Functions of BNIP3 in Mammary Tumorigenesis

描述(申请人提供)：乳腺癌转移到肺、骨、肝和脑是美国女性每年确诊的最常见癌症的致命阶段。肿瘤的缺氧和坏死与乳腺癌的转移和预后不良密切相关，尽管这种相关性的分子基础还不是很清楚。BNIP3是一种低氧诱导的细胞死亡调节因子，BNIP3活性的丧失增加了小鼠移植瘤中乳腺肿瘤细胞系的转移潜能。我们实验室的机制研究表明，在培养的乳腺肿瘤细胞中，BNIP3在促进自噬和限制坏死方面发挥了关键作用。目前的工作将扩大我们对BNIP3功能的分子洞察，通过研究BNIP3在靶向线粒体进行自噬方面的作用以及这如何有助于乳腺肿瘤细胞对低氧的适应性反应(目标1)。利用原发肿瘤阵列，我们将检验BNIP3水平和改变的亚细胞定位对预测人类乳腺癌进展的统计学意义(目标2)。利用结构-功能分析，我们检查了可能解释乳腺癌进展过程中BNIP3失活的分子机制(目标2)。这项拟议的工作还将使用最先进的成像技术来监测乳腺癌小鼠模型中乳腺肿瘤进展和转移过程中BNip3的表达，并监测BNip3基因敲除对癌症易感小鼠乳腺肿瘤转移到肺部的发生率和潜伏期的影响(目标3)。这项工作通过确定BNIP3作为乳腺癌进展的假定标记物和确定BNIP3作为转移抑制因子的新角色具有临床意义。公共卫生相关性：转移是人类癌症发展过程中最后也是最致命的一步，就乳腺癌而言，肿瘤细胞扩散到肺、骨、肝和脑是预后不佳的生存因素。本工作的意义在于将BNIP3失活定义为肿瘤进展的标志，表征其在乳腺癌中的分子功能和失活机制，以及确定其是否具有转移抑制作用。使用来自人类原发乳腺癌和小鼠模型的数据来确定BNIP3是否在预防乳腺癌转移中发挥作用，我们的工作旨在确定BNIP3是否可能作为乳腺癌进展的分子标记物，以及防止BNIP3失活的干预措施是否可能降低乳腺癌转移的发生率。

DESCRIPTION (provided by applicant): Breast cancer metastasis to the lungs, bones, liver and brain is the fatal stage in the most common form of cancer diagnosed annually in women in the US. Tumor hypoxia and necrosis are tightly correlated with metastasis and poor prognosis in breast cancer, although the molecular basis of this correlation is not well defined. BNIP3 is a hypoxia- inducible regulator of cell death and loss of BNIP3 activity increased the metastatic potential of breast tumor cell lines in mouse xenografts. Mechanistic studies from our lab have indicated a critical role for BNIP3 in promoting autophagy and limiting necrosis in mammary tumor cells in culture. The current work will extend our molecular insight into the functions of BNIP3 by examining the molecular mechanism underlying the role of BNIP3 in targeting mitochondria for autophagy and how this contributes to the adaptive response of breast tumor cells to hypoxia (Aim 1). Making use of primary tumor arrays, we will examine the statistical significance of BNIP3 levels and altered sub-cellular localization for predicting progression of human breast cancer (Aim 2). Using structure-function analyses, we examine molecular mechanisms that may explain BNIP3 inactivation during breast cancer progression (Aim 2). The proposed work will also use state-of-the-art imaging techniques to monitor BNip3 expression during mammary tumor progression and metastasis in mouse models of breast cancer and to monitor the effect of BNip3 gene knockout on the incidence and latency of breast tumor metastasis to the lungs in cancer-prone mice (Aim 3). This work has clinical significance by identifying BNIP3 as a putative marker of breast cancer progression and defining a novel role for BNIP3 as a metastasis suppressor. PUBLIC HEALTH RELEVANCE: Metastasis is the last and most deadly step in the progression of human cancers and in the case of breast cancer the spread of tumor cells to the lungs, bones, liver and brain is a poor prognosis for survival. The significance of the current work lies in defining inactivation of BNIP3 as a marker of tumor progression, characterizing its molecular function and mechanism of inactivation in primary human breast cancer, and in determining whether it functions as a metastasis suppressor. Using data from primary human breast cancers and from mouse models to determine whether BNIP3 plays a role in preventing breast cancer metastasis, our work aims to determine whether BNIP3 might be useful as a molecular marker of breast cancer progression and if intervention to prevent BNIP3 inactivation is likely to reduce the incidence of breast cancer metastasis.