Zörnig M, Busch G, Beneke R, Gulbins E, Lang F, Ma A, Korsmeyer S, Möröy T
Institut für Molekularbiologie und Tumorforschung, IMT, Philipps Universität Marburg, Germany.
Oncogene. 1995 Nov 16;11(10):2165-74.
Coexpression of the proto-oncogenes c-myc and bcl-2 under the control of the immunoglobulin enhancer E mu provokes the rapid development of primitive lymphoid tumors in transgenic mice. In the present study we show that the myc family members N-myc and L-myc also cooperate with bcl-2 in oncogenesis and can provoke the development of more mature pre-B, B and T cell type lymphomas. The analysis of prelymphomatous B-cells from single E mu N-myc and bcl-2-Ig transgenic animals and from young, tumor free, double transgenic E mu N-myc/bcl-2-Ig mice revealed that E mu directed expression of N-myc leads to very rapid apoptosis after explantation and culturing compared to B-cells from normal mice. As expected, B-cells from bcl-2-Ig transgenics were protected to a certain degree from apoptosis. Strikingly however, B-cells from E mu N-myc/bcl-2-Ig double transgenic animals were found to be almost completely resistant towards a number of different apoptotic stimuli. Furthermore, after treatment with H2O2, which can trigger apoptosis, B-cells from E mu N-myc animals reach levels of intracellular free Ca2+ concentrations that are comparable to B-cells from normal mice, whereas B-cells from bcl-2-Ig or E mu N-myc/bcl-2-Ig double transgenic mice show no increase in intracellular Ca2+ concentrations after stimulation with H2O2. These findings suggest that the prevention of apoptosis conferred by bcl-2 correlates with the inhibition of intracellular Ca2+ fluxes whereas induction of apoptosis mediated by N-myc requires normal Ca2+ levels. We hypothesize therefore that the regulation of intracellular Ca2+ concentrations represent one important parameter in the oncogenic cooperation between bcl-2 and N-myc.
原癌基因c-myc和bcl-2在免疫球蛋白增强子Eμ的控制下共表达，可促使转基因小鼠迅速发生原始淋巴细胞肿瘤。在本研究中，我们发现myc家族成员N-myc和L-myc在肿瘤发生过程中也与bcl-2协同作用，并可引发更成熟的前B、B和T细胞型淋巴瘤的发生。对来自单个Eμ N-myc和bcl-2-Ig转基因动物以及年轻、无肿瘤的双转基因Eμ N-myc/bcl-2-Ig小鼠的淋巴瘤前期B细胞进行分析，结果显示，与正常小鼠的B细胞相比，Eμ指导的N-myc表达在体外培养后会导致非常快速的细胞凋亡。正如预期的那样，bcl-2-Ig转基因小鼠的B细胞在一定程度上受到保护，免于凋亡。然而，令人惊讶的是，发现来自Eμ N-myc/bcl-2-Ig双转基因动物的B细胞对多种不同的凋亡刺激几乎完全具有抗性。此外，在用可触发凋亡的H2O¬2处理后，Eμ N-myc动物的B细胞内游离Ca2+浓度水平与正常小鼠的B细胞相当，而bcl-2-Ig或Eμ N-myc/bcl-2-Ig双转基因小鼠的B细胞在用H2O¬2刺激后细胞内Ca2+浓度没有增加。这些发现表明，bcl-2赋予的凋亡预防与细胞内Ca2+通量的抑制相关，而N-myc介导的凋亡诱导需要正常的Ca2+水平。因此，我们推测细胞内Ca2+浓度的调节是bcl-2和N-myc之间致癌协同作用的一个重要参数。
