title: The novel mTOR inhibitor Torin-2 induces autophagy and downregulates the expression of UHRF1 to suppress hepatocarcinoma cell growth.
abstract: Mammalian target of rapamycin (mTOR) is frequently upregulated in hepatocellular carcinoma (HCC). Blockage of mTOR was found to induce marked reduction in HCC growth in preclinical models. In the present study, we tested a novel mTOR inhibitor, Torin-2, for its antitumor efficacy in HCC cell lines Hep G2, SNU-182 and Hep 3B2.1-7. The HCC cell lines were cultured in vitro. These cells were treated with Torin-2. Cell apoptosis was evaluated by Annexin V staining. Cell proliferation and cell cycle progression were determined by Ki67 staining and propidium iodide staining, respectively. mTOR signaling, autophagy induction and expression of ubiquitin-like containing PHD and RING finger domains 1 (UHRF1) were assessed by western blot analysis. The UHRF1 mRNA level was determined by real-time PCR. We found that Torin-2 effectively suppressed the growth and survival of HCC cell lines, demonstrated by reduced proliferation and a high rate of apoptosis. Further study elucidated that in addition to blocking mTOR complex 1 (mTORC1)-associated cell cycle progression and induction of autophagy, Torin-2 downregulated transcription of UHRF1, an essential regulator of DNA methylation that is highly expressed in HCC cell lines. Consistently, the level of DNA (cytosine-5)-methyltransferase 1 (DNMT1) was higher after treatment of the HCC cell lines with Torin-2. The downregulation of UHRF1 by Torin-1 was partially due to a decrease in the UHRF1 mRNA level. Torin-2 effectively inhibited HCC cell proliferation through induction of autophagy. Torin‑2-induced downregulation of UHRF1 expression may also contribute to its antitumor effect. Our research provides new clues regarding the antitumor effects of Torin-2 and sheds light on a novel therapeutic approach for HCC.
authors.affiliation: Department of Surgical Oncology, The First Hospital of Quanzhou Affiliated to Fujian Medical University, Fujian, Quanzhou 362000, P.R. China.
authors.forename: Congren
authors.initials: C
authors.lastname: Wang
authors.affiliation: Department of Obstetrics and Gynecology, The Second Affiliated Hospital of Fujian Medical University, Fujian, Quanzhou 362000, P.R. China.
authors.forename: Xuejin
authors.initials: X
authors.lastname: Wang
authors.affiliation: Department of Surgical Oncology, The First Hospital of Quanzhou Affiliated to Fujian Medical University, Fujian, Quanzhou 362000, P.R. China.
authors.forename: Zijian
authors.initials: Z
authors.lastname: Su
authors.affiliation: Department of Surgical Oncology, The First Hospital of Quanzhou Affiliated to Fujian Medical University, Fujian, Quanzhou 362000, P.R. China.
authors.forename: Hongjiang
authors.initials: H
authors.lastname: Fei
authors.affiliation: Department of Surgical Oncology, The First Hospital of Quanzhou Affiliated to Fujian Medical University, Fujian, Quanzhou 362000, P.R. China.
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Liu
authors.affiliation: Department of Surgical Oncology, The First Hospital of Quanzhou Affiliated to Fujian Medical University, Fujian, Quanzhou 362000, P.R. China.
authors.forename: Qunxiong
authors.initials: Q
authors.lastname: Pan
mesh_terms: D001343:Autophagy / Q000187:drug effects; D022762:CCAAT-Enhancer-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D006528:Carcinoma, Hepatocellular / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology; D049109:Cell Proliferation / Q000187:drug effects; D019175:DNA Methylation / Q000187:drug effects; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D056945:Hep G2 Cells; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy / Q000235:genetics* / Q000473:pathology; D009287:Naphthyridines / Q000008:administration & dosage*; D012333:RNA, Messenger / Q000096:biosynthesis; D015398:Signal Transduction / Q000187:drug effects; D058570:TOR Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics; D044767:Ubiquitin-Protein Ligases
chemical_list: C558529:9-(6-aminopyridin-3-yl)-1-(3-(trifluoromethyl)phenyl)benzo(h)(1,6)naphthyridin-2(1H)-one; D022762:CCAAT-Enhancer-Binding Proteins; D009287:Naphthyridines; D012333:RNA, Messenger; C406364:UHRF1 protein, human; D044767:Ubiquitin-Protein Ligases; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases