The Mechanical Function Of HIPK2 In Epithelial-mesenchymal Transition And Metastasis Of Non-small Cell Lung Cancer

BackgroundBecause of our environmental problems, the incidence rate of lung cancer is increasing year by year and already been classed as one of the main malignant tumors that must be prevented and treated. Depending on the cell types of lung cancer, it could be classified into non-small cell lung cancer (NSCLC) and small cell lung cancer (SCLC), and NSCLC accounts for 80%-85% of the total number of lung cancers. At present, the main therapeutic options for lung cancer is surgery, combining with radiotherapy, chemotherapy, Chinese medicine and immune therapy. However, metastasis has been found in other parts of the bodies when about 85% non-small cell lung cancer patients are diagnosed, affecting the surrounding lymph nodes and organs. As a consequence, the therapeutic effect of operation was relatively poor. Investigating the reasons and mechanisms of lung cancer metastasis is conducive to early diagnosis and comprehensive treatment.Recent studies indicated that the epithelial-mesenchymal transition (EMT) is the key procedure in the development process of lung cancer. Based on the process of EMT, lung cancer cells get stronger ability of invasion and metastasis, and are easier to form metastatic foci by invading surrounding tissues from the primary tumor. Therefore, the current research focus of lung cancer molecular targeted therapy is finding new genes which could regulate EMT and conducting an in-depth study of the basic molecular mechanisms.A novel family of proteins were discovered through yeast two-hybrid technology by Kim et al. in 1998. The proteins contain a conserved protein kinase domain that is separated from a domain that interacts with homeoproteins and hence are termed homeodomain-interacting protein kinases (HIPKs):HIPK1, HIPK2, and HIPK3. HIPK2 was identificated as a serine/threonine kinase and it is mainly located in the nucleus. HIPK2 could induce or inhibit transcription, and regulate cell differentiation, proliferation and apoptosis. When DNA damaged or under the oxidative stress, HIPK2 was able to activate the tumor suppressor gene p53, thereby promotes cells apoptosis. As a tumor suppressor, HIPK2 plays an efficient role in tumorigenesis and metastasis of various tumors, but the specific effect of HIPK2 in non-small cell lung cancer is unclear.ObjectiveTo investigate the role of homeodomain interacting protein kinase 2 (HIPK2) in epithelial-mesenchymal transition and metastasis in non-small cell lung cancer cell, and to explore the possible related mechanism.MethodsA549 and H520 cells were transfected with pcDNA3.1-HIPK2 and the control plasmid with lipidosome 2000. HIPK2 silencing and control cell lines were constructed in A549 by transfecting with HIPK2-shRNA and the control plasmid by lentivirus. A549-shHIPK2 cell lines were transfected with ZEB1-shRNA and the control plasmid with lipidosome 2000.The expression of HIPK2 and EMT markers were detected with Western blotting. The migration and invasion ability of cells were detected through wound scratch assay, Transwell assay and Matrigel assay.ResultsHIPK2 promoted the expression of epithelial cell markers, inhibited the expression of mesenchymal cell markers, and repressed the EMT process; meanwhile, HIPK2 weakened the migratory and invasive capacities of NSCLC cells. Conversely, silencing HIPK2 expression generated the opposite effects. The enhanced migratory and invasive capacities induced by HIPK2 silencing were reversed by silencing transcription factor ZEB1.ConclusionHIPK2 repressed EMT, migration and invasion of NSCLC cells; the possible mechanism is related to the transcription factor ZEB1.