Role of the signal transducer and activator of transcription-3 in epithelial cell differentiation

动物体内的细胞通常会停止分裂，变成特化的细胞和组织。这一基本过程被称为“分化”。如果分化受到干扰，那么细胞可能会无法控制地分裂，导致各种疾病。 我们建议研究乳房上皮细胞分化的机制，乳房上皮细胞通常产生乳汁。我们将以培养的能够在培养皿中增殖和分化的细胞系HC11为模型，在适当的条件下。HC11细胞来自乳腺导管的上皮细胞，在培养中的行为与它们在动物中的行为相似；如果在生长介质中加入催乳素，那么HC11细胞就会产生乳蛋白，也就是说，它们被转化为产奶细胞。 为了发生分化，HC11细胞必须相互黏附。这是通过细胞表面的一种叫做“钙粘附素”的蛋白质来实现的，这种蛋白质像“尼龙搭扣”一样互相粘连。有趣的是，我们的实验室最近证明，除了这种结构作用外，钙粘附素还激活一种名为“STAT3”的蛋白质。由于分化需要细胞与细胞的黏附，从而激活STAT3，我们建议研究钙粘素/STAT3通路在HC11细胞分化中的作用。 我们的初步结果表明，用一种药物抑制STAT3可以阻止HC11细胞的分化，也就是说，这一过程确实需要STAT3。我们现在将通过检测一种能够导致细胞过度增殖的高活性形式的STAT3的作用，来研究分化的途径，而不是细胞增殖的途径。我们还将研究我们发现的其他与STAT3相互作用的分子(称为Rac、CDC42、IL6和gp130)的作用，通过使用药物或遗传方法增加或降低它们在细胞中的活性，然后检查这些操作对分化的影响。 预期的好处和意义：拟议的项目可能揭示一条从钙粘素参与到STAT3激活的新途径，作为细胞分化和增殖之间平衡的核心决定因素，这可能是细胞决定遵循这些根本相反的途径之一的关键。这些结果将揭示基本生物过程的分子基础。所获得的知识可能适用于需要钙粘附素参与和生长抑制的其他类型的情况，例如脂肪细胞、肌肉或软骨的分化，具有多种应用，如哺乳、肥胖、免疫、癌症或胚胎发育。 推进这项研究的学生将获得细胞生物学机制方面的宝贵专业知识，并在工业和学术研究中产生影响。

Cells in the body of an animal often stop dividing and change into specialised cells and tissues. This fundamental process is called "differentiation". If differentiation is disturbed, then the cells may divide uncontrollably and cause a variety of diseases. We are proposing to study the mechanism of differentiation of breast epithelial cells, which normally produce milk. We will use as model the cultured cell line HC11 which is able to multiply as well as differentiate in a petri dish, under the appropriate conditions. HC11 cells are derived from the epithelial cells that line the ducts of the breast, and behave in culture in a manner that resembles their behaviour in the animal; if prolactin, the lactation hormone, is added to the growth medium, then HC11 cells produce milk proteins, that is they are converted into milk-producing cells. For differentiation to occur, HC11 cells must adhere to one another. This happens through proteins on the cell surface called "cadherins" that stick to each other like “velcro”. Interestingly, our lab recently demonstrated that besides this structural role, cadherins also activate a protein called "Stat3". Since cell to cell adhesion is required for differentiation, which would activate Stat3, we are proposing to examine the role of the cadherin/Stat3 pathway upon the differentiation of HC11 cells. Our preliminary results demonstrated that inhibition of Stat3 with a drug prevents differentiation of HC11 cells, that is, Stat3 is indeed required for this process. We will now investigate the pathway of differentiation, as opposed to cell multiplication, by examining the effect of a hyperactive form of Stat3, which is able to cause overproliferation of the cells. We will also study the role of other molecules that we found to interact with Stat3 (called Rac, Cdc42, IL6 and gp130), by increasing or decreasing their activity in the cell using drugs or genetic methods, then examining the effect that these manipulations have upon differentiation. Anticipated benefits and significance: The project proposed may expose a novel pathway leading from cadherin engagement to Stat3 activation, as being a central determinant of the balance between cell differentiation vs multiplication, that is may be a key for the decision of the cell to follow one or the other of these fundamentally opposite paths. These results will reveal the molecular underpinnings of fundamental biological processes. The knowledge gained may be applicable to other types of situations where cadherin engagement and growth arrest are necessary, such as differentiation of fat cells, muscle or cartilage with a large variety of applications, such as lactation, obesity, immunity, cancer or embryonic development. The students who advance this research will obtain valuable expertise on Cell Biology mechanisms and make an impact in both industrial and Academic research.