Notch-YAP正反馈调控乳腺癌细胞自我更新及肺转移的机制研究

Distant metastasis of breast cancer most commonly occurs in the lung. Our recent studies have found that the activation of Notch signaling could increase the expression of YAP, a key transcription factor in Hippo pathway, whereas the up-regulation of YAP could in turn facilitate Notch signaling activation, leading to a Notch-YAP positive feedback loop. Intriguingly, we found that during the Notch-YAP positive feedback, the capacity of breast cancer cells resisting bone morphogenetic protein (BMP4) in the lung microenvironment was enhanced, the expression of progenitor cell transcription factor (SOX4) was up-regulated and the incidence of lung metastasis increased in mice. Thus, we speculate that Notch-YAP positive feedback could relieve the inhibitory effect of tumor suppressor signal BMP on SOX4 in lung microenvironment to increase the expression of SOX4 to facilitate breast cancer cell self-renewal and therefore promotes lung metastasis. When Notch-YAP positive feedback entered the nucleus, it could accelerate breast cancer cell proliferation and enhance invasion ability. To test our hypothesis, clinical pathology informations, culture mode in vitro and nude mouse model would be designed and lots of technologies such as molecular biology technology, Laser capture microscopic cutting, Optical in vivo Imaging technology will be conducted. This study will help us to delineate the molecular mechanisms of Notch-YAP positive feedback in mediating breast cancer cell self - renewal and lung metastasis, and provide potential therapeutic targets.

乳腺癌远处转移最易发生于肺脏。课题组近期研究发现Notch信号通路的激活能够上调Hippo通路关键转录因子YAP表达，而YAP上调又能促进Notch通路活化，存在Notch-YAP正反馈，在这一正反馈过程中，乳腺癌细胞对抗肺脏微环境中骨成型蛋白BMP4能力增强，祖细胞转录因子SOX4表达增加，小鼠肺转移发生率增高。我们推测：Notch-YAP正反馈能够解除肺脏微环境中肿瘤抑制信号BMP4对SOX4的抑制作用，提高SOX4的表达，促进乳腺癌细胞自我更新，进而促进肺转移；Notch-YAP正反馈入核后促进乳腺癌细胞的增殖及侵袭。为证实该假说，我们将从临床病理、体外细胞培养、裸鼠乳腺癌原位及肺转移模型三个层次，采用分子生物学、显微切割捕获、动物活体成像，探究乳腺癌细胞Notch-YAP正反馈调控乳腺癌自我更新及肺转移的具体机制，从新角度阐明乳腺癌肺转移的机制并提供潜在治疗靶点。

Notch1和YAP1 / TAZ信号均与乳腺癌转移有关，但是，这两种信号通路如何相互作用以促进乳腺癌转移的分子机制仍知之甚少。在这里，我们检查了Notch1和YAP1 / TAZ信号之间的关系，发现Notch1与YAP1 / TAZ呈正相关。 N1ICD（Notch1细胞内结构域）的过表达抑制了β-TrCP介导的YAP1 / TAZ的降解。同时，上调的YAP1与TEAD家族结合以促进Notch配体JAG1表达，导致Notch1信号激活，这表明在乳腺癌中存在Notch1-YAP1阳性反馈环，该环促进乳腺癌细胞的迁移和转移。入侵。 Notch1与乳腺癌的肺转移高度相关，动物实验表明，Notch1-YAP1阳性反馈环促进了乳腺癌细胞的肺转移。此外，肺源性抗转移信号BMP4抑制了MDA-MB-231细胞的微球形成和干性标志物的表达，而Notch1-YAP1阳性反馈环可以逆转BMP4的抑制作用。我们的新数据表明，Notch1-YAP1阳性反馈环通过调节自我更新和抑制BMP4信号传导来促进乳腺癌的肺转移。