Cowden Syndrome–Affected Patients with PTEN Promoter Mutations Demonstrate Abnormal Protein Translation

• Published in: American journal of human genetics 2007-10, Vol.81 (4), p.756-767
• Main Authors: Teresi, Rosemary E., Zbuk, Kevin M., Pezzolesi, Marcus G., Waite, Kristin A., Eng, Charis
• Format: Article
• Language: English
• Subjects: 5' Untranslated Regions; Base Sequence; Binding sites; Binding Sites - genetics; Biological and medical sciences; Breast cancer; Breast Neoplasms - genetics; Breast Neoplasms - metabolism; Case-Control Studies; Cell growth; Cell Line, Tumor; Chromosomes; Dermatology; DNA - genetics; DNA - metabolism; DNA Primers - genetics; Female; Fundamental and applied biological sciences. Psychology; Gene expression; General aspects. Genetic counseling; Genetics of eukaryotes. Biological and molecular evolution; Hamartoma Syndrome, Multiple - genetics; Hamartoma Syndrome, Multiple - metabolism; HeLa Cells; Hereditary diseases of the skin. Congenital diseases of the skin. Haemangioma of the skin, of mucosae and of soft tissue; Humans; Luciferases - genetics; Luciferases - metabolism; Medical genetics; Medical sciences; Models, Molecular; Molecular and cellular biology; Mutation; Nucleic Acid Conformation; Point Mutation; Promoter Regions, Genetic; Protein Binding; Protein Biosynthesis; Proteins; PTEN Phosphohydrolase - genetics; PTEN Phosphohydrolase - metabolism; Recombinant Proteins - genetics; Recombinant Proteins - metabolism; RNA, Messenger - chemistry; RNA, Messenger - genetics; Syndrome; Transcription Factors - metabolism; Transfection
• ISSN: 0002-9297; 1537-6605
• DOI: 10.1086/521051

Germline mutations of PTEN (phosphatase and tensin homolog deleted on chromosome 10) are associated with the multihamartomatous disorder Cowden syndrome (CS). Moreover, patients with CS with germline PTEN promoter mutations have aberrant PTEN protein expression and an increased frequency of breast cancer. Here, we examined the downstream effect of five PTEN promoter variants (−861G/T, −853C/G, −834C/T, −798G/C, and −764G/A) that are not within any known cis-acting regulatory elements. Clinically, all five of these patients have been given diagnoses of breast, thyroid, and/or endometrial cancer. We demonstrated that protein binding to the PTEN promoter (−893 to −755) was not altered in the five variants when compared with the wild-type (WT) promoter. However, reporter assays indicated that three of the variants (−861G/T, −853C/G, and −764G/A) demonstrated an ∼50% decrease in luciferase activity compared with the WT construct. PTEN messenger RNA (mRNA) levels were not altered in these variants, whereas secondary structure predictions indicated that different PTEN 5′ untranslated region transcript-folding patterns exist in three variants, suggesting an inhibition of protein translation. This was confirmed by PTEN protein analysis. These data indicate that variants causing large mRNA secondary structure alterations result in an inhibition of protein translation and a decrease in PTEN protein expression. These data emphasize the importance of PTEN promoter nucleotide variations and their ability to lead to CS progression by a novel regulatory mechanism. Importantly, these patients have a high prevalence of breast, thyroid, and endometrial malignancies; thus, understanding of the mechanism of PTEN dysfunction in these patients will lead to more-sensitive molecular diagnostic and predictive testing and, ultimately, to rational targeted therapies to treat or prevent malignancy.