BRAF(V600E) mutation influences hypoxia-inducible factor-1alpha expression levels in papillary thyroid cancer.
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.
Zerilli
Monica
M
Department of Human Pathology, University of Palermo, Palermo, Italy.
Zito
Giovanni
G
Martorana
Anna
A
Pitrone
Maria
M
Cabibi
Daniela
D
Cappello
Francesco
F
Giordano
Carla
C
Rodolico
Vito
V
D000231:Adenocarcinoma, Papillary / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D000293:Adolescent; D000328:Adult; D000368:Aged; D014408:Biomarkers, Tumor / Q000378:metabolism; D045744:Cell Line, Tumor; D005260:Female; D015972:Gene Expression Regulation, Neoplastic; D055785:Gene Knockdown Techniques; D020868:Gene Silencing; D006801:Humans; D008297:Male; D008875:Middle Aged; D006899:Mixed Function Oxygenases; D009154:Mutation; D048493:Proto-Oncogene Proteins B-raf / Q000235:genetics* / Q000378:metabolism; D034741:RNA, Small Interfering / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000096:biosynthesis / Q000235:genetics*; D013964:Thyroid Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D013965:Thyroidectomy; D014162:Transfection; D055815:Young Adult
D014408:Biomarkers, Tumor; D034741:RNA, Small Interfering; D012097:Repressor Proteins; D006899:Mixed Function Oxygenases; C439790:HIF1AN protein, human; C482119:BRAF protein, human; D048493:Proto-Oncogene Proteins B-raf