title: SIN1, a critical component of the mTOR-Rictor complex, is overexpressed and associated with AKT activation in medullary and aggressive papillary thyroid carcinomas.
abstract: BACKGROUND
  Mammalian target of rapamycin (mTOR) forms 2 active complexes in the cell: the rapamycin-sensitive mTOR-Raptor (mTORC1) and the rapamycin-insensitive mTOR-Rictor (mTORC2). The latter activates AKT kinase, which promotes tumor cell survival and proliferation by multiple downstream targets. Mammalian stress-activated protein kinase interacting protein 1 (SIN1), an essential subunit of the mTORC2 complex, maintains the integrity of the complex and substrate specificity and regulates Akt activation. The role of mTOR-Rictor complex activation in thyroid carcinogenesis remains unknown. Therefore, we investigated expression patterns of Sin1 in the cells lines of thyroid carcinoma and tumors and their association with AKT activation, histologic type, and tumor aggressiveness.
  
  
  METHODS
  Tissue specimens from 42 patients with thyroid cancer, including follicular (5), papillary (18), medullary (16), and poorly differentiated (3) carcinomas were analyzed via immunohistochemistry for SIN1 expression and AKT phosphorylation at Ser473 residue (Ser473-p-AKT). Eight of 18 papillary carcinomas were aggressive histologic variants. In addition, expression of Sin1 and activation of AKT kinase were analyzed in fresh-frozen tissue samples (normal/tumor), primary cell cultures (papillary thyroid carcinoma [PTC]), and an established thyroid cancer cell line (medullary thyroid carcinoma) by Western blotting.
  
  
  RESULTS
  With immunohistochemistry, we found that Sin1 was overexpressed in medullary thyroid carcinomas and aggressive variants of papillary thyroid carcinoma compared with conventional papillary and follicular carcinomas (P < .001). Sin1 expression correlated with AKT activation in the entire study group (P = .002). Using Western blot analysis, we found that Sin1 and p-AKT were detected at a greater level in cultured primary cells from aggressive PTC compared with conventional PTC as well as in cell lines of medullary and anaplastic thyroid carcinoma. High expression levels of SIN1 were detected in papillary thyroid carcinomas compared with benign nodules in immunoblots in which we used fresh-frozen patient samples. Two of the Sin1 protein isoforms, p76 and p55, were detected predominantly in PTC samples.
  
  
  CONCLUSIONS
  Sin1, a critical factor of the mTORC2 complex is overexpressed in clinically aggressive thyroid cancer types and is associated strongly with activation of AKT kinase. Sin1-dependent AKT activation might represent a target for experimental therapy.
authors.affiliation: Department of Surgery, Hygeia Hospital, Athens, Greece.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Moraitis
authors.affiliation: First Department of Pathology, National and Kapodistrian University of Athens School of Medicine, Athens, Greece.
authors.forename: Maria
authors.initials: M
authors.lastname: Karanikou
authors.affiliation: First Department of Pathology, National and Kapodistrian University of Athens School of Medicine, Athens, Greece.
authors.forename: Chryssa
authors.initials: C
authors.lastname: Liakou
authors.affiliation: Department of Pharmacology, University of Thessaly, Larissa, Greece.
authors.forename: Konstantinos
authors.initials: K
authors.lastname: Dimas
authors.affiliation: Department of Surgery, Hygeia Hospital, Athens, Greece.
authors.forename: George
authors.initials: G
authors.lastname: Tzimas
authors.affiliation: First Department of Pathology, National and Kapodistrian University of Athens School of Medicine, Athens, Greece.
authors.forename: Sofia
authors.initials: S
authors.lastname: Tseleni-Balafouta
authors.affiliation: First Department of Pathology, National and Kapodistrian University of Athens School of Medicine, Athens, Greece.
authors.forename: Efstratios
authors.initials: E
authors.lastname: Patsouris
authors.affiliation: First Department of Pathology, National and Kapodistrian University of Athens School of Medicine, Athens, Greece; Department of Pathology, Karolinska University Hospital and Karolinska Institute, Stockholm, Sweden.
authors.forename: George Z
authors.initials: GZ
authors.lastname: Rassidakis
authors.affiliation: Department of Surgery, Hygeia Hospital, Athens, Greece; Department of Endocrine Surgery, Karolinska University Hospital and Karolinska Institute, Stockholm, Sweden. Electronic address: markouvaraki@hotmail.com.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Kouvaraki
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000235:genetics; D000328:Adult; D000368:Aged; D001707:Biopsy, Needle; D015153:Blotting, Western; D002277:Carcinoma / Q000235:genetics* / Q000473:pathology; D018278:Carcinoma, Neuroendocrine; D002291:Carcinoma, Papillary; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D007150:Immunohistochemistry; D008297:Male; D008875:Middle Aged; D051058:Oncogene Protein v-akt / Q000235:genetics; D012494:Sampling Studies; D012680:Sensitivity and Specificity; D058570:TOR Serine-Threonine Kinases / Q000235:genetics; D000077273:Thyroid Cancer, Papillary; D013964:Thyroid Neoplasms / Q000235:genetics* / Q000473:pathology; D015533:Transcriptional Activation
chemical_list: D048868:Adaptor Proteins, Signal Transducing; C493277:MAPKAP1 protein, human; C546842:MTOR protein, human; D051058:Oncogene Protein v-akt; D058570:TOR Serine-Threonine Kinases