| Summary: | 博士 === 國立中興大學 === 分子生物學研究所 === 102 === Luteolin (3’,4’,5,7-tetrahydroxyflavone) is a common flavonoid in many types of plants and has several beneficial biological effects, including anti-inflammation, anti-oxidant, and anti-cancer properties. However, the detail mechanisms of luteolin in suppressing tumor invasion and metastasis are poorly understood. Here, we investigated the effects of luteolin on suppressing glioblastoma tumor cell invasion and migration activity. Under the non-cytotoxic doses (15 and 30 μM), luteolin exhibited an inhibitory effect on migration and invasion in U87 and T98G glioblastoma cells. Additionally, filopodia assembly in U87 cells was markedly suppressed after luteolin treatment. The treatment of luteolin also showed a decrease of Cdc42 (cell division cycle 42) protein levels and reduced PI3K/AKT activation, whereas there was no association between this decrease and phosphorylated ERK or altered transcription levels of Cdc42. Over expression of constitutive Cdc42 (Q61L) using transient transfection in U87 cells induced a partial cell migration, but did not affected the degradation of the protein levels of Cdc42 after luteolin treatment. Moreover, inhibition of the proteaosome pathway by MG132 caused a significant recovery in the migration ability of U-87 cells and augmented the Cdc42 protein levels after luteolin treatment, suggesting that pharmacological inhibition of migration via luteolin treatment is likely to preferentially facilitate the protein degradation of Cdc42. Taken together, the study demonstrated that flavonoids of luteolin prevent the migration of glioblastoma cells by affecting PI3K/AKT activation, modulating the protein expression of Cdc42 and facilitating their degradation via the proteaosome pathway.
In secondary section, dynamin-related protein 1 (DRP1) is an 80-kDa GTPase, which is involved in mitochondrial fission, mitochondrial protein imports and cisplatin cytotoxicity, suggesting an association with disease progression of cancer. This study investigated the predictive value of DRP1 in glioblastoma multiforme (GBM) to radiotherapy. Using immunohistochemistry, DRP1 expression was measured in 47 GBM patients. Expression of DRP1 was confirmed by immunoblotting. Correlation between DRP1 expression and clinicopathological parameters was analyzed by statistical analysis. Difference of patient’s survival was compared by a log-rank test. The Results showed that DRP1 expression was detected in 41 GBM patients. Among these, nuclear DRP1 (DRP1nuc) was detected in 33 (80.5%) patients. A significant difference was found in cumulative survival between patients with high DRP1 levels and those with low DRP1 levels (p = 0.0398). In vitro, DRP1 was identified in both T98G and U87 cell lines. DRP1 expression in T98G was higher than U87 cells. Silencing of DRP1 reduced cell proliferation, metastatic potential, and radiation resistance in both T98G and GBM stem cells. Shikonin, a compound extracted from Chinese medicinal herb Lithospermum erythrorhizon, inhibited DRP1 expression and induced autophagy. Although SAHA did not evidently decrease DRP1 levels, it increased the frequency of apoptotic cells. Moreover, both shikonin and SAHA reduced nuclear DRP1 and increased radiosensitivity, suggesting that both drugs radiosensitized GBM cells. In conclusion, our results suggest that DRP1 overexpression is a prospective radioresistant phenotype in GBM. DRP1 could be a potential target for improving radiotherapy.
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