IGF-1 Signaling & ER crosstalk in mammary cancer in vivo

描述（由申请人提供）：胰岛素样生长因子1 （Insulin like growth factor 1, IGF-1）刺激细胞增殖，抑制细胞凋亡，从而影响包括乳腺癌在内的多种上皮肿瘤的发生进展。细胞培养实验已经确定了两个主要的信号通路，介导IGF-1对体外细胞转化和增殖的影响。研究表明，这两种途径都参与与雌激素受体（ER）的串扰，并通过磷酸化特定丝氨酸残基来增强受体的活性。转基因模型也证明了IGF-1在乳腺发育和肿瘤发生中的重要性。然而，许多模型利用激素或妊娠诱导的启动子，排除了内质网串扰或激素操纵影响的分析。我们已经开始研究一种新的BK5。IGF-1转基因模型，其中K5启动子是组成性的而不是激素调节的，并将转基因表达定向到乳腺的肌上皮细胞。肌上皮或基底层与导管上皮相邻，由具有上皮和肌肉特征的特化细胞组成。因此，该模型可以评估激素对igf -1促进乳腺肿瘤发生的作用，并概括了导管上皮细胞对局部产生的生长因子的旁分泌暴露。BK5的初步研究。IGF-1模型表明，分泌旁/近分泌暴露于IGF-1刺激导管增生，并使腺上皮明显更容易发生dmba引发的癌变。信号分析表明，与野生型肿瘤相比，转基因肿瘤具有更高的PI3K-Akt通路激活。初步研究还表明，乳腺腺癌在信息和蛋白水平上均表达功能性内质网。本研究的目的是验证IGF-1在体内主要通过激活PI3K-Akt通路刺激乳腺肿瘤发生的假设，并需要下游ER的激活（串扰）。一个必然的假设，即igf -1介导的内质网激活有助于他莫昔芬耐药性，也将在拟议的研究中得到解决。具体目的如下：1)研究PI3K-Akt通路在体内乳腺肿瘤发生中的作用。2)评估IGF-1介导的内质网信号激活（串扰）在乳腺肿瘤发生和体内他莫昔芬/抗雌激素耐药发展中的重要性。

DESCRIPTION (provided by applicant): Insulin like growth factor 1 (IGF-1) stimulates proliferation and inhibits apoptosis, thereby affecting the development and progression of a variety of epithelial tumors, including breast cancer. Cell culture experiments have identified two major signaling pathways that mediate the effects of IGF-1 on cellular transformation and proliferation in vitro. Studies show that both pathways are involved in crosstalk with the estrogen receptor (ER) and enhance receptor activity through phosphorylation of specific serine residues. Transgenic models also demonstrate the importance of IGF-1 in mammary development and tumorigenesis. However, many models utilize hormonally- or pregnancy-induced promoters that preclude analysis of ER crosstalk or the impact of hormonal manipulation. We have initiated studies with a new BK5.IGF-1 transgenic model in which the K5 promoter is constitutively and not hormonally regulated and directs transgene expression to the myoepithelial cells in the mammary gland. The myoepithelial or basal layer lies adjacent to the ductal epithelium and is composed of specialized cells with both epithelial and muscular characteristics. Thus, this model allows assessment of hormonal contributions to IGF-1-promoted mammary tumorigenesis and also recapitulates the paracrine exposure of ductal epithelial cells to locally produced growth factor. Preliminary studies with the BK5.IGF-1 model indicate that paracrine/juxtacrine exposure to IGF-1 stimulates ductal hyperplasia and renders the glandular epithelium significantly more susceptible to DMBA-initiated carcinogenesis. Signaling analyses show that transgenic tumors have increased activation of the PI3K-Akt pathway compared to wild type tumors. Preliminary studies also demonstrate that mammary adenocarcinomas express functional ER as detected at both the message and protein level. The goal of the proposed studies is to test the hypothesis that IGF-1 stimulates mammary tumorigenesis in vivo predominantly through activation of the PI3K-Akt pathway and requires downstream activation of ER (crosstalk). A corollary hypothesis, that IGF-1-mediated activation of ER contributes to tamoxifen resistance, will also be addressed in the proposed studies. The following specific aims will be performed: 1) Investigate the contribution of the PI3K-Akt pathway to mammary tumorigenesis in vivo. 2) Evaluate the importance of IGF-1 mediated activation of ER signaling (crosstalk) in mammary tumorigenesis and in the development of tamoxifen/antiestrogen resistance in vivo.