Circular RNA circ_0074027 indicates a poor prognosis for NSCLC patients and modulates cell proliferation, apoptosis, and invasion via miR-185-3p mediated BRD4/MADD activation

Circular RNAs play an imperative role in cancer development and metastasis by regulating oncogenic and tumor-suppressive pathways. However, the role and mechanism of circ_0074027 in non-small-cell lung cancer (NSCLC) have not been elucidated. The expression levels of circ_0074027 were detected by qRT-PCR. The link between circ_0074027 expression and clinicopathologic parameters was analyzed by Fisher's exact test. The prognostic role of circ_0074027 was investigated by Kaplan-Meier and Cox regression analysis. Cell counting kit-8 and flow cytometric assays were utilized to evaluate NSCLC cell proliferation and apoptosis, respectively. Wound scratch and Transwell tests were applied to detect cell migratory and invasive capacities. The interaction potential of circ_0074027 and miR-185-3p was analyzed by the circBank database, and verified by dual-luciferase reporter assay. The downstream gene of miR-185-3p was also investigated. Circ_0074027 was elevated in NSCLC specimens and cell lines. Overexpressed circ_0074027 was related to more advanced TNM stages, poorer differentiation grade, and worse overall survival. Upregulated circ_0074027 increased the proliferation of H1299 cells by inhibiting cell apoptosis. Cell migration and invasion were enhanced after circ_0074027 overexpression. Silenced circ_0074027 caused the opposite effects in the A549 cell line. For mechanism investigation, circ_0074027 directly sponges miR-185-3p to enhance bromodomain-containing protein 4 (BRD4) and MAPK-activating death domain-containing protein (MADD) expression levels at the posttranscriptional level. Furthermore, we found the oncogenic function of circ_0074027 is attributed to its modulation of BRD4 and MADD. Collectively, upregulated circ_0074027 in NSCLC accelerates cell progression via miR-185-3p/BRD4/MADD pathway as a competing endogenous RNA.