Gorshtein Alexander, Rubinfeld Hadara, Kendler Efrat, Theodoropoulou Marily, Cerovac Vesna, Stalla Günter K, Cohen Zvi R, Hadani Moshe, Shimon Ilan
Institute of Endocrinology and Metabolism and Felsenstein Medical Research Center, Rabin Medical Center, Beilinson Campus, Petach Tikva 49100, Israel.
Endocr Relat Cancer. 2009 Sep;16(3):1017-27. doi: 10.1677/ERC-08-0269. Epub 2009 Jun 9.
The effect of mammalian target of rapamycin (mTOR) inhibitors on pituitary tumors is unknown. Akt overexpression was demonstrated in pituitary adenomas, which may render them sensitive to the anti-proliferative effects of these drugs. The objective of the study was to evaluate the anti-proliferative efficacy of the mTOR inhibitor, rapamycin, and its orally bioavailable analog RAD001 on the GH-secreting pituitary tumor GH3 and MtT/S cells and in human GH-secreting pituitary adenomas (GH-omas) in primary cell cultures. Treatment with rapamycin or RAD001 significantly decreased the number of viable cells and cell proliferation in a dose- and time-dependent manner. This was reflected by decreased phosphorylation levels of the downstream mTOR target p70S6K. Rapamycin treatment of GH3 cells induced G0/G1 cell cycle arrest. In other tumor cell types, this was attributed to a decrease in cyclin D1 levels. However, rapamycin did not affect cyclin D1 protein levels in GH3 cells. By contrast, it decreased cyclin D3 and p21/CIP, which stabilizes cyclin D/cyclin-dependent kinase 4 (cdk4) complexes. Rapamycin inhibited FCS-induced retinoblastoma phosphorylation and subsequent E2F-transcriptional activity. In response to decreased E2F activity, the expression of the E2F-regulated genes cyclin E and cdk2 was reduced. Our results showed that mTOR inhibitors potently inhibit pituitary cell proliferation, suggesting that mTOR inhibition may be a promising anti-proliferative therapy for pituitary adenomas. This therapeutic manipulation may have beneficial effects particularly for patients harboring invasive pituitary tumors resistant to current treatments.
雷帕霉素哺乳动物靶点（mTOR）抑制剂对垂体肿瘤的影响尚不清楚。已证实在垂体腺瘤中存在Akt过表达，这可能使它们对这些药物的抗增殖作用敏感。本研究的目的是评估mTOR抑制剂雷帕霉素及其口服生物利用度类似物RAD001对分泌生长激素的垂体肿瘤GH3和MtT/S细胞以及原代细胞培养中的人分泌生长激素垂体腺瘤（GH瘤）的抗增殖功效。用雷帕霉素或RAD001处理以剂量和时间依赖性方式显著降低了活细胞数量和细胞增殖。这通过下游mTOR靶点p70S6K磷酸化水平的降低得以体现。用雷帕霉素处理GH3细胞诱导了G0/G1细胞周期停滞。在其他肿瘤细胞类型中，这归因于细胞周期蛋白D1水平的降低。然而，雷帕霉素不影响GH3细胞中细胞周期蛋白D1的蛋白水平。相比之下，它降低了细胞周期蛋白D3和p21/CIP，后者可稳定细胞周期蛋白D/细胞周期蛋白依赖性激酶4（cdk4）复合物。雷帕霉素抑制了胎牛血清（FCS）诱导的视网膜母细胞瘤磷酸化及随后的E2F转录活性。作为对E2F活性降低的反应，E2F调节基因细胞周期蛋白E和cdk2的表达减少。我们的结果表明，mTOR抑制剂能有效抑制垂体细胞增殖，提示mTOR抑制可能是一种有前景的垂体腺瘤抗增殖疗法。这种治疗手段可能对患有对当前治疗耐药的侵袭性垂体肿瘤的患者尤其有益。
