Differential expression of folate receptor alpha in pituitary adenomas and its relationship to tumor behavior

Folate receptor alpha (FRα) plays a pivotal role in the tumorigenesis of some malignant tumors, but its role and clinical significance in pituitary adenomas remain unclear.

To identify a possible biomarker for the diagnosis of nonfunctional pituitary adenomas (NFAs) that could also be used to assess tumor behavior.

Sporadic pituitary tumor specimens (n = 76) and normal pituitary glands (n = 7) were examined. FRα protein and mRNA expression were quantified by immunohistochemistry and quantitative reverse transcriptase polymerase chain reaction, respectively. We verified the differential expression of FRα in pituitary adenomas and evaluated the associations of FRα expression with Ki-67 labeling index (LI) and clinicopathologic characteristics of NFAs. Statistical significance was determined by using the Student t test or one-way analysis of variance.

FRα mRNA and protein was uniquely overexpressed in NF (immunohistochemically positive) and NF (immunohistochemically negative) adenomas but not in functional adenomas (adrenocorticotropic hormone, growth hormone, and prolactin) or normal adenohypophysial tissues (P < .001). The expression of FRα was positively correlated with tumor invasiveness, size and Ki-67 LI in NFAs.

FRα may play an important role in the development and progression of NFAs. Therefore, FRα may be useful as a molecular biomarker for the diagnosis of NFAs and assessment of tumor invasiveness.