Bonaccorsi Lorella, Nosi Daniele, Quercioli Franco, Formigli Lucia, Zecchi Sandra, Maggi Mario, Forti Gianni, Baldi Elisabetta
Department of Clinical Physiopathology, Andrology Unit, Viale Pieraccini 6, I-50139 Florence, Italy.
Steroids. 2008 Oct;73(9-10):1030-7. doi: 10.1016/j.steroids.2008.01.028. Epub 2008 Feb 15.
Androgens and the androgen receptor (AR) are involved both in early tumorigenesis of prostate cancer (PCa) and in androgen-refractory disease. The role of AR signalling has also been highlighted by the fusion gene TMPRSS2:ERG recently identified in the majority of PCa. Several data indicate that re-expression of AR in PCa cell lines confers a less aggressive phenotype. We observed that re-expression of AR in the AR-negative cells PC3 decreases anchorage-independent growth and Matrigel invasiveness of PC3-AR cells where plasma membrane interaction between AR and EGFR led to an interference with downstream signalling and internalization of activated EGFR. Our data evidenced a shift of EGFR internalization pathway from the clathrin-coated pit one mediating signalling and recycling of EGFR to the lipid raft-mediated one mainly involved in lysosomal degradation of EGFR. These effects involved an altered recruitment to EGFR of the adaptor proteins Grb2 and c-Cbl followed by a reduced ubiquitination of EGFR. Our preliminary results suggest that in PC3-AR cells a pool of classical AR is located within cholesterol-rich membrane microdomains (namely as lipid rafts) and a population of EGFR is within cholesterol-rich membrane microdomains too. However, AR and EGFR membrane interaction that is increased by rapid androgen signalling is not within cholesterol-rich membrane microdomains. Our data enlighten that the crosstalk between genotropic and non-genotropic AR signalling interferes with signalling of EGFR in response to ligand leading to a lower invasive phenotype of AR-positive PCa cells.
雄激素和雄激素受体(AR)既参与前列腺癌(PCa)的早期肿瘤发生,也参与雄激素难治性疾病。最近在大多数PCa中发现的融合基因TMPRSS2:ERG也突出了AR信号传导的作用。多项数据表明,PCa细胞系中AR的重新表达赋予了较低侵袭性的表型。我们观察到,在AR阴性细胞PC3中重新表达AR会降低PC3-AR细胞的非锚定依赖性生长和基质胶侵袭性,其中AR与表皮生长因子受体(EGFR)之间的质膜相互作用导致对下游信号传导的干扰以及活化EGFR的内化。我们的数据证明,EGFR内化途径从介导EGFR信号传导和再循环的网格蛋白包被小窝途径转变为主要参与EGFR溶酶体降解的脂筏介导途径。这些效应涉及衔接蛋白Grb2和c-Cbl向EGFR募集的改变,随后是EGFR泛素化减少。我们的初步结果表明,在PC3-AR细胞中,一部分经典AR位于富含胆固醇的膜微区(即脂筏)内,并且一部分EGFR也位于富含胆固醇的膜微区内。然而,快速雄激素信号传导增强的AR与EGFR膜相互作用并不在富含胆固醇的膜微区内。我们的数据表明,基因性和非基因性AR信号传导之间的相互作用干扰了EGFR对配体的信号传导,导致AR阳性PCa细胞的侵袭性表型降低。