Asymmetric Cell Division and Mammary Gland Development

不对称细胞分裂和乳腺发育

• 批准号: 7864598
• 负责人: WEIMIN ZHONG
• 金额: $ 24.83万
• 依托单位: YALE UNIVERSITY
• 依托单位国家: 美国
• 财政年份: 2010
• 资助国家: 美国
• 起止时间: 2010-07-10 至 2012-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/7864598
• 关键词: Aftercare; Behavior; Breast Carcinoma; Cancer Biology; Cell Fraction; Cell division; Cells; Development; Disease; Drosophila genus; Embryonic Development; Equilibrium; Gene Expression; Gene Targeting; Genes; Goals; Growth; Individual; Invertebrates; Laboratories; Lactation; Lead; Malignant Epithelial Cell; Malignant Neoplasms; Mammary gland; Measures; Mediating; Molecular Profiling; Mus; Mutate; Nervous system structure; Neurons; Pregnancy; Process; Production; Relapse; Research; Stem cells; Variant; cancer cell; cancer stem cell; daughter cell; insight; interest; killings; malignant breast neoplasm; mammary gland development; mouse Numb protein; mutant; neoplastic cell; nerve stem cell; novel therapeutics; numb protein; prevent; progenitor; public health relevance; relating to nervous system; research study; segregation; self-renewal; stem; tumor; tumorigenic

DESCRIPTION (provided by applicant): Mammary glands undergo extensive proliferation, branching and terminal differentiation during pregnancy to prepare for lactation, and there is growing evidence that stem cells at least partly drive this process. There is also growing interest in the connection between stem cells and cancer. The apparent similarity between the ability of cancer cells to grow uncontrollably and that of the stem cells to continuously self-renew has led to the notion that cancers are diseases of stem cells. It posits that only a fraction of the cells within the tumor mass can generate tumors and such cancer stem cells cause relapse and prevent cure. Indeed, stem-cell markers are expressed by a small but highly tumorigenic subset of breast carcinoma cells. In this application, we seek to perform exploratory experiments - using mammalian numb proteins and the insights we obtained from our studies in the nervous system as entry point - to examine the contribution of two modes of cell division - symmetric vs. asymmetric - in regulating the behavior of putative stem cells during mammary gland growth, as a means to identify markers and essential regulators of mammary stem cells. If successful, our research will not only help us to better understand mammary development but also point to new avenues for exploring the connection between stem cells and tumor cells and provide insights for devising novel therapeutic measures for treating breast cancer. Asymmetric cell division is an attractive means for stem cells to balance self-renewal and differentiation - namely, by producing one daughter cell that remains as a stem cell and the other that differentiates. In invertebrates like Drosophila, the Numb protein makes the two daughter cells different after an asymmetric division by segregating primarily into one daughter cell to promote its fate. Recent findings from our laboratory show that neural stem (progenitor) cells use asymmetric numb segregation to balance self-renewal and differentiation during mouse embryogenesis. Mammalian numb proteins are encoded by two genes, m-numb (Numb) and numblike (Numbl), which have largely overlapping functions. When both Numb and Numbl are mutated, neural progenitor cells lose their ability to self-renew as both daughter cells become neurons. Conversely, forcing numb proteins to segregate symmetrically into both daughter cells inhibits neuron production by forcing both to choose self-renewal. In this exploratory R21 application, we hypothesize that numb-mediated asymmetric cell divisions are also used by stem/progenitor cells when they drive mammary gland development during pregnancy and that markers and essential regulators of mammary stem cells can be identified using mutant mammary glands in which the ratio between stem/progenitor and differentiated cells is skewed by changes in numb segregation. Aim 1 will examine the importance of numb-mediated asymmetric cell division in mammary gland development by using Cre-loxP-mediated gene targeting to replace the endogenous numb proteins with individual variants that segregate either symmetrically or asymmetrically. Aim 2 intends to identify markers and essential regulators of mammary stem cells by comparing gene expression profiles between mammary glands in which the two numb genes are mutated and those containing only a symmetrically segregating numb protein. PUBLIC HEALTH RELEVANCE: A fundamental issue in cancer biology and treatment is why killing the vast majority of cancer cells do not lead to a cure. The apparent similarity between tumor cells and stem cells has led to the notion that cancers are diseases of stem cells. It is believed that only a fraction of the cells within the tumor mass is capable of generating tumors. Since stem cells have limitless capability to self-renew and generate large numbers of progeny, a few remaining cancer stem cells after treatment may be sufficient to form new tumors and, consequently, cause relapse and prevent cure. In this application, we seek to perform exploratory experiments to identify genes and cellular mechanisms that regulate the behavior of stem cells during mammary gland growth. If successful, our research will not only help us to better understand mammary development but also point to new avenues for exploring the connection between stem cells and tumor cells and provide insights for devising novel therapeutic measures for treating breast cancer.

