VEGF signaling in Mammary Tumorigenesis

这项提议将检验出人意料的假设，即α6β4整合素(称为‘β4’)有助于 通过非细胞自主机制促进乳腺肿瘤的发生和转移。这一假设 起源于观察到β4在乳腺癌干细胞(CSC)中低表达或缺失，但 它有助于乳腺癌的形成和转移。这项提议的一个主要目标是 调和这些不一致的观察结果，了解β4如何促进肿瘤的形成和转移。 有趣的是，三阴性乳腺癌(TNBCs)包含一个独特的细胞亚群，其特征是 β4整合素的高表达(β4高)有别于CSCs(β4-/低/CD24low/CD44High)，表现为基础 上皮分化，缺乏干细胞特性。这些观察表明，对β4的抑制是 这是CSC功能所必需的。事实上，我们意外地观察到，β4在CSCs中的表达促进了它们的 分化并抑制它们的自我更新。第一个具体目标将研究 它将关注一种令人兴奋的可能性，即它涉及到β4的能力 调节局部粘连和细胞骨架张力，导致干细胞特性降低。这一目标将 同时测试细胞骨架张力的改变在促进分化中起因果作用的可能性。 CSCs的数量。 第二个具体目标将评估β4High亚群发挥非细胞自治作用的假设 对CSCs的监管。换句话说，β4High亚群的一个关键功能是扩大CsC种群。 更具体地说，有人认为这个不同的亚群参与了与CSC的旁分泌信号 由甲状旁腺激素相关蛋白(PTHrP)介导，这一信号有助于扩张 CSCs的数量。这一假说是基于观察到β4调节甲状旁腺素rp的表达，以及β4高 在乳腺肿瘤中，亚群和CSCs近在咫尺。此外，我们的初步数据显示，β4High 亚种群有助于维持自我更新和生存。这些观察结果解释了 β-4整合素在肿瘤起始和转移中的作用而不表达于肿瘤干细胞 最终的具体目标是在体内研究CSCs与β4High细胞的关系，并评价其 在肿瘤发生和转移中的相对贡献。第一组实验将检验两者是否 CSCs和β4High细胞是有效的肿瘤形成和转移所需的细胞 TNBC。第二个亚目标通过以下方式更深入地探讨CSCs与β4High细胞的关系 评估CSCs在体内的分化程度及其与β4High细胞的相关性 利基市场。这些目标将通过使用报告构建物来标记这些不同的种群来促进。这 该方法将使我们能够解决几个关键问题，包括CSC(GFP)的差异化频率 在体内，β-4High和CSCs在“小生境”中的关系以及CSCs和β-4High细胞的相对频率 转移瘤。

This proposal will examine the unanticipated hypothesis that the α6β4 integrin (referred to as `β4') contributes to the initiation and metastasis of breast tumors by a non-cell autonomous mechanism. This hypothesis derives from the observations that the expression of β4 is low or absent in breast cancer stem cells (CSCs) but that it contributes to the formation and metastasis of breast cancers. A major goal of this proposal is to reconcile these discrepant observations and understand how β4 contributes to tumor formation and metastasis. Interestingly, triple-negative breast cancers (TNBCs) contain a distinct sub-population of cells characterized by high expression of the β4 integrin (β4high) that is distinct from CSCs (β4-/low/CD24low/CD44high), exhibits basal epithelial differentiation and lacks stem cell properties. These observations indicate that repression of β4 is necessary for CSC function. In fact, we observed unexpectedly that β4 expression in CSCs promotes their differentiation and inhibits their self-renewal. The first specific aim will investigate the mechanism that underlies this phenomenon and it will focus on the exciting possibility that it involves the ability of β4 to modulate focal adhesions and cytoskeletal tension resulting in diminished stem cell properties. This aim will also test the possibility that alterations in cytoskeletal tension have a causal role in promoting the differentiation of CSCs. The second specific aim will evaluate the hypothesis that the β4high sub-population exerts non-cell autonomous regulation of CSCs. In other terms, a key function of the β4high subpopulation is to expand the CSC population. More specifically, it is proposed that this distinct sub-population engages in paracrine signaling with CSCs mediated by parathyroid hormone-related protein (PTHrP) and that this signaling contributes to the expansion of CSCs. This hypothesis is based on the observations that β4 regulates PTHrP expression and that the β4high sub-population and CSCs are in proximity in breast tumors. Also, our preliminary data indicate that the β4high sub-population helps to maintain self-renewal and survival. These observations provide an explanation for how the β4 integrin contributes to tumor initiation and metastasis without being expressed in CSCs. The final specific aim will study the relationship between CSCs and β4high cells in vivo and evaluate their relative contribution to tumor initiation and metastasis. The first set of experiments will examine whether both CSCs and β4high cells are required for efficient tumor formation and metastasis using a transgenic model of TNBC. The second sub-aim probe more deeply into the relationship between CSCs and β4high cells by evaluating the extent to which CSCs differentiate in vivo and assessing their association with β4high cells in niches. These goals will be facilitated by the use of reporter constructs to tag these distinct populations. This approach will allow us to address several key issues including the frequency that CSCs (GFP+) differentiate in vivo, the association of β4high and CSCs in `niches' and the relative frequency of CSCs and β4high cells in metastases.