title: TMP21 modulates cell growth in papillary thyroid cancer cells by inducing autophagy through activation of the AMPK/mTOR pathway.
abstract: OBJECTIVE
  To investigate the role of transmembrane protein (TMP) 21 in human thyroid cancer.
  
  
  METHODS
  The recombinant expression vector pcDNA3.1 (+)-TMP21 and specific small interfering RNAs (siRNA) against TMP21 were transfected into a papillary thyroid cancer cell line (TPC1). After transfection, the expression of TMP21 was confirmed by quantitative real-time polymerase chain reaction (qRT-PCR) and Western blotting. Moreover, cell viability and apoptosis rate were respectively determined by 3-(4, 5-dimethylthiazol-2-yl)-2, 5-diphenyltetrazolium bromide (MTT) colorimetric assay and flow cytometry (FCM). Additionally, Western blotting was performed to analyze the adenosine monophosphate (AMP)-activated protein kinase (AMPK)/mammalian target of rapamycin (mTOR) pathways associated protein (P-AMPKα(Thr172), P-mTOR(Ser2448), light chain (LC)-II/LC3-I, and P-S6K(Thr389)) after pre-treatment with AMPK inhibitor, compound C (Com C) and siTMP21.
  
  
  RESULTS
  The TMP21 protein level and cell viability were significantly higher, but apoptotic rate was significantly lower by transfection with pcDNA3.1-TMP21 than those in control group (P < 0.05), and reverse results were obtained by transfection with siTMP21. However, qRT-PCR showed different results due to the feedback inhibition of mRNA. Besides, silencing of TMP21 significantly reduced the levels of P-mTOR(Ser2448) and P-S6K(Thr389) (P < 0.05), but significantly increased the levels of P-AMPKα(Thr172) and LC3-II/LC3-I compared with the control group (P < 0.01). Whereas, the levels of P-AMPKα(Thr172) and LC3-II/LC3-I were significantly decreased by Com C compared with the control group (P < 0.05).
  
  
  CONCLUSIONS
  TMP21 modulates cell growth in TPC1 cells by inducing autophagy, which may be associated with activation of AMPK/mTOR pathway.
authors.affiliation: Department of General Surgery, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine Shanghai 200011, China.
authors.forename: Xiaobo
authors.initials: X
authors.lastname: Xu
authors.affiliation: Department of General Surgery, Shanghai Fengcheng Hospital Shanghai 201411, China.
authors.forename: Hongqiang
authors.initials: H
authors.lastname: Gao
authors.affiliation: Department of General Surgery, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine Shanghai 200011, China.
authors.forename: Jian
authors.initials: J
authors.lastname: Qin
authors.affiliation: Department of General Surgery, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine Shanghai 200011, China.
authors.forename: Liu
authors.initials: L
authors.lastname: He
authors.affiliation: Department of General Surgery, Shanghai Ninth People's Hospital, Shanghai JiaoTong University School of Medicine Shanghai 200011, China.
authors.forename: Wenyong
authors.initials: W
authors.lastname: Liu
mesh_terms: D055372:AMP-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism*; D017209:Apoptosis; D001343:Autophagy / Q000187:drug effects; D002277:Carcinoma / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D002291:Carcinoma, Papillary; D045744:Cell Line, Tumor; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival; D004789:Enzyme Activation; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D029543:Nucleocytoplasmic Transport Proteins; D010766:Phosphorylation; D047428:Protein Kinase Inhibitors / Q000494:pharmacology; D034622:RNA Interference; D015398:Signal Transduction; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000201:enzymology* / Q000235:genetics / Q000473:pathology; D013997:Time Factors; D014162:Transfection
chemical_list: D008565:Membrane Proteins; D029543:Nucleocytoplasmic Transport Proteins; D047428:Protein Kinase Inhibitors; C484395:TMED10 protein, human; C546842:MTOR protein, human; D058570:TOR Serine-Threonine Kinases; D055372:AMP-Activated Protein Kinases
keywords: AMPK/mTOR; Thyroid cancer; autophagy; transmembrane protein 21