垂体肿瘤中PPAR-γ的表达及格列酮类药物的功能活性：格列酮类药物的任何抗增殖作用均独立于PPAR-γ受体的证据。

PPAR-gamma expression in pituitary tumours and the functional activity of the glitazones: evidence that any anti-proliferative effect of the glitazones is independent of the PPAR-gamma receptor.

作者信息

Emery Michelle N, Leontiou Chrysanthia, Bonner Sarah E, Merulli Chiara, Nanzer Alexandra M, Musat Madalina, Galloway Malcolm, Powell Michael, Nikookam Khash, Korbonits Márta, Grossman Ashley B

机构信息

Department of Endocrinology, St. Bartholomew's and the Royal London School of Medicine and Dentistry, London, UK.

出版信息

Clin Endocrinol (Oxf). 2006 Sep;65(3):389-95. doi: 10.1111/j.1365-2265.2006.02610.x.

DOI:10.1111/j.1365-2265.2006.02610.x

PMID:16918962

Abstract

OBJECTIVE

It has been reported that both normal pituitary and pituitary tumours express PPAR-gamma, a nuclear hormone receptor, the expression being more abundant in pituitary tumours, and that this is the basis for the reported antiproliferative effects of the thiazolidinedione, rosiglitazone, in animal models. However, the mechanisms for the responsivity to rosiglitazone have remained unclear.

DESIGN AND MEASUREMENTS

To investigate this further, 'real-time' PCR was used to assess PPAR-gamma mRNA expression, and Western blotting and immunohistochemistry to study its protein expression, in 46 human pituitary tumours and normal pituitary tissue. Cell proliferation of the GH3 pituitary cell line was assessed by [3H]-thymidine-incorporation after 48 h rosiglitazone and pioglitazone (10(-4) M- 10(-10) M) treatment alone, or rosiglitazone in combination with the PPAR-gamma antagonist GW9662.

RESULTS

PPAR-gamma mRNA and protein was found to be expressed in normal pituitary and was variably expressed in pituitary tumours, but were increased specifically in nonfunctioning pituitary adenomas. However, very little staining was observed with immunohistochemistry, with only occasional cell nuclei stained, and no difference was detectable between controls and tumours. Rosiglitazone at 10(-4) M and 10(-5) M concentrations inhibited cell proliferation (10(-4) M 14.0% +/- 1.5% and 10(-5) M 67% +/- 4%[mean +/- SEM]vs Control 100% +/- 3%, P < 0.0001) while lower concentrations showed no significant effect. Following withdrawal of rosiglitazone 10(-5) M, the cells fully recovered at a further 48 h, while lower doses showed a 'rebound' of stimulation. Pioglitazone was of similar potency to rosiglitazone in inhibiting proliferation. The PPAR-gamma antagonist did not show a significant reversal of the antiproliferative effect of rosiglitazone, and indeed suppressed proliferation on its own.

CONCLUSIONS

Our data suggest that the antiproliferative action of rosiglitazone is probably not via PPAR-gamma.

摘要

目的

据报道，正常垂体及垂体肿瘤均表达核激素受体PPAR-γ，在垂体肿瘤中其表达更为丰富，这也是噻唑烷二酮类药物罗格列酮在动物模型中具有抗增殖作用的基础。然而，对罗格列酮产生反应的机制仍不清楚。

设计与测量

为进一步研究这一问题，采用“实时”PCR评估46例人类垂体肿瘤及正常垂体组织中PPAR-γ mRNA的表达，并通过蛋白质印迹法和免疫组织化学研究其蛋白表达。单独用罗格列酮和吡格列酮（10⁻⁴ M - 10⁻¹⁰ M）处理48小时后，或罗格列酮与PPAR-γ拮抗剂GW9662联合处理后，通过[³H] - 胸腺嘧啶掺入法评估GH3垂体细胞系的细胞增殖情况。

结果

发现PPAR-γ mRNA和蛋白在正常垂体中表达，在垂体肿瘤中表达各异，但在无功能垂体腺瘤中特异性增加。然而，免疫组织化学观察到的染色很少，仅偶尔有细胞核被染色，对照组和肿瘤组之间未检测到差异。10⁻⁴ M和10⁻⁵ M浓度的罗格列酮抑制细胞增殖（10⁻⁴ M为14.0% ± 1.5%，10⁻⁵ M为67% ± 4%[平均值 ± 标准误]，而对照组为100% ± 3%，P < 0.0001），而较低浓度则无显著影响。撤去10⁻⁵ M的罗格列酮后，细胞在再过48小时时完全恢复，而较低剂量则出现刺激“反弹”。吡格列酮在抑制增殖方面与罗格列酮效力相似。PPAR-γ拮抗剂并未显著逆转罗格列酮的抗增殖作用，实际上其自身就能抑制增殖。