LncRNA FER1L4 induces apoptosis and suppresses EMT and the activation of PI3K/AKT pathway in osteosarcoma cells via inhibiting miR-18a-5p to promote SOCS5.

Previous studies have determined that long non-coding RNA (lncRNA) Fer-1-like protein 4 (FER1L4) is suppressed in osteosarcoma (OS) and inhibits the tumorigenesis in a variety of cancer. However, the precise biological of FER1L4 in OS has not been cleared. The aim of this study is to investigate the roles and potential mechanisms of FER1L4 in apoptosis and epithelial-mesenchymal transition (EMT) in OS. In the present study, the levels of FER1L4 were decreased significantly in OS tissues and cell lines compared with non-tumorous tissues or hFOB1.19. Knockdown of FER1L4 in OS cells decreased the apoptosis rate, but increased the OS cell proliferation, upregulated the expression levels of CD133 and Nanog, as well as promoted Twist1 expression, increased the N-cadherin and Vimentin expression. In turn, the opposite trends were observed upon overexpression of FER1L4. In addition, the expression of PI3K, p-AKT (Ser470) and p-AKT (Thr308) was upregulated by siFER1L4, while decreased upon overexpression of FER1L4. MicroRNA (miRNA) -18a-5p, an osteosarcoma-promoting miRNA which was suggested a target of FER1L4 in osteosarcoma, was identified to be a functional target of FER1L4 on the regulating of cell apoptosis and EMT, presently. The effects of FER1L4 overexpression on the markers of cell apoptosis, proliferation, EMT, and stemness and PI3K/AKT signaling were all reversed by miR-18a-5p upregulation. Furthermore, the suppressor of cytokine signaling 5 (SOCS5) was confirmed a target gene of miR-18a-5p by luciferase gene reporter assay and SOCS5 suppression by miR-18a-5p attenuated the effects of FER1L4 overexpression on the OS cells apoptosis and the expressed levels of PI3K, AKT, Twist1, N-cadherin and Vimentin. In conclusion, our data indicated thatthe overexpression of FER1L4 promoted apoptosis and inhibited the EMT markers expression and PI3K/AKT signaling pathway activation in OS cells via downregulating miR-18a-5p to promote SOCS5.

Ye F ，Tian L ，Zhou Q ，Feng D ... -  《-》

Overexpression of FER1L4 promotes the apoptosis and suppresses epithelial-mesenchymal transition and stemness markers via activating PI3K/AKT signaling pathway in osteosarcoma cells.

Novel long non-coding RNA Fer-1-like protein 4 (FER1L4) has been identified as a tumor suppressor in endometrial carcinoma, ovarian cancer, hepatocellular carcinoma, esophageal squamous cell carcinoma. However, the function of FER1L4 in osteosarcoma has not been clear. The aim of the research was to explore the effects of FER1L4 in osteosarcoma. Results showed that FER1L4 was observed to be lowly expressed in osteosarcoma cell lines (US-O2, MG-63 and SaOS-2 cells), especially MG63 cells. Besides, overexpression of FER1L4 remarkably repressed the proliferation, migration and invasion of MG63 cells. FER1L4-induced apoptotic cell death leaded to the activation of caspase-3 and Bax/Bcl2. Moreover, epithelial-mesenchymal transition (EMT) was tremendously suppressed by increased FER1L4, evidences were the increased E-cadherin and reduced vimentin and fibronectin. Blocking FER1L4 expression by sh-FER1L4 treatment increased the expression of SOX9, CD44, ALDH1, Nanog and Oct4, indicating that FER1L4 could effectively decrease cell stemness in osteosarcoma. Furthermore, the protein levels of p-AKT and p-PI3K were remarkably suppressed when FER1L4 was knocked down. In conclusion, the study indicated that FER1L4 acted as a tumor suppressor in osteosarcoma via activating PI3K/AKT pathway may be a new prognostic biomarker and potential therapeutic target for osteosarcoma intervention.

Ma L ，Zhang L ，Guo A ，Liu LC ，Yu F ，Diao N ，Xu C ，Wang D ... -  《-》

Long noncoding RNA OIP5-AS1 causes cisplatin resistance in osteosarcoma through inducing the LPAATβ/PI3K/AKT/mTOR signaling pathway by sponging the miR-340-5p.

