Prolactin as a Growth Factor in Breast Cancer

描述(申请人提供)：乳腺癌受遗传、环境、饮食和荷尔蒙因素的影响。催乳素(PRL)在啮齿动物乳腺肿瘤发生中的作用已被广泛接受，但其在人类乳腺癌中的作用一直存在争议。催乳素是一种多效性激素，由垂体和非垂体部位在不同的调节机制下产生。最近的研究发现PRL及其受体(PRL-R)在人乳腺中表达，但产生PRL的细胞类型、其表达的调控以及体内局部PRL是否促进乳腺癌生长等问题尚未解决。 初步结果：我们发现人乳房外植体PRL的从头合成和释放随时间的增加而增加。脂肪组织中PRL的产生明显高于腺体或恶性组织。PRL的表达在乳腺前脂肪细胞分化的早期就被诱导，而其受体(PRLR)的表达则逐渐增加，与ieptin的升高相平行。PRL和PRL-R在两种人脂肪肉瘤细胞系中均有表达。为了验证本地生产的PRL促进肿瘤生长的概念，我们将PRL转录本稳定地导入乳腺癌细胞。在体外，高表达PRL的克隆比对照组生长更快，并在裸鼠体内形成更快的肿瘤生长。来自PRL过表达克隆的肿瘤细胞PRL-R和抗凋亡剂Bcl2水平升高。我们的主要前提是乳房脂肪组织是局部催乳素的主要来源，催乳素是促进肿瘤生长的细胞因子。为了更好地了解乳房脂肪PRL，我们将首先测定乳房脂肪组织和前脂肪细胞中PRL及其受体的生化特性和调节。然后，我们将产生具有四环素诱导的PRL表达的癌细胞，并分析旁分泌/自分泌PRL在体外和体内刺激肿瘤生长的机制。 假设：脂肪PRL的产生通常受到紧张性抑制的抑制，但肿瘤产生的PRL刺激因子可以克服这种抑制。局部PRL的升高激活了促有丝分裂和抗凋亡信号，从而刺激了肿瘤生长。 具体目标1将表征乳房脂肪组织中的催乳素及其受体。\ 特定目的2将定义乳房前脂肪细胞和脂肪肉瘤细胞中PRL表达的控制。 具体目标3将检测可诱导的PRL表达对肿瘤生长和基因表达的影响。长期目标：建立PRL作为乳腺癌的有丝分裂原/抗凋亡因子，为未来乳腺癌治疗的设计奠定基础。

DESCRIPTION (provided by applicant): Breast cancer is affected by genetic, environmental, dietary and hormonal factors. The role of prolactin (PRL) in mammary tumorigenesis in rodents is well accepted but its involvement in human breast cancer has been controversial. PRL is a pleiotropic hormone that is produced by pituitary and non-pituitary sites under dissimilar regulatory mechanisms. Recent studies revealed expression of PRL and its receptor (PRL-R) in the human breast but the cell type that produces PRL, the regulation of its expression and whether local PRL promotes breast cancer growth in vivo have not been resolved. Preliminary Results: We found de-novo synthesis and time-dependent increases in PRL expression and release from human breast explants. PRL production was significantly higher in adipose than in glandular or malignant tissues. PRL expression was induced early during differentiation of breast preadipocytes whereas the expression of its receptor (PRLR) increased progressively, paralleling the rise in ieptin. Both PRL and the PRL-R were also expressed in two human liposarcoma cell lines. To test the concept that locally-produced PRL promotes tumor growth, the PRL transcript was stably transfected into breast cancer cells. Clones overexpressing PRL grew faster than controls in vitro and formed faster growing tumors in nude mice. Tumors derived from the PRL-overexpressing clones had increased levels of the PRL-R and the anti-apoptotic agent Bcl-2. Our main premise is that breast adipose tissue is the major source of local PRL which acts as a cytokine to promote tumor growth. To gain more understanding of breast adipose PRL, we will first determine the biochemical properties and regulation of PRL and its receptor in breast adipose tissue and preadipocytes. We will then generate cancer cells with a tetracycline-inducible PRL expression and analyze the mechanism by which paracrine/autocrine PRL stimulates tumor growth in vitro and in vivo. Hypothesis: Adipose PRL production is normally suppressed by tonic inhibition, but tumors produce PRL stimulatory factors that overcome this inhibition. The rise in local PRL activates mitogenic and anti-apoptotic signaling that stimulate tumor growth. Specific Aim 1 will characterize PRL and its receptor in breast adipose tissue. \ Specific Aim 2 will define the control of PRL expression in breast preadipocytes and liposarcoma cells. Specific Aim 3 will examine the effects of inducible PRL expression on tumor growth and gene expression. Long Term Goal: To establish PRL as a mitogen/anti-apoptotic factor in breast cancer, serving as the foundation for the design of future breast cancer therapy.