Functions of BNIP3 in Mammary Tumorigenesis

描述（由申请人提供）：乳腺癌转移到肺、骨、肝和脑是美国女性每年诊断出的最常见的癌症形式中的致命阶段。肿瘤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尚未明确。BNIP3是一种缺氧诱导的细胞死亡调节剂，BNIP3活性的丧失增加了小鼠异种移植乳腺肿瘤细胞系的转移潜力。我们实验室的机制研究表明，BNIP3在促进培养的乳腺肿瘤细胞自噬和限制坏死中起关键作用。目前的工作将通过研究BNIP3在靶向线粒体进行自噬中的作用的分子机制以及这如何促进乳腺肿瘤细胞对缺氧的适应性反应来扩展我们对BNIP3功能的分子洞察力（目的1）。利用原发肿瘤阵列，我们将检验BNIP3水平和亚细胞定位改变对预测人类乳腺癌进展的统计学意义（目的2）。通过结构-功能分析，我们研究了乳腺癌进展过程中BNIP3失活的分子机制（目的2）。本研究还将利用最先进的成像技术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基因敲除对乳腺癌易感小鼠乳腺肿瘤向肺部转移的发生率和潜伏期的影响（目的3）。这项工作具有临床意义，确定了BNIP3作为乳腺癌进展的一个假定标记物，并确定了BNIP3作为转移抑制因子的新作用。公共卫生相关性：转移是人类癌症进展的最后也是最致命的一步，在乳腺癌的情况下，肿瘤细胞扩散到肺部、骨骼、肝脏和大脑是生存的不良预后。本研究的意义在于将BNIP3的失活定义为肿瘤进展的标志，明确其在原发性人乳腺癌中的分子功能和失活机制，并确定其是否具有转移抑制作用。利用原发人类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，以及预防BNIP3失活的干预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.