Fibroblast growth factor 2 and estrogen control the balance of histone 3 modifications targeting MAGE-A3 in pituitary neoplasia.
OBJECTIVE
Four members of the fibroblast growth factor receptor (FGFR) family transduce signals of a diverse group of FGF ligands. The FGFR2-IIIb isoform is abundantly present in the normal pituitary gland with contrasting down-regulation in neoplastic pituitary cells. cDNA profiling identified the cancer-testis antigen melanoma-associated antigen A3 (MAGE-A3) as a putative target negatively regulated by FGFR2.


METHODS
Comparisons were made between normal and neoplastic human and mouse pituitary cells. Gene expression was examined by reverse transcription-PCR, DNA methylation was determined by methylation-specific PCR and combined bisulfite restriction analysis, and histone modification marks were identified by chromatin immunoprecipitation.


RESULTS
Normal human pituitary tissue that expresses FGFR2-IIIb does not express MAGE-A3; in contrast, pituitary tumors that are FGFR2 negative show abundant MAGE-A3 mRNA expression. MAGE-A3 expression correlates with the presence and extent of DNA promoter methylation; more frequent and higher-degree methylation is present in the normal gland compared with pituitary tumors. Conversely, pituitary tumors are hypomethylated, particularly in females where MAGE-A3 expression is nearly thrice higher than in males. Estradiol treatment induces MAGE-A3 through enhanced histone 3 acetylation and diminished methylation. The effects of estradiol are directly opposed by FGF7/FGFR2-IIIb. Down-regulation of MAGE-A3 results in p53 transcriptional induction, also through reciprocal histone acetylation and methylation modifications.


CONCLUSIONS
These findings highlight MAGE-A3 as a target of FGFR2-IIIb and estrogen action and provide evidence for a common histone-modifying network in the control of the balance between opposing signals.
Zhu
Xuegong
X
Department of Medicine, University of Toronto, Toronto, Ontario, Canada.
Asa
Sylvia L
SL
Ezzat
Shereen
S
D000818:Animals; D000951:Antigens, Neoplasm / Q000235:genetics / Q000378:metabolism*; D015153:Blotting, Western; D049109:Cell Proliferation; D019175:DNA Methylation; D004967:Estrogens / Q000378:metabolism*; D005260:Female; D016222:Fibroblast Growth Factor 2 / Q000378:metabolism*; D015870:Gene Expression; D015972:Gene Expression Regulation, Neoplastic; D006657:Histones / Q000235:genetics*; D006801:Humans; D007150:Immunohistochemistry; D047468:Immunoprecipitation; D008297:Male; D051379:Mice; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D020411:Oligonucleotide Array Sequence Analysis; D010911:Pituitary Neoplasms / Q000235:genetics / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000951:Antigens, Neoplasm; D004967:Estrogens; D006657:Histones; C072013:MAGEA3 protein, human; D009363:Neoplasm Proteins; D012333:RNA, Messenger; D016222:Fibroblast Growth Factor 2