An Ets2-specific transcriptional program in tumor-associated macrophages promotes metastasis. Mus musculus

Macrophages have been implicated in breast cancer progression and metastasis, but relatively little is known about the genes and pathways that are involved. Using a conditional allele of Ets2 in the mouse, we have identified Ets2 as a critical gene in tumor associated macrophages (TAMs) that specifically promotes mammary tumor metastasis. Loss of Ets2 in TAMs decreased the frequency and size of lung metastases without impacting primary tumor burden. Expression profiling of isolated tumor macrophages established that Ets2 deficiency resulted in the de-repression of a defined set of anti-angiogenic genes. Activation of this transcriptional program correlated with decreased angiogenesis in metastatic tumors and decreased metastatic growth. Comparison of this Ets2-specific TAM expression profile with human breast cancer profiles revealed a macrophage gene expression signature that could predict overall survival of estrogen receptor negative patients. In summary, we have identified a critical factor, Ets2, in TAMs that represses a transcriptional program to promote the growth of mammary tumor metastases in the lung. Overall design: Breast TAMs were isolated from early-stage PyMT-induced mammary tumors expressing Ets2 and also from the tumors with Ets2-deficient TAMs. Since macrophages have also been implicated in normal mammary gland remodeling, normal remeodeling macrophages were also purified from females expressing Ets2 and the ones where Ets2 is deleted in the macrophages. One RNA sample was extracted from each genetic group for gene-expression profiling.

巨噬细胞已被证实与乳腺癌进展及转移密切相关，但目前对其参与调控的相关基因与通路仍知之甚少。本研究借助小鼠Ets2条件性等位基因模型，鉴定出Ets2是肿瘤相关巨噬细胞（tumor associated macrophages, TAMs）中特异性促进乳腺肿瘤转移的关键基因。TAMs中Ets2缺失可降低肺转移的发生频率与转移灶体积，却不会影响原发肿瘤负荷。对分离获得的肿瘤巨噬细胞进行表达谱分析后发现，Ets2缺陷会导致一组明确的抗血管生成基因发生去抑制现象。该转录程序的激活与转移性肿瘤内血管生成减少及转移灶生长受限存在显著相关性。将该Ets2特异性TAM表达谱与人类乳腺癌数据集进行比对后发现，存在一类巨噬细胞基因表达特征，可用于预测雌激素受体阴性患者的总生存期。综上，本研究鉴定出肿瘤相关巨噬细胞中的关键因子Ets2，其通过抑制特定转录程序，促进肺部乳腺肿瘤转移灶的生长。

实验总体设计：从表达Ets2的PyMT诱导早期乳腺肿瘤，以及TAMs中Ets2缺失的同类肿瘤中分离乳腺TAMs。鉴于巨噬细胞同样参与正常乳腺组织重塑过程，本研究同时从表达Ets2的野生型雌性小鼠，以及巨噬细胞中特异性敲除Ets2的雌性小鼠中纯化正常重塑相关巨噬细胞。从每个遗传组中提取一份RNA样本用于基因表达谱分析。