PDF(Pubmed)
Abstract：
BACKGROUND: The aberrant amplification of mammary luminal progenitors is at the origin of basal-like breast cancers associated with BRCA1 mutations. Integrins mediate cell-matrix adhesion and transmit mechanical and chemical signals that drive epithelial stem cell functions and regulate tumor progression, metastatic reactivation, and resistance to targeted therapies. Consistently, we have recently shown that laminin-binding integrins are essential for the expansion and differentiation of mammary luminal progenitors in physiological conditions. As over-expression of the laminin-binding α6 integrin (Itgα6) is associated with poor prognosis and reduced survival in breast cancer, we here investigate the role of Itgα6 in mammary tumorigenesis.
METHODS: We used Blg-Cre; Brca1F/F; Trp53F/F mice, a model that phenocopies human basal-like breast cancer with BRCA1 mutations. We generated mutant mice proficient or deficient in Itgα6 expression and followed tumor formation. Mammary tumors and pretumoral tissues were characterized by immunohistochemistry, flow cytometry, RT-qPCR, Western blotting and organoid cultures. Clonogenicity of luminal progenitors from preneoplastic glands was studied in 3D Matrigel cultures.
RESULTS: We show that Itga6 deletion favors activation of p16 cell cycle inhibitor in the preneoplastic tissue. Subsequently, the amplification of luminal progenitors, the cell of origin of Brca1-deficient tumors, is restrained in Itgα6-deficient gland. In addition, the partial EMT program operating in Brca1/p53-deficient epithelium is attenuated in the absence of Itgα6. As a consequence of these events, mammary tumor formation is delayed in Itgα6-deficient mice. After tumor formation, the lack of Itgα6 does not affect tumor growth but rather alters their differentiation, resulting in reduced expression of basal cell markers.
CONCLUSIONS: Our data indicate that Itgα6 has a pro-tumorigenic role in Blg-Cre; Brca1F/F; Trp53F/F mice developing basal-like mammary tumors. In particular, we reveal that Itgα6 is required for the luminal progenitor expansion and the aberrant partial EMT program that precedes the formation of BRCA1 deficient tumors.
METHODS: We used Blg-Cre; Brca1F/F; Trp53F/F mice, a model that phenocopies human basal-like breast cancer with BRCA1 mutations. We generated mutant mice proficient or deficient in Itgα6 expression and followed tumor formation. Mammary tumors and pretumoral tissues were characterized by immunohistochemistry, flow cytometry, RT-qPCR, Western blotting and organoid cultures. Clonogenicity of luminal progenitors from preneoplastic glands was studied in 3D Matrigel cultures.
RESULTS: We show that Itga6 deletion favors activation of p16 cell cycle inhibitor in the preneoplastic tissue. Subsequently, the amplification of luminal progenitors, the cell of origin of Brca1-deficient tumors, is restrained in Itgα6-deficient gland. In addition, the partial EMT program operating in Brca1/p53-deficient epithelium is attenuated in the absence of Itgα6. As a consequence of these events, mammary tumor formation is delayed in Itgα6-deficient mice. After tumor formation, the lack of Itgα6 does not affect tumor growth but rather alters their differentiation, resulting in reduced expression of basal cell markers.
CONCLUSIONS: Our data indicate that Itgα6 has a pro-tumorigenic role in Blg-Cre; Brca1F/F; Trp53F/F mice developing basal-like mammary tumors. In particular, we reveal that Itgα6 is required for the luminal progenitor expansion and the aberrant partial EMT program that precedes the formation of BRCA1 deficient tumors.
摘要：
背景：乳腺管腔祖细胞的异常扩增是与BRCA1突变相关的基底样乳腺癌的起源。整合素介导细胞-基质粘附，传递驱动上皮干细胞功能和调节肿瘤进展的机械和化学信号，转移再激活,以及对靶向治疗的抵抗力。始终如一，我们最近发现层粘连蛋白结合整合素对于生理条件下乳腺前体细胞的扩增和分化是必不可少的。由于层粘连蛋白结合α6整合素（Itgα6）的过表达与乳腺癌预后不良和生存率降低有关，我们在这里研究Itgα6在乳腺肿瘤发生中的作用。
方法：我们使用Blg-Cre;Brca1F/F;Trp53F/F小鼠，一种表型模拟具有BRCA1突变的人基底样乳腺癌的模型。我们产生了富含或缺乏Itgα6表达的突变小鼠，并跟踪肿瘤形成。乳腺肿瘤和肿瘤前组织通过免疫组织化学进行表征，流式细胞术,RT-qPCR,蛋白质印迹和类器官培养。在3DMatrigel培养物中研究了来自癌前腺体的腔祖细胞的克隆性。
结果：我们发现Itga6缺失有利于p16细胞周期抑制剂在肿瘤前组织中的激活。随后，腔祖细胞的扩增，Brca1缺陷肿瘤的起源细胞，被限制在缺乏Itgα6的腺体中。此外,在不存在Itgα6的情况下，在Brca1/p53缺陷上皮中操作的部分EMT程序减弱。由于这些事件,在缺乏Itgα6的小鼠中，乳腺肿瘤的形成被延迟。肿瘤形成后,缺乏Itgα6不影响肿瘤生长，而是改变其分化，导致基底细胞标志物的表达降低。
结论：我们的数据表明，Itgα6在Blg-Cre;Brca1F/F;Trp53F/F小鼠发展为基底样乳腺肿瘤中具有促肿瘤发生的作用。特别是,我们发现，在BRCA1缺陷型肿瘤形成之前，腔祖细胞扩张和异常部分EMT程序需要Itgα6。
方法：我们使用Blg-Cre;Brca1F/F;Trp53F/F小鼠，一种表型模拟具有BRCA1突变的人基底样乳腺癌的模型。我们产生了富含或缺乏Itgα6表达的突变小鼠，并跟踪肿瘤形成。乳腺肿瘤和肿瘤前组织通过免疫组织化学进行表征，流式细胞术,RT-qPCR,蛋白质印迹和类器官培养。在3DMatrigel培养物中研究了来自癌前腺体的腔祖细胞的克隆性。
结果：我们发现Itga6缺失有利于p16细胞周期抑制剂在肿瘤前组织中的激活。随后，腔祖细胞的扩增，Brca1缺陷肿瘤的起源细胞，被限制在缺乏Itgα6的腺体中。此外,在不存在Itgα6的情况下，在Brca1/p53缺陷上皮中操作的部分EMT程序减弱。由于这些事件,在缺乏Itgα6的小鼠中，乳腺肿瘤的形成被延迟。肿瘤形成后,缺乏Itgα6不影响肿瘤生长，而是改变其分化，导致基底细胞标志物的表达降低。
结论：我们的数据表明，Itgα6在Blg-Cre;Brca1F/F;Trp53F/F小鼠发展为基底样乳腺肿瘤中具有促肿瘤发生的作用。特别是,我们发现，在BRCA1缺陷型肿瘤形成之前，腔祖细胞扩张和异常部分EMT程序需要Itgα6。
