PROGESTERONE RECEPTOR IN BREAST DEVELOPMENT AND CANCER

描述（由申请人提供）：考虑到孕激素(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获得P作为内分泌乳腺原在体内作用的更多机制理解。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（+）细胞令人惊讶地不增殖，但与PR阴性（-）细胞亚群密切相关，这些细胞对P有反应而增殖；在人和大鼠乳腺中也有类似的PR表达的细胞组织模式。重要的是，这种独特的乳腺PR表达模式的脱轨与许多异常的乳腺生长表型（包括肿瘤）有关。上述观察结果有力地支持了我们的假设，即正常腺体中p -作用的进化保守细胞机制，即PR+细胞接受、转导p -增殖信号，然后（通过旁分泌途径）传递给邻近的PR-细胞，这些细胞随后被导向增殖途径。我们的假设预测了上皮内旁分泌分子通路的存在，该通路介导p -增殖信号；Wnt-4通路被认为是这样一个通路。为了验证我们的假设，Specific Aim 1将使用我们的PR-LacZ报告小鼠，最近生成的pr增强绿色荧光蛋白敲入小鼠，荧光激活细胞分选和乳腺上皮移植方法，在细胞水平上查询P在正常乳腺中提出的旁分泌作用机制的功能重要性。特异性目的2将通过四环素调节表达系统（TET-ON系统）暂时控制PR敲除（PRKO）小鼠乳腺上皮中PR的表达，确定早期乳腺发育过程中PR表达对PR在成体腺体中的功能的发育重要性。利用TET-ON系统和PRKO， Specific Aim 3将探讨Wnt-4是否是小鼠乳腺中p -增殖信号的真正旁分泌介质。最后，Specific Aim 4将采用正常乳腺和PRKO乳腺的比较转录谱来确定p -乳腺信号的旁分泌介质的完整谱。微阵列方法在小鼠乳腺肿瘤模型中的应用（在上一个资助期开发）也将揭示激素依赖性或非依赖性乳腺肿瘤特异性的特征基因网络；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.