Mir-335 Negatively Regulates The Biological Characteristics Of Osteosarcoma Stem Cells And The Underlying Mechanism

Evidence is accumulating to link cancer stem cells to the pathogenesis and progression of osteosarcoma.The aim of this study was to investigate the role of miR-3 35 in osteosarcoma stem cells.We first enriched osteosarcoma stem cells using three different methods,and showed that the expression of miR-335 in osteosarcoma stem cells was lower than their differentiated counterparts.The cells were divided into different populations according to their miR-335 status using specific detection probe.We demonstrated that cells expressing miR-335 possessed decreased stem cell-like properties,including lower expression of cell surface marker CD 117+/Stro-1+,down-regulated expression of stem cell-related genes,and decreased spheroid formation efficiency.Using gain or loss of function assays,we found that the miR-335 antagonist promoted stem cell-like properties as well as invasion,whereas miR-335 expression resulted in the opposite effect,miR-335 was predicted to incompletely complement with POU5F1 3'UTR.Using a luciferase reporter and transfection assay,POU5F1 was confirmed to be downregulated by miR-335 at the post-transcriptional level.We determined whether miR-335 affected cytotoxicity of traditional chemotherapy and found that pre-miR-335 enhanced sensitivity,whereas anti-miR-335 promoted chemoresistance.Furthermore,we investigated the inhibitory effect of miR-335 on in vivo tumor formation,and found that a combination of pre-miR-335 with cisplatin further reduced the tumor size,and miR-335 decreased the sphere formation capacity induced by cisplatin.In conclusion,this study showed that miR-335 negatively regulated osteosarcoma stem cell-like properties by targeting POU5F1.The miR-335 could target stem cells to synergize with traditional chemotherapeutic agents to inhibit the growth of osteosarcoma cells.