Pathological and Therapeutic Aspects of Long noncoding RNAs in osteosarcoma

Bone mesenchymal stem cell-derived extracellular vesicles containing NORAD promote osteosarcoma by miR-30c-5p

Osteosarcoma is a bone tumor that often affects children, adolescents and young people. Non-coding RNA activated by DNA damage (NORAD) can promote the proliferation of cancer cells in multiple tumors. Thus, the current study set out to explore the role of NORAD derived from extracellular vesicles (EVs) of bone mesenchymal stem cells (BMSCs) in osteosarcoma. First, NORAD was highly expressed in osteosarcoma cells and tissues, which might be associated with the progression and metastasis of osteosarcoma. We isolated EVs from the characterized BMSCs, and found that NORAD was transferred from BMSCs to osteosarcoma cells via EVs in the co-culture system. Consequently, NORAD delivered by BMSC-derived EVs promoted the proliferation and invasion of osteosarcoma cells. Subsequently, bioinformatics analyses suggested potential binding relationship between NORAD and microRNA-30c-5p (miR-30c-5p) as well as between miR-30c-5p and Krueppel-like factor 10 (KLF10), and the results of which were further verified by dual luciferase reporter gene assay, RNA immunoprecipitation, and RNA pull-down assay. Mechanistically, NORAD acted as a sponge of miR-30c-5p and up-regulated the expression of KLF10 where miR-30-c-5p mimic declined the effect induced by NORAD on cancer cells. The osteosarcoma cells were injected into mice to develop tumor growth and metastasis models. In these two models, injection of BMSC-EVs elevated NORAD expression and KLF10 but reduced miR-30c-5p expression, whereby suppressing tumor growth and lung metastasis. To conclude, BMSC-EVs deliver NORAD to osteosarcoma cells to regulate the miR-30c-5p/KLF10 axis, thereby accelerating the progression and metastasis of osteosarcoma.

LncRNA MALAT1 facilitates lung metastasis of osteosarcomas through miR-202 sponging

Lungs are the primary metastatic sites for osteosarcomas responsible for associated mortality. Recent data has documented role of long non-coding RNAs (lncRNAs) in proliferation and growth of osteosarcoma cells. We evaluated a role of lncRNAs in the lung metastasis of osteosarcoma with the goal of identifying a unique signature. Comparison of different lncRNAs in tumor samples from osteosarcoma with and without lung metastasis led to identification of MALAT1 as the most differentially upregulated lncRNA in the osteosarcoma patients with lung metastasis. MALAT1 was also high in osteosarcoma cells KRIB and MALAT1’s targeted downregulation in these cells led to decreased invasive potential and identification of miR-202 as the miRNA that is sponged by MALAT1. In the lung metastasis in vivo model, parental KRIB cells metastasized to lungs and such metastasis was significantly inhibited in KRIB cells with downregulated MALAT1. Ectopic miR-202 expression attenuated KRIB downregulation-mediated effects on lung metastasis. In yet another in vivo model involving parental SAOS-2 and lung-metastatic derivatives SAOS-2-LM, MALAT1 expression was found to be elevated in lung metastatic cells, which also correlated with reduced miR-202. In conclusion, MALAT1-miR-202 represents a potential lncRNA-miRNA signature that affects lung metastasis of osteosarcomas and could potentially be targeted for therapy.

The long non-coding RNA-ROR promotes osteosarcoma progression by targeting miR-206

The long intergenic non-protein coding RNA regulator of reprogramming (lncRNA-ROR) has been reported to play crucial regulatory roles in the pathogenesis and progression of multiple cancers. However, whether ROR is associated with the initiation and development of osteosarcoma (OS) remains unclear. Here, we found that ROR expression level was significantly up-regulated in OS tissue samples compared to adjacent normal tissues, and the elevated ROR was closely correlated with advanced tumour-node-metastasis (TNM) stage and lymph node metastasis and poor overall survival rate. Functional assays showed that ROR knockdown suppressed the OS cell proliferation, colony formation, migration and invasion in vitro, and retarded tumour growth in vivo. In addition, miR-206 was verified to be a target miRNA of ROR using bioinformatics online program and luciferase report assay. miR-206 inhibition partially rescued the inhibitory effects on OS cells induced by ROR knockdown. In conclusion, these results suggested that ROR function as an oncogene in OS by sponging miR-206 and might be a potential therapeutic target for patients with OS.

Knockdown of long non-coding RNA HOXD-AS1 inhibits the progression of osteosarcoma

Long non-coding RNA HOXD-AS1 (HOXD-AS1) has recently been shown to be involved in the development and progression of multiple cancers. However, the expression, significance, and biological function of HOXD-AS1 in osteosarcoma (OS) remain unknown. Here, we found that the expression level of HOXD-AS1 was significantly upregulated in OS tissues and cells. Furthermore, high expression of HOXD-AS1 was positively associated with the clinical and pathological characteristics of OS, including tumor stage and lymph node metastasis, and negatively correlated with overall survival rate. in vitro assays confirmed that knockdown of HOXD-AS1 suppressed cell proliferation, colony formation, migration, and invasion, and promoted cell cycle arrest at G1 stage and apoptosis in OS cells. in vivo assays confirmed that knockdown of HOXD-AS1 significantly decreased tumor growth in xenograft mice, and decreased tumor size and weight. Importantly, we also showed that knockdown of HOXD-AS1 significantly reduced signal transducer and activator of transcription 3 and its target protein (CyclinD1, Bcl-2, and MMP-2) expression in vitro and in vivo. Moreover, overexpression of STAT3 could reverse the suppression of proliferation ability induced by sh-HOXD-AS1 in U2OS cells. Collectively, our data indicated that HOXD-AS1 might be an oncogenic long non-coding RNA (lncRNA) and might be a potential attractive therapeutic target for OS.

miR-143-3p inhibits the proliferation, migration and invasion in osteosarcoma by targeting FOSL2

Osteosarcoma (OS) is the most common type of primary malignant bone tumor and mainly occurs in children and adolescent. Because of its early migration and invasion, OS has a poor prognosis. It has been reported that mircoRNAs (miRNAs) play a crucial role in the occurrence and development of multiple tumors. In this study, we identified the aberrant-expression of miR-143-3p in osteosarcoma and examined the role of miR-143-3p in OS development. Further, we searched the miR-143-3p target gene and verified its accuracy by luciferase experiments. Finally, we explored the relationship between miR-143-3p and FOS-Like antigen 2 (FOSL2). Our data indicated that miR-143-3p expression was substantially lower in OS tissues and cell-line compared with normal tissues, and was lower in patients with poor prognosis. In addition miR-143-3p inhibited OS cell proliferation and metastasis while promoting apoptosis. We next showed that FOSL2 was directly targeted by miR-143-3p and could reverse the inhibition caused by miR-143-3p. Finally, we found FOSL2 expression in OS cells was significantly higher compared with normal cells and negatively correlated with miR-143-3p. Thus, miR-143-3p directly and negatively targets FOSL2 to affect OS characteristics. This provides a new target for the treatment of OS and deserves further study.