Glioblastoma multiforme (GBM) is a treatment-resistant malignancy with poor prognosis. Temozolomide (TMZ) is widely used as a first-line drug for GBM. Although this improves patient prognosis, it does not completely eradicate the tumour. Even after total surgical resection, GBM can exhibit uncontrollable invasiveness at the tumour margins owing to activation of matrix metalloproteinases (MMPs) such as MMP-2 and -9; these degrade collagen IV in the basement membrane, which normally prevents cancer invasion. TMZ induces DNA damage and activates transcription factors including c-jun, c-fos, nuclear factor-κβ, and early growth response protein-1, which have putative binding sites on the MMP-9 promoter. TMZ may therefore enhance tumour invasion by stimulating MMP-9 transcription and enzymatic activity. To test this hypothesis, we investigated MMP-2 and -9 mRNA transcription and activity in GBM cell lines treated with TMZ. Human A172 GBM cells were exposed to TMZ (25% and 50% inhibitory concentrations) for 24 or 48h; cell cycle distribution and mRNA levels of MMP-2 and -9 were evaluated using flow cytometry and semi-quantitative reverse transcription PCR, respectively. MMP-2 and -9 enzymatic activities were assessed using gelatin zymography in human A172 and U373 MG GBM cells exposed to TMZ under the same conditions. TMZ altered A172 cell cycle distribution, but not MMP-2 or -9 mRNA levels. TMZ did not affect MMP-2 or -9 enzymatic activities in A172 or U373 MG cells. These findings indicated that TMZ is therefore unlikely to promote GBM invasiveness.
Keywords: Glioblastoma; Matrix metalloproteinase 2; Matrix metalloproteinase 9; Semi-quantitative reverse transcription-PCR; Temozolomide.
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