A negative feedback loop of H19/miR-675/VDR mediates therapeutic effect of cucurmin in the treatment of glioma

Curcumin (CUR) shows a remarkable antitumor activity against a wide range of cancers such as glioma, but its underlying mechanism remains elusive. In this study, we aimed to explore the potential role of H19/miR-675/vitamin D receptor (VDR) in the effect of CUR against glioma. Real-time polymerase chain reaction and western-blot analysis were used to study the effect of CUR or 1,25-dihydroxyvitamin D (1,25(OH)₂D₃) on the expression of H19, miR-675, and VDR. In addition, the effect of H19 on VDR expression was also studied. Furthermore, the expression of H19, miR-675, and VDR between CUR-loaded nanoparticles (NPs) and NP groups was compared, and the interaction among H19, miR-675, and VDR was analyzed by in-silicon and luciferase assays. In a dose-dependent manner, CUR and 1,25(OH)₂D3 both downregulated the expression of H19 and miR-675 but increased the expression of VDR. In addition, H19 evidently reduced the mRNA and protein levels of VDR. Furthermore, VDR was confirmed as a target gene of miR-675, which significantly reduced the expression of VDR. Finally, the administration of CUR evidently decreased tumor volume. CUR-loaded NP group exhibited lower levels of H19 and miR-675, while the NP group showed higher levels of VDR mRNA and protein. In summary, it is the first time that the involvement of a negative feedback loop of H19/miR-675/VDR has been demonstrated in the development of glioma. Therefore, H19 might serve as a new biomarker for the diagnosis and treatment of glioma.