title: SMAD4 gene promoter mutations in patients with thyroid tumors.
abstract: As a key component of the transforming growth factor beta (TGFB) pathway, which regulates the expression of thyroid-specific genes, tumor suppressor SMAD4 is crucial for thyroid development and function. Aberrant expression of SMAD4 in thyroid tumor tissue was reported and mutations affecting the coding region have been detected, but a potential role of mutations in SMAD4 gene regulatory regions remains unexplored. The aim of this study was to analyze SMAD4 gene promoters in thyroid tumors. A total of 76 thyroidectomy specimens were studied, including 42 malignant and 34 benign tumors. The presence of mutations in four SMAD4 gene promoters was analyzed in thyroid tumor tissue and peripheral blood by PCR and DNA sequencing. The expression and intracellular localization of endogenous SMAD4 protein in selected tumor samples was studied by immunostaining and confocal microscopy. Of three novel variants detected, two were within promoter A (-204T/C and -5C/T) and one in promoter D (-180delA). Unlike somatic mutations previously detected in the nearby region, germline mutation -180delA in promoter D doesn't appear to affect SMAD4 expression in the thyroid tumor tissue. However, all newly detected SMAD4 promoter variants affect predicted binding sites of transcription factors involved in cell cycle regulation and should be further characterized functionally. Although not directly involved in carcinogenesis, detected variants may alter SMAD4 transcriptional regulation to some extent. Considering that dosage dependence is of great importance for the role of SMAD4 protein as a tumor suppressor, potential clinical significance of SMAD4 gene promoter mutations is worth further investigation.
authors.affiliation: Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Vojvode Stepe 444A, 11010 Belgrade, Serbia. Electronic address: aleksni@imgge.bg.ac.rs.
authors.forename: Aleksandra
authors.initials: A
authors.lastname: Nikolic
authors.affiliation: Institute of Human Genetics, Medical Faculty, University of Belgrade, Visegradska 26, 11000 Belgrade, Serbia.
authors.forename: Momcilo
authors.initials: M
authors.lastname: Ristanovic
authors.affiliation: Center for Endocrine Surgery, Clinic for Endocrinology, Clinical Center of Serbia, Dr Koste Todorovica 8, 11000 Belgrade, Serbia; School of Medicine, University of Belgrade, Dr Subotica 8, 11000 Belgrade, Serbia.
authors.forename: Vladan
authors.initials: V
authors.lastname: Zivaljevic
authors.affiliation: Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Vojvode Stepe 444A, 11010 Belgrade, Serbia.
authors.forename: Aleksandra Divac
authors.initials: AD
authors.lastname: Rankov
authors.affiliation: Institute of Molecular Genetics and Genetic Engineering, University of Belgrade, Vojvode Stepe 444A, 11010 Belgrade, Serbia.
authors.forename: Dragica
authors.initials: D
authors.lastname: Radojkovic
authors.affiliation: Center for Endocrine Surgery, Clinic for Endocrinology, Clinical Center of Serbia, Dr Koste Todorovica 8, 11000 Belgrade, Serbia; School of Medicine, University of Belgrade, Dr Subotica 8, 11000 Belgrade, Serbia.
authors.forename: Ivan
authors.initials: I
authors.lastname: Paunovic
mesh_terms: D000328:Adult; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D014644:Genetic Variation; D060005:Genotyping Techniques; D006801:Humans; D008297:Male; D008875:Middle Aged; D009154:Mutation; D011401:Promoter Regions, Genetic; D051901:Smad4 Protein / Q000235:genetics* / Q000378:metabolism; D013961:Thyroid Gland / Q000473:pathology; D013964:Thyroid Neoplasms / Q000235:genetics*; D014157:Transcription Factors
chemical_list: C497796:SMAD4 protein, human; D051901:Smad4 Protein; D014157:Transcription Factors
keywords: Mutation; Promoter; SMAD4; Thyroid tumor