The diagnostic effect of serum miR-139-5p as an indicator in osteosarcoma

1. Introduction

Osteosarcoma (OS) is a primary malignant bone tumor with high incidence in young children and adolescents around the world [1, 2]. Though multimodality treatments including chemotherapy and surgical resection have greatly increased the survival rate of OS patients in the past few decades, the prognosis remains very poor mainly due to its high risk of metastasis or recurrence [3, 4]. Early detection of OS contribute to improve the clinical outcome of this malignancy, it is therefore very important to identify novel biomarkers for the diagnosis and prognosis of OS.

MicroRNAs (miRNAs) are a class of single-stranded non-coding RNAs that bind to the 3’-untranslated region (UTR) of target mRNAs, leading to mRNA degradation or translational repression [5, 6]. MiRNAs were found to play critical roles in multiple biological processes of cancer progression either through their oncogenic or tumor suppressive functions [7, 8]. It has been reported that several abnormally expressed miRNAs in the peripheral blood such as miR-21 [9], miR-95-3p [10], miR-490-3p [11], were associated with OS and identified as blood-based biomarkers. MiR-139-5p is one of the most common cancer-associated miRNAs. For instance, miR-139-5p was reduced in ovarian cancer [17], hepatocellular carcinoma [18, 19], glioblastoma multiforme [20], endometrial cancer [21], paediatric low-grade glioma [22], nasopharyngeal carcinoma [23], bladder cancer [24, 25], lung cancer [26], tongue squamous cell carcinoma [27], esophageal squamous cell carcinoma [28] and acted as a tumor suppressor miR. On the contrary, miR-139-5p expression was upregulated in prostate cancer [29] and acted as an oncomiR. However, the role of serum miR-139-5p in OS diagnosis and prognosis remained unclear.

In this study, we investigated the expression of miR-139-5p in the blood samples from OS patients and healthy volunteers, thereby evaluating the correlation between serum miR-139-5p expression and clinical variables of OS. Our findings suggested that miR-139-5p served a promising biomarker for prognosis and prognosis of OS.

2. Materials and methods

MiRNAs are stably detectable in the serum and the expression patterns of serum miRNAs are closely associated with various cancers, and can be used as non-invasive indicators for diagnosing and monitoring human cancer. In the present study, we found that miR-139-5p expression was significantly decreased in OS patients, and reduced serum miR-139-5p levels were associated with distant metastasis and advanced tumor stage. Patients with low serum miR-139-5p expression had shorter overall survival. Moreover, univariate and multivariate analyses revealed that serum miR-139-5p was an independent marker for predicting poorer overall survival in OS subjects. The data showed detection of serum miR-139-5p expression could be further evaluated as a reliable biomarker for OS diagnosis and prognosis. We speculated that methylation of miR-139-5p in its promoter region is the major reason accounting for the reduction of miR-139-5p in OS. Increased methylation of miR-139-5p has been reported in non small lung cell carcinoma and head and neck cancer [12, 13]. Therefore, the OS cells might secret less miR-139-5p into the circulating system. Exosomes, which contain proteins, DNA, mRNA, miRNA, and lipids, are important mediators for cellular communication and can be detected in the biofluids [14]. It is also possible that less miR-139-5p is packaged into the exosomes, leading to the downregulation of miR-139-5p in the serum samples from OS patients.

Indeed, to date, some studies had reported the suppressive role of miR-139-5p in OS. Shi et al showed miR-139-5p was significantly downregulated in both OS tissues and cell lines. MiR-139-5p directly targeted DNMT1, and high miR-139-5p expression greatly inhibited OS cell growth, migration and invasion in vitro and suppressed tumor growth in vivo [15]. Likewise, Delsin et al. revealed miR-139-5p levels in OS samples were dramatically lower than those in non-tumor controls, indicating miR-139-5p acted as a tumor suppressor [16].

