Tumor Progression of Nuclear EGFR in Breast Cancer

简介(申请人提供)：在上一个资助期内，我们已成功完成所有三个建议目标。以核HER2(ErbB2)为模型，我们将研究扩展到核EGFR，并取得了很大的进展。目前的竞争性更新建议是进一步研究核EGFR的新功能和EGFR从细胞表面向细胞核转运的分子机制。我们以前报道过，EGFR复合体识别并结合到细胞周期蛋白D1转录的AT富含序列(ATR)。后来，我们证明了EGFR与STAT3在细胞核内相互作用，EGFR/STAT3复合体识别iNOS启动子的ATRs和STAT结合序列，并共同调节iNOS基因的转录。细胞周期蛋白D1和诱导型一氧化氮合酶都参与了肿瘤的进展，增加了核内EGFR参与肿瘤进展的可能性。为了支持这一点，我们和其他人已经证明，在乳腺癌、卵巢癌、食道癌和口腔癌中，核EGFR与不良的临床结果相关。我们发现，核内的EGFR与已知的核特异性抗原--增殖细胞核抗原相互作用，并使染色质结合的增殖细胞核抗原在Tyr-211残基上磷酸化，从而稳定活性的增殖细胞核抗原并刺激DNA复制。此外，我们在细胞核中发现了几个有趣的与EGFR相互作用的蛋白质，包括RHA和SWI/SNF复合体。RHA是一种DNA结合蛋白，可以识别与ATRS序列相同的DNA序列，并可能成为核EGFR的DNA结合伙伴，因为核EGFR没有DNA结合域。SWI/SNF是一种参与染色质重塑的蛋白质复合体。这些新发现的EGFR相互作用蛋白已被证明在肿瘤进展中发挥作用。最后，扩展我们的观察，即胞吞作用和核孔复合体(NPC)参与了EGFR和HER2的核转移，我们有初步的结果表明，细胞表面的EGFR向核的转移涉及一种逆行转移机制。因此，我们假设，核EGFR通过转录上调促肿瘤基因，并与参与染色质重塑的关键蛋白质复合体相互作用，促进肿瘤进展。这项建议的长期目标是了解核EGFR的新功能及其在肿瘤进展中的作用。提出了三个特异靶点：特异靶1：核EGFR的转录调控与肿瘤进展；特异靶2：核EGFR和染色质重塑复合体SWI/SNF在乳腺肿瘤发生发展中的作用；特异靶3：EGFR从细胞表面向细胞核转运的分子机制。由于EGFR长期以来被认为是一种细胞表面受体，其核功能几十年来一直被忽视。随着越来越多的证据表明核内存在受体酪氨酸激酶，并逐渐发现它们的核功能和核EGFR在多种人类癌症中的预后价值，目前的提议代表着一个及时的项目，它解决了关键但几乎被忽视的问题。 公共卫生相关性：这项建议的长期目标是了解核EGFR的新功能及其在肿瘤进展中的作用。随着越来越多的证据表明核内存在受体酪氨酸激酶，并逐渐发现它们的核功能，包括核内EGFR在多种人类癌症中的预后价值，目前的提议代表着一个及时的项目，它解决了关键但几乎被遗忘的问题。

DESCRIPTION (provided by applicant): In the last funding period, we have successfully completed all three proposed aims. Using nuclear HER2 (ErbB2) as a model, we extended our investigation to nuclear EGFR and much progress has been made. The current competitive renewal proposal is to further investigate the novel functions of nuclear EGFR and molecular mechanism of EGFR trafficking from the cell surface to the nucleus. We previously reported that the EGFR complex recognizes and binds to an AT-rich sequence (ATRS) of cyclin D1 transcription. Later, we demonstrated that EGFR interacts with STAT3 in the nucleus and the EGFR/STAT3 complex recognizes the ATRS and STAT binding sequence of the iNOS promoter and co-regulates the transcription of the iNOS gene. Both cyclin D1 and iNOS contribute to tumor progression raising the possibility that nuclear EGFR may be involved in tumor progression. In support of this, we and others have shown that nuclear EGFR correlates with poor clinical outcomes in breast, ovarian, esophagus, and oral cancers. We showed that nuclear EGFR interacts with PCNA, a well-known nucleus-specific antigen and phosphorylates the chromatin-bound PCNA at Tyr-211 residue resulting in stabilization of active PCNA and stimulation of DNA replication. In addition, we identified several interesting proteins interacting with EGFR in the nucleus including RHA and the SWI/SNF complex. RHA is a DNA-binding protein that recognizes the DNA sequence identical to the ATRS sequence and may be a potential candidate to be a DNA-binding partner of nuclear EGFR, which does not have a DNA-binding domain. SWI/SNF is a protein complex involved in chromatin remodeling. These newly identified EGFR interacting proteins have been shown to play a role in tumor progression. Finally, extending our observation that endocytosis and the nuclear pore complex (NPC) are involved in the nuclear translocation from cell surface for both EGFR and HER2 we have preliminary results to suggest that a retrograde transport mechanism is involved in the trafficking of cell surface EGFR to the nucleus. Thus, we hypothesize that nuclear EGFR contributes to tumor progression through transcriptional upregulation of tumor promoting genes and interacting with critical protein complexes involved in chromatin remodeling. The long-term goal of this proposal is to understand the novel functions of nuclear EGFR and their roles in the tumor progression. Three specific Aims are proposed: Specific Aim 1: Transcriptional regulation and tumor progression of nuclear EGFR; Specific Aim 2: Nuclear EGFR and chromatin remodeling complex SWI/SNF in breast tumor development; Specific Aim 3: Molecular mechanism of EGFR trafficking from cell surface to nucleus. As EGFR has long been considered a cell surface receptor, its nuclear functions have been overlooked for decades. With increasing evidence of receptor tyrosine kinases in the nucleus and gradual discovery of their nuclear functions and prognostic value of nuclear EGFR in multiple human cancers, the current proposal represents a timely project that addresses the critical but "almost neglected" issues. PUBLIC HEALTH RELEVANCE: The long-term goal of this proposal is to understand the novel functions of nuclear EGFR and their roles in the tumor progression. With increasing evidence of receptor tyrosine kinases in the nucleus and gradual discovery of their nuclear functions including prognostic value of nuclear EGFR in multiple human cancers, the current proposal represents a timely project that addresses the critical but "almost forgotten" issues.