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Objective To explore the expression of circ_0006692 in NSCLC and its relation with clinicopathological characteristics and related mechanism. Methods We collected 50 pairs of NSCLC tissues and adjacent tissues. The expression of circ_0006692 was detected by qRT-PCR and its relation with clinicopathological features was analyzed. We constructed lung cancer A549 cell line with circ_0006692 overexpression and knockdown. Cell proliferation, migration and invasion were detected by MTS, colony forming, wound healing and Transwell invasion assays. qRT-PCR and Western blot were used to detect the effect of circ_0006692 expression change on EMT-related gene expression. Results The expression of circ_0006692 in NSCLC was significantly higher than that in adjacent tissues (P < 0.05). The expression level of circ_0006692 was closely related to tumor size, TNM stage and pulmonary membrane invasion (P < 0.05). circ_0006692 knockdown inhibited cell proliferation, invasion and metastasis, while its overexpression promoted cell proliferation, invasion and metastasis. circ_0006692 knockdown inhibited the expression of EMT-related genes CDH2 and MMP7 in A549 cells and promoted the expression of CDH1. Conclusion The upregulated expression of circ_0006692 in NSCLC is closely related to tumor size, TNM stage and pulmonary membrane invasion. circ_0006692 expression could regulate the proliferation, invasion, metastasis and EMT progression of lung cancer A549 cells.

Objective To investigate the expression of ARL4C in NSCLC and its correlation with clinicopathological features, as well as its role in EGFR-TKI resistance. Methods We collected the tumor and adjacent tissues of 63 NSCLC patients. The mRNA expression of ARL4C was detected by qRT-PCR and the relation between ARL4C and clinicopathological features was analyzed. The expressions of ARL4C in TKI-resistant cell line, control cell line and ARL4C overexpressing cell line were assessed by qRT-PCR and Western blot. The changes of cell activity and IC50 were detected by MTS. Transwell invasion assay was used to detect the effect of ARL4C expression on cell invasion. Results The expression level of ARL4C in NSCLC tissues was lower than that in adjacent tissues (P < 0.05). The expression of ARL4C in NSCLC was closely related to lymph node metastasis, TNM stage and pulmonary membrane invasion (P < 0.05). Compared with control cell line HCC827, the expression levels of ARL4C mRNA and protein in TKI-resistant cell line HCC827/ER and the IC50 of ARL4C overexpressing TKI-resistant cell line HCC827/ER/ARL4C-OE were significantly lower (P < 0.05). Transwell assay results showed that the overexpression of ARL4C inhibited the invasion of lung cancer cell line (P < 0.05). Conclusion The abnormal expression of ARL4C is closely related to lymph node metastasis, TNM stage and pulmonary membrane invasion of NSCLC. Overexpression of ARL4C may improve the sensitivity of NSCLC cells to EGFR-TKI and inhibit the invasion of NSCLC cells.

Cancer patients who initially benefit from Erlotinib, a drug targeting EGFR path, eventually develop resistance to the drug. The underlying mechanism is largely unknown. This study investigated the role of ARL4C in Erlotinib resistance development of NSCLC. qRT-PCR and Western blotting were performed to analyze the expression of mRNA and protein of ARL4C in two NSCLC cell lines (HCC827 and PC-9). Several assays (MTS, colony formation, transwell migration, luciferase reporter, and chromatin-immunoprecipitation) were used to explore the role of ARL4C in biofunctional changes of Erlotinib-resistant cells and their associations with Jak2/Stat 5/ β -catenin signaling. Results demonstrated that (1) long-term use of Erlotinib resulted in downregulation of ARL4C ; (2) overexpression of ARL4C could regain the sensitivity to Erlotinib in the drug-resistant HCC827/ER cells, while downregulation of ARL4C increased HCC827, and PC-9 cells' resistance to the drug; (3) Erlotinib-induced downregulation of ARL4C resulted in phosphorylation of Jak2/Stat5 and upregulation of β -catenin and their related molecules Axin2, CD44, Ccnd1, Lgr-5 , and MMP7 , which promoted the malignant behaviors of Erlotinib-resistant cells; (4) chromatin immunoprecipitation and luciferase reporter assay revealed that Stat5 could bind to β -catenin promoter to upregulate molecules to maintain the malignant behaviors, which might count for how Erlotinib-resistant cell survived while EGFR path was blocked; (5) the expression of ARL4C was not associated with known EGFR gene mutations in both Erlotinib-resistant cells and NSCLC tissues. Our data suggest that Erlotinib resistance of NSCLCs is associated with downregulation of ARL4C via affecting Jak/Stat/ β -catenin signaling. ARL4C could serve as a biomarker to predict the effectiveness of TKI targeting therapy and a potential therapeutic target for overcoming Erlotinib resistance in NSCLC. [ABSTRACT FROM AUTHOR]