MiR-1224-5p Activates Autophagy, Cell Invasion and Inhibits Epithelial-to-Mesenchymal Transition in Osteosarcoma Cells by Directly Targeting PLK1 Through PI3K/AKT/mTOR Signaling Pathway

Bicheng Jin; Dongfang Jin; Zhaozhen Zhuo; Bo Zhang; Kun Chen

doi:10.2147/OTT.S274451

MiR-1224-5p Activates Autophagy, Cell Invasion and Inhibits Epithelial-to-Mesenchymal Transition in Osteosarcoma Cells by Directly Targeting PLK1 Through PI3K/AKT/mTOR Signaling Pathway

Onco Targets Ther. 2020 Nov 17:13:11807-11818. doi: 10.2147/OTT.S274451. eCollection 2020.

Authors

Bicheng Jin¹, Dongfang Jin², Zhaozhen Zhuo³, Bo Zhang^#¹, Kun Chen^#⁴

Affiliations

¹ Department of Surgery, Guizhou Electric Power Staff Hospital, Guiyang, Guizhou Province, People's Republic of China.
² Department of Clinical Laboratory, Jinhua People's Hospital, Jinhua, Zhejiang Province, People's Republic of China.
³ Prenatal Diagnosis Center, Guizhou Provincial People's Hospital, Guiyang, Guizhou Province, People's Republic of China.
⁴ Guizhou Provincial People's Hospital Scientific Research Center Laboratory, Guiyang, Guizhou Province, People's Republic of China.

^# Contributed equally.

Abstract

Background: Osteosarcoma (OS) is one of the most common malignant bone tumors with a poor overall prognosis. MiR-1224-5p plays an important role in cancer, but its function and mechanism in OS have not been studied.

Materials and methods: The expression of miR-1224-5p and PLK1 was detected by qRT-PCR in OS cells, adjacent tissues, and cell lines. Dual-luciferase reporter gene assay was used to verify the interaction between miR-1224-5p and PLK1. The expression of miR-1224-5p and PLK1 was intervened by transfection with miR-1224-5p mimic, NC mimic, pc-NC and PLK1, respectively. MTT, colony formation assay, Transwell and flow cytometry were used to observe the cell proliferation, invasion and apoptosis. Western blot was used to detect the expression levels of PLK1, PI3K/AKT/mTOR signaling pathway-related proteins, autophagy-related proteins, and epithelial-mesenchymal transition (EMT)-related proteins in the cells.

Results: We found that miR-1224-5p was down-regulated and PLK1 expression was up-regulated in OS tissues and cells. On the other hand, it is further confirmed that PLK1 was a target gene of miR-1224-5p. Overexpression of miR-1224-5p inhibited the proliferation, invasion while promoted the apoptosis of OS cells, whereas overexpression of PLK1 promoted the proliferation, invasion and inhibited the apoptosis of OS cells. In the miR-1224-5p group (overexpression of miR-1224-5p), PI3K, AKT, and mTOR protein phosphorylation levels were significantly reduced, while autophagic activity was significantly activated, and the degree of EMT was significantly reduced. But the results in the PLK1 group (overexpression of PLK1) were the opposite. In addition, overexpression of miR-1224-5p reversed the effect of PLK1 upregulation on OS cells.

Conclusion: MiR-1224-5p targets PLK1 to inhibit PI3K/AKT/mTOR signaling pathway, thus mediating the proliferation, invasion, apoptosis, autophagy and EMT in OS cells.

Keywords: PLK1; autophagy; epithelial-mesenchymal transition (EMT); miR-1224-5p; osteosarcoma (OS).

Grants and funding

NHC Key Laboratory of Pulmonary Immune-related Diseases is supported by the non-profit central research Institute fund of Chinese academy of medical sciences (2019PT320003).