Epidermal growth factor receptor (EGFR) is found to express at high levels in a variety of solid tumors including gliomas. This study was to examine the effect of an EGFR-tyrosine kinase inhibitor (AG1478) alone or in combination with cisplatin (CDDP) on the growth of glioma cells (U87). U87 glioma cells were treated with AG1478 (10 μmol/L) or CDDP (25 μmol/L) as a single agent or in combination for 24 or 48 h. The expression of EGFR and the components in its downstream signaling pathway [extracellular signal-regulated kinase (ERK), protein kinase B (AKT)] in U87 glioma cells was detected by Western blotting. Cell growth, cell cycle distribution and cell apoptosis were determined by MTT method and flow cytometry, respectively. The results showed that CDDP could induce the activation of EGFR and the components in its downstream signaling pathways in a concentration-dependent manner. The combined treatment of AG1478 with CDDP could inhibit the proliferation of U87 glioma cells, arrest the cell cycle and promote cell apoptosis. In the EGFR signaling pathway, AG1478 decreased the phosphorylation of ERK, AKT and EGFR in U87 glioma cells. It was concluded that the combined treatment of AG1478 and CDDP may exert synergistic inhibitory effects on the growth of glioma cells by suppressing the activities of EGFR, AKT and ERK.

LRIG family shares similar structures that include a signal peptide, an extracellular region consisting of a leucine-rich repeat domain and three immunoglobulin-like domains, a transmembrane domain, and a cytoplasmic tail. After activation of EGFR, the extracellular LRR domain and immunoglobulin-like domains of LRIG1 can bind to the extracellular parts of EGFR, resulting in recruitment of c-Cbl to the cytoplasmic domains, and induction of EGFR degradation. This study investigated the effects of overexpression of leucine-rich repeats and LRIG1 on cisplatin (CDDP) sensitivity in the glioma cell line U251 and explored the possible mechanisms mediating this effect. We found that CDDP could inhibit the growth of U251 cell line and induced activation of the EGFR. Overexpression of LRIG1 increased the inhibitory effect of CDDP on the U251 cell line via the inhibition of proliferation and induction of apoptosis. The mechanisms underlying the effect of the combined treatment of LRIG1 and CDDP could be that LRIG1 blocked CDDP-induced EGFR activation and regulated the apoptosis proteins. These findings suggest that upregulation of LRIG1 expression enhances the CDDP sensitivity in the glioma cell line U251.

No abstract

No abstract