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Up-regulation of microRNA let-7c by quercetin inhibits pancreatic cancer progression by activation of Numbl

Clifford C. Nwaeburu, Natalie Bauer, Zhefu Zhao, Alia Abukiwan, Jury Gladkich, Axel Benner and Ingrid Herr _

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Oncotarget. 2016; 7:58367-58380. https://doi.org/10.18632/oncotarget.11122

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Clifford C. Nwaeburu1, Natalie Bauer1, Zhefu Zhao1, Alia Abukiwan1, Jury Gladkich1, Axel Benner2, Ingrid Herr1

1Team Molecular OncoSurgery, Section Surgical Research, Department of General, Visceral and Transplantation Surgery, University of Heidelberg, Heidelberg, Germany

2Department of Biostatistics, German Cancer Research Center (DKFZ), Heidelberg, Germany

Correspondence to:

Ingrid Herr, email: [email protected]

Keywords: cancer, microRNA, phytochemicals, stem cell signaling

Received: May 10, 2016    Accepted: July 19, 2016    Published: August 08, 2016


Pancreatic Ductal Adenocarcinoma (PDA) is a highly malignant tumor with poor prognosis. MicroRNAs (miRs) may offer novel therapeutic approaches to treatment. The polyphenol quercetin, present in many fruits and vegetables, possesses anti-carcinogenic properties. To unravel the effect of quercetin to miR signaling we performed miR profiling in PDA cells before and after quercetin treatment, followed by biostatistical analysis. miR let-7c was among the top up-regulated candidates after quercetin treatment, as measured by qRT-PCR and confirmed in two established and one primary PDA cell lines. By computational analysis we identified the Notch-inhibitor Numbl as let-7c target gene. This was strengthened by luciferase assays, where lipofected let-7c mimics induced a Numbl 3-UTR wild type construct, but not the mutated counterpart. Let-7c induced Numbl mRNA and protein expression but inhibited Notch just like quercetin. It also inhibited colony formation, wound healing, and protein expression of progression markers. In vivo xenotransplantation of PDA cells and subsequent intravenous injection of let-7c resulted in a significant decrease in tumor mass without obvious toxic effects in the fertilized chick egg model. The delivery rate of the miR mimics to the tumor mass was 80%, whereas minor amounts were present in host tissue. By immunohistochemistry we demonstrated that let-7c inhibited Notch and progression markers but up-regulated Numbl. These findings show that quercetin-induced let-7c decreases tumor growth by posttranscriptional activation of Numbl and indirect inhibition of Notch.

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