A novel circular RNA circPPFIA1 promotes laryngeal squamous cell carcinoma progression through sponging miR-340-3p and regulating ELK1 expression

Abnormal expression of circular RNA (circRNA) is closely related to the occurrence and development of many cancers. By screening the expression of circRNA, we identified a novel circRNA termed as has_circ_0023326 in laryngeal squamous cell carcinoma (LSCC). We verified the expression of circPPFIA1 and found that it was upregulated in LSCC tissues compared to the adjacent normal tissues. Functional studies were carried out to detect the effect of circPPFIA1 expression on the phenotype of LSCC cells. These results suggest that circPPFIA1 knockdown can suppress the proliferation, migration, and invasion of LSCC cells, while circPPFIA1 overexpression can promote these processes. Mechanistically, miR-340-3p was predicted to be the target miRNA sponged by circPPFIA1 as confirmed through the luciferase assay and rescue experiments. In addition, miR-340-3p was found to target ELK1 and inhibit its expression. Taken together, circPPFIA1 promotes the progression of LSCC via the miR-340-3p/ELK1 signaling axis, which may serve as a novel prognostic or therapeutic target for LSCC.

Reduced Ets Domain-containing Protein Elk1 Promotes Pulmonary Fibrosis via Increased Integrin αvβ6 Expression

Idiopathic pulmonary fibrosis (IPF) is a progressive fibrotic lung disease with high mortality. Active TGFβ1 is considered central to the pathogenesis of IPF. A major mechanism of TGFβ1 activation in the lung involves the epithelially restricted αvβ6 integrin. Expression of the αvβ6 integrin is dramatically increased in IPF. How αvβ6 integrin expression is regulated in the pulmonary epithelium is unknown. Here we identify a region in the β6 subunit gene (ITGB6) promoter acting to markedly repress basal gene transcription, which responds to both the Ets domain-containing protein Elk1 (Elk1) and the glucocorticoid receptor (GR). Both Elk1 and GR can regulate αvβ6 integrin expression in vitro. We demonstrate Elk1 binding to the ITGB6 promoter basally and that manipulation of Elk1 or Elk1 binding alters ITGB6 promoter activity, gene transcription, and αvβ6 integrin expression. Crucially, we find that loss of Elk1 causes enhanced Itgb6 expression and exaggerated lung fibrosis in an in vivo model of fibrosis, whereas the GR agonist dexamethasone inhibits Itgb6 expression. Moreover, Elk1 dysregulation is present in epithelium from patients with IPF. These data reveal a novel role for Elk1 regulating ITGB6 expression and highlight how dysregulation of Elk1 can contribute to human disease.