Title miR-122 targets pyruvate kinase M 2 and affects metabolism ofhepatocellular carcinoma

In contrast to normal differentiated cells that depend on mitochondrial oxidative phosphorylation for energy production, cancer cells have evolved to utilize aerobic glycolysis (Warburg’s effect), with benefit of providing intermediates for biomass production. MicroRNA-122 (miR-122) is highly expressed in normal liver tissue regulating a wide variety of biological processes including cellular metabolism, but is reduced in hepatocellular carcinoma (HCC). Overexpression of miR-122 was shown to inhibit cancer cell proliferation, metastasis, and increase chemosensitivity, but its functions in cancer metabolism remains unknown. The present study aims to identify the miR-122 targeted genes and to investigate the associated regulatory mechanisms in HCC metabolism. We found the ectopic overexpression of miR-122 affected metabolic activities of HCC cells, evidenced by the reduced lactate production and increased oxygen consumption. Integrated gene expression analysis in a cohort of 94 HCC tissues revealed miR-122 level tightly associated with a battery of glycolytic genes, in which pyruvate kinase (PK) gene showed the strongest anti-correlation coefficient (Pearson r = 20.6938, p = ,0.0001). In addition, reduced PK level was significantly associated with poor clinical outcomes of HCC patients. We found isoform M2 (PKM2) is the dominant form highly expressed in HCC and is a direct target of miR-122, as overexpression of miR-122 reduced both the mRNA and protein levels of PKM2, whereas PKM2 re-expression abrogated the miR-122-mediated glycolytic activities. The present study demonstrated the regulatory role of miR-122 on PKM2 in HCC, having an implication of therapeutic intervention targeting cancer metabolic pathways. Citation: Liu AM, Xu Z, Shek FH, Wong K-F, Lee NP, et al. (2014) miR-122 Targets Pyruvate Kinase M2 and Affects Metabolism of Hepatocellular Carcinoma. PLoS ONE 9(1): e86872. doi:10.1371/journal.pone.0086872 Editor: Jin Q. Cheng, H.Lee Moffitt Cancer Center & Research Institute, United States of America Received June 17, 2013; Accepted December 16, 2013; Published January 23, 2014 Copyright: 2014 Liu et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This study was supported by grants from National (973) Basic Science Research Program (2013CB911300) (www.973.gov.cn), National Natural Science Foundation of China (www.nsfc.gov.cn) to Dr. JM Luk (Grant No. 81128080) and Dr. Z Xu (Grant No. 81000880), a grant from Jiangsu Provincial 12th Five-Year Program on Developing Health by Technology and Education Project (www.jswst.gov.cn) to Dr. J Chen. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The co-corresponding author John M. Luk is a PLOS ONE Editorial Board member, and this does not alter the authors’ adherence to all the PLOS ONE policies on sharing data and materials. * E-mail: michelle.xuzhi@gmail.com (ZX); dr.johnluk@gmail.com (JML) . These authors contributed equally to this work.