Gadd45a sensitizes medulloblastoma cells to irradiation and suppresses MMP-9-mediated EMT.

Abstract

Medulloblastomas are the most common malignant tumors of the central nervous system during childhood. Radiation-induced medulloblastoma tumor recurrences are aggressive and metastatic in nature. In the present study, we demonstrate that Gadd45a expression can sensitize medulloblastoma cells to radiotherapy. We have elucidated the role of Gadd45a in ionizing radiation (IR)-induced G2-M arrest and invasion and metastatic potential of the medulloblastoma cancer cell lines DAOY and D283. We demonstrate that Gadd45a is induced by IR and results in p53 phosphorylation. The role of IR-induced Gadd45a in G2-M arrest is demonstrated by fluorescence-activated cell sorting analysis in the cells treated with siRNA Gadd45a and Ov-exp Gadd45a. We show that Ov-exp Gadd45a aggravates G2-M blockage and also increases binding of Gadd45a to Cdc2 by immunocytochemistry analysis. Furthermore, we show the anti-tumorigenic role of Gadd45a to be mediated by the negative regulation of IR-induced cancer cell invasion and migration-associated proteins, such as matrix metallopeptidase (MMP)-9 and β-catenin. When compared with IR treatment alone, Ov-exp Gadd45a plus IR treatment resulted in decreased nuclear localization and increased membrane localization of β-catenin, and this was further confirmed by membrane distribution. We also show that Ov-exp Gadd45a resulted in downregulation of MMP-9 and suppression of epithelial-mesenchymal transition (EMT). Alternatively, inhibition of MMP-9 (pM) resulted in upregulation of Gadd45a and suppression of EMT. The anti-tumor effect of pM was correlated with increased expression of Gadd45a protein in nude mice intracranial tumors. Taken together, our studies demonstrate that upregulation of Gadd45a or suppression of MMP-9 (pM) with IR retards medulloblastoma tumor metastatic potential.

• Authors: Swapna Asuthkar, Arun Kumar Nalla, Christopher S Gondi, Dzung H Dinh, Meena Gujrati, Sanjeeva Mohanam, Jasti S Rao
• Journal: Neuro-oncology (Neuro Oncol) Vol. 13 Issue 10 Pg. 1059-73 (Oct 2011) ISSN: 1523-5866 [Electronic] England
• PMID: 21813510 (Publication Type: Journal Article, Research Support, N.I.H., Extramural)

Chemical References

• Cell Cycle Proteins
• GADD45A protein, human
• Nuclear Proteins
• Matrix Metalloproteinase 9

Topics

• Animals
• Cell Cycle (radiation effects)
• Cell Cycle Proteins (metabolism)
• Cell Line, Tumor
• Cell Proliferation (radiation effects)
• Cell Separation
• Cerebellar Neoplasms (metabolism, pathology)
• Epithelial-Mesenchymal Transition (physiology, radiation effects)
• Flow Cytometry
• Fluorescent Antibody Technique
• Humans
• Immunoblotting
• Immunohistochemistry
• Immunoprecipitation
• In Situ Nick-End Labeling
• Matrix Metalloproteinase 9 (metabolism)
• Medulloblastoma (metabolism, pathology)
• Mice
• Mice, Nude
• Nuclear Proteins (metabolism)
• Radiation Tolerance (physiology)
• Reverse Transcriptase Polymerase Chain Reaction
• Signal Transduction (physiology, radiation effects)
• Xenograft Model Antitumor Assays