PLOD1, a target of miR-34c, contributes to cell growth and metastasis via repressing LATS1 phosphorylation and inactivating Hippo pathway in osteosarcoma

Although dysregulated PLOD1 was reported in many cancers, its function in osteocarcoma (OS) progression and potential mechanism are totally unknown. In the present study, we found that the mRNA expression of PLOD1 was significantly upregulated in OS cells and tissues. The high expression of PLOD1 was correlated with the aggressive phenotypes of OS and poor prognosis. Gain- or loss-of-function assays demonstrated that PLOD1 promoted proliferation, migration, and invasion of OS cells in vitro, as well as tumorigenicity and metastasis in vivo. We found that PLOD1 inactivated Hippo-YAP pathway through inhibiting phosphorylation-LATS1 (p-LATS1) and -YAP (p-YAP). Immunofluorescence results validated that nuclear distribution of YAP was increased by PLOD1 overexpression and was decreased by PLOD1 depletion. Furthermore, PLOD1 was demonstrated as a target of miR-34c, which inhibited the luciferase activity of PLOD1 mRNA 3′-UTR and PLOD1 expression at both mRNA and protein levels. The expression of miR-34c was downregulated in OS tissues and negatively correlated with PLOD1 mRNA expression. We found that restoration of PLOD1 abolished the miR-34c induced inhibition of cell growth and invasion. More importantly, miR-34c led to upregulation of p-LATS1 and p-YAP, and reducing of nuclear YAP and TAZ in OS cells. The mice tumors, which formed from miR-34c lentivirus vectors, have relatively low expression of PLOD1 and nuclear YAP staining. Taken together, our findings revealed that PLOD1 promoted tumorigenesis and metastasis in OS, and the dysregulated miR-34c/PLOD1/Hippo pathway affected OS progression, providing a potential therapeutic strategy for treatment.