Figure 5.

PTPRA overexpression promotes cell growth due to cell cycle arrest in lung cancer cells. (A) Immunoblot analysis of PTPRA expression in stably transfected H520 clones. Total protein lysates from an empty vector transfected clone (NC) and from one PTPRA cDNA transfected clone were immune blotted with anti-PTPRA. Activation of c-Src kinase activity, used as a result of PTPRA expression. Proteins were blotted with Src phosphorylation and dephosphorylation antisera. (B) Effect of PTPRA expression on the growth rate. The proliferation of stable H520 cell lines was examined using a Cell Counting kit. (C and D) Cell cycle distribution in an empty vector transfected clone (NC) and stable PTPRA expressing line. Exponentially growing cells were trypsinized, fixed, and stained with propidium iodide, and fluorescence measured by flow cytometry. (E) Cell cycle G1/S checkpoint signaling pathways were checked. Cells from an empty vector transfected clone (NC) and from one PTPRA cDNA transfected clones were lysed, and lysates were subjected to protein gel blot assays. The antibodies against p21, cyclin D1, cyclin D3, p27 and p18 were used to determine the effect of PTPRA upregulation on the activities of the cell cycle pathways.