Role of the signal transducer and activator of transcription-3 upon 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。这个基本过程被称为“分化”。如果分化受到干扰，那么细胞可能会不受控制地分裂，导致各种疾病，如癌症。***我们建议研究乳腺上皮细胞的分化机制，乳腺上皮细胞通常产生乳汁。我们一直在使用HC11细胞系作为模型，它来源于乳房，其行为方式与动物的行为相似；如果在生长培养基中加入催乳素，即泌乳激素，那么它们就会转化为产乳细胞。为了发生分化，HC11细胞也必须相互粘附。这是通过细胞表面一种叫做“钙粘蛋白”的蛋白质来实现的，这种蛋白质像“魔术贴”一样粘在一起。有趣的是，我们的实验室最近证明，除了这种结构作用，钙粘蛋白还激活一种名为“Rac”的蛋白质，而这种蛋白质反过来又激活“Stat3”。由于细胞间的粘附是分化所必需的，这将激活Rac，我们建议研究cadherin/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：将低水平的过度活跃的Rac （RacV12）引入细胞可以促进分化，而高水平的RacV12则可以阻止分化并促进细胞增殖。我们现在将通过检查与Rac相互作用的其他细胞成分（如Stat3， IL6等）的过度活跃形式的影响来研究分化机制，通过使用药物或遗传方法增加或减少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：该项目可能会揭示从钙粘蛋白参与到Stat3激活的新途径，作为细胞分化与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基本相反途径中的一个或另一个的关键。实际上，如果癌症是由活化的Rac驱动的，那么就不需要药物完全抑制Rac来治愈癌症，因为低残留水平实际上会导致分化并逆转癌症。所获得的知识可能适用于需要钙粘蛋白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，具有各种各样的应用，例如免疫、癌症或胚胎发育。***推进本研究的学生将获得有关细胞生物学机制的宝贵专业知识，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.