1] Division of Toxicology, Leiden/Amsterdam Center for Drug Research, Leiden University, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands [2] Division of Molecular Pathology, Netherlands Cancer Institute, 1066 CX Amsterdam, The Netherlands.
Division of Toxicology, Leiden/Amsterdam Center for Drug Research, Leiden University, Einsteinweg 55, P.O. Box 9502, 2300 RA Leiden, The Netherlands.
Br J Cancer. 2014 May 27;110(11):2747-55. doi: 10.1038/bjc.2014.219. Epub 2014 May 8.
Elevated expression of focal adhesion kinase (FAK) occurs in numerous human cancers including colon-, cervix- and breast cancer. Although several studies have implicated FAK in mammary tumour formation induced by ectopic oncogene expression, evidence supporting a role for FAK in spontaneous mammary tumour development caused by loss of tumour suppressor genes such as p53 is lacking. Alterations in the tumour suppressor gene p53 have been implicated in over 50% of human breast cancers. Given that elevated FAK expression highly correlates with p53 mutation status in human breast cancer, we set out to investigate the importance of FAK in p53-mediated spontaneous mammary tumour development.
To directly assess the role of FAK, we generated mice with conditional inactivation of FAK and p53. We generated female p53(lox/lox)/FAK(+/+)/WapCre, p53(lox/lox)/FAK(flox/+)/WapCre and p53(lox/lox)/FAK(flox/-)/WapCre mice, and mice with WapCre-mediated conditional expression of p53(R270H), the mouse equivalent of human p53(R273H) hot spot mutation, together with conditional deletion of FAK, P53(R270H/+)/FAK(lox/+)/WapCre and p53(R270H/+)/FAK(flox/-)/WapCre mice. All mice were subjected to one pregnancy to induce WapCre-mediated deletion of p53 or expression of p53 R270H, and Fak genes flanked by two loxP sites, and subsequently followed the development of mammary tumours.
Using this approach, we show that FAK is important for p53-induced mammary tumour development. In addition, mice with the mammary gland-specific conditional expression of p53 point mutation R270H, the mouse equivalent to human R273H, in combination with conditional deletion of Fak showed reduced incidence of p53(R270H)-induced mammary tumours. In both models these effects of FAK were related to reduced proliferation in preneoplastic lesions in the mammary gland ductal structures.
Mammary gland-specific ablation of FAK hampers p53-regulated spontaneous mammary tumour formation. Focal adhesion kinase deletion reduced proliferative capacity of p53 null and p53(R270H) mammary epithelial cells but did not lead to increased apoptosis in vivo. Our data identify FAK as an important regulator in mammary epithelial cell proliferation in p53-mediated and p53(R270H)-induced mammary tumour development.
黏着斑激酶（FAK）在包括结肠癌、宫颈癌和乳腺癌在内的多种人类癌症中表达升高。尽管有几项研究表明 FAK 在异位致癌基因表达诱导的乳腺肿瘤形成中起作用，但缺乏证据支持 FAK 在 p53 等肿瘤抑制基因缺失引起的自发性乳腺肿瘤发展中的作用。抑癌基因 p53 的改变与超过 50%的人类乳腺癌有关。鉴于 FAK 表达水平的升高与人类乳腺癌中 p53 突变状态高度相关，我们着手研究 FAK 在 p53 介导的自发性乳腺肿瘤发展中的重要性。
为了直接评估 FAK 的作用，我们生成了条件性失活 FAK 和 p53 的小鼠。我们生成了 p53(lox/lox)/FAK(+/+)/WapCre、p53(lox/lox)/FAK(flox/+)/WapCre 和 p53(lox/lox)/FAK(flox/-)/WapCre 小鼠，以及 WapCre 介导的条件性表达 p53(R270H)的小鼠，p53(R270H)是人类 p53(R273H)热点突变的小鼠等效物，同时条件性删除 FAK，生成 p53(R270H/+)/FAK(lox/+)/WapCre 和 p53(R270H/+)/FAK(flox/-)/WapCre 小鼠。所有小鼠均进行一次妊娠，以诱导 WapCre 介导的 p53 缺失或 p53 R270H 的表达，以及 Fak 基因被两个 loxP 位点包围，并随后观察乳腺肿瘤的发展。
通过这种方法，我们表明 FAK 对 p53 诱导的乳腺肿瘤发展很重要。此外，在乳腺组织中特异性表达 p53 点突变 R270H 的小鼠中，该突变与人类 R273H 相对应，同时条件性缺失 Fak 后，p53(R270H)诱导的乳腺肿瘤的发生率降低。在这两种模型中，FAK 的这些作用与乳腺导管结构中前瘤病变的增殖减少有关。
乳腺组织特异性 FAK 缺失可阻碍 p53 调节的自发性乳腺肿瘤形成。FAK 缺失降低了 p53 缺失和 p53(R270H)乳腺上皮细胞的增殖能力，但在体内并未导致细胞凋亡增加。我们的数据将 FAK 确定为 p53 介导和 p53(R270H)诱导的乳腺肿瘤发展中乳腺上皮细胞增殖的重要调节因子。
