BRAF(V600E) mutation influences hypoxia-inducible factor-1alpha expression levels in papillary thyroid cancer.

Abstract

Hypoxia-inducible factor-1alpha is found frequently overexpressed in solid tumors cells, exerting an important role in angiogenesis, glucose metabolism, cell proliferation, survival and invasion. In thyroid carcinomas, hypoxia-inducible factor-1alpha expression was found increased in differentiated, poorly differentiated, medullary and anaplastic variants. Hypoxia represents the principal stimulus responsible for hypoxia-inducible factor-1alpha induction. Other nonhypoxic stimuli increase hypoxia-inducible factor-1alpha synthesis through the activation of phosphatidylinositol 3-kinase and mitogen-activated protein kinase pathways in a cell-type-specific manner. We have previously shown the role of BRAF(V600E) mutation in papillary thyroid cancer cells as a factor that facilitates tumor cell growth and progression. In this study, we tested the hypothesis that BRAF(V600E) mutation influences hypoxia-inducible factor-1alpha expression in papillary thyroid carcinoma cells. We analyzed 27 papillary thyroid carcinomas, 13 of which presented BRAF(V600E) mutation. In tumor tissues, immunoreactivity for hypoxia-inducible factor-1alpha was detected in the majority of analyzed BRAF(V600E) mutated cases. Transcriptional analyses revealed elevated hypoxia-inducible factor-1alpha levels with significant differences between wild-type and mutated group. A BRAF wild-type papillary thyroid carcinoma cell line and a BRAF(V600E) mutated papillary thyroid carcinoma cell line were selected to study the effects of BRAF mutation on hypoxia-inducible factor-1alpha expression in vitro. Knockdown of mutant BRAF(V600E) or both the wild type and the BRAF(V600E) by RNA interference induced a significant reduction of hypoxia-inducible factor-1alpha expression at mRNA and protein levels. Pharmacological inhibition of BRAF significantly reduces hypoxia-inducible factor-1alpha expression levels in papillary thyroid carcinoma cell line harboring BRAF(V600E) mutation. Our results suggest that hypoxia-inducible factor-1alpha is expressed in papillary thyroid carcinomas and is regulated not only by hypoxia but also by BRAF(V600E)-mediated signaling pathway.

• Authors: Monica Zerilli, Giovanni Zito, Anna Martorana, Maria Pitrone, Daniela Cabibi, Francesco Cappello, Carla Giordano, Vito Rodolico
• Journal: Modern pathology : an official journal of the United States and Canadian Academy of Pathology, Inc (Mod Pathol) Vol. 23 Issue 8 Pg. 1052-60 (Aug 2010) ISSN: 1530-0285 [Electronic] United States
• PMID: 20473281 (Publication Type: Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Biomarkers, Tumor
• RNA, Small Interfering
• Repressor Proteins
• Mixed Function Oxygenases
• HIF1AN protein, human
• BRAF protein, human
• Proto-Oncogene Proteins B-raf

Topics

• Adenocarcinoma, Papillary (genetics, metabolism, pathology)
• Adolescent
• Adult
• Aged
• Biomarkers, Tumor (metabolism)
• Cell Line, Tumor
• Female
• Gene Expression Regulation, Neoplastic
• Gene Knockdown Techniques
• Gene Silencing
• Humans
• Male
• Middle Aged
• Mixed Function Oxygenases
• Mutation
• Proto-Oncogene Proteins B-raf (genetics, metabolism)
• RNA, Small Interfering (genetics, metabolism)
• Repressor Proteins (biosynthesis, genetics)
• Thyroid Neoplasms (genetics, metabolism, pathology)
• Thyroidectomy
• Transfection
• Young Adult