Targeting EGFR and c Src Synergy In Breast Cancer

成功治疗晚期乳腺癌的困难在很大程度上导致今年估计有41 200人死于乳腺癌。即使是最近的治疗进展也只能将晚期乳腺癌患者的平均生存期从20个月提高到25个月。因此，需要通过识别新的靶点来开发新的治疗方法来改善这些患者的寿命。此前，两种酪氨酸激酶EGFR和c-Src分别在24%和70%的乳腺癌细胞系和肿瘤中过表达，并与晚期疾病相关（3,6,18,21）。虽然单独来看，EGFR和c-Src都没有直接促进肿瘤发生的发展，但当这些分子共同过表达时，它们表现出惊人的生物协同作用（15）。具体来说，这种共过表达导致裸鼠的肿瘤发生，并与小鼠成纤维细胞模型中EGFR上酪氨酸845和1101的新磷酸化相关（5,15）。本研究旨在通过(1)在乳腺癌转基因小鼠模型中测试EGFR和c-Src的生物学协同作用，(2)确定c-Src在EGFR上的结合位点，(3)分析pY845和c-Src结合位点的互补肽对egf诱导的DNA合成、转化和肿瘤发生的影响，来验证共同过表达的EGFR和c-Src之间的协同作用是乳腺癌肿瘤发生的一个重要步骤。将MMTV-EGFR转基因小鼠与MMTV-c-Src转基因小鼠杂交，并评价其肿瘤形成情况，建立乳腺癌转基因小鼠模型。EGFR的缺失和点突变体将用于识别c-Src在EGFR上的结合位点。将pY845或EGFR上c-Src结合位点对应的肽注入到移植到裸鼠身上的肿瘤中，研究这些肽抑制肿瘤发生的能力。

The difficulty in successfully treating advanced stage breast cancer contributes greatly to the 41,200 estimated deaths due to breast cancer this year. Even recent advances in therapies only improve the average survival of patients with advanced breast cancer from 20 months to 25 months. Therefore, the development of new therapeutics by identifying new targets is needed to improve the life span of these patients. Previously, two tyrosine kinases, the EGFR and c-Src, were demonstrated to be overexpressed in 24% and 70%, respectively, of breast cancer cell lines and tumors studied and correlating with advanced disease (3, 6, 18, 21). Although alone neither the EGFR nor c-Src have shown to directly contribute to the development of tumorigenesis, these molecules exhibit striking biological synergism when co-overexpressed (15). Specifically, this co-overexpression leads to tumorigenesis in nude mice and correlates with the novel phosphorylation at tyrosine 845 and 1101 on the EGFR in a mouse fibroblast model (5, 15). This proposal is designed to test the hypothesis that the synergistic interactions between co-overexpressed EGFR and c-Src is a contributing step in breast cancer tumongenesis by (1) testing the biological synergy of EGFR and c-Src in a transgenic mouse model of breast cancer, (2) determining the binding site on the EGFR for c-Src, and (3) analyzing the effect of peptides complementary to pY845 and the c-Src binding site on EGF-induced DNA synthesis, transformation, and tumorigenesis. A transgenic mouse model for breast cancer will be developed by crossing MMTV-EGFR transgenic mice with MMTV-c-Src transgenic mice and evaluating the mice for tumor formation. Deletion and point mutants of the EGFR will be utilized to identify the binding site on the EGFR for c-Src. Peptides corresponding to pY845 or the c-Src binding site on the EGFR will be adminstered into tumors xenografted onto nude mice to study the ability of the peptides to inhibit tumorigenesis.