BackgroundTGF-β promotes tumor invasion and metastasis through inducing epithelial-mesenchymal transition (EMT) in non-small cell lung cancer (NSCLC). Circular RNAs (circRNAs) are recognized as functional non-coding RNAs involved in human cancers. However, whether and how circRNAs contribute to TGF-β-induced EMT and metastasis in NSCLC remain vague. Here, we investigated the regulation and function of Circular RNA hsa_circ_0008305 (circPTK2) in TGF-β-induced EMT and tumor metastasis, as well as a link between circPTK2 and transcriptional intermediary factor 1 γ (TIF1γ) in NSCLC.MethodsCircular RNAs were determined by human circRNA Array analysis, real-time quantitative reverse transcriptase PCR and northern blot. Luciferase reporter, RNA-binding protein immunoprecipitation (RIP), RNA pull-down and fluorescence in situ hybridization (FISH) assays were employed to test the interaction between circPTK2 and miR-429/miR-200b-3p. Ectopic overexpression and siRNA-mediated knockdown of circPTK2, TGF-β-induced EMT, Transwell migration and invasion in vitro, and in vivo experiment of metastasis were used to evaluate the function of circPTK2. Transcription and prognosis analyses were done in public databases.ResultsCircPTK2 and TIF1γ were significantly down-regulated in NSCLC cells undergoing EMT induced by TGF-β. CircPTK2 overexpression augmented TIF1γ expression, inhibited TGF-β-induced EMT and NSCLC cell invasion, whereas circPTK2 knockdown had the opposite effects. CircPTK2 functions as a sponge of miR-429/miR-200b-3p, and miR-429/miR-200b-3p promote TGF-β-induced EMT and NSCLC cell invasion by targeting TIF1γ. CircPTK2 overexpression inhibited the invasion-promoting phenotype of endogenous miR-429/miR-200b-3p in NSCLC cells in response to TGF-β. CircPTK2 overexpression significantly decreased the expression of Snail, an important downstream transcriptional activator of TGF-β/Smad signaling. In an in vivo experiment of metastasis, circPTK2 overexpression suppressed NSCLC cell metastasis. Moreover, circPTK2 expression was dramatically down-regulated and positively correlated with TIF1γ expression in human NSCLC tissues. Especially, circPTK2 was significantly lower in metastatic NSCLC tissues than non-metastatic counterparts.ConclusionOur findings show that circPTK2 (hsa_circ_0008305) inhibits TGF-β-induced EMT and metastasis by controlling TIF1γ in NSCLC, revealing a novel mechanism by which circRNA regulates TGF-β-induced EMT and tumor metastasis, and suggesting that circPTK2 overexpression could provide a therapeutic strategy for advanced NSCLC.Electronic supplementary materialThe online version of this article (10.1186/s12943-018-0889-7) contains supplementary material, which is available to authorized users.

Negative regulation of the signal mediated by the programmed cell death protein 1 (PD-1)/programmed death-ligand 1 (PD-L1) pathway can effectively inhibit the function of T and B cells, which play a key role in the regulation of immune response. Recently, emerging evidence has suggested that the expression of PD-L1 is related to the mutation status of the epidermal growth factor receptor (EGFR). Moreover, the activation of the EGFR signaling pathway can induce expression of PD-L1. In the present study, we demonstrated that activated EGFR can upregulate the expression of PD-L1 through the interleukin 6/Janus kinase/signal transducer and activator of transcription 3 (IL-6/JAK/STAT3) signaling pathway in non-small cell lung cancer (NSCLC) cells. Cells treated with epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) can downregulate the activation of the IL-6/JAK/STAT3 pathway, which subsequently reduces the expression of PD-L1. Furthermore, silencing of PD-L1 expression in NSCLC cells correlated with inhibition of cell proliferation and enhanced tumor cell apoptosis. In summary, our research indicates that EGFR is involved in the regulation of PD-L1 expression and cell proliferation via the IL-6/JAK/STAT3 signaling pathway in NSCLC. The present study suggests the potential of combined targeted therapy with immunotherapy in the treatment of NSCLC.

Epithelial-mesenchymal transition (EMT), a key step in the early stages of cancer metastasis, is orchestrated by several signaling pathways, including IL-6/JAK/STAT3 and TGF-β/Smad signaling. However, an association between the two signaling pathways during the EMT process is largely unknown. Here, we focused on lung cancer and demonstrated that TGF-β1 induced the phosphorylation of Smad3 (p-Smad3), upregulation of Snail, a fibroblast-like morphology, and downregulation of E-cadherin as well as upregulation of vimentin in lung cancer cell lines. SIS3 (an inhibitor of Smad3) suppressed TGF-β1-induced activation of Smad3, upregulation of Snail and the EMT process. Importantly, the JAK2/STAT3-specific inhibitor AG490 blocked Stat3 phosphorylation, resulting in attenuated levels of TGF-β1-induced p-Smad3, Snail, MMP2, and Smad-mediated PAI-1 promoter reporter gene activity in A549 and H1650 cells. Subsequently, AG490 inhibited TGF-β-induced cell migration and invasion. Moreover, exogenous IL-6 treatment stimulated Stat3 activation, enhanced TGF-β-induced expression of p-Smad3 and Snail, aggravated the EMT process, and increased lung cancer cell migration and invasion induced by TGF-β1. Our findings show that the JAK/STAT3 pathway is required for TGF-β-induced EMT and cancer cell migration and invasion via upregulation of the expression of p-Smad3 and Snail, and the IL-6/JAK/STAT3 and TGF-β/Smad signaling synergistically enhance EMT in lung carcinomas. The present study suggests a novel rationale for inhibiting cancer metastasis using anti-IL-6/JAK/STAT3 and anti-TGF-β/Smad therapeutic strategies.

IFN-γ was not always successful as an antitumor agent. It also can promote tumor cells to evade immune surveillance. Researchers should be cautious in using IFN-γ as a therapeutic agent for cancer treatment.

BackgroundCD73 (ecto-5′-nucleotidase) is implicated in the development of many types of cancer. CD73 inhibitors are currently being tested in clinical trials for the treatment of cancer. Understanding the molecular and cellular actions of CD73 inhibitors is the key to improving this line of therapy.MethodsQuantitative real-time PCR (qRT-PCR) was used to detect the expression of CD73 and miR-30a-5p; Western blot and immunohistochemical assays were used to investigate the levels of CD73 and other proteins. Flow cytometry was used to determine cell cycle stage and apoptosis. CCK-8 and clonogenic assays were used to investigate cell proliferation. Wound healing, migration and invasion assays were used to investigate the motility of cells. A lung carcinoma xenograft mouse model was used to investigate the in vivo effects of CD73 and miR-30a-5p.ResultsIn the present study, we found that CD73 is overexpressed and miR-30a-5p is underexpressed in non-small cell lung cancer tissues compared with adjacent noncancerous. Further, we showed that CD73 is a direct target of miR-30a-5p by luciferase reporter assays, qRT-PCR and western blot analysis. We also found that overexpression of miR-30a-5p in these non-small cell lung cancer cell lines inhibited cell proliferation in vitro and in vivo. Moreover, the epithelial-to-mesenchymal phenotype was suppressed and cell migration and invasion were inhibited; these effects were brought about via the EGF signaling pathway.ConclusionsOur findings reveal a new post-transcriptional mechanism of CD73 regulation via miR-30a-5p and EGFR-related drug resistance in non-small cell lung cancer.Electronic supplementary materialThe online version of this article (doi:10.1186/s12943-017-0591-1) contains supplementary material, which is available to authorized users.