BackgroundThe T790M mutation of epithelial growth factor receptor (EGFR) is a major cause of the acquired resistance to EGFR tyrosine kinase inhibitor (EGFR-TKIs) treatment for lung cancer patients. The Hippo pathway effector, TAZ, has emerged as a key player in organ growth and tumorigenesis, including lung cancer.ResultsIn this study, we have discovered high TAZ expression in non-small cell lung cancer (NSCLC) cells harboring dual mutation and TAZ depletion sensitized their response to EGFR-TKIs. Mechanistically, knockdown of TAZ in T790M-induced resistant cells leaded to reduced anchorage-independent growth in vitro, tumor formation and resistance to gefitinib in vivo, correlated with epithelial-mesenchymal transition (EMT) and suppressed migration and invasion. Furthermore, we confirmed CTGF and AXL, novel EMT markers and potential therapeutic targets for overcoming EGFR inhibitor resistance, as directly transcriptional targets of TAZ.ConclusionsTaken together, this study suggests that expression of TAZ is an intrinsic mechanism of T790M-induced resistance in response to EGFR-TKIs. Combinational targeting on both EGFR and TAZ may enhance the efficacy of EGFR-TKIs in acquired resistance of NSCLC.Electronic supplementary materialThe online version of this article (doi:10.1186/2045-3701-5-7) contains supplementary material, which is available to authorized users.

BackgroundCisplatin is the standard first‐line chemotherapeutic agent for the treatment of non‐small cell lung cancer (NSCLC). However, resistance to chemotherapy has been a major obstacle in the management of NSCLC. Aldehyde dehydrogenase 1A1 (ALDH1A1) overexpression has been observed in a variety of cancers, including lung cancer. The purpose of this study was to investigate the effect of ALDH1A1 expression on cisplatin resistance and explore the mechanism responsible.MethodsReverse transcriptase‐PCR was applied to measure the messenger RNA expression of ALDH1A1, while Western blot assay was employed to evaluate the protein expression of ALDH1A1, B‐cell lymphoma 2, Bcl‐2‐like protein 4, phospho‐protein kinase B (p‐AKT) and AKT. A short hairpin RNA was used to knockdown ALDH1A1 expression. A 3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyltetrazolium bromide assay was used to determine the effect of ALDH1A1 decrease on cell viability. The cell apoptotic rate was tested using flow cytometry assay.Results ALDH1A1 is overexpressed in cisplatin resistant cell line A549/DDP, compared with A549. ALDH1A1 depletion significantly decreased A549/DDP proliferation, increased apoptosis, and reduced cisplatin resistance. In addition, the phosphoinositide 3‐kinase (PI3K) / AKT pathway is activated in A549/DDP, and ALDH1A1 knockdown reduced the phosphorylation level of AKT. Moreover, the combination of ALDH1A1‐short hairpin RNA and PI3K/AKT pathway inhibitor LY294002 markedly inhibited cell viability, enhanced apoptotic cell death, and increased cisplatin sensitivity.ConclusionThese results suggest that ALDH1A1 depletion could reverse cisplatin resistance in human lung cancer cell line A549/DDP, and may act as a potential target for the treatment of lung cancers resistant to cisplatin.

Background:The klotho (KL) gene is an anti-aging gene that has recently been shown to also function as a general tumor suppressor. However, there is currently only limited information regarding the potential molecular signals for regulation of Klotho without identifying precise molecular mechanisms or interactions. Methods: We performed a mass spectrometry (MS) assay to screen candidate proteins complexed with Klotho derived from immunoprecipitation in human non-small cell lung cancer (NSCLC) cells, and identified Rab8 to be the protein that most prominently interacts with Klotho. We further investigated whether Rab8 can regulate trafficking of Klotho and which process it would modulate using surface biotinylation assay, immunofluorescence and fluorescence ratio microscopy. Furthermore, we explored whether Rab8 is involved in Klotho-mediated function in NSCLC, and verified the results which we found in vivo using xenograft mouse model. Findings: We report discovery of Rab8 as a Klotho-interacting protein that acts as a critical modulator of Klotho surface expression in human NSCLC. In particular, we report that Rab8 is co-localized and associated with Klotho, and Klotho trafficking is regulated by Rab8. Moreover, we found that Rab8 modulates surface levels of Klotho via a post-biosynthetic pathway, as opposed to an endocytic pathway. Furthermore, we demonstrate that Rab8 is involved in Klotho-mediated regulation of cell proliferation, migration, invasiveness, epithelial-mesenchymal transition (EMT), and Wnt-β-catenin signaling in NSCLC. Additionally, Rab8 overexpression was also found to increase Klotho-mediated inhibition of NSCLC tumorigenesis in vivo . Interpretation: Overall, our findings suggest that Rab8 GTPase can regulate Klotho-mediated inhibition of Wnt signaling activity by modulating translocation of Klotho onto the cell surface, which in turn affects Klotho-mediated inhibition of cell proliferation, migration and invasiveness in NSCLC. These results have important implications for the development of new therapeutic targets, Klotho-related research in the context of NSCLC as well as other areas, and provide a working model for Rab8 function in the context of cancer and cancer biology.