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

动物体内的细胞通常停止分裂，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，那么细胞可能会无法控制地分裂，导致多种疾病，如癌症。*我们建议研究正常产奶的乳房上皮细胞分化的机制。我们一直使用来源于乳房的细胞系HC11作为模型，其行为方式与它们在动物中的行为相似；如果将催乳素，即催乳激素添加到生长介质中，它们就会转化为产奶细胞。*为了发生分化，HC11细胞也必须相互黏附。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“RAC”的蛋白质，该蛋白质进而激活“STAT3”。由于分化需要细胞与细胞的黏附，从而激活RAC，我们建议研究钙粘素/RAC/STAT3通路在HC11细胞分化中的作用。*我们的初步结果显示了一个有趣的现象：在细胞中引入低水平的高活性形式的RAC(RacV12)可促进分化，而高水平的RAC可阻止分化并促进细胞增殖。我们现在将通过检测其他与RAC相互作用的细胞成分(如STAT3、IL6等)的高活性形式，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来研究分化的机制，然后检查这些操作对分化的影响。*预期的益处和意义：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。在实践中，如果癌症是由激活的RAC驱动的，就不需要一种完全抑制RAC的药物来治愈癌症，因为低残留水平实际上会导致分化和逆转癌症。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，并在学术和工业研究中产生影响。

Cells in the body of an animal often stop dividing and change into specialized 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 such as cancer. *** We are proposing to study the mechanism of differentiation of breast epithelial cells, which normally produce milk. We have been using as model the cell line HC11 which is derived from breast and behaves in a manner that resembles their behavior in the animal; if prolactin, the lactation hormone is added to the growth medium, then they are converted into milk-producing cells.*** For differentiation to occur, HC11 cells must also 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 "Rac", which, in turn, activates “Stat3”. Since cell to cell adhesion is required for differentiation, which would activate Rac, we are proposing to examine the role of the cadherin/Rac/Stat3 pathway upon the differentiation of HC11 cells. *** Our preliminary results demonstrate an interesting phenomenon: Introduction of low levels of a hyperactive form of Rac (RacV12) into the cell increases differentiation, while high levels prevent differentiation and promote cell multiplication. We will now investigate the mechanism of differentiation by examining the effect of hyperactive forms of other cellular components that interact with Rac, such as Stat3, IL6 and others, 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. In practical terms, if eg a cancer is driven by activated Rac there would be no need for a drug to inhibit Rac completely to cure the cancer, since low residual levels would actually cause differentiation and reverse the cancer. 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 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 Academic and industrial research.