MYCN-regulated miRNA-92 inhibits secretion of the tumor suppressor DICKKOPF-3 (DKK3) in neuroblastoma

Abstract

The MYCN oncogene is frequently amplified in neuroblastoma. It is one of the most consistent markers of bad prognosis for this disease. Dickkopf-3 (DKK3) is a secreted protein of the DKK family of Wnt regulators. It functions as a tumor suppressor in a range of cancers, including neuroblastoma. MYCN was recently found to downregulate DKK3 mRNA. In this study, we show that MYCN knockdown in MYCN-amplified (MNA) neuroblastoma cell lines increases secretion of endogenous DKK3 to the culture media. MicroRNAs (miRNAs) are ∼20 nt long single-stranded RNA molecules that downregulate messenger RNAs by targeting the 3' untranslated region (3'UTR). Many miRNAs regulate genes involved in the pathogenesis of cancer and are extensively deregulated in different tumors. Using miRNA target prediction software, we found several MYCN-regulated miRNAs that could target the 3'UTR sequence of DKK3, including mir-92a, mir-92b and let-7e. Luciferase expression from a reporter vector containing the DKK3-3'UTR was decreased when this construct was cotransfected with mir-92a, mir-92b or let-7e in HEK293 cells. Mutation of the mir-92 seed sequence in the 3'UTR completely rescued the observed decrease in reporter expression when cotransfected with mir-92a and mir-92b. Antagomir and miRNA-mimic transfections in neuroblastoma cell lines confirmed that DKK3 secretion to the culture media is regulated by mir-92. Consistent with reports from other cancers, we found DKK3 to be expressed in the endothelium of primary neuroblastoma samples and to be absent in tumors with MYCN amplification. Our data demonstrate that MYCN-regulated miRNAs are able to modulate the expression of the tumor suppressor DKK3 in neuroblastoma.

MicroRNA-92a promotes cell viability and invasion in cervical cancer via directly targeting Dickkopf-related protein 3

“…Additionally, overexpression of DKK3 significantly attenuated the effects of miR-92a upregulation on HeLa cell viability and invasion, suggesting that miR-92a promotes cervical cancer cell viability and invasion via directly targeting DKK3. In fact, the targeting relationship between miR-92a and DKK3 has also been indicated in neuroblastoma (31). Therefore, the present study expands the understanding of miR-92a in the regulation of DKK3 in human cancer.…”

N-myc and Noncoding RNAs in Neuroblastoma

“…Mir-92a was further shown to directly target the tumor suppressor DKK3 (Dickkopf-3) mRNA, resulting in decreased secretion of DKK3 from neuroblastoma cell (65). This observation has been confirmed by De Brouwer and colleagues (66).…”

Effect of Resveratrol on microRNA Profile and Apoptosis in HL-60 Leukemia and Raji Lymphoma Cells

“…Çalışmamızda HL-60 hücre hattında resveratrol uygulamasının ardından azalan miRNA'lardan biri olan hsa-miR92a aslında miR-17-92 gen kümesi ailesine ait bir miRNA'dır. Bu gen kümesinin fazla ekspresyonu veya amplifikasyonu akut myeloid lösemi, akut lenfoblastik lösemi ve pek çok kanser türünde saptanmıştır (31)(32)(33)(34)(35)(36)(37). Yapılan bir çalışmada, miR-92a'nın inhibisyonu sonrası HL-60 hücre hattında, kanser hücrelerinin canlılığının, proliferasyonunun azaldığı ve apoptozun indüklendiği gösterilmiştir (37).…”