Expression Of EGFR And FAK In Human Prostate Cancer Tissues And The Effect Of EGFR Inhibitor Gefitinib In Prostate Cancer Cell Lines

Part 1Objective:To study the role and the relation of EGFR and FAK in Pathogenesis in Prostate cancer.Methods:Immunohistochemistry staining was used to detect the expression of EGFR and FAK in 78 cases of prostate cancer and 28 cases of metastatic prostate cancer. The relationship between EGFR and FAK were analyzed with chi-square test.Results:1) The pattern of EGFR expression:54 cases of Prostate cancer were stained with EGFR positively in 78 patients. Most of the stain was found in the membrane and cytoplasm of the positive cells.96% positive staining was found in the 28 cases of metastatic prostate cancer tissues.2) The positive rate was related to the Gleason.2) The pattern of FAK expression:52 cases of Prostate cancer were stained with FAK in 78 patients and the stain was found in the cytoplasm of the positive cells. Also 96% positive staining was detected in the 28 cases of metastatic prostate cancer tissues. 2) The positive rate was related to the Gleason.3) The relationship between EGFR and FAK:In 78 Prostate cancer specimens, both positive expressions were found in 40 cases, while both negative in 12 cases. The correlation beween EGFR and FAK was found by chi-square test (P<0.05).Conclusion:(1) There were correlations between the expression of EGFR and FAK in prostate cancer tissue. More high level of EGFR and FAK, higer score of Gleason grading.(2) In metastatic prostate cancer, the expression of EGFR and FAK were stronger than cancer tissue suggesting that both protein may be involved in prostate cancer metastasis Part 2Objective:The study aim to investigate the effect of small. molecular tyrosine kinase inhibitor gefitinib in prostate cancer cell lines PC-3 and DU-145 in vitro, and to explore its possible mechanisms in signal transduction pathway including cell proliferation and invasion.Methods:Western Blot was performed to detect the inhibition effect of gefitinib in prostate cancer cell line PC-3; Effect of gefitinib on prostate cells proliferation were investigated by tetracarboxylic based tetrazolium (MTT) assay for cell viability using two prostate cancer cell line PC-3 and DU-145; The phosphorylation level of FAK397, invasion-related protein were investigated using Western Blot under gefitinib treatment. Transwell assay was used to check the anti-invasion function of gefitinib on PC-3 prostate cancer.Results:5uM gefitinib can inhibit the phosphorylation of EGFR on its 1068 site, while limited inhibiton effect using the Src inhibitor PP2 and the Erk inhibitor U0126; MTT assay showed that the epidermal growth factor (EGF) had different role on the two prostate cancer cell lines:the proliferation of DU-145 was enhanced compared to PC-3, almost no effect on it using the same concentration. Further Western Blot assay using PC-3 cells found that gefitinib can inhibit the phosphrylation of protein FAK in 397 site, suggesting that gefitinib can inhibit FAK autophosphorylation; Transwell experiments confirmed gefitinib inhibits PC-3 cell penetrating activity.Conclusion:The EGFR inhibitor gifitinib can inhibit the cell proliferation and induce apoptosis in prostate cancer cells with different pattern. Gifitinib induced the cell apoptosis in DU-145, while no effect even high concentration in PC-3 cells. Gifitinib inhibit the PC-3 invasion through inhibit phosphorylation of FAK.