Endocrine Abstracts

Introduction: The peroxisome proliferator-activated receptors gamma (PPARγ) are nuclear receptors which are detected in normal and pathological tissues. Our earlier study showed the overexpression of PPARγ in human adrenal tumors and pituitary adenomas in comparison to normal glands. The in vitro experiments indicated that ligands of PPARγ inhibit growth of many tumors including pituitary adenomas, thyroid cancers and adrenal carcinomas. However, the data concerning the effects of PPARγ ligands on adrenal tumors is very scarce.

Objective: In the present study, we investigated the action of PPARγ ligands rosiglitazone on growth of human adrenocortical tumors in vitro.

Materials and methods: Ten surgically removed adenomas (five non-functioning adenomas, four aldosterone-secreting tumor and one cortisol-secreting adenoma) were examined. The adrenal tumors cells were exposed in the primary culture to rosiglitazone at the concentration of 10⁻³, 10^-4 and 10⁻⁵ M for 24 hours. To measure cell growth the modified colorimetric Mossman method detecting the viable cells was applied. Moreover, the immunohistochemical evaluation of PPARγ expression in paraffin sections of adrenal tumors was performed. The study protocol was approved by local Ethical Committee of Medical University of Lodz.

Results: We have shown that rosiglitazone significantly inhibited the cell growth in 9 out 10 examined adrenal tumor in a dose-dependent manner. Rosiglitazone was the most effective at concentration of 10⁻³ M. PPARγ receptors were found in all tissue, but the number of cells with positive immunoreaction was the lowest in aldosterone-secreting adenoma, which was insensitive to rosiglitazone.

Conclusions: Our results suggest that rosiglitazone may be useful in the treatment of human adrenocortical adenoma. However, the efficacy of PPARγ ligands requires a confirmation in study performed on the larger group of adrenal tumors.