Landry F, Chapdelaine A, Bégin L R, Chevalier S
Department of Surgery (Urology), McGill University, Montreal, Quebec, Canada.
J Urol. 1996 Jan;155(1):386-90.
Considering the hypothesis that androgen-independent but growth factor dependent epithelial cell division may be important in the development and progression of prostate cancer and that protein tyrosine kinases and phosphotyrosine protein phosphatases are key enzymes modulating the levels of specific phosphotyrosylated proteins implicated in several growth factor regulated signal transduction pathways, our aim was to study the cellular distribution of phosphotyrosine proteins in normal and hyperplastic dog prostates as well as in those of castrated dogs supplemented with either androgens or estrogens in order to modify the relative proportion of basal versus secretory epithelial cells.
Following the determination of optimal conditions to specifically detect phosphotyrosine proteins by a rabbit polyclonal antibody directed against phosphotyrosine, immunohistochemistry was performed on prostate tissue sections from these experimental animals. In addition to morphological criteria, an antibody to high molecular weight cytokeratins and antisera against arginine esterase were used to selectively identify basal and secretory cells. Since prostatic acid phosphatase may be involved in the local regulation of phosphotyrosine proteins, its distribution was also evaluated with a human prostatic acid phosphatase antiserum.
In all prostatic tissues examined, basal epithelial cells were preferentially and specifically stained with antiphosphotyrosine. The staining intensity per basal cell was highest in the estrogen-supplemented dogs. In addition, basal cells were numerically increased and all were highly immunoreactive for high molecular weight cytokeratins. In prostates displaying a well-differentiated glandular epithelium, the number of positive basal cells and their staining intensity varied in the following order: normal < hyperplastic < androgen-supplemented dogs. At all times, the levels of phosphotyrosine proteins in prostatic acid phosphatase and arginine esterase positive cells (secretory) remained low. Fibroblasts and smooth muscle cells were unreactive to antiphosphotyrosine, even though estrogen supplementation increased the prostatic stromal volume.
The preferential localization of phosphotyrosine proteins in basal cells, their increased level per cell and the number of positive cells in the different experimental animals support the concept that basal cells represent the stem cells of the prostate. The sex steroid-mediated up-regulation of protein phosphorylation on tyrosine residues in these cells suggests that their proliferation is likely to involve growth factor regulated signal transduction pathways. In this respect, the lack of maturation of basal cells and the differentiation of secretory cells induced by androgen deprivation, combined with estrogen stimulation, favors the activation of these pathways and cell growth. On the other hand, the activation of glandular cell differentiation and the increase of stromal volume do not alter the threshold level of protein tyrosine kinase and phosphatase activities in secretory cells, fibroblasts and smooth muscle cells.
考虑到雄激素非依赖性但生长因子依赖性上皮细胞分裂可能在前列腺癌的发生和发展中起重要作用，并且蛋白质酪氨酸激酶和磷酸酪氨酸蛋白磷酸酶是调节与几种生长因子调节的信号转导途径相关的特定磷酸酪氨酸化蛋白水平的关键酶，我们的目的是研究磷酸酪氨酸蛋白在正常和增生性犬前列腺以及补充雄激素或雌激素的去势犬前列腺中的细胞分布，以改变基底上皮细胞与分泌上皮细胞的相对比例。
在用针对磷酸酪氨酸的兔多克隆抗体确定特异性检测磷酸酪氨酸蛋白的最佳条件后，对这些实验动物的前列腺组织切片进行免疫组织化学检测。除形态学标准外，还使用高分子量细胞角蛋白抗体和抗精氨酸酯酶抗血清来选择性识别基底细胞和分泌细胞。由于前列腺酸性磷酸酶可能参与磷酸酪氨酸蛋白的局部调节，因此也用人前列腺酸性磷酸酶抗血清评估其分布。
在所有检查的前列腺组织中，基底上皮细胞优先且特异性地被抗磷酸酪氨酸抗体染色。在补充雌激素的犬中，每个基底细胞的染色强度最高。此外，基底细胞数量增加，并且所有细胞对高分子量细胞角蛋白均具有高免疫反应性。在显示出良好分化的腺上皮的前列腺中，阳性基底细胞的数量及其染色强度按以下顺序变化：正常＜增生＜补充雄激素的犬。在所有时间，前列腺酸性磷酸酶和精氨酸酯酶阳性细胞（分泌细胞）中的磷酸酪氨酸蛋白水平均保持较低。成纤维细胞和平滑肌细胞对抗磷酸酪氨酸无反应，尽管补充雌激素会增加前列腺基质体积。
磷酸酪氨酸蛋白在基底细胞中的优先定位、每个细胞中其水平的增加以及不同实验动物中阳性细胞的数量支持了基底细胞代表前列腺干细胞的概念。这些细胞中酪氨酸残基上蛋白质磷酸化的性类固醇介导表明其增殖可能涉及生长因子调节的信号转导途径。在这方面，雄激素剥夺诱导的基底细胞缺乏成熟和分泌细胞分化，再加上雌激素刺激，有利于这些途径的激活和细胞生长。另一方面，腺细胞分化的激活和基质体积的增加不会改变分泌细胞、成纤维细胞和平滑肌细胞中蛋白质酪氨酸激酶和磷酸酶活性的阈值水平。
