Investigation of the Role of Btk in Drug Resistant Lung Cancer and Development of New Treatment Strategy

Non-small cell lung cancer (NSCLC), a leading cause of tumor-related deaths in Taiwan and worldwide. The prevalence of lung cancer in Taiwan, regardless of sex, has increased remarkably in the past decades. According to the statistical data of Ministry of Health and Welfare in 2015, lung cancer has become the leading cause of death in Taiwan, with 5-year survival around 16.3%. Although the contributing factors of lung cancer may be related to life styles, dietary habits and environmental elements, the definite causes were not ascertained. EGFR and KRAS mutations and deregulation of the EGFR/KRAS pathways, both have different components, are considered critical for tumorigenesis and progression of lung cancer. Bruton’s tyrosine kinase (BTK) belongs to the group of non-receptor or cytoplasmic tyrosine kinases, and is a member of the TEC family tyrosine kinases. It was firstly found that BTK plays a crucial role in B ell development and mast cell activation. Recently, it has been reported that BTK is present in certain tumor subtypes and in other relevant cells that are contributing to the tumor microenvironment such as dendritic cells, macrophages, myeloid derived suppressor cells and endothelial cells. As a result, BTK could be a novel target of treatment for lung cancer. Our preliminary data by immunohistochemical (IHC) staining and western blot showed increased expression of BTK protein in lung cancer cells as compared to their non-tumor counterparts. Furthermore, using clinicopathologic analysis of large Prognoscan database cohorts, we established a negative correlation between BTK expression and patients’ outcome. Meanwhile, BTK inhibitor ibrutinib exhibited modest suppression of growth in drug-resistant (for EGFR TKI) lung cancer cell line H1975. In this three-year project, we will comprehensively investigate the role of the BTK gene in lung tumorigenesis and progression and disclose underlying molecular mechanisms, with emphasis on drug-resistant lung cancer cells. In the first year, we will explore the expression of BTK and its related upstream regulators and downstream effectors in lung cancer using IHC staining of primary NSCLC tissue samples. This data will be collated and statistically correlated with patients’ clinical data. In the second year, we will investigate the role of BTK in lung cancer cell proliferation, epithelial-to-mesenchymal (EMT), and cancer stem cell phenotype, as well as determine the underlying molecular mechanisms, and also apply BTK inhibitors along with other inhibitors to see their combined effects on drug-resistant lung cancer cells. This will be carried out by using loss and gain of BTK function, and functional assays such as the colony formation, invasion, migration and spheroid formation assays in lung cancer tissues and cell lines. In the third year, we will validate the in vitro findings by examining BTK activities in vivo, evaluate the therapeutic effect of BTK inhibitors in animals and investigate its clinical significance, using tumor xenograft NOD-SCID mice models. We anticipate that this current study will demystify the role and molecular mechanisms of BTK in the tumorigenesis of lung cancer and provide relevant information for effective anti-lung cancer therapeutic strategy, including combined targeted therapy.