Combining Ellagic Acid with Temozolomide Mediates the Cadherin Switch and Angiogenesis in a Glioblastoma Model

OBJECTIVE: We aimed to evaluate the combined effect of ellagic acid (EA) and temozolomide (TEM) on the cadherin switch and angiogenesis in the C6 glioma cell line. METHODS: A total of 100 mu M EA and 100 mu M TEM were applied to rat C6 glioma cells for 24, 48, and 72 hours. Cell proliferation was detected by 5-bromo-2'-deoxyuridine immunohistochemistry. The messenger RNA and protein levels of E-cadherin, N-cadherin, and vascular endothelial growth factor (VEGF) were determined by real-time polymerase chain reaction and their immunohistochemistry, respectively, subsequent to EA treatment combined with TEM. RESULTS: EA in combination with TEM conspicuously reduced the viability of C6 glioma cells at all incubation times (P < 0.001). EA upregulated the expression of E-cadherin at the gene and protein levels in a time-independent manner (P < 0.05 and P < 0.001, respectively). By the presence of TEM, the increase was exaggerated at 24-hour incubation (P < 0.01). Conversely, EA reduced N-cadherin expression and immunoreactivity in a time-independent manner (P < 0.05 and P < 0.001, respectively), and combination with TEM enhanced this effect at the 24th hour (P < 0.001). Combination also downregulated the gene expression (P < 0.001) and immunoreactivity of VEGF only at 72 hours (P < 0.001). CONCLUSIONS: A successful therapeutic efficacy of EA combined with TEM is suggested probably by inhibiting the cadherin switch and angiogenesis.