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01.12.2018 | Research | Ausgabe 1/2018 Open Access

Molecular Cancer 1/2018

Suppression of PDHX by microRNA-27b deregulates cell metabolism and promotes growth in breast cancer

Molecular Cancer > Ausgabe 1/2018
Steven C. Eastlack, Shengli Dong, Cristina Ivan, Suresh K. Alahari
Wichtige Hinweise

Electronic supplementary material

The online version of this article (https://​doi.​org/​10.​1186/​s12943-018-0851-8) contains supplementary material, which is available to authorized users.



The disruption of normal gene regulation due to microRNA dysfunction is a common event in cancer pathogenesis. MicroRNA-27b is an example of an oncogenic miRNA, and it is frequently upregulated in breast cancer. MicroRNAs have been found to deregulate tumor metabolism, which typically manifests as heightened cellular glucose uptake in consort with increased flux through glycolysis, followed by the preferential conversion of glycolytic pyruvate into lactate (a phenomenon known as the Warburg Effect). Pyruvate Dehydrogenase, an enzyme complex linking glycolysis with downstream oxidative metabolism, represents a key location where regulation of metabolism occurs; PDHX is a key structural component of this complex and is essential for its function.


We sought to characterize the role of miR-27b in breast cancer by identifying novel transcripts under its control. We began by utilizing luciferase, RNA, and protein assays to establish PDHX as a novel target of miR-27b. We then tested whether miR-27b could alter metabolism using several metabolite assay kits and performed a seahorse analysis. We also examined how the altered metabolism might affect cell proliferation. Lastly, we confirmed the relevance of our findings in human breast tumor samples.


Our data indicate that Pyruvate Dehydrogenase Protein X is a credible target of miR-27b in breast cancer. Mechanistically, by suppressing PDHX, miR-27b altered levels of pyruvate, lactate and citrate, as well as reducing mitochondrial oxidation and promoting extracellular acidification. These changes corresponded with an increased capacity for cell proliferation. In human breast tumor samples, PDHX expression was deficient, and low levels of PDHX were associated with reduced patient survival.


MicroRNA-27b targets PDHX, resulting in an altered metabolic configuration that is better suited to fuel biosynthetic processes and cell proliferation, thereby promoting breast cancer progression.
Additional file 1: Figure S1. 3’UTRs of PLK2 and PPP1CCC are targeted by miR-27b. Luciferase assays showing the change in luminescence following miR-27b transient transfection verse control of the genes PLK2 (A) and PPP1CCC (B). The putative binding sites are indicated in the boxes below. A cut-off was set for each program giving a binary prediction indicated as 1 or 0. These were tallied and those targets predicted by the most algorithms were considered the best potential targets. Figure S2. Luciferase assays for 3’-UTRs not targeted by miR-27b. While prediction algorithms indicated these seven would be good candidates for miR-27b targeting, the predictions could not be validated experimentally. Figure S3. Scherf Cell line database evaluation of the expression of PDHX in 11 different types of cancer. Data was accessed using Oncomine platform. Figure S4. PDHX expression across a panel of cancer types using the BioExpress gene expression database. Figure S5. PDHX expression according to breast adenocarcinoma subtype within the Curtis Breast Statistics dataset. Data was accessed using Oncomine platform. For the Invasive Ductal Breast Carcinoma, p = 6.0E-4. For Invasive Lobular Breast Carcinoma subtype, p = 5.2E-8. The number of patient samples in each category is indicated in parentheses. Figure S6. XY correlation plots of miR-27b with PDHX (A), C9orf3 with PDHX (B) and C9orf3 with miR-27b (C) by RNA-seq across a panel of 52 tissue types retrieved online from the GTEx database. Figure S7. Graphical representations of the GTEx RNA-seq expression data of miR-27b, PDHX, and C9orf3 across the panel of 52 human tissue types. (PDF 623 kb)
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