The cancer/testis antigen melanoma-associated antigen-A3/A6 is a novel target of fibroblast growth factor receptor 2-IIIb through histone H3 modifications in thyroid cancer.
OBJECTIVE
Fibroblast growth factor (FGF) signals play fundamental roles in development and tumorigenesis. Thyroid cancer is an example of a tumor with nonoverlapping genetic mutations that up-regulate mitogen-activated protein kinase. We reported recently that FGF receptor 2 (FGFR2) is down-regulated through extensive DNA promoter methylation in thyroid cancer. Reexpression of the FGFR2-IIIb isoform impedes signaling upstream of the BRAF/mitogen-activated protein kinase pathway to interrupt tumor progression. In this analysis, we examined a novel target of FGFR2-IIIb signaling, melanoma-associated antigen-A3 and A6 (MAGE-A3/6).


METHODS
cDNA microarray analysis was done on human WRO thyroid cancer cells transfected with FGFR2-IIIb or empty vector. Identified gene target was confirmed by reverse transcription-PCR and Western blotting. Gene regulation was examined by treatment of WRO cells with the methylation inhibitor 5'-azacytidine followed by methylation-specific PCR and reverse transcription-PCR and by chromatin immunoprecipitation.


RESULTS
Gene expression profiling identified the cancer/testis antigen MAGE-A3/6 as a novel target of FGFR2-IIIb signaling. MAGE-A3/6 regulation was mediated through DNA methylation and chromatin modifications. In particular, FGF7/FGFR2-IIIb activation resulted in histone 3 methylation and deacetylation associated with the MAGE-A3/6 promoter to down-regulate gene expression.


CONCLUSIONS
These data unmask a complex repertoire of epigenetically controlled signals that govern FGFR2-IIIb and MAGE-A3/6 expression. Our findings provide insights into the interrelationship between novel tumor markers that may also represent overlapping therapeutic targets.
Kondo
Tetsuo
T
Department of Pathology, Princess Margaret Hospital, University Health Network, University of Toronto, Toronto, Ontario, Canada.
Zhu
Xuegong
X
Asa
Sylvia L
SL
Ezzat
Shereen
S
D000951:Antigens, Neoplasm / Q000235:genetics*; D045744:Cell Line, Tumor; D019175:DNA Methylation; D044127:Epigenesis, Genetic; D051523:Fibroblast Growth Factor 7 / Q000502:physiology; D015972:Gene Expression Regulation, Neoplastic; D006657:Histones / Q000378:metabolism*; D006801:Humans; D009363:Neoplasm Proteins / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D011401:Promoter Regions, Genetic; D020033:Protein Isoforms / Q000502:physiology; D051497:Receptor, Fibroblast Growth Factor, Type 2 / Q000502:physiology*; D015398:Signal Transduction; D013964:Thyroid Neoplasms / Q000235:genetics / Q000378:metabolism*
D000951:Antigens, Neoplasm; C496453:FGF7 protein, human; D006657:Histones; C072013:MAGEA3 protein, human; D009363:Neoplasm Proteins; D020033:Protein Isoforms; D051523:Fibroblast Growth Factor 7; D051497:Receptor, Fibroblast Growth Factor, Type 2; C065104:keratinocyte growth factor receptor