Genetic Mapping of Breast Cancer Risk in the Tumor Microenvironment

 描述(申请人提供)：乳腺癌是最常见的女性恶性肿瘤，具有高度的遗传性，但大多数乳腺癌风险仍未确定。可遗传因素构成乳腺癌风险的大多数方面[例如，发病率、发病年龄、转移进展和无病生存]。除了影响肿瘤细胞的变异体 遗传性直接(即致瘤性)与肿瘤微环境的多个组成部分(如组织重塑、血管生成和免疫)有关，这些因素也影响肿瘤的发生和发展。然而，肿瘤微环境中潜在差异的遗传变异(S)很少成为遗传图谱研究的重点，因此仍然缺乏明确的定义。我们的目标是开发一种新的遗传模型来评估肿瘤微环境中的乳腺癌风险。我们开发了一种新的乳腺癌模型(称为共生异种移植模型-CXM)，该模型专注于通过肿瘤微环境影响肿瘤进展的菌株特异性变异(S)的基因图谱。共体鼠是指通过选择性育种将整个染色体导入到另一个近交系的等基因背景中的老鼠。因此，观察到的表型可以与单个染色体相连，然后通过比较序列分析和/或选择性回交进一步阐明，以产生较小的同源基因。在CXM中，共生和亲本菌株被转化为SCID(严重联合免疫缺陷)，这样原位移植的人乳腺癌细胞可以在体内进行测试。由于人类乳腺癌细胞在不同品系之间没有差异，乳腺癌进展中的任何差异(例如，原发部位生长、血管生成和远端转移)完全是由于肿瘤微环境中的遗传差异，而不是恶性肿瘤细胞。CXM利用具有特定属性(例如，三阴性、促转移等)的转基因标记的人类癌细胞。因此，它能够在具有不同乳腺癌遗传易感性的菌株背景下测试临床相关的癌症模型。使用CXM，我们发现大鼠3号染色体上的BN衍生遗传变异(S)显著抑制肿瘤生长和血道转移，而淋巴管和淋巴道转移完全不受影响。我们假设肿瘤生长和血液转移的减少是由于BN大鼠3号染色体上的遗传变异(S)引起的肿瘤血管的改变(S)。为了检验这一假说并阐明其遗传机制(S)，我们建议(1)缩小致病基因(S)，并通过对两个乳腺癌细胞系的CXM分析来表征抑制乳腺癌进展的潜在机制(S)：(2)确定改变SSBN3IL2R大鼠肿瘤血管和血液转移的血管特异性遗传和分子机制(S)；以及(3)检测WISP2/WNT信号通路在降低SSBN3IL2R组大鼠乳腺癌风险中的作用。这些研究将为肿瘤微环境在乳腺癌风险中的作用提供机械性的见解。

 DESCRIPTION (provided by applicant): Breast cancer is the most prevalent female malignancy and is highly heritable, yet the majority of breast cancer risk remains undefined. Heritable factors underlie most aspects of breast cancer risk [e.g., incidence, age-of- onset, metastatic progression, and disease-free survival]. In addition to variants that impact tumor cells directly (i.e., tumorigenicity), heritability is implicated in multiple components of the tumor microenvironment [e.g., tissue remodeling, angiogenesis, and immunity], which also impact tumorigenesis and progression. However, the genetic variant(s) underlying differences in the tumor microenvironment have rarely been the focus of genetic mapping studies and as such, remain poorly defined. Our goal is to develop a new genetic model to assess breast cancer risk in the tumor microenvironment. We have developed a new model of breast cancer (termed the Consomic Xenograft Model - CXM) that focuses on genetic mapping of strain-specific variant(s) that impact tumor progression through the tumor microenvironment. A consomic rat is one in which an entire chromosome is introgressed into the isogenic background of another inbred strain by selective breeding. Thus, observed phenotypes can be linked to single chromosomes and then further elucidated by comparative sequence analysis and/or selective backcrossing to yield smaller congenics. In CXM, the consomic and parental strains are converted to SCID (severe combined immunodeficiency), so that orthotopically xenografted human breast cancer cells can be tested in vivo. Because the human breast cancer cells are not varied between strains, any differences in breast cancer progression (e.g., primary site growth, vasculogenesis, and distal metastasis) are due solely to genetic differences in the tumor microenvironment, not the malignant cancer cells. CXM utilizes transgenically tagged human cancer cells with defined properties (e.g., triple-negative, pro-metastatic, etc.). Thus, it enables testing of clinically relevant cancer models in strain backgrounds with varying genetic predispositions to breast cancer. Using CXM, we found that BN-derived genetic variant(s) on rat chromosome 3 significantly suppress tumor growth and hematogenous metastasis, whereas lymphatic vasculature and lymphogenous metastasis were completely unaffected. We hypothesize that decreased tumor growth and hematogenous metastasis are due to alterations in the tumor blood vasculature caused by the genetic variant(s) on BN rat chromosome 3. To test this hypothesis and elucidate the genetic mechanism(s), we propose to (1) narrow the causative gene(s) and characterize the underlying mechanism(s) that inhibit breast cancer progression using CXM analysis of two breast cancer cell lines; (2) identify the blood vessel-specific genetic and molecular mechanism(s) that alter tumor blood vasculature and hematogenous metastasis in the SSBN3IL2R consomic rat; and (3) test the role of the WISP2/WNT signaling pathway in decreased breast cancer risk in the SSBN3IL2R consomic rat. These studies will provide mechanistic insight to the role of the tumor microenvironment in breast cancer risk.