title: Role of tissue transglutaminase 2 in the acquisition of a mesenchymal-like phenotype in highly invasive A431 tumor cells.
abstract: BACKGROUND
  Cancer progression is closely linked to the epithelial-mesenchymal transition (EMT) process. Studies have shown that there is increased expression of tissue tranglutaminase (TG2) in advanced invasive cancer cells. TG2 catalyzes the covalent cross-linking of proteins, exhibits G protein activity, and has been implicated in the modulation of cell adhesion, migration, invasion and cancer metastasis. This study explores the molecular mechanisms associated with TG2's involvement in the acquisition of the mesenchymal phenotype using the highly invasive A431-III subline and its parental A431-P cells.
  
  
  RESULTS
  The A431-III tumor subline displays increased expression of TG2. This is accompanied by enhanced expression of the mesenchymal phenotype, and this expression is reversed by knockdown of endogenous TG2. Consistent with this, overexpression of TG2 in A431-P cells advanced the EMT process. Furthermore, TG2 induced the PI3K/Akt activation and GSK3β inactivation in A431 tumor cells and this increased Snail and MMP-9 expression resulting in higher cell motility. TG2 also upregulated NF-κB activity, which also enhanced Snail and MMP-9 expression resulting in greater cell motility; interestingly, this was associated with the formation of a TG2/NF-κB complex. TG2 facilitated acquisition of a mesenchymal phenotype, which was reversed by inhibitors of PI3K, GSK3 and NF-κB.
  
  
  CONCLUSIONS
  This study reveals that TG2 acts, at least in part, through activation of the PI3K/Akt and NF-κB signaling systems, which then induce the key mediators Snail and MMP-9 that facilitate the attainment of a mesenchymal phenotype. These findings support the possibility that TG2 is a promising target for cancer therapy.
authors.affiliation: Institute of Biochemical Sciences, National Taiwan University, Taipei, Taiwan.
authors.forename: Chun-Yu
authors.initials: CY
authors.lastname: Lin
authors.forename: Pei-Hsun
authors.initials: PH
authors.lastname: Tsai
authors.forename: Chithan C
authors.initials: CC
authors.lastname: Kandaswami
authors.forename: Geen-Dong
authors.initials: GD
authors.lastname: Chang
authors.forename: Chia-Hsiung
authors.initials: CH
authors.lastname: Cheng
authors.forename: Chang-Jen
authors.initials: CJ
authors.lastname: Huang
authors.forename: Ping-Ping
authors.initials: PP
authors.lastname: Lee
authors.forename: Jiuan-Jiuan
authors.initials: JJ
authors.lastname: Hwang
authors.forename: Ming-Ting
authors.initials: MT
authors.lastname: Lee
mesh_terms: D000369:Aged, 80 and over; D045744:Cell Line, Tumor; D058750:Epithelial-Mesenchymal Transition / Q000235:genetics* / Q000502:physiology; D005260:Female; D019204:GTP-Binding Proteins; D006801:Humans; D020780:Matrix Metalloproteinase 9 / Q000235:genetics / Q000378:metabolism / Q000502:physiology; D016328:NF-kappa B / Q000378:metabolism / Q000502:physiology; D009361:Neoplasm Invasiveness; D009369:Neoplasms / Q000235:genetics / Q000378:metabolism / Q000473:pathology*; D051058:Oncogene Protein v-akt / Q000378:metabolism / Q000502:physiology; D010641:Phenotype; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism / Q000502:physiology; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D015398:Signal Transduction / Q000235:genetics / Q000502:physiology; D014162:Transfection; D011503:Transglutaminases / Q000235:genetics / Q000502:physiology*
chemical_list: D019204:GTP-Binding Proteins; D020780:Matrix Metalloproteinase 9; D016328:NF-kappa B; D051058:Oncogene Protein v-akt; D019869:Phosphatidylinositol 3-Kinases; D000091345:Protein Glutamine gamma Glutamyltransferase 2; D011503:Transglutaminases; C000717608:TGM2 protein, human