2‐methoxyestradiol restrains non‐small cell lung cancer tumorigenesis through regulating circ_0010235/miR‐34a‐5p/NFAT5 axis

BACKGROUND: Non‐small cell lung cancer (NSCLC) is one of the most prevalent and severe malignant tumors in the world and its molecular mechanism is still unclear. In recent years, increasing evidence indicates the significant roles of circRNAs in NSCLC. It has been determined that 2‐methoxyestradiol (2‐MeOE2) exerts antitumor roles in many cancers. However, the molecular mechanism of 2‐MeOE2 in regulating the development of lung cancer needs further elucidation. METHODS: The expression levels of circ_0010235, microRNA‐34a‐5p (miR‐34a‐5p), and nuclear factor of activated T cells 5 (NFAT5) were detected by quantitative real‐time polymerase chain reaction (qRT‐PCR). Cell proliferation, apoptosis and invasion were detected by cell counting kit‐8 (CCK‐8), 5‐ethynyl‐2′‐deoxyuridine (EdU) assay, flow cytometry and transwell assays, respectively. The interaction between miR‐34a‐5p and circ_0010235 or NFAT5 was predicted by bioinformatic software and confirmed by dual‐luciferase reporter assay. RESULTS: Our data showed 2‐MeOE2 hindered cell proliferation, invasion and induced apoptosis in NSCLC, which could be reversed by upregulation of circ_0010235 and NFAT5 or miR‐34a‐5p knockdown. Circ_0010235 and NFAT5 expression levels were increased, and miR‐34a‐5p expression level was decreased in NSCLC tissues and cells. In addition, 2‐MeOE2 treatment suppressed the expression of circ_0010235 and NFAT5 while promoted the expression of miR‐34a‐5p. Furthermore, circ_0010235 functioned as a molecular sponge of miR‐34a‐5p to regulate NFAT5 expression. Knockdown of circ_0010235 or 2‐MeOE2 treatment constrained tumor growth in vivo, and circ_0010235 depletion enhanced the inhibitory effect of 2‐MeOE2 on tumor growth in vivo. CONCLUSION: These findings demonstrated that 2‐MeOE2 retarded NSCLC progression by modulating the circ_0010235/miR‐34a‐5p/NFAT5 axis, thus providing a new perspective for 2‐MeOE2 treatment in NSCLC.