Targeting EGFR and c Src Synergy In Breast Cancer

成功治疗晚期乳腺癌的困难是今年估计有4.12万人死于乳腺癌的主要原因。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，需要通过确定新的靶点来开发新的治疗方法，以提高这些患者的寿命。以前，两种酪氨酸激酶，EGFR和c-Src，分别在所研究的与晚期疾病相关的乳腺癌细胞系和肿瘤中分别有24%和70%过表达(3，6，18，21)。虽然单独的EGFR和c-Src都没有显示出对肿瘤发生发展的直接贡献，但当共过表达时，这些分子表现出显著的生物协同作用。具体地说，这种共过度表达导致裸鼠肿瘤的发生，并与小鼠成纤维细胞模型中EGFR上新的酪氨酸845和1101的磷酸化相关(5，15)。本建议旨在验证以下假设，即共过表达的EGFR和c-Src之间的协同作用是乳腺癌发生中的一个重要步骤：(1)在乳腺癌转基因小鼠模型中检测EGFR和c-Src的生物协同作用；(2)确定c-Src在EGFR上的结合部位；(3)分析与pY845互补的多肽和c-Src结合部位对EGF诱导的DNA合成、转化和肿瘤形成的影响。通过将MMTV-EGFR转基因小鼠与MMTV-c-Src转基因小鼠杂交，并评估这些小鼠的肿瘤形成情况，将建立乳腺癌的转基因小鼠模型。将利用EGFR的缺失和点突变来确定EGFR上c-Src的结合位点。与pY845或EGFR上的c-Src结合部位相对应的多肽将被注入裸鼠移植瘤中，以研究这些多肽抑制肿瘤形成的能力。

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.