Long non-coding RNA SNHG5 sponges miR-26a to promote the tumorigenesis of osteosarcoma by targeting ROCK1

Highlights

• Upregulated SNHG5 was correlated with clinical and prognosis in OS patients.

• SNHG5 sponged miR-26a and promoted cell proliferation, invasion and migration.

• SNHG5 activated the ROCK signaling pathway through miR-26a-ROCK1 axis.

Abstract

Background

Osteosarcoma (OS) is one of the most common invasive malignancies of the bone. The long non-coding RNA (lncRNA) SNHG5 (small nucleolar RNA host gene 5) has been consistently shown to be involved in many cancers, although its precise function in osteosarcoma remains poorly understood. In this study, we investigated the role of SNHG5 in OS progression and the underlying mechanism.

Methods

SNHG5 expression in 32 OS tissues and 4 OS cell lines was measured by quantitative real-time PCR (qRT-PCR). Migration, invasion, proliferation and cell cycle profiles were analyzed by established assays to determine the biological functions of SNHG5 and miR-26a in OS cells. The binding sites of miR-26a in SNHG5 and ROCK1 were predicted by the RNAhybrid 2.2 program. Luciferase reporter assay was then used to validate the direct targeting of SNHG5 with miR-26a and of Rho-associated coiled coil-containing protein kinase 1 (ROCK1) with miR-26a. The effect of SNHG5 on the ROCK signaling pathway was assessed by western blotting.

Results

Elevated expression of SNHG5 was correlated with poor clinical outcome and prognosis in OS patients. SNHG5 functioned as a sponge for miR-26a and promoted proliferation, invasion and migration, and accelerated G1 to S phase transition in OS cells. SNHG5 functioned as a competing endogenous RNA (ceRNA) for miR-26a and activated the ROCK signaling pathway through the miR-26a-ROCK1 axis.

Conclusion

SNHG5 acts as an oncogene in OS via the SNHG5-miR-26a-ROCK1 axis and is therefore a potential novel therapeutic target for OS treatment.

Introduction

Osteosarcoma (OS) is one of the most common invasive malignancies of the bone. The epidemiological distribution of osteosarcoma is bimodal, with the first peak seen in young adults i.e. the second decade of life, and the second incidence peak in the sixth and eighth decades of life along with Paget’s disease or other benign lesions [1]. The incidence of OS in females is lower than that of males irrespective of age. The treatment regimen for OS is adjuvant chemotherapy and surgery [2]. Although several drugs like ifosfamide, cisplatin, epirubicin, doxorubicin and etoposide have shown a positive therapeutic effect on OS [3], the survival rate is still between 10–30% [3]. Therefore, it is important to identify novel prognostic predictors for OS.

Long non-coding RNAs (LncRNAs), a group of non-coding RNAs longer than 200 nt [4], have been shown to play important roles in tumorigenesis and chemo-resistance and are therefore potential therapeutic targets for cancer. The small nucleolar RNA host gene 5 (SNHG5), also called U50HG, is 524 nucleotides long lncRNA with 6 exons and encodes the snoRNAs U50 and U50’. The SNHG5 gene is located at the site of chromosomal translocation breakpoint, and has been shown to be aberrantly expressed in many human cancers such as gastric cancer (GS), malignant melanoma (MM) and chronic myeloid leukemia (CML). However, the function of SNHG5 in OS is still unclear [5].

microRNAs (miRNAs or miRs) are single-stranded small non-coding RNAs about 19–25 bases in length [6], and play critical roles in regulating gene expression through translational repression [7]. Recent studies show that miRs are key factors in both tumor repression and progression, and act by down-regulating the oncogenes or tumor suppressors respectively [8]. The miR-26a can function as an oncogene in cholangiocarcinoma and glioma [9,10], and as a tumor suppressor in OS [11]. In this study, multiple target prediction programs were applied to identify potential miR-26a target gene and found Rho-associated coiled coil-containing protein kinase 1 (ROCK1) as a putative candidate. A previous study has shown that ROCK1, a class of the miRs target gene, is up-regulated in OS [12]. ROCK1 phosphorylate a variety of protein substrates at serine or threonine residues, including myosin light chain (MLC)6 and the myosin binding subunit of MLC phosphatase (MYPT) [13]. However, not much is known about the interaction between miR-26a and ROCK1 in OS.

In this study, we provide evidence of a novel SNHG5-miR-26a-ROCK1 axis in OS progression, which opens a new direction for further mechanistic studies on OS and its treatment.