivity of glioma cells in vitro via JNK signaling.
abstract: Despite therapeutic interventions including surgery, chemotherapy and radiotherapy, glioblastoma multiforme (GBM) has a very poor prognosis and novel therapies are required. MDA-7 (IL-24), when expressed via a recombinant replication defective adenovirus, Ad.mda-7, has profound anti-proliferative and cytotoxic effects in a variety of tumor cells, but not in non-transformed cells. The present studies examined the combined impact of Ad.mda-7 and ionizing radiation on the proliferation and survival of GBM cells. Ad.mda-7 reduced the proliferation of rodent and human glioma cells in MTT assays and in colony formation assays. The anti-proliferative effects of Admda-7 were enhanced by radiation in a greater than additive fashion. In vitro, this cellular change correlated with enhanced cell numbers in G1/G0 and G2/M phases of the cell cycle, implying Ad.mda-7 radiosensitizes tumor cells in a cell cycle-independent manner. The radiosensitizing effects were not observed in cultures of non-transformed primary astrocytes. The enhanced reduction in growth correlated with increased necrosis and DNA degradation. Ad.mda-7 enhanced p38 and ERK1/2 activity but did not alter JNK or Akt activity. Irradiation of cells expressing MDA-7 suppressed ERK1/2 activity and dramatically enhanced JNK1/2 activity without altering either Akt or p38 activity. Inhibition of JNK1/2, but not p38, signaling abolished the radiosensitizing properties of MDA-7. Inhibition of neither ERK1/2 nor PI3K signaling enhanced the anti-proliferative effects of Ad.mda-7, whereas combined inhibition of both pathways enhanced cell killing, suggesting that ERK and PI3K signaling can be protective against MDA-7 lethality.
mesh_terms: D000256:Adenoviridae / Q000235:genetics; D000818:Animals; D017209:Apoptosis / Q000502:physiology / Q000528:radiation effects*; D015153:Blotting, Western; D001932:Brain Neoplasms / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D002455:Cell Division / Q000187:drug effects / Q000528:radiation effects; D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins / Q000378:metabolism; D004307:Dose-Response Relationship, Radiation; D016147:Genes, Tumor Suppressor; D005910:Glioma / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy*; D005982:Glutathione Transferase / Q000378:metabolism; D007378:Interleukins / Q000235:genetics / Q000627:therapeutic use*; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases / Q000378:metabolism*; D020928:Mitogen-Activated Protein Kinases / Q000378:metabolism; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011839:Radiation, Ionizing; D011838:Radiation-Sensitizing Agents / Q000627:therapeutic use*; D051381:Rats; D011916:Rats, Inbred F344; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D016159:Tumor Suppressor Protein p53 / Q000378:metabolism; D048051:p38 Mitogen-Activated Protein Kinases; D000099180:Interleukin-24
chemical_list: D050759:Cyclin-Dependent Kinase Inhibitor p21; D016213:Cyclins; D005982:Glutathione Transferase; D007378:Interleukins; D048031:JNK Mitogen-Activated Protein Kinases; D048670:MAP Kinase Kinase 4; D019950:Mitogen-Activated Protein Kinase 1; D048052:Mitogen-Activated Protein Kinase 3; D020929:Mitogen-Activated Protein Kinase Kinases; D020928:Mitogen-Activated Protein Kinases; D017346:Protein Serine-Threonine Kinases; D011518:Proto-Oncogene Proteins; D051057:Proto-Oncogene Proteins c-akt; D011838:Radiation-Sensitizing Agents; D016159:Tumor Suppressor Protein p53; D048051:p38 Mitogen-Activated Protein Kinases; D000099180:Interleukin-24; C493958:Cdkn1a protein, rat; C494920:Akt1 protein, rat