Combining single cell approaches and a developmental perspective to discover stem cell control circuits and the cellular and molecular bases of cancer heterogeneity

 描述（由申请人提供）：肿瘤内异质性混淆分子分类学，促进转移，并增加治疗失败的机会。了解肿瘤内异质性的起源并制定有效的对策应能改善癌症预后。该提案侧重于基底样乳腺癌（BLBC）肿瘤内异质性的细胞和分子起源，因为这些癌症经常抵抗化疗，目前缺乏药物开发的分子靶点。BLBC与其他乳腺癌亚型不同，因为它表现出与胚胎发生期间产生的胎儿乳腺干细胞（fMaSC）相关的基因表达特征。重要的是，fMaSC样癌细胞具有很强的致瘤性，并且与“乳腺癌”显著不同。 癌症干细胞”最近受到了广泛关注。该项目将确定驱动胚胎乳腺细胞进入干细胞状态的分子程序，并使用基因编辑技术生成一种新的小鼠模型，使实验室能够根据它们表达的细胞角蛋白真实的识别fMaSCs。这种实验方法将允许实验室选择性地消除这些细胞，以明确确定这些细胞是否是乳腺内唯一的干细胞，以及其他细胞是否可以在受伤，炎症，肥胖等情况下获得干细胞。该项目将在fMaSCs或其分化后代中诱导p53突变，并询问是否出现不同类型的肿瘤，并评估细胞和分子异质性。该项目将确定其他BLBC相关突变，如BRCA1（单独或与p53突变组合）或环境挑战（如炎症或肥胖）是否会引起相同的影响。将所得肿瘤的基因表达特征与人BLBC的基因表达特征进行比较，以生成更忠实地反映人类疾病的小鼠模型。最后，该项目将应用单细胞测序和复杂的生物信息学方法：1）破译干细胞状态产生的机制，2）评估肿瘤细胞群内的异质性，3）确定fMaSC胚胎抗原是否在人BLBC中可检测到。这些抗原以及发现的驱动fMaSC状态的途径将为开发肿瘤选择性、免疫和分子靶向疗法提供新的靶点。BLBC中的fMaSC样细胞类似于真正的多能胚胎乳腺干细胞，并且包括癌症中一种新的且未充分研究的细胞类型。在不同的实体瘤中已经描述了具有类似干细胞样属性的细胞，这表明这些研究的结果可能与癌症生物学具有普遍相关性。

 DESCRIPTION (provided by applicant): Intra-tumoral heterogeneity confounds molecular taxonomy, fuels metastasis, and increases the chances of treatment failure. Understanding the origins of intra-tumoral heterogeneity and developing effective countermeasures should improve cancer outcomes. This proposal focuses on the cellular and molecular origins of intra-tumoral heterogeneity in basal-like breast cancer (BLBC), as these cancers frequently resist chemotherapy and currently lack molecular targets for drug development. BLBC is distinguishable from other breast cancer subtypes, as it exhibits a gene expression signature that is associated with fetal mammary stem cells (fMaSCs) generated during embryogenesis. Importantly, fMaSC-like cancer cells are very tumorigenic and differ significantly from the "breast cancer stem cells" that have received much recent attention. This project will determine the molecular programs that drive embryonic mammary cells into the stem cell state, and use gene editing technologies to generate a new mouse model that will enable the lab to identify fMaSCs in real time based on the cytokeratins they express. This experimental approach will allow the lab to selectively eliminate these cells to determine unambiguously if these are the only stem cells within the mammary gland, and whether other cells can acquire stemness in response to wounding, inflammation, obesity, etc. p53 mutations are frequently found in BLBC and contribute to both genetic heterogeneity and increased reprogramming efficiency. This project will induce p53 mutations in fMaSCs or their differentiated progeny and ask whether different types of tumors arise, and assess cellular and molecular heterogeneity. This project will determine whether other BLBC relevant mutations, such as BRCA1 (alone or in combination with p53 mutations) or environmental challenges (such as inflammation or obesity) elicit the same effects. Gene expression signatures of resulting tumors will be compared to those of human BLBC to generate mouse models that reflect the human disease more faithfully. Finally, this project will apply single cell sequencing and sophisticated bioinformatic approaches to: 1) decipher the mechanisms by which the stem cell state is generated, 2) assess heterogeneity within the tumor cell population, and 3) determine whether fMaSC embryonic antigens are detectable in human BLBC. Such antigens, and the pathways discovered to drive the fMaSC state, will provide new targets for developing tumor-selective, immune- and molecularly targeted therapies. The fMaSC-like cells in BLBC resemble bona-fide multi-potent embryonic mammary stem cells, and comprise a new and understudied cell type in cancer. Cells with similar stem-like attributes have been described in diverse solid tumors, indicating that findings from these studies will likely have general relevance for cancer biology.