The abnormal expression of long noncoding RNAs (lncRNAs) plays an important role in the regulation of human cancer progression and drug resistance. The lncRNA OPI5-AS1 is a crucial regulator in some cancers; however, its role in cisplatin resistance of osteosarcoma remains unclear. We found that OIP5-AS1 was significantly upregulated in cisplatin-resistant (CR) osteosarcoma cells MG63-CR and SaOS2-CR compared with the corresponding parental cells. OIP5-AS1 silencing suppressed cell growth in vitro and in vivo, and promoted apoptosis of MG63-CR and SaOS2-CR cells, indicating that knockdown of OIP5-AS1 significantly decreased cisplatin resistance in MG63-CR and SaOS2-CR cells. This conclusion was supported by the decreased expression of the drug resistance-related factors multidrug resistance-associated protein 1 (MRP1) and P-glycoprotein (P-gp) upon OIP5-AS1 silencing. In addition, OIP5-AS1 downregulation suppressed the PI3K/AKT/mTOR signaling pathway. Importantly, we demonstrated that OIP5-AS1 functions as a competing endogenous RNA of miR-340-5p and regulates the expression of lysophosphatidic acid acyltransferase (LPAATβ), which is a target of miR-340-5p. Moreover, downregulation of miR-340-5p partly reversed the inhibitory effect of OIP5-AS1 knockdown on the PI3K/AKT/mTOR pathway and therefore counteracted cisplatin resistance in MG63-CR and SaOS2-CR cells. In conclusion, OIP5-AS1 causes cisplatin resistance in osteosarcoma through inducing the LPAATβ/PI3K/AKT/mTOR signaling pathway by sponging the miR-340-5p. Our results contribute to a better understanding of the function and mechanism of OIP5-AS1 in osteosarcoma cisplatin resistance.

Song L ，Zhou Z ，Gan Y ，Li P ，Xu Y ，Zhang Z ，Luo F ，Xu J ，Zhou Q ，Dai F ... -  《-》

Long Noncoding RNA FER1L4 Suppresses Tumorigenesis by Regulating the Expression of PTEN Targeting miR-18a-5p in Osteosarcoma.

Novel long non-coding RNA Fer-1-like protein 4 (FER1L4) has been reported to play crucial regulatory roles in tumor progression. However, its clinical significance and biological role in osteosarcoma (OS) is completely unknown. The aim of the present study was to investigate the role of FER1L4 in OS progression and the underlying mechanism. We analyzed the expression levels of FER1L4 in tissues of OS patients and cell lines via quantitative RT-PCR (qRT-PCR). The effect of FER1L4 on cell proliferation, colony formation, migration and invasion was analyzed by cell counting kit-8 (CCK-8), colony formation, wound healing and transwell invasion assay, respectively. Novel targets of FER1L4 were selected through a bioinformatics soft and confirmed using a dual-luciferase reporter system and qRT-PCR. To detect the role of FER1L4 in vivo tumorigenesis, tumor xenografts were created. We found that the expression of FER1L4 was significantly downregulated in OS tissues and cell lines; moreover, low expression of FER1L4 was associated with advanced tumor-nude-metastasis (TNM) stage, lymph node metastases, and poor overall survival. Functional assays showed that upregulation of FER1L4 significantly inhibited OS cell proliferation, colony formation, migration, and invasion in vitro, as well as suppressed tumor growth in vivo. Assays performed to determine the underlying mechanism, indicated that FER1L4 interacted directly with miR-18a-5p. Subsequently, we found that FER1L4 significantly increased PTEN expression, a known target of miR-18a-5p, in OS cells. Furthermore, PTEN was found to be down-regulated, and positively correlated with FER1L4 in OS tissues. These findings suggest that FER1L4, acting as a competing endogenous RNA (ceRNA) of miR-18a-5p, exerts its anti-cancer role by modulating the expression of PTEN. Thus, FER1L4 may be a novel target for the prevention and treatment of OS.

Fei D ，Zhang X ，Liu J ，Tan L ，Xing J ，Zhao D ，Zhang Y ... -  《-》

miR-17-5p promotes proliferation and epithelial-mesenchymal transition in human osteosarcoma cells by targeting SRC kinase signaling inhibitor 1.

MicroRNA-17-5p (miR-17-5p) and epithelial-mesenchymal transition (EMT) have been reported to participate in the development and progression of multiple cancers. However, the relationship between the miR-17-5p and EMT in osteosarcoma (OS) is still poorly understood. This study was to investigate the effects of the miR-17-5p and its potential mechanism in regulating proliferation, apoptosis, and EMT of human OS. Quantitative real-time PCR was used to detect the miR-17-5p and SRC kinase signaling inhibitor 1 (SRCIN1) messenger RNA expression in OS specimens and cell lines. After transfection with miR-17-5p inhibitors, proliferation, apoptosis, migration, and invasion of OS cells were assessed by using the Cell Counting Kit-8, the annexin V-FITC apoptosis, wound-healing, and transwell assays. The SRCIN1 was validated as a target of the miR-17-5p through bioinformatics algorithms and luciferase reporter assay. Moreover, the expression of EMT markers, E-cadherin, N-cadherin, and Snail was identified by the Western blot analysis. MiR-17-5p was significantly upregulated in OS tumor samples and cell lines. It inhibited proliferation and EMT, and promoted apoptosis in OS. The SRCIN1 was identified as a direct target of the miR-17-5p. Silenced miR-17-5p could change the expression of EMT markers, such as upregulating the expression of E-cadherin, and downregulating the expression of N-cadherin and Snail through targeting the antioncogenic SRCIN1. These findings suggest that the miR-17-5p promotes cell proliferation, and EMT in human OS by directly targeting the SRCIN1, and reveal a branch of the miR-17-5p/SRCIN1/EMT signaling pathway involved in the progression of OS.

Zhao X ，Xu Y ，Sun X ，Ma Y ，Zhang Y ，Wang Y ，Guan H ，Jia Z ，Li Y ，Wang Y ... -  《-》