PROGESTERONE RECEPTOR IN BREAST DEVELOPMENT AND CANCER

描述(申请人提供)：考虑到孕酮(P)-增殖信号对乳腺发育和肿瘤发生的重要性，我们的长期目标是利用实验小鼠遗传学来更机械地了解P在体内作为内分泌乳源的作用。为此，我们最近的研究表明，在增殖的小鼠乳腺中，大多数PR阳性()细胞令人惊讶地是非增殖的，但与PR阴性(-)细胞亚群密切相关，后者对P有反应而增殖；在人和大鼠乳腺中也存在类似的PR表达的细胞组织模式。重要的是，这种独特的乳腺PR表达模式的脱轨与一些异常的乳腺生长表型有关，包括肿瘤。上述观察结果有力地支持了我们的假设，即在正常的腺体中，PR细胞接收、传递P-增殖信号，然后(通过旁分泌途径)将P-增殖信号传递给邻近的PR-细胞，然后PR-细胞被定向到一条增殖途径。我们的假设预测了上皮内旁分泌分子通路(S)的存在，该通路介导了P-增殖信号；WNT-4通路被认为是一条这样的通路。为了验证我们的假设，《特定目标1》将利用我们的PR-LacZ报告小鼠，一种最近产生的PR增强的绿色荧光蛋白敲击小鼠，荧光激活的细胞分类和乳腺上皮移植方法，在细胞水平上质疑P提出的旁分泌作用机制在正常乳腺中的功能重要性。具体目的2将通过使用四环素调节表达系统(Tet-On系统)来暂时控制PR基因敲除(PRKO)小鼠乳腺上皮中PR的表达，从而确定PR在乳房发育早期的表达对PR在成年腺体中功能的发育重要性。利用Tet-On系统和PRKO，特殊目标3将解决WNT-4是否是小鼠乳腺中P-增殖信号的真正旁分泌介体。最后，特殊目标4将使用正常乳腺和PRKO乳腺的比较转录图谱来识别P-乳腺信号的旁分泌介质的完整谱。将微阵列方法应用于小鼠乳腺肿瘤模型(在最后一次资助期间开发)还将揭示激素依赖或非激素依赖的乳腺肿瘤特有的特征基因网络；这一目标也将为未来乳腺癌的诊断、预后和/或治疗提供重要的分子靶点。

DESCRIPTION (provided by applicant): Considering the importance of the progesterone (P)-proliferative signal to mammary development and tumorigenesis, our long-term goal is to exploit experimental mouse genetics to gain a more mechanistic understanding of P's role as an endocrine mammogen, in vivo. Toward this end, our recent studies revealed that in the proliferating murine mammary gland, the majority of PR positive (+) cells were surprisingly nonproliferative but were in close association with a subgroup of PR negative (-) cells which proliferate in response to P; a similar cellular organization pattern for PR expression occurs in the human and rat mammary gland. Importantly, derailment of this distinct patterning for mammary PR expression is linked to a number of aberrant mammary growth phenotypes, including neoplasia. The foregoing observations strongly support our hypothesis of an evolutionary conserved cellular mechanism for P-action in the normal gland in which PR+ cells receive, transduce, and then relay (via a paracrine pathway) the P-proliferative signal to neighboring PR- cells, which are then directed toward a pathway of proliferation. Our hypothesis predicts the existence of an intraepithelial paracrine molecular pathway(s), which mediates the P-proliferative signal; the Wnt-4 pathway has been implicated as such a pathway. To test our hypothesis, Specific Aim 1 will employ our PR-LacZ reporter mouse, a recently generated PR-enhanced green fluorescent protein knockin mouse, fluorescence-activated cell sorting, and mammary epithelial transplantation approaches to query-at the cellular level-the functional importance of P's proposed paracrine mechanism of action in the normal mammary gland. Specific Aim 2 will define the developmental importance of PR expression during early mammary development to PR's function in the adult gland by using the tetracycline regulated expression system (the TET-ON system) to temporally control PR expression in the mammary epithelium of the PR knockout (PRKO) mouse. Using the TET-ON system and the PRKO, Specific Aim 3 will address whether Wnt-4 is a bona-fide paracrine mediator of the P-proliferative signal in the murine mammary gland. Finally, Specific Aim 4 will employ comparative transcriptional profiling of normal and PRKO mammary glands to identify the complete spectrum of paracrine mediators of the P-mammary signal. Application of microarray approaches to murine mammary tumor models (developed during the last grant period) will also uncover signature gene-networks specific for either hormone-dependent or -independent breast tumors; this aim should also furnish important molecular targets for future breast cancer diagnosis, prognosis and/or therapy.