Limonta P, Moretti R M, Dondi D, Marelli M M, Motta M
Department of Endocrinology, University of Milano, Italy.
J Steroid Biochem Mol Biol. 1994 Jun;49(4-6):347-50. doi: 10.1016/0960-0760(94)90278-x.
Testosterone (T) is the major exogenous stimulus for the growth of prostatic carcinoma. It is believed that the proliferative action of T may be mediated by locally expressed growth modulatory factors. Recent evidence from our laboratory suggests that a LHRH (or a LHRH-like) loop might be expressed in human prostatic tumor cells. To verify this hypothesis, we have studied whether a mRNA for LHRH is expressed in the human androgen-responsive prostatic cancer cell line LNCaP, using the reverse transcription-polymerase chain reaction technique in the presence of a pair of specific oligonucleotide primers. A cDNA band of the expected size was obtained from LNCaP cells; this band hybridized with a 32P-labeled LHRH oligonucleotide probe and its sequence showed a complete match with the reported sequence of the human placental LHRH cDNA. These observations indicate that the mRNA coding for LHRH is expressed in LNCaP cells and suggest that a LHRH (or a LHRH-like) peptide might be produced by these cells. To clarify the possible action of this peptide, LNCaP cells were grown in a steroid-free medium and treated with a LHRH antagonist. The treatment resulted in a significant increase of tumor cell growth. These data clearly indicate that the LHRH system expressed in LNCaP cells plays an inhibitory role on cell proliferation, and that this system seems to be regulated in a negative way by steroids. An EGF/TGF alpha autocrine stimulatory loop (peptides, receptors, intracellular signals) is also functional in these cells. Treatment of LNCaP cells grown in serum-free conditions (i.e. in the absence of exogenous growth factors) with a monoclonal antibody against the EGF receptor, or with immunoneutralizing antibodies against EGF or TGF alpha, resulted in a significant decrease of cell proliferation. T positively regulates this EGF/TGF alpha system by increasing the concentration of EGF binding sites. The present data indicate that an inhibitory LHRH (or LHRH-like) system is expressed in LNCaP cells and participates in the local mechanisms regulating tumor cell proliferation together with an EGF/TGF alpha stimulatory loop. Both systems appear to be modulated by T.
睾酮（T）是前列腺癌生长的主要外源性刺激因素。据信，T的增殖作用可能由局部表达的生长调节因子介导。我们实验室最近的证据表明，人前列腺肿瘤细胞中可能表达了促性腺激素释放激素（LHRH）（或LHRH样）环路。为了验证这一假设，我们使用逆转录-聚合酶链反应技术，在一对特异性寡核苷酸引物存在的情况下，研究了人雄激素反应性前列腺癌细胞系LNCaP中是否表达LHRH的信使核糖核酸（mRNA）。从LNCaP细胞中获得了预期大小的互补脱氧核糖核酸（cDNA）条带；该条带与32P标记的LHRH寡核苷酸探针杂交，其序列与报道的人胎盘LHRH cDNA序列完全匹配。这些观察结果表明，编码LHRH的mRNA在LNCaP细胞中表达，提示这些细胞可能产生LHRH（或LHRH样）肽。为了阐明该肽的可能作用，将LNCaP细胞在无类固醇培养基中培养，并用LHRH拮抗剂处理。该处理导致肿瘤细胞生长显著增加。这些数据清楚地表明，LNCaP细胞中表达的LHRH系统对细胞增殖起抑制作用，并且该系统似乎受到类固醇的负调控。表皮生长因子（EGF）/转化生长因子α（TGFα）自分泌刺激环路（肽、受体、细胞内信号）在这些细胞中也有功能。用抗EGF受体单克隆抗体或抗EGF或TGFα免疫中和抗体处理在无血清条件下（即不存在外源性生长因子）培养的LNCaP细胞，导致细胞增殖显著减少。T通过增加EGF结合位点的浓度对该EGF/TGFα系统起正向调节作用。目前的数据表明，抑制性LHRH（或LHRH样）系统在LNCaP细胞中表达，并与EGF/TGFα刺激环路一起参与调节肿瘤细胞增殖的局部机制。这两个系统似乎都受T的调节。
