Galectin-3 as a marker distinguishing functioning from silent corticotroph adenomas

Galectin-3 (Gal-3) belongs to the family of carbohydrate-binding proteins with high affinity for galactoside and is involved in many biological processes including cell growth and differentiation, cell adhesion, tumor progression, apoptosis and metastasis. The aim of this study was to disclose differences in the expression of Gal-3 in silent and functioning corticotroph pituitary adenomas.

We examined 30 pituitary adenomas (19 functioning corticotroph, 11 silent corticotroph adenomas). Two prolactinomas and 2 functioning somatotroph adenomas served as positive controls. Antigen retrieval was done by three-minute incubation via pressure boiler in citrate buffer solution, pH 6.0. A polymer was used as a secondary link to DAB chromogen. The independent variables t-test was used for comparison of the mean expression of Gal-3 in the two different corticotroph adenoma subgroups.

Eighteen of the functioning corticotroph adenomas (94.73%) were positive for Gal-3 with a cytoplasmic and focally membranous distribution; two cases also exhibited nuclear expression, whereas 9 of the silent corticotroph adenomas (81.81%) had zero or<1% expression of Gal-3 (p=0.001).

Gal-3 is highly expressed in functioning corticotroph adenomas of the pituitary gland, while silent adenomas exhibit very focal to null expression of Gal-3. This observation can be used in the pathological diagnosis to separate functioning from silent corticotroph adenomas of the pituitary.