Besides OS, accumulating evidence revealed miR-139-5p played as a tumor suppressor in different tumor types. In ovarian cancer, the expression of miR-139-5p was reduced in cancerous tissues and cell lines, and enforced miR-139-5p expression markedly repressed the oncogenic activities of cancer cells both in vitro and in vivo through regulating ROCK2 [17]. Hua and colleagues showed miR-139-5p overexpression inhibited aerobic glycolysis, proliferation and metastasis of hepatocellular carcinoma (HCC), ETS1 was identified as the downstream target [18]. Similar study was conducted on HCC cells showing miR-139-5p expression was inversely correlated with ZEB1 and ZEB2, miR-139-5p upregulation or ZEB1/ZEB2 inhibition attenuated carcinogenesis and metastasis of HCC [19]. In glioblastoma multiforme (GBM), ectopic miR-139-5p expression decreased ZEB1 and ZEB2 expression and caused the inhibition of GBM cell migration and invasion, low miR-139-5p expression predicted poor overall survival of GBM patients [20]. In endometrial cancer (EC), miR-139-5p expression was decreased in EC tissues in comparison with matched normal tissues, enhanced miR-139-5p expression restrained cell viability and migration via targeting HOXA10 [21]. Moreover, Catanzaro et al. reported high miR-139-5p resulted in decreased cell proliferation in pediatric low-grade gliomas cells by regulating PI3K/AKT signaling [22]. In nasopharyngeal carcinoma (NPC), Shao et al. found reintroduction of miR-139-5p inhibited NPC cell proliferation, invasion and epithelial-to-mesenchymal transition [23]. In bladder cancer (BC), the levels of miR-139-5p were relatively lower in BC tissues. MiR-139-5p upregulation was attributed to reduced invasion and migration of BC cells, the direct targets of miR-139-5p were Bmi1 [24] and MMP11 [25]. Also, a reduced level of miR-139-5p was found in lung cancer tissues compared with normal samples, increased expression of miR-139-5p significantly inhibited lung cancer cell proliferation, metastasis, and induced apoptosis by negatively regulating c-Met oncogene [26]. In tongue squamous cell carcinoma (TSCC), Duz et al. showed miR-139-5p levels in saliva samples were underexpressed in TSCC patients. MiR-139-5p expression was significantly elevated after treatment, and showed good performance to identify TSCC patients from healthy controls [27]. Similarly, the downregulation of miR-139-5p was closely associated with aggressive features of esophageal squamous cell carcinoma (ESCC) patients, high miR-139-5p expression dramatically repressed cell proliferation capability and induction of apoptosis in ESCC cells in vitro by degrading NR5A2 [28].

In contrast, miR-139-5p was frequently and highly expressed in blood samples of prostate cancer (PC) patients, thus enabling discrimination between PC patients and benign prostatic hyperplasia (BPH) subjects, suggesting that miR-139-5p functioned as an oncogene [29]. Interestingly, miR-139-5p was found to function as a tumor suppressor in early-stage colorectal cancer (CRC) by some reports. For example, downregulation of miR-139-5p was noted in cancer tissues compared to normal tissues. Re-expression of miR-139-5p decreased CRC cell migration and invasion, enhanced chemotherapeutic sensitivity in vitro, as well as suppressed metastasis in vivo by directly targeting BCL2 [30], AMFR and NOTCH1 [31]. Whereas, Miyoshi et al. reported miR-139-5p overexpression can promote CRC cell colonization and enhance peritoneal metastasis. The levels of miR-139-5p were significantly elevated in patients with recurrent CRC and liver metastatic CRC, and the patients with high miR-139-5p expression had significantly worse prognosis [32]. The controversial properties of miR-139-5p suggested this miR might behave differently depending on cancer progression.

5. Conclusions

Conclusively, our study highlights the potential role of serum miR-139-5p expression for the early diagnosis and prognosis of OS. We found serum miR-139-5p expression was markedly downregulated in OS patients, and low miR-139-5p expression was associated with poor prognosis. Therefore, serum miR-139-5p might be useful as a non-invasive biomarker for OS.