Circulating microRNA-21 as a novel biomarker for hepatocellular carcinoma

Background & Aims

Several groups have reported the significance of circulating microRNA as a biochemical marker of cancer. To our knowledge, however, there are no reports on the significance of circulating microRNA in hepatocellular carcinoma. The aim of this study was to evaluate the significance of plasma microRNA-21 level as a biochemical marker for hepatocellular carcinoma.

Methods

Plasma microRNA-21 level was measured by qRT-PCR in 10 patients before and after curative resection of hepatocellular carcinoma. Plasma microRNA-21 was also compared in other groups of: 126 patients with hepatocellular carcinoma, 30 patients with chronic hepatitis, and 50 healthy volunteers. The power of microRNA-21 in differentiating hepatocellular carcinoma from chronic hepatitis or from healthy volunteers was compared to that of α-fetoprotein.

Results

In the 10-patient group, plasma microRNA-21 levels significantly diminished after surgery compared with the pre-operative values (p = 0.0125). Plasma microRNA-21 level in the 126 patients with hepatocellular carcinoma was significantly higher than in patients with chronic hepatitis and healthy volunteers (p <0.0001, p <0.0001, respectively). ROC analysis of plasma microRNA-21 yielded an AUC of 0.773 with 61.1% sensitivity and 83.3% specificity when differentiating hepatocellular carcinoma from chronic hepatitis, and an AUC of 0.953 with 87.3% sensitivity and 92.0% specificity when differentiating hepatocellular carcinoma from healthy volunteers. Both sets of values were superior to α-fetoprotein and improved for the combination of microRNA-21 and α-fetoprotein.

Conclusions

Plasma microRNA-21 level is a promising biochemical marker for hepatocellular carcinoma.

Introduction

MicroRNA (miRNA) is a small noncoding RNA gene product known to post-transcriptionally modulate gene expression by negatively regulating the stability or translational efficiency of its target mRNAs [1], [2]. MiRNAs control a wide array of biological processes, such as cell differentiation, proliferation, and apoptosis. Aberrant expressions of miRNAs have been widely reported in human cancers with both up- and down-regulation detected in neoplastic cells compared with their normal counterparts [3], [4]. Several recent studies reported that miRNAs are stably detectable in plasma and serum [4], [5], [6]. Mitchell et al. [5] reported that tumor-associated circulating miRNAs are stably detectable in the plasma of human prostate cancer xenograft mouse models and prostate cancer patients, suggesting that their detection could differentiate cancer-bearing individuals from healthy controls. The finding also raised the possibility that assaying miRNAs in plasma or serum may serve as a novel approach for blood-based detection of human cancers. Actually, since the above study, several investigators have reported the significance of some types of plasma miRNAs as biochemical markers for human cancers [7], [8], [9], [10], [11], [12], [13].

Hepatocellular carcinoma (HCC) is a common cancer worldwide, especially in Japan and other East Asian countries, and the third most frequent cause of cancer-related deaths in the world [14]. One of the reasons for the high mortality in HCC is that the tumors are frequently detected at a stage when curative resection is no longer feasible because of intrahepatic and extrahepatic metastases. Today, the diagnosis of HCC relies on the finding of a liver mass in radiology imaging studies including ultrasonography, computed tomography (CT), and/or magnetic resonance imaging (MRI). However, the diagnosis of small lesions is relatively inaccurate [15]. One of the common approaches used for screening HCC in a high risk-population is serum tumor markers such as α-fetoprotein (AFP) and protein induced by vitamin K absence or antagonists-II (PIVKA-II). However, the sensitivity and specificity of high serum AFP and PIVKA-II levels for HCC were reported to range from 39–64% and 76–91%, and 41–77% and 72–98%, respectively, suggesting that elevated serum AFP and PIVKA-II levels have insufficient sensitivity and specificity [16], [17], [18]. Accordingly, to identify novel biochemical markers for early detection of HCC is desirable.

To our knowledge, there are no reports on the significance of circulating miRNAs in HCC. In this study, we focused on miRNA-21, which is one of the first miRNAs detected abundantly in certain human cancers [4], [19], [20], [21]. miRNA-21 targets tumor suppressor genes, such as PDCD4, PTEN, and matrix metalloproteinase inhibitors, such as TIMP3 and RECK. Furthermore, miRNA-21 increased cell proliferation and suppressed apoptosis in a cancer xenograft model, further defining miRNA-21 as an oncogenic miRNA [22], [23], [24], [25]. Overexpression of miRNA-21 is reported in many types of cancers [26], [27], [28], [29]. Also in HCC, it is previously reported that the expression was significantly increased in cancer tissues and cell lines, and that miRNA-21 contributed to the malignant potential such as cell proliferation, migration, and invasion by reducing the aforementioned targets [30], [31]. In other studies, miRNA-21 was reported to be secreted by cells and detected in plasma [5], [32]. It was also confirmed that plasma miRNA-21 was a useful biomarker for some types of cancer [5], [7], [9], [13]. Thus, we postulated that plasma miRNA-21 expression could be a novel biochemical marker for HCC. In the present study, we evaluated the usefulness of plasma miRNA-21 as a biochemical marker for HCC by comparing the expression in patients with HCC and control patients. In addition, we also examined the prognostic significance of plasma miRNA-21 and investigated the correlation between miRNA-21 expression in tumoral tissue and its plasma levels.