Tumor Progression of Nuclear EGFR in Breast Cancer

描述（由申请人提供）：在上一个资助期内，我们成功地完成了所有三个拟议目标。以细胞核HER 2（ErbB 2）为模型，我们将研究扩展到细胞核EGFR，并取得了很大进展。目前的竞争性更新建议是进一步研究细胞核EGFR的新功能和EGFR从细胞表面运输到细胞核的分子机制。我们以前报道，EGFR复合物识别并结合到细胞周期蛋白D1转录的AT丰富序列（ATRS）。后来，我们证明了EGFR与细胞核中的STAT 3相互作用，EGFR/STAT 3复合物识别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有助于肿瘤的进展，这增加了细胞核EGFR可能参与肿瘤进展的可能性。为了支持这一点，我们和其他人已经表明，核EGFR与乳腺癌，卵巢癌，食管癌和口腔癌的临床预后不良相关。我们发现，核EGFR与PCNA，一个众所周知的核特异性抗原和磷酸化的染色质结合的PCNA在Tyr-211残基导致稳定的活性PCNA和刺激DNA复制。此外，我们确定了几个有趣的蛋白质与EGFR相互作用的细胞核，包括RHA和SWI/SNF复合物。RHA是识别与ATRS序列相同的DNA序列的DNA结合蛋白，并且可能是核EGFR的DNA结合伴侣的潜在候选者，其不具有DNA结合结构域。SWI/SNF是参与染色质重塑的蛋白质复合物。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，即内吞作用和核孔复合物（NPC）参与EGFR和HER 2从细胞表面的核转位，我们有初步结果表明，逆行转运机制参与细胞表面EGFR到细胞核的运输。因此，我们假设，核EGFR有助于肿瘤的进展，通过转录上调肿瘤促进基因和相互作用的关键蛋白质复合物参与染色质重塑。该计划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。提出了三个具体目的：具体目的1：核EGFR的转录调控和肿瘤进展;具体目的2：乳腺肿瘤发展中的核EGFR和染色质重塑复合物SWI/SNF;具体目的3：EGFR从细胞表面运输到细胞核的分子机制。由于EGFR长期以来被认为是细胞表面受体，其核功能几十年来一直被忽视。随着越来越多的证据表明，受体酪氨酸激酶在细胞核和逐步发现其核功能和预后价值的核EGFR在多种人类癌症，目前的建议是一个及时的项目，解决了关键的，但“几乎被忽视”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.