Ionizing radiation enhances matrix metalloproteinase-2 secretion and invasion of glioma cells through Src/epidermal growth factor receptor-mediated p38/Akt and phosphatidylinositol 3-kinase/Akt signaling pathways.
Glioblastoma is a severe type of primary brain tumor, and its highly invasive character is considered to be a major therapeutic obstacle. Several recent studies have reported that ionizing radiation (IR) enhances the invasion of tumor cells, but the mechanisms for this effect are not well understood. In this study, we investigated the possible signaling mechanisms involved in IR-induced invasion of glioma cells. IR increased the matrix metalloproteinase (MMP)-2 promoter activity, mRNA transcription, and protein secretion along with the invasiveness of glioma cells lacking functional PTEN (U87, U251, U373, and C6) but not those harboring wild-type (WT)-PTEN (LN18 and LN428). IR activated phosphatidylinositol 3-kinase (PI3K), Akt, and mammalian target of rapamycin, and blockade of these kinases by specific inhibitors (LY294002, Akt inhibitor IV, and rapamycin, respectively) and transfection of dominant-negative (DN) mutants (DN-p85 and DN-Akt) or WT-PTEN suppressed the IR-induced MMP-2 secretion in U251 and U373 cells. In addition, inhibitors of epidermal growth factor receptor (EGFR; AG490 and AG1478), Src (PP2), and p38 (SB203580), EGFR neutralizing antibody, and transfection of DN-Src and DN-p38 significantly blocked IR-induced Akt phosphorylation and MMP-2 secretion. IR-induced activation of EGFR was suppressed by PP2, whereas LY294002 and SB203580 did not affect the activations of p38 and PI3K, respectively. Finally, these kinase inhibitors significantly reduced the IR-induced invasiveness of these cells on Matrigel. Taken together, our findings suggest that IR induces Src-dependent EGFR activation, which triggers the p38/Akt and PI3K/Akt signaling pathways, leading to increased MMP-2 expression and heightened invasiveness of PTEN mutant glioma cells.
Park
Chang-Min
CM
Laboratory of Functional Genomics, Korea Institute of Radiological and Medical Sciences, Seoul, Korea.
Park
Myung-Jin
MJ
Kwak
Hee-Jin
HJ
Lee
Hyung-Chahn
HC
Kim
Mi-Suk
MS
Lee
Seung-Hoon
SH
Park
In-Chul
IC
Rhee
Chang Hun
CH
Hong
Seok-Il
SI
D000818:Animals; D045744:Cell Line, Tumor; D017931:DNA Primers; D066246:ErbB Receptors / Q000502:physiology* / Q000528:radiation effects; D015971:Gene Expression Regulation, Enzymologic; D015972:Gene Expression Regulation, Neoplastic; D017930:Genes, Reporter; D005909:Glioblastoma / Q000473:pathology; D005910:Glioma / Q000473:pathology*; D020778:Matrix Metalloproteinase 2 / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D009361:Neoplasm Invasiveness; D051059:PTEN Phosphohydrolase / Q000235:genetics / Q000378:metabolism; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism* / Q000528:radiation effects; D010766:Phosphorylation; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism* / Q000528:radiation effects; D011839:Radiation, Ionizing; D051381:Rats; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000528:radiation effects; D014162:Transfection; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism* / Q000528:radiation effects
D017931:DNA Primers; D019869:Phosphatidylinositol 3-Kinases; D066246:ErbB Receptors; D051057:Proto-Oncogene Proteins c-akt; D048051:p38 Mitogen-Activated Protein Kinases; D051059:PTEN Phosphohydrolase; D020778:Matrix Metalloproteinase 2