The role of apoptosis in pituitary adenomas in the field of conventionally used therapeutic approaches.

The aim of the study was to investigate the mechanism of action of somatostatin analogues (SSA), ionizing radiation, and their combination on pituitary adenoma cells with special emphasis on proliferative and apoptotic activity. In the 14 GH-secreting adenomas pretreated with SSA before surgery, more prominent regressive changes were found accompanied by compensatory increase in perivascular fibrosis than in the reference group of 17 unpretreated adenomas. The proliferative Ki-67 labeling index was significantly lower in the treated group (median 1.6 per 1000) than in the untreated patients (median 5.0 per 1000). Apoptosis was detected in only 2 of the 14 pretreated adenomas, and it was more frequent (9/17) and more prominent in the untreated group. In cell lines, the SSA had minimal antiproliferative effect, and they were unable to induce apoptosis. Ionizing radiation at doses of 5-20 Gy induced apoptosis in the corticotroph cell line AtT20 with no cell-cycle block. In the somatotroph GH3 cell line, the early (premitotic) apoptosis was detectable using only a high dose of 200 Gy; after irradiation with doses of 20-50 Gy, apoptosis appeared with the latency of 48-72 hours, and was preceded by cell-cycle arrest in the G(2)/M phase. The treatment with somatostatin-14 during irradiation increased the percentage of apoptotic cells in culture 10 days after irradiation (11% versus 3% using 20 Gy).

The influence of treatment with somatostatin analogues on morphology, proliferative and apoptotic activity in GH-secreting pituitary adenomas.

With the aim to investigate histopathological changes and proliferative and apoptotic activity in GH-secreting adenomas we compared 14 cases pre-treated with somatostatin analogues before surgery with a reference group of 17 un-pretreated ones. Besides routine histology, immunocytochemical detection of all pituitary hormones, caspase-3, cytokeratin-18, and "M30 antigen", its apoptosis-specific fragment was performed. Proliferation activity of the tumour was determined by the Ki-67 antigen expression. In treated adenomas more prominent regressive changes were found accompanied by compensatory increase in perivascular fibrosis. The Ki-67 labelling index was lower in treated group (mean 2.5, median 1.6 per mille) than in untreated patients (mean 9.4, median 5.0 per mille). The difference was statistically significant (p=0.049 using Mann-Whitney Rank Sum Test). Apoptosis was detected in only 2 of the 14 pre-treated adenomas, and it was more frequent (9/17) and more prominent in the untreated group.

Effect of therapeutic doses of ionising radiation on the somatomammotroph pituitary cell line, GH3.

Ionising radiation is used for the treatment of pituitary tumours as fractionated radiotherapy, where the total dose reaching the tumour area is in the range of 40-50 Gy, or during stereotactic radiosurgery, where the total dose reaching the tumour area during one session is in the range of 20-90 Gy. In this study, we investigated the effect of ionising radiation of (60)Co (dose rate of 3 Gy/min, similar to that used during gamma knife procedure) on the mode of cell death of the somatomammotroph pituitary cell line, GH3, an immortalized cell line derived from a rat pituitary adenoma. We found that the basic mechanism of cell death induced by irradiation of this GH3 cell line by gamma-rays was programmed cell death-apoptosis. Doses of 20-50 Gy were shown to inhibit proliferation in these cells. 24 hours after irradiation with a dose of 20 and 50 Gy, cells were shown to accumulate in the G(2)/M phase of cell cycle. This cell cycle arrest lasted for at least ten days. Apoptosis was detected 72 hours towards until the end of the study (10 days). However, a significant number of cells were still alive ten days following irradiation. We conclude that ionising radiation doses of 20 and 50 Gy induce pituitary GH3 cell apoptosis following cell cycle arrest in the G(2)/M phase.