Circ_0072995 Promotes Cell Carcinogenesis via Up-Regulating miR-149-5p-Mediated SHMT2 in Breast Cancer

Circ_0072995 is a novel identified circRNA and has been identified to involve in the metastasis of breast cancer. However, the detailed function and mechanism of circ_0072995 in the biological property of breast cancer cell remain vague.

The expression of circ_0072995, microRNA (miR)-149-5p and serine hydroxymethyltransferase 2 (SHMT2) mRNA was detected using quantitative real-time polymerase chain reaction. Western blot was used to detect the protein levels of SHMT2, hexokinase-2 (HK-2), lactate dehydrogenase a chain (LDHA), and glucose transporter 1 (GLUT1). Cell proliferation, apoptosis, migration, and invasion were analyzed using cell counting kit-8 assay, flow cytometry, caspase-3 activity analysis, cell adhesion assay and transwell assay, respectively. Glucose metabolism was calculated by measuring glucose uptake, lactate production, and adenosine triphosphate (ATP) levels. The interaction between miR-149-5p and circ_0072995 or SHMT2 was confirmed by dual-luciferase reporter assay. In vivo tumorigenesis was performed using the murine xenograft model.

Circ_0072995 and SHMT2 were up-regulated in breast cancer tissues and cell lines, and knockdown of circ_0072995 or SHMT2 suppressed cell malignant properties and anaerobic glycolysis; importantly, SHMT2 overexpression attenuated the anticancer action of circ_0072995 knockdown in breast cancer. Besides, we also found circ_0072995 directly targeted miR-149-5p, thereby regulating its downstream gene SHMT2 by competitively binding to miR-149-5p. Additionally, xenograft analysis showed circ_0072995 silencing suppressed tumor growth via regulating SHMT2 and miR-149-5p in vivo.

This study demonstrated that circ_0072995 promoted cell malignant phenotypes and anaerobic glycolysis in breast cancer via up-regulating SHMT2 through sponging miR-149-5p, indicating a promising molecular target for breast cancer treatment.