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了今年41，200例乳腺癌死亡。即使是最新的治疗进展，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，以延长这些患者的寿命。以前，两种酪氨酸激酶，EGFR和c-Src，被证明分别在24%和70%的乳腺癌细胞系和研究的肿瘤中过表达，并与晚期疾病相关（3，6，18，21）。尽管EGFR和c-Src均未单独显示直接促进肿瘤发生的发展，但当共同过表达时，这些分子表现出惊人的生物协同作用（15）。具体而言，这种共过表达导致裸鼠中的肿瘤发生，并与小鼠成纤维细胞模型中EGFR上酪氨酸845和1101处的新磷酸化相关（5，15）。该提议旨在通过以下方式检验共过表达的EGFR和c-Src之间的协同相互作用是乳腺癌肿瘤发生中的贡献步骤的假设：（1）在乳腺癌的转基因小鼠模型中检验EGFR和c-Src的生物协同作用，（2）确定c-Src在EGFR上的结合位点，和（3）分析与pY 845互补的肽和c-Src结合位点对EGF诱导的DNA合成、转化和肿瘤发生的作用。将通过将MMTV-EGFR转基因小鼠与MMTV-c-Src转基因小鼠杂交并评价小鼠的肿瘤形成来开发乳腺癌转基因小鼠模型。EGFR的缺失突变体和点突变体将用于鉴定EGFR上c-Src的结合位点。将对应于pY 845或EGFR上的c-Src结合位点的肽施用到异种移植到裸鼠上的肿瘤中，以研究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.