Kahan C, Julius D, Pouysségur J, Seuwen K
Centre de Biochimie-CNRS, Université de Nice-Sophia Antipolis, France.
Exp Cell Res. 1992 Jun;200(2):523-7. doi: 10.1016/0014-4827(92)90204-l.
5-HT1c receptors have been shown to act as protooncogenes in NIH 3T3 cells, inducing ligand-dependent focus formation. In order to assess their mitogenic and oncogenic potential in a different cell system, we transfected these receptors into CCL39 hamster fibroblasts, a well-characterized growth factor-dependent cell line. Cell clones expressing functional receptors were isolated and tested for (a) growth factor dependence of proliferation measuring thymidine incorporation in response to varying doses of serum, (b) the response to serotonin alone or in combination with other growth factors, and (c) the capacity for anchorage-independent proliferation. In the absence or presence of serotonin, the large majority of the clones isolated showed normal morphology and normal growth factor dependence and was unable to grow in soft agar. None of the clones showed a significant response to serotonin alone in DNA synthesis reinitiation experiments, but synergy was observed between serotonin and the tyrosine kinase activating growth factors EGF and FGF. However, the major part of this effect could be abolished by an antagonist of 5-HT1b receptors, which are endogenous in CCL39 cells. The same receptor was found to mediate a significant mitogenic response to the neurotransmitter in Ha-ras-transfected cells. The fact that 5-HT1c receptors do not readily induce a transformed phenotype in CCL39 cells clearly distinguishes them from strong dominantly acting oncogene products like RAS, SRC, or FMS.
5-HT1c受体已被证明在NIH 3T3细胞中作为原癌基因发挥作用，诱导配体依赖性灶形成。为了评估它们在不同细胞系统中的促有丝分裂和致癌潜力，我们将这些受体转染到CCL39仓鼠成纤维细胞中，这是一种特征明确的生长因子依赖性细胞系。分离出表达功能性受体的细胞克隆，并对其进行以下测试：(a) 通过测量不同剂量血清刺激下的胸腺嘧啶掺入来检测增殖对生长因子的依赖性；(b) 单独或与其他生长因子联合使用时对血清素的反应；(c) 非锚定依赖性增殖能力。在血清素存在或不存在的情况下，分离出的绝大多数克隆表现出正常的形态和正常的生长因子依赖性，并且无法在软琼脂中生长。在DNA合成重新启动实验中，没有一个克隆对单独的血清素表现出显著反应，但在血清素与酪氨酸激酶激活生长因子EGF和FGF之间观察到协同作用。然而，这种效应的主要部分可以被5-HT1b受体拮抗剂消除，5-HT1b受体是CCL39细胞内源性的。在Ha-ras转染细胞中，发现相同的受体介导对神经递质的显著促有丝分裂反应。5-HT1c受体在CCL39细胞中不容易诱导转化表型这一事实清楚地将它们与RAS、SRC或FMS等强大的显性作用癌基因产物区分开来。
