表皮生长因子受体蛋白乙酰化信号通路在癌症发生过程中的作用及在靶向抗癌治疗中的应用

Epidermal growth factor receptor (EGFR) is a cell membrane tyrosine kinase receptor and plays a pivotal role in regulating cell growth, differentiation, cell cycle, and tumorigenesis. Deregulation of EGFR could cause many diseases including cancers. Intensive investigation of EGFR alteration in human cancers has led to profound progress in developing drugs to target EGFR-mediated cancers. While exploring possible synergistic enhancement of therapeutic efficacy by combining EGFR tyrosine kinase inhibitors (TKI) with other anti-cancer agents, we observed that suberoylanilide hydroxamic acid (SAHA, a deacetylase inhibitor) sensitized TKI-induced cancer cell death, which further led us to question whether SAHA-mediated sensitization to TKI was associated with EGFR acetylation. Interestingly, it has been reported that an HDAC inhibitor (HDACi), TSA, enhanced EGFR phosphorylation in ovarian cancer cells. EGFR acetylation has also been reported recently. These observations indicate that there might be an intrinsic correlation between acetylation and phosphorylation of EGFR. In other words, the interplay between EGFR acetylation and phosphorylation maybe contribute to HDACi-augmented EGFR phosphorylation. .In this proposal, we showed that CBP acetyltransferase acetylated EGFR. We also demonstrated the protein-protein interaction between CBP and EGFR as well as the enhancement of EGFR acetylation by CBP. Moreover, EGFR acetylation enhanced EGFR tyrosine phosphorylation and augmented its association with Src kinase. Acetylation-deficient EGFR mutant (EGFR-K3R) significantly reduced the function and activity of EGFR. Furthermore, ectopic expression of EGFR-K3R mutant abrogated its ability to respond to EGF-induced cell proliferation, DNA synthesis, and anchorage-independent growth using cell-based assays. In addition, we demonstrated that EGFR expression was associated with SAHA resistance in the treatment of cancer cells that were overexpressing EGFR. All these data support that EGFR plays an important role in SAHA resistance in breast carcinoma cells that we tested. .The combination therapy of HDACi with TKI has been proposed for treating cancers with aberrant expression of EGFR. The evidence from pre-clinical or clinical trials demonstrated significant enhancement of therapeutic efficacy by using such a combination therapy. Here we propose to test the hypothesis that EGFR acetylation determines initiation of EGFR phosphorylation and could sensitize EGFR-expressing cancer cells to respond to TKI. Significance of our study will elucidate another possible underlying molecular mechanism by which HDACis mediate sensitization to TKI. The further results will unveil a critical role of EGFR acetylation that regulates EGFR tyrosine phosphorylation and may provide an experiment-based rationale for combinatorial targeted therapy.

表皮生长因子受体（EGFR）信号通路在许多癌症的发生和恶化中起了关键作用。异常的EGFR表达和脑胶质细胞瘤，肺癌和乳腺癌密切相关。在深入研究EGFR蛋白质转录后修饰的过程中，我们发现EGFR乙酰化在EGFR信号通路的激活和调控中起了关键性的启动作用。EGFR乙酰化可能与肺癌和乳腺癌发生，恶变和转移密切相关。在治疗EGFR过度表达的肺癌和乳腺癌的过程中，如果单独使用去乙酰化酶抑制剂来治疗有诱导癌症恶化的趋势。初步观察表明：其原因可能是由于去乙酰化酶抑制剂增加了EGFR乙酰化，由此增强了EGFR信号通路的激活，进而加剧了癌症的恶变。在此我们提出计划根据以前的研究为基础，进一步深入剖析EGFR乙酰化的分子机理，并以此为基础来探索更有效的靶向抗癌治疗方案和措施。为有效的治疗EGFR异常表达的癌症提供实验和临床治疗的依据。

表皮生长因子受体（EGFR）的异常表达和功能失调在多种恶性肿瘤中起了关键性的调控作用。特别是表皮生长因子受体转录后的修饰对其在信号传导和其它的生物功能的影响尤其重要。 其中表皮生长因子受体的酪氨酸磷酸化被公认为是至为关键的环节。上述的生物现象在癌症的多个环节中均有表现。如癌症的初始化和癌细胞形成，诱导癌细胞恶化和转移和对抗癌治疗的耐受等。临床上常见的恶性程度高和死亡率高的癌症如脑胶质细胞瘤，肺癌和乳腺癌都被证实与其异常的表达和酪氨酸磷酸化密切相关。.. 不仅仅表皮生长因子受体的酪氨酸磷酸化，我们在以往对表皮生长因子受体的深入研究中还进一步发现表皮生长因子受体乙酰化在表皮生长因子受体信号通路的激活和调控中起了关键性的启动作用。也就是说表皮生长因子受体的乙酰化对表皮生长因子受体的磷酸化具有调控作用。本研究项目的主要目标就是进一步深入揭示表皮生长因子受体的乙酰化是如何调控表皮生长因子受体的磷酸化，以及这一全新调控通路是如何在诱导癌症恶化，加速癌症的进程和对抗抗癌症治疗中发挥其关键性的作用。..我们目前的研究结果揭示：1. EGFR在多种癌症中均有不同程度的乙酰化。如乳腺癌和肺癌。2. EGFR乙酰化不仅仅在癌细胞的表面，而且在线粒体中也有表现。EGFR乙酰化与EGFR的酪氨酸磷酸化呈紧密的正相关联系。3. EGFR乙酰化是其酪氨酸磷酸化的关键环节，是诱导其过度的酪氨酸磷酸化的主要诱因。 与此同时,异常高水平的EGFR的乙酰化和酪氨酸磷酸化又和癌细胞转移相关联。4. EGFR的乙酰化是造成癌症耐受和对抗各种针对EGFR药物的抗癌治疗的主要因素之一。5. 同时抑制EGFR的乙酰化和酪氨酸磷酸化能更有效地抑制癌细胞的恶性生长和转移。 . . 这些结果证明同时抑制EGFR的乙酰化和酪氨酸磷酸化在临床治疗方面能够更加有效地治疗与此相关的癌症,防止癌细胞转移和提高癌症治疗的预后。