Balañá M E, Labriola L, Salatino M, Movsichoff F, Peters G, Charreau E H, Elizalde P V
Instituto de Biología y Medicina Experimental (IBYME), Obligado 2490, Buenos Aires 1428, Argentina.
Oncogene. 2001 Jan 4;20(1):34-47. doi: 10.1038/sj.onc.1204050.
The present study focused on interactions between signaling pathways activated by progestins and by type I and II receptor tyrosine kinases (RTKs) in mammary tumors. An experimental model in which the synthetic progestin medroxyprogesterone acetate (MPA) induced mammary adenocarcinomas in Balb/c mice was used. MPA-stimulated proliferation, both in vivo and in vitro, of progestin-dependent tumors induced up-regulation of ErbB-2 protein levels and tyrosine phosphorylation of this receptor. Combinations of antisense oligodeoxynucleotides (ASODNs) directed to ErbB-2 mRNA with ASODNs directed to the insulin-like growth factor-I receptor (IGF-IR) were used to study the effect of the simultaneous block of these receptors on the MPA-induced proliferation of epithelial cells from the progestin-dependent C4HD line. Neither synergistic nor additive effects on the inhibition of MPA-induced proliferation of C4HD cells were observed as a result of the combination of these ASODNs. Suppression of IGF-IR expression by ASODNs resulted in complete abrogation of MPA-induced phosphorylation of ErbB-2 in C4HD cells, whereas blockage of ErbB-2 did not affect IGF-IR phosphorylation. These results show the existence of a hierarchical interaction between IGF-IR and ErbB-2, by means of which IGF-IR directs ErbB-2 phosphorylation. We demonstrated, for the first time, that this hierarchical interaction involves physical association of both receptors, resulting in the formation of a heteromeric complex. Furthermore, confocal laser microscopy experiments demonstrated that MPA was able to induce co-localization of ErbB-2 and IGF-IR. This hetero-oligomer was also found in MCF-7 human breast cancer cells in which association of IGF-IR and ErbB-2 was induced by heregulin and IGF-I. Oncogene (2001) 20, 34 - 47.
本研究聚焦于孕激素以及I型和II型受体酪氨酸激酶（RTK）激活的信号通路之间在乳腺肿瘤中的相互作用。采用了一种实验模型，即合成孕激素醋酸甲羟孕酮（MPA）可在Balb/c小鼠中诱发乳腺腺癌。MPA在体内和体外刺激孕激素依赖性肿瘤的增殖，导致ErbB-2蛋白水平上调以及该受体的酪氨酸磷酸化。将针对ErbB-2 mRNA的反义寡脱氧核苷酸（ASODN）与针对胰岛素样生长因子-I受体（IGF-IR）的ASODN联合使用，以研究同时阻断这些受体对MPA诱导的孕激素依赖性C4HD系上皮细胞增殖的影响。这些ASODN联合使用并未观察到对MPA诱导的C4HD细胞增殖抑制的协同或相加作用。ASODN抑制IGF-IR表达导致C4HD细胞中MPA诱导的ErbB-2磷酸化完全消除，而阻断ErbB-2并不影响IGF-IR磷酸化。这些结果表明IGF-IR和ErbB-2之间存在层级相互作用，通过这种相互作用IGF-IR指导ErbB-2磷酸化。我们首次证明这种层级相互作用涉及两种受体的物理缔合，导致形成异源复合物。此外，共聚焦激光显微镜实验表明MPA能够诱导ErbB-2和IGF-IR共定位。在MCF-7人乳腺癌细胞中也发现了这种异源寡聚体，其中IGF-IR和ErbB-2的缔合是由神经调节蛋白和IGF-I诱导的。《癌基因》（2001年）第20卷，第34 - 47页 。
