Immunohistochemical detection of PPARγ receptors in the human pituitary adenomas: correlation with PCNA

The occurrence of peroxisome proliferator-activated receptors gamma (PPARγ) was investigated in 51 human pituitary adenomas and in 6 non-tumoral human pituitary tissue samples. Moreover, the correlation between PPARγ and the proliferating cells nuclear antigen (PCNA) - immunocytochemical proliferation marker was evaluated. The receptors and PCNA were detected by immunohistochemical methods using the polyclonal anti-PPARγ and the monoclonal anti-PCNA antibodies, respectively. PPARγ were found in all examined tissues. The mean percentage of cells with positive nuclear reaction was 3-fold higher in pituitary adenomas in comparison with non-tumoral pituitary tissues. The strongest expression of PPARγ was observed in somatotropinomas. Besides the nuclear reaction, which is typical for PPARγ, positive immunostaining was also observed in the cytoplasm. It was clearly stronger in pituitary adenomas than in non-tumoral pituitary tissues. A slight, statistically insignificant tendency towards negative correlation between PPARγ and PCNA was found in somatotropinomas, prolactinomas, corticotropinomas and gonadotropinomas. On the other hand, in null cell adenomas and "silent" corticotropinomas, a strong positve correlation between the expression of PPARγ and PCNA was observed. The strong expression of PPARγ in human pituitary adenomas and its possible involvement in control of cell proliferation in these tumors give a good reason for the attempts of their treatment with PPARγ ligands