Sheng Tan

Screening of the entire let-7 family of microRNAs (miRNA) by in situ hybridization identified let-7g as the only member, the diminished expression of which was significantly associated with lymph node metastasis and poor survival in breast cancer patients. Abrogation of let-7g expression in otherwise nonmetastatic mammary carcinoma cells elicited rapid metastasis from the orthotopic location, through preferential targets, Grb2-associated binding protein 2 (GAB2) and fibronectin 1 (FN1), and consequent activation of p44/42 mitogen-activated protein kinase (MAPK) and specific matrix metalloproteinases. Treatment with estrogen or epidermal growth factor specifically reduced the expression of mature let-7g through activation of p44/42 MAPK and subsequently stimulated expression of GAB2 and FN1, which, in turn, promoted tumor invasion. We thus identify let-7g as a unique member of the let-7 miRNA family that can serve as a prognostic biomarker in breast cancer and also propose a paradigm used by specific signaling molecules via let-7g to cooperatively promote breast cancer invasion and metastasis. Thus, let-7 family members neither possess equivalent clinicopathologic correlation nor function in breast cancer.

// Ying Qi 1 , Hong Sain Ooi 2 , Jun Wu 3 , Jian Chen 1 , Xiaoli Zhang 1 , Sheng Tan 4 , Qing Yu 4 , Yuan-Yuan Li 5, 6 , Yani Kang 1 , Hua Li 1 , Zirui Xiong 4 , Tao Zhu 4 , Bingya Liu 1, 7 , Zhifeng Shao 1 , Xiaodong Zhao 1 1 School of Biomedical Engineering, Bio-ID Research Center, State Key Laboratory for Oncogenes and Related Genes, Shanghai Jiao Tong University, Shanghai, China 2 Department of Biomedicine, Aarhus University, Aarhus, Denmark 3 Department of Automation, Shanghai Jiao Tong University, Shanghai, China 4 Laboratory of Molecular Tumor Pathology, School of Life Sciences, University of Science and Technology of China, Hefei, Anhui, China 5 Shanghai Center for Bioinformatics Technology, Shanghai, China 6 Shanghai Engineering Research Center of Pharmaceutical Translation, Shanghai, China 7 Department of Surgery, Shanghai Key Laboratory of Gastric Neoplasms, Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China Correspondence to: Bingya Liu, e-mail: bingyaliu@sjtu.edu.cn Xiaodong Zhao, e-mail: xiaodongzhao@sjtu.edu.cn Keywords: EZH2, RIP-seq, MALAT1, gastric cancer, transcriptional silencing Received: September 29, 2015      Accepted: January 23, 2016      Published: February 09, 2016 ABSTRACT EZH2, the catalytic component of polycomb repressive complex 2 (PRC2), is frequently overexpressed in human cancers and contributes to tumor initiation and progression, in part through transcriptional silencing of tumor suppressor genes. A number of noncoding RNAs (ncRNAs) recruit EZH2 to specific chromatin loci, where they modulate gene expression. Here, we used RNA immunoprecipitation sequencing (RIP-seq) to profile EZH2-associated transcripts in human gastric cancer cell lines. We identified 8,256 transcripts, including both noncoding and coding transcripts, some of which were derived from cancer-related loci. In particular, we found that long noncoding RNA (lncRNA) MALAT1 binds EZH2, suppresses the tumor suppressor PCDH10 , and promotes gastric cellular migration and invasion. Our work thus provides a global view of the EZH2-associated transcriptome and offers new insight into the function of EZH2 in gastric tumorigenesis.

Metastasis is the leading cause of death in patients with hepatocellular carcinoma (HCC) and microRNAs have been implicated to influence this process. Emerging evidence indicates that miR-198 is down-regulated in HCC compared to normal liver parenchyma, but the functional roles of miR-198 in HCC cells remains unexplored. Herein, we show that miR-198 directly targets c-MET via its 3′UTR. Forced expression of miR-198 decreased c-MET expression at both mRNA and protein levels and consequently diminished HGF induced phosphorylation of p44/42 MAPK in HCC cells. Forced expression of miR-198 inhibited HGF promotion of HCC cell migration and invasion in a c-MET dependent manner. In conclusion, we have identified miR-198 as a novel suppressor of HCC cell invasion by negative regulation of the HGF/c-MET pathway.

INTRODUCTION: Estrogen signaling is pivotal in the progression of estrogen receptor positive breast cancer primarily by the regulation of cell survival and proliferation. Micro (mi)RNAs have been demonstrated to be regulated by estrogen to mediate estrogenic effects. Herein, we determined the role of estrogen regulated miR-26 and its underlying molecular mechanisms associated with estrogen receptor (ER)+ breast cancer proliferation. METHODS: The expression of miR-26a and miR-26b was evaluated by real-time quantitative (RT)-PCR. The expression of miR-26a or miR-26b was modulated in ER+ breast cancer cells (MCF-7 and T47D) and tumor cell growth in vitro and an in vivo xenograft model was determined. Bioinformatics analyses were utilized to screen for estrogen responsive genes, which were also predicted to be targeted by miR-26. Luciferase reporter assays were performed to confirm miR-26 regulation of the 3' UTR of target genes. The levels of miR-26 target genes (CHD1, GREB1 and KPNA2) were evaluated by western blotting and immunohistochemistry. RESULTS: Estrogen reduced the expression of miR-26a and miR-26b in ER+ breast cancer cells. Forced expression of miR-26a or miR-26b significantly inhibited the estrogen stimulated growth of ER+ breast cancer cells and tumor growth in xenograft models, whereas miR-26a/b depletion increased the growth of ER+ breast cancer cells in the absence of estrogen treatment. Screening of estrogen responsive genes, which were also predicted to be targeted by miR-26, identified GREB1 and nine other genes (AGPAT5, AMMECR1, CHD1, ERLIN1, HSPA8, KPNA2, MREG, NARG1, and PLOD2). Further verification has identified nine genes (AGPAT5, CHD1, ERLIN1, GREB1, HSPA8, KPNA2, MREG, NARG1 and PLOD2) which were directly targeted by miR-26 via their 3' UTR. Functional screening suggested only three estrogen regulated miR-26 target genes (CHD1, GREB1 and KPNA2) were involved in the regulation of estrogen promoted cell proliferation. Depletion of either CHD1, GREB1 or KPNA2 significantly abrogated the enhanced growth of ER+ breast cancer cells due to miR-26 depletion. We further demonstrated that estrogen stimulated c-MYC expression was both sufficient and necessary for the diminished expression of miR-26a and miR-26b. CONCLUSIONS: We have identified a novel estrogen/MYC/miR-26 axis that mediates estrogen stimulated cell growth via CHD1, GREB1 and KPNA2.