生长激素细胞瘤，但不是无功能垂体腺瘤，维持着一种功能性凋亡 RET/Pit1/ARF/p53 途径，该途径可被过量 GDNF 阻断。
Somatotropinomas, but not nonfunctioning pituitary adenomas, maintain a functional apoptotic RET/Pit1/ARF/p53 pathway that is blocked by excess GDNF.
机构信息
Centre for Investigations in Medicine of the USC (E.D.-R., A.R.G.-G., M.G.-L., C.D., C.V.A.), University of Santiago de Compostela, Santiago de Compostela, Spain 15782; Department of Endocrinology (I.B.), University Hospital (University Hospital of Santiago de Compostela), Instituto de Investigación Sanitaria, Santiago de Compostela, Spain 15706; Departments of Cell Biology, Physiology, and Immunology (A.I.-C., E.G.-P., R.M.L., J.P.C.), and Morphological Sciences (L.J.-R.), University of Cordoba, and Reina Sofia University Hospital (P.B., M.A.G.), Maimonides Institute for Research in Biomedicine of Cordoba, Córdoba, Spain 14014; Departments of Endocrinology and Pathology (A.L., M.A.J., A.S., E.V.), Hospital Universitario Virgen del Rocío, Instituto de Biomedicina de Sevilla, University of Sevilla, Sevilla, Spain 41013; Department of Endocrinology (F.J.T.), Hospital Virgen de la Victoria, and Department of Endocrinology (J.A.G.-A.), Hospital Carlos Haya, Malaga, Spain 29010; and CIBER Fisiopatología de la Obesidad y Nutrición (CIBERobn) 15706, spain (A.I.-C., F.J.T., P.B., I.B., C.D., R.M.L., J.P.C., C.V.A.), Spain 15706.
出版信息
Endocrinology. 2014 Nov;155(11):4329-40. doi: 10.1210/en.2014-1034. Epub 2014 Aug 19.
Acromegaly is caused by somatotroph cell adenomas (somatotropinomas [ACROs]), which secrete GH. Human and rodent somatotroph cells express the RET receptor. In rodents, when normal somatotrophs are deprived of the RET ligand, GDNF (Glial Cell Derived Neurotrophic Factor), RET is processed intracellularly to induce overexpression of Pit1 [Transcription factor (gene : POUF1) essential for transcription of Pituitary hormones GH, PRL and TSHb], which in turn leads to p19Arf/p53-dependent apoptosis. Our purpose was to ascertain whether human ACROs maintain the RET/Pit1/p14ARF/p53/apoptosis pathway, relative to nonfunctioning pituitary adenomas (NFPAs). Apoptosis in the absence and presence of GDNF was studied in primary cultures of 8 ACROs and 3 NFPAs. Parallel protein extracts were analyzed for expression of RET, Pit1, p19Arf, p53, and phospho-Akt. When GDNF deprived, ACRO cells, but not NFPAs, presented marked level of apoptosis that was prevented in the presence of GDNF. Apoptosis was accompanied by RET processing, Pit1 accumulation, and p14ARF and p53 induction. GDNF prevented all these effects via activation of phospho-AKT. Overexpression of human Pit1 (hPit1) directly induced p19Arf/p53 and apoptosis in a pituitary cell line. Using in silico studies, 2 CCAAT/enhancer binding protein alpha (cEBPα) consensus-binding sites were found to be 100% conserved in mouse, rat, and hPit1 promoters. Deletion of 1 cEBPα site prevented the RET-induced increase in hPit1 promoter expression. TaqMan qRT-PCR (real time RT-PCR) for RET, Pit1, Arf, TP53, GDNF, steroidogenic factor 1, and GH was performed in RNA from whole ACRO and NFPA tumors. ACRO but not NFPA adenomas express RET and Pit1. GDNF expression in the tumors was positively correlated with RET and negatively correlated with p53. In conclusion, ACROs maintain an active RET/Pit1/p14Arf/p53/apoptosis pathway that is inhibited by GDNF. Disruption of GDNF's survival function might constitute a new therapeutic route in acromegaly.
肢端肥大症是由生长激素细胞腺瘤（生长激素细胞瘤 [ACROs]）引起的，这些腺瘤会分泌生长激素。人和啮齿动物的生长激素细胞表达 RET 受体。在啮齿动物中，当正常的生长激素细胞被剥夺 RET 配体 GDNF（胶质细胞衍生的神经营养因子）时，RET 在细胞内被加工，诱导 Pit1 的过度表达[对垂体激素 GH、PRL 和 TSHb 的转录至关重要的转录因子（基因：POUF1）]，这反过来又导致 p19Arf/p53 依赖性细胞凋亡。我们的目的是确定相对于无功能垂体腺瘤（NFPAs），人 ACROs 是否保持 RET/Pit1/p14ARF/p53/凋亡途径。在 8 个人类 ACRO 和 3 个 NFPAs 的原代培养中研究了无 GDNF 和有 GDNF 存在时的细胞凋亡。平行的蛋白提取物用于分析 RET、Pit1、p19Arf、p53 和磷酸化 Akt 的表达。当 GDNF 剥夺时，ACRO 细胞而非 NFPAs 呈现出明显的凋亡水平，而 GDNF 的存在则阻止了凋亡。凋亡伴随着 RET 加工、Pit1 积累和 p14ARF 和 p53 的诱导。GDNF 通过激活磷酸化 Akt 来防止所有这些作用。人 Pit1（hPit1）的过表达直接诱导了垂体细胞系中的 p19Arf/p53 和凋亡。通过计算机研究，在鼠、大鼠和 hPit1 启动子中发现了 2 个 CCAAT/增强子结合蛋白 alpha（cEBPα）的共有结合位点，它们的保守性为 100%。删除 1 个 cEBPα 位点可防止 RET 诱导的 hPit1 启动子表达增加。使用 TaqMan qRT-PCR（实时 RT-PCR）对 RET、Pit1、Arf、TP53、GDNF、类固醇生成因子 1 和 GH 在整个 ACRO 和 NFPA 肿瘤的 RNA 中进行了检测。ACRO 腺瘤而非 NFPA 腺瘤表达 RET 和 Pit1。肿瘤中 GDNF 的表达与 RET 呈正相关，与 p53 呈负相关。总之，ACRO 保持着活跃的 RET/Pit1/p14Arf/p53/凋亡途径，该途径被 GDNF 抑制。破坏 GDNF 的生存功能可能成为肢端肥大症的新治疗途径。
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