MiR-361-5p acts as a tumor suppressor in prostate cancer by targeting signal transducer and activator of transcription-6(STAT6)

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Highlights

  • The role of miR-361-5p in prostate cancer (PCa) has not been evaluated until date.

  • We found that the expression of miR-361-5p in CRPC was lower than in ADPC.

  • MiR-361-5p suppressed DU145 cell proliferation and triggered apoptosis.

  • STAT6 is a direct target of miR-361-5p.

  • STAT6 enhances the expression of Bcl-xL at the transcriptional level.

Abstract

Castration-resistant prostate cancer (CRPC), whose pathogenesis is known to be regulated by microRNAs (miRNAs), has a poor prognosis. In our present study, we found that the expression of miR-361-5p in CRPC was lower than in androgen-dependent prostate cancer (ADPC), indicating that miR-361-5p may play an important role in the progression of ADPC to CRPC. The role of miR-361-5p in prostate cancer (PCa) has not been evaluated until date. Our findings suggest that miR-361-5p is a suppressor in CRPC. Signal transducer and activator of transcription-6 (STAT6), a direct target of miR-361-5p, enhances the expression of B-cell lymphoma-extra large (Bcl-xL), while miR-361-5p inhibits its expression through STAT6. Therefore, miR-361-5p has great clinical significance in preventing the malignant progression of PCa.

Introduction

According to the figures of the American Cancer Society, the number of new cases of prostate cancer (PCa) and related deaths in the USA for 2013 is estimated at 238,590 and 29,720, respectively. PCa presents the highest morbidity and the second highest mortality among American male cancer patients [1]. In recent years the morbidity and mortality of PCa are in obvious rising in China [2]. Castration-resistant prostate cancer (CRPC) has limited therapeutic options and poor prognosis, and is currently the leading cause of death among male cancer patients [3]. However, the mechanisms of the initiation and progression of PCa remain unclear.

MicroRNAs (miRNAs) are small (approximately 22 nucleotides in length) non-coding single-stranded RNAs that regulate expression of target genes by interacting with and binding to the 3′-untranslated regions (3′-UTR) of their target mRNAs [4]. Altered miRNA regulation is involved in PCa pathogenesis via the modulation of oncogenes and tumor suppressors that subsequently affect the downstream signaling pathways [5], [6], [7]. For instance, hsa-let-7c, hsa-miR-21 and hsa-miR-375 were found to be significantly up-regulated in PCa, whereas hsa-miR-143 and hsa-miR-145 were determined to be significantly down-regulated [8]. In a previous study, we revealed that the ubiquitous loss of miR-146a is a critical mechanism for the overexpression of EGFR in CRPC [9].

MiR-361 is encoded on Xq21.2, in an intron between exons 9 and 10 of CHM/choroideremia (Rab escort protein 1), and gives rise to two mature miRNA species, miR-361-3p and the predominant miR-361-5p [10], [11]. A previous study revealed that miR-361-5p is down-regulated in a transplantable metastatic versus a non-metastatic PCa xenograft line, both derived from one patient’s primary cancer [12]. Another study validated miR-361-5p as being differentially expressed in matched primary and metastatic clear cell renal cell carcinoma pairs, and indicated that miR-361-5p may suppress cell growth and proliferation in tumor development, metastasis and progression [13]. A latest report demonstrates that miR-361 is differentially expressed between both PCa groups [clinical progression free survival (CPFS) vs. clinical failure (CF)] and the non-malignant benign prostate hyperplasia (BPH) samples [14]. Additionally, miRNA-microarray analysis and qRT-PCR demonstrated that miR-361-5p expression in CRPC was lower than in androgen-dependent prostate cancer (ADPC) in our study. Our findings indicated that miR-361-5p might play an important role in the progression of ADPC to CRPC. However, miR-361-5p has not been described as an oncomiR until now, and its relevance in the development and progression of PCa remains undetermined. Therefore, we selected miR-361-5p as a subject of our future studies. The inhibitory effects of miR-361-5p on DU145 were revealed by the CCK-8, colony formation, flow cytometry and tumor formation assay in our study. Down-regulation of signal transducer and activator of transcription-6 (STAT6) by utilizing siRNA influenced cell viability and induced apoptosis in DU145, as evaluated by the CCK-8, colony formation and flow cytometry assay. We indicated that miR-361-5p could repress the expression of STAT6 by binding to its 3′-UTR. Further, the down-regulation of STAT6 inhibited B-cell lymphoma-extra large (Bcl-xL) expression at the transcriptional level. Thus, our results suggested that miR-361-5p inhibited PCa and can thus be exploited as a new therapeutic target in CRPC.

Section snippets

Tissue samples

PCa tissues obtained from 19 early-stage patients that underwent radical prostatectomy and had never received any previous treatment, were considered as having ADPC. All patients were in T2, including six patients with a Gleason score of <7, eight patients with a Gleason score of 7 and five patients with a Gleason score of >7. Nine patients were diagnosed with CRPC, since their serum prostate-specific antigen (PSA) levels continued to increase during maximum androgen deprivation therapy. All

Expression of miR-361-5p in CRPC tissues is lower than in ADPC tissues

In our study, evaluating three ADPC and three CRPC miRNA chips, the expression of miR-361-5p in the CRPC group was lower than in that in the ADPC group (Fig. 1A). To verify our microarray results, we detected the expression of miR-361-5p in 16 ADPC tissues and 6 CRPC tissues by qRT-PCR. A similar trend of regulated miR-361-5p expression was observed (Fig. 1B). Therefore, we concluded that altered expression of miR-361-5p might be associated with the progression of PCa.

Effects of miR-361-5p in DU145 in vitro

We examined the expression

Discussion

Androgen ablation therapy for PCa can result in a regression of tumor size and reduce PSA levels. However, most ADPCs inevitably progress to CRPCs [16]. To date, the mechanisms for the progression of PCa remain unclear. Recently, accumulating evidence has associated dysregulated expression patterns of miRNAs to various types of human cancers, including PCa [17]. Previous studies have reported that miRNA play a critical role in tumorigenicity, tumor progression and drug resistance [18]. We

Acknowledgments

This study was supported by National Natural Science Foundation of China (81370849, 81300472, 81070592 and 81202034), Natural Science Foundation of Jiangsu Province (BL2013032 and BK2012336) and Nanjing City (201201053) and Southeast University (3290002402), Science Foundation of Ministry of Education of China (20120092120071). Fundamental Research Funds for the Central Universities and Graduate Innovative Foundation of Jiangsu Province (CXZZ13_0133).

References (25)

  • Y. Pang et al.

    MicroRNAs and prostate cancer

    Acta Biochim. Biophys. Sin.

    (2010)
  • J. Szczyrba et al.

    The microRNA profile of prostate carcinoma obtained by deep sequencing

    Mol. Cancer Res.

    (2010)
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      Currently, microRNAs (miRNAs) are a kind of short RNAs (19–25 nt s in length) without coding protein capacity, which participate in the regulation of gene expression by competitively binding with the 3′-untranslated regions (UTR) of target [15]. In a recent publication, miR-361-3p has been confirmed as a tumor suppressor by targeting signal transducer and activator of transcription-6 (STAT6) in prostate cancer [16]. Moreover, it was previously reported that miR-361-3p could exert the suppressive effect on NSCLC [17].

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    These authors contributed equally to this work.

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