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

动物体内的细胞经常停止分裂，变成专门的细胞和组织。这一基本过程被称为“分化”。如果分化受到干扰，那么细胞可能会不受控制地分裂并导致各种疾病。 我们建议研究乳腺上皮细胞的分化机制，这些细胞通常产生乳汁。我们将使用培养的细胞系HC 11作为模型，其能够在培养皿中在适当的条件下增殖和分化。HC 11细胞来源于乳腺导管的上皮细胞，在培养中的行为与动物的行为相似;如果在生长培养基中加入催乳素，即泌乳激素，那么HC 11细胞就会产生乳蛋白，也就是说，它们会转化为产乳细胞。 为了发生分化，HC 11细胞必须彼此粘附。这是通过细胞表面的一种叫做“钙粘蛋白”的蛋白质来实现的，这种蛋白质像“尼龙搭扣”一样相互粘在一起。有趣的是，我们的实验室最近证明，除了这种结构作用外，钙粘蛋白还激活了一种名为“Stat 3”的蛋白质。由于细胞与细胞的粘附是分化所必需的，这将激活Stat 3，我们建议检查HC 11细胞分化后的钙粘蛋白/Stat 3通路的作用。 我们的初步结果表明，用药物抑制Stat 3可以阻止HC 11细胞的分化，也就是说，Stat 3确实是这个过程所必需的。我们现在将研究分化的途径，而不是细胞增殖，通过检查的影响，一个过度活跃的形式的Stat 3，这是能够导致过度增殖的细胞。我们还将研究我们发现与Stat 3相互作用的其他分子（称为Rac、Cdc 42、IL 6和gp 130）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，然后检查这些分子的作用。操作对分化的影响。 预期的益处和意义：所提出的项目可能揭示从钙粘蛋白参与到Stat 3激活的新途径，作为细胞分化与增殖之间平衡的中心决定因素，这可能是细胞决定遵循这些根本相反的路径中的一个或另一个的关键。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其他类型的情况下，其中钙粘蛋白的参与和生长停滞是必要的，如分化的脂肪细胞，肌肉或软骨与各种各样的应用，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，并对工业和学术研究产生影响。

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.