| The epidermal growth factor receptor (EGFR) is overexpressed by a great many of malignancies, including the human renal cell carcinoma, whose incidence ranks the second in that of the urinary tumors. It has been reported that the overexpression of EGFR plays a key role in pathological processes such as tumorigenesis, progression, and metastasis. The overexpression of EGFR has also been shown to be correlated with tumor grade, tumor size, lymph node metastasis, survival and resistance to chemotherapy in patients. Binding of its ligants (mainly EGF and TGF- a ) to the extracellular domains, EGFR activates the intracellular domain of tyrosine kinase which is essential for activation of numerous downstream effectors, including phospholipase C y, PI3K / AKT and MAPK, with the ultimate cellular response being DNA synthesis and cell proliferation. Ligand-induced stimulation of cell growth depends on activation of the tyrosine kinase in the EGFR. Tyrphostin AG1478 is a small molecular weight compound that has been shown to preferentially inhibit the EGFR tyrosine kinase and thus may inhibit EGFR-dependent cell growth.In this study, human renal cell carcinoma line of GRC-1 was exposed to a-5-series of different concentrations of AG1478. MTT assay was employed to investigate the effects done by AG1478 on the growth and proliferation ability of GRC-1 cells. Changes of cell morphology were observed by light microscope and electron microscope. And FCM and DNA electrophoresis were used to detect the cell apoptosis. As a result, GRC-1 cell line was signally inhibited by AG1478. MTT assay showed that AG1478 restrained the proliferation of GRC-1 cells at low concentrations with a dose-response relationship. Cell cycles were observed to be arrested in GI phase. With the light microscope, we observed that in contrast to the control group, the GRC-1 cells were decreased in quantity, and turned into fusiform in shape by 10 u mol/L of AG1478. The overlapping growth manner disappeared. With the electron microscope, we observed a series of alterations that supported the apoptosis: the microvillus lessened or disappeared, cytoplasm concentrated, mitochondria and lysosomes swelled, and heterochromatin massed and spreaded around the karyotheca. Early and late apoptosis was detected by FCM and DNA electrophoresis respectively.The results above suggest that EGFR plays a critical role in the biological behaviors of human renal cell carcinoma. And highly selective EGFR tyrosine kinase inhibitor is of potential to be developed into drugs for the treatment of kidney neoplasms. |
