Reciprocal Interaction of lncRNA HOTAIR and miR-214-3p Contribute to the Solamargine-Inhibited PDPK1 Gene Expression in Human Lung Cancer Cells

Abstract

Background: Solamargine (SM), a natural plant based photochemical has been shown to have anti-cancer properties. However, the underlying mechanism of this effect remains to be determined. Methods: Cell viability and growth were measured via MTT and Cell-Light EdU assays. The expressions of HOTAIR, miR-214-3p andPDPK1 were examined via qRT-PCR and Western blot, respectively. The promoter activity of HOTAIR and PDPK1 were determined using Secrete-Pair Dual Luminescence Assay. Luciferase reporter assays and RNA immunoprecipitation determined the interactions among miR-214-3p, HOTAIR and PDPK1. Exogenous expressions of HOTAIR and PDPK1 were carried out by transient transfection assays. A mouse xenograft tumor model was used to further evaluate the effects of SM in vivo. Findings: SM inhibited the growth of non-small cell lung cancer (NSCLC) cells, which was not observed in cells stably transfected with PDPK1. While silencing of HOTAIR reduced cell growth, over-expression of HOTAIR resisted the SM mediated inhibition of cell growth. SM increased the expression of miR-214-3p and there was a reciprocal interaction between the HOTAIR and miR-214-3p. Furthermore, SM inhibited PDPK1 gene expression and the physical binding of miR-214-3p to PDPK1 3-UTR. MiR-214-3p mimics inhibited PDPK1 expression. Intriguingly, HOTAIR could directly bind to miR-124-3p and sequestered miR-214-3p from the target gene PDPK1. Finally, in a feedback mechanism, over-expression of PDPK1 reduced the HOTAIR and miR-214-3p expressions, and neutralized the SM-inhibited cell growth. Similar results were observed in vivo. Interpretation: SM inhibited NSCLC cell growth through the reciprocal interaction between HOTAIR and miR-214-3p, which ultimately suppressed PDPK1 gene expression. This unveils a novel molecular mechanism underlying the anti-cancer effect of SM in human lung cancer. Funding Statement: This work was supported in part by the grants from the National Nature Scientific Foundation of China (Nos. 81403216, 81673845, 81703551 and 81871863), the Science and Technology Program of Guangzhou (No. 201607010385), the Major Program of National Natural Science Foundation of Guangdong (No. 2018B030311061), the Discipline of Integrated Chinese and Western Medicine in Guangzhou University of Chinese Medicine (No. A1-Af-D018161Z1513), the Special Science and Technology Join fund from Guangdong Provincial Department of Science and Technology-Guangdong Academy of Traditional Chinese Medicine (No. 2014A020221024). The funders did not play a role in manuscript design, data collection, data analysis, interpretation nor writing of the manuscript. Declaration of Interests: The authors declare that they have no competing interests. Ethics Approval Statement: Animal studies were performed according to the protocols approved by the Institutional Animal Care and Use Committee of Guangdong Provincial Hospital of Chinese Medicine (Ethics Approval Number 2017037) and the National Institutes of Health guidelines for the care and use of Laboratory animals (NIH Publications No. 8023, revised 1978).