title: Expression of the ring ligase PRAJA2 in thyroid cancer.
abstract: BACKGROUND
  In thyroid cells, binding of TSH to its receptor increases cAMP levels, sustaining thyrocytes growth and hormone production. The main cAMP effector enzyme is protein kinase A (PKA). Praja2 is a widely expressed RING (Really Interesting New Gene) ligase, which degrades the regulatory subunits of PKA, thus controlling the strength and duration of PKA signaling in response to cAMP. Differentiated thyroid cancer expresses a functional TSH receptor, and its growth and progression are positively regulated by TSH and cAMP signaling.
  
  
  OBJECTIVE
  We aimed to analyze the expression of praja2 in a group of 36 papillary thyroid cancer (PTC), 14 benign nodules, and six anaplastic thyroid cancers (ATC).
  
  
  METHODS
  We measured praja2 mRNA levels by quantitative RT-PCR and praja2 expression by Western blot and immunohistochemistry. Possible association between praja2 mRNA and the presence of known mutations was evaluated.
  
  
  RESULTS
  We found a statistical significant increase of mRNA levels in PTC tissue samples, compared with benign nodules and ATC. In particular, mRNA levels were maximal in differentiated thyroid cancer (PTC), progressively decreasing in more aggressive tumors, ATC having the lowest amount of praja2 mRNA. Accordingly, higher levels of praja2 protein were detected in lysates from PTC, compared with ATC. By immunohistochemistry, in PTC sections we observed a marked increase of cytoplasmic praja2 signal, which significantly decreased in less differentiated thyroid tumors, completely disappearing in ATC. Studies in cultured cells stably expressing RET/PTC1 oncogene or mutant BRAF revealed a direct correlation between praja2 mRNA levels and malignant phenotype of transformed cells. Similar results were obtained using thyroid cancer tissues carrying the same mutations.
  
  
  CONCLUSIONS
  praja2 is markedly overexpressed in differentiated thyroid cancer, and its levels inversely correlate with the malignant phenotype of the tumor. Thus, praja2 is a novel cancer-related gene whose expression is linked to the histotype and mutational status of the thyroid tumor.
authors.affiliation: Section of Endocrinology and Metabolism, Department of Internal Medicine, Endocrinology, and Metabolism and Biochemistry, Policlinico Santa Maria alle Scotte, Viale Bracci 1, University of Siena, 53100 Siena, Italy.
authors.forename: Silvia
authors.initials: S
authors.lastname: Cantara
authors.forename: Francesco
authors.initials: F
authors.lastname: D'Angeli
authors.forename: Paolo
authors.initials: P
authors.lastname: Toti
authors.forename: Luca
authors.initials: L
authors.lastname: Lignitto
authors.forename: Maria Grazia
authors.initials: MG
authors.lastname: Castagna
authors.forename: Serena
authors.initials: S
authors.lastname: Capuano
authors.forename: Bellur S
authors.initials: BS
authors.lastname: Prabhakar
authors.forename: Antonio
authors.initials: A
authors.lastname: Feliciello
authors.forename: Furio
authors.initials: F
authors.lastname: Pacini
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002291:Carcinoma, Papillary / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002478:Cells, Cultured; D004252:DNA Mutational Analysis; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D013961:Thyroid Gland / Q000378:metabolism*; D013964:Thyroid Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; C577689:PJA2 protein, human; D044767:Ubiquitin-Protein Ligases