Shah G V, Rayford W, Noble M J, Austenfeld M, Weigel J, Vamos S, Mebust W K
Department of Urologic Surgery, University of Kansas Medical Center, Kansas City 66103.
Endocrinology. 1994 Feb;134(2):596-602. doi: 10.1210/endo.134.2.8299557.
Our recent study has shown that a calcitonin (CT)-like immunoreactive substance(s) is secreted by cultured prostate cells, and secretion of this material is significantly higher in malignant than in benign prostate cells. To test the hypothesis that prostatic CT may serve as a paracrine/neuroendocrine factor, the present study investigated for the presence of CT receptors in the prostate gland. Signal transduction mechanisms activated by CT were examined, and the study also tested its effects on prostate cell proliferation, as assessed by [3H]thymidine incorporation. The results show that high affinity binding sites for [125I]salmon CT were present in plasma membrane fractions of human prostate tissue specimens and the prostate cancer LnCaP cell line. The maximal binding for CT receptors was 564 +/- 163 fmol/mg protein, and the apparent dissociation constant (Kd) was 2.89 +/- 0.58 nM. CT induced a dose-dependent increase in cAMP generation in LnCaP cells. The effect of CT on cytoplasmic Ca2+ transients of LnCaP cells was examined by videofluoromicroscopy. CT (100 nM) induced a rapid and sharp increase in cytoplasmic Ca2+ concentrations in LnCaP cells. The CT-induced increase in cytoplasmic Ca2+ transients appeared to be biphasic (spike and plateau), and this increase was 4- to 10-fold during the initial phase. The profile of this response is characteristic of the activated Ca2+/phospholipid second messenger system. CT also caused a dose-dependent increase in [3H]thymidine incorporation by LnCaP cells. These results suggest that a locally secreted CT-like peptide(s) induces mitogenic responses in prostate cancer cells. This action seems to be mediated through activation of signaling mechanisms, leading to the accumulation of two different second messengers, cAMP and calcium. Activation of dual second messenger systems by CT receptors suggests that the peptide hormone may play an important role in rapidly growing cell populations during the process of tumor formation.
我们最近的研究表明，培养的前列腺细胞可分泌一种降钙素（CT）样免疫反应物质，且该物质在恶性前列腺细胞中的分泌量显著高于良性前列腺细胞。为验证前列腺CT可能作为旁分泌/神经内分泌因子这一假说，本研究调查了前列腺中CT受体的存在情况。检测了CT激活的信号转导机制，该研究还通过[3H]胸腺嘧啶核苷掺入法评估了其对前列腺细胞增殖的影响。结果显示，人前列腺组织标本和前列腺癌LnCaP细胞系的质膜组分中存在[125I]鲑鱼CT的高亲和力结合位点。CT受体的最大结合量为564±163 fmol/mg蛋白，表观解离常数（Kd）为2.89±0.58 nM。CT诱导LnCaP细胞中cAMP生成呈剂量依赖性增加。通过视频荧光显微镜检查了CT对LnCaP细胞胞质Ca2+瞬变的影响。CT（100 nM）诱导LnCaP细胞胞质Ca2+浓度迅速急剧增加。CT诱导的胞质Ca2+瞬变增加似乎呈双相性（峰值和平台期），在初始阶段这种增加为4至10倍。这种反应特征是活化的Ca2+/磷脂第二信使系统所具有的。CT还使LnCaP细胞的[3H]胸腺嘧啶核苷掺入呈剂量依赖性增加。这些结果表明，局部分泌的CT样肽可诱导前列腺癌细胞的促有丝分裂反应。这种作用似乎是通过信号转导机制的激活介导的，导致两种不同的第二信使cAMP和钙的积累。CT受体对双第二信使系统的激活表明，该肽激素可能在肿瘤形成过程中快速生长的细胞群体中发挥重要作用。
