C-Jun N-terminal kinase is involved in the regulation of proliferation and apoptosis by integrin-linked kinase in human retinoblastoma cells

Abstract

To determine the presence of integrin-linked kinase (ILK) in tissue samples of retinoblastoma patients, and to explore the function of ILK in human Y79 retinoblastoma cells. The expression of ILK was studied in samples of retinoblastoma patients by immunohistochemistry. In vitro, specific small interfering RNA (siRNA) targeting ILK was transfected into Y79 retinoblastoma cells using liposome. Silencing of ILK expression was measured by reverse transcription-polymerase chain reaction (RT-PCR), real-time PCR and Western blotting assays. Then the regulation of cell proliferation and apoptosis was assessed by Cell Counting Kit-8(CCK-8), Annexin V-FITC/ propidium iodide (PI) immunofluorescence, and flow cytometry assays. Furthermore, the involvement of c-Jun N-terminal kinase signal pathway was tested by JNK signal transduction inhibitor assay. Positive staining for ILK was detected in 15 of the 17 retinoblastoma tissue samples. Specific siRNA targeting ILK significantly silenced ILK expression in Y79 retinoblastoma cells, as confirmed by RT-PCR, real-time PCR and Western blotting assays (P < 0.01). This was accompanied by decreased cell proliferation (P < 0.05) and enhanced apoptosis (P < 0.01). The phosphorylation status of JNK and c-Jun was constitutively activated by ILK siRNA (P < 0.01), and JNK inhibitor simultaneously reversed the effects on cell proliferation and apoptosis induced by ILK siRNA. Our results demonstrated that ILK promoted proliferation and suppressed apoptosis via repressing phosphorylations of the JNK signal pathway in human retinoblastoma cells. This might provide a potential therapeutic target in the treatment of this deadly disease.