描述（由申请人提供）：乳腺在怀孕期间经历了广泛的增殖，分支和末端分化以准备哺乳，并且越来越多的证据表明干细胞至少部分驱动了这一过程。对干细胞与癌症之间的联系也越来越感兴趣。癌细胞无法控制生长的能力与干细胞不断自我更新的能力之间的明显相似性导致了癌症是干细胞疾病的观念。它认为，只有肿瘤质量内的细胞的一部分才能产生肿瘤，这种癌症干细胞会导致复发并防止治愈。实际上，干细胞标记是由乳腺癌细胞的小但高度肿瘤的子集表达的。 In this application, we seek to perform exploratory experiments - using mammalian numb proteins and the insights we obtained from our studies in the nervous system as entry point - to examine the contribution of two modes of cell division - symmetric vs. asymmetric - in regulating the behavior of putative stem cells during mammary gland growth, as a means to identify markers and essential regulators of mammary stem cells.如果成功的话，我们的研究不仅将帮助我们更好地了解乳腺发育，而且还指出了探索干细胞与肿瘤细胞之间联系的新途径，并为设计新的治疗乳腺癌治疗方法提供了见解。不对称细胞分裂是干细胞平衡自我更新和分化的一种有吸引力的手段 - 即，通过产生一个保持作为干细胞的子细胞，另一种是区分的子细胞。在像果蝇这样的无脊椎动物中，麻木蛋白在不对称分裂后通过主要将一个子细胞隔离到一个子细胞以促进其命运而使两个子细胞不同。我们实验室的最新发现表明，神经茎（祖细胞）细胞使用不对称的麻木隔离来平衡小鼠胚胎发生过程中的自我更新和分化。哺乳动物麻木的蛋白质由两个基因（Numb）和Numblike（Numbl）编码，它们在很大程度上重叠了函数。当麻木和Numbl突变时，神经祖细胞会在两个子细胞成为神经元时失去自我更新的能力。相反，迫使麻木蛋白对称分离为两个子细胞，通过迫使两者选择自我更新来抑制神经元的产生。 In this exploratory R21 application, we hypothesize that numb-mediated asymmetric cell divisions are also used by stem/progenitor cells when they drive mammary gland development during pregnancy and that markers and essential regulators of mammary stem cells can be identified using mutant mammary glands in which the ratio between stem/progenitor and differentiated cells is skewed by changes in numb segregation. AIM 1将通过使用CRE-LoXP介导的基因靶向来替代内源性麻木蛋白，用对称或不对称分离的个体变体来替代内源性麻木蛋白，从而研究麻木介导的不对称细胞分裂在乳腺发育中的重要性。 AIM 2打算通过比较乳腺之间的基因表达谱鉴定标记和基本调节剂，其中两个麻木基因被突变而仅包含对称分离麻木蛋白的乳腺。 公共卫生相关性：癌症生物学和治疗中的一个基本问题是为什么杀死绝大多数癌细胞不会治愈的原因。肿瘤细胞和干细胞之间的明显相似性导致癌症是干细胞疾病的观念。据认为，肿瘤质量中只有一小部分能够产生肿瘤。由于干细胞具有自我更新并产生大量后代的能力，因此治疗后剩下的少数癌症干细胞可能足以形成新的肿瘤，因此会导致复发并防止治愈。在此应用中，我们试图执行探索性实验，以确定调节乳腺生长过程中干细胞行为的基因和细胞机制。如果成功的话，我们的研究不仅将帮助我们更好地了解乳腺发育，而且还指出了探索干细胞与肿瘤细胞之间联系的新途径，并为设计新的治疗乳腺癌治疗方法提供了见解。