雷帕霉素靶蛋白（mTOR）是乳腺癌细胞内最重要的自噬和周期调控通路之一，但其介导细胞自噬和周期进程之间的关系未见报道。本项目首次揭示mTOR抑制剂可通过自噬－溶酶体途径促进乳腺癌细胞Cyclin D1降解进而诱导G1期阻滞，后续拟在人源肿瘤异种移植瘤模型（PDTX）和类器官三维培养（3D-Organoid）的临床原代乳腺癌细胞中加以确证。Cyclin D1高表达为乳腺导管原位癌（DCIS）易发展为侵袭性乳腺癌的肿瘤标记。课题前期结果显示mTOR抑制剂可促进Cyclin D1蛋白由细胞核向细胞浆再分布，进而促进其在胞浆中降解。下一步拟探讨靶向mTOR信号通路干预Cyclin D1介导的乳房“癌前病变”的可能性。课题成果有助于揭示Cyclin D1调控新机制和研发mTOR抑制剂用于乳腺癌的早期治疗。

The mammalian target of rapamycin (mTOR) is known to be involved in regulation of autophagy and G1 cell cycle process. However, it remains unknown whether rapalog-induced autophagy plays a critical role in its regulation of cell cycle. We, for the first time, report that rapalog everolimus could stimulate autophagy-mediated Cyclin D1 degradation in breast cancer cells. Inhibiting mTOR with everolimus rapidly increased the degradation of Cyclin D1 in transformed human mammary epithelial cells, while 3-Methyladenine, a classic autophagy inhibitor, could attenuate everolimus-induced Cyclin D1 degradation. Moreover, other classic autophagy inhibitors including chloroquine and bafilomycin A1 could also attenuate everolimus-induced down-regulation of Cyclin D1 protein. Similarly, knockdown of autophagy related gene 7 (Atg-7) also repressed everolimus-triggered degradation of Cyclin D1. In addition, everolimus-induced autophagy occurred earlier than its induction of G1 arrest and blockade of autophagy attenuated everolimus-induced G1 cell cycle arrest. We also found that everolimus stimulated autophagy and decreased Cyclin D1 protein levels in explant human breast tissue. These data support the conclusion that the autophagy induced by rapalogs in human mammary epithelial cells appears to cause Cyclin D1 protein degradation resulting in G1 cell cycle arrest. ..We also found the increased levels and accumulation of Cyclin D1 in the nucleus in human breast cancer tissues compared to adjacent non-tumor tissues, while rapamycin induced nuclear export of Cyclin D1 and decreased Cyclin D1 levels in human breast tissues ex vivo, which is consistent with previous data that mTOR inhibitors triggered Cyclin D1 nuclear export, ubiquitination and degradation by the 26S proteasome. Cyclin D1 expression level also is also a candidate biological markers predictive of invasive recurrence in ductal carcinoma in situ (DCIS). Next, we investigate the role of Cyclin D1 in rapalogs-induced inhibition of DCIS progress to invasive breast cancer...Our findings contribute to our knowledge of the interplay between autophagy and cell cycle regulation mediated by mTOR signaling, Cyclin D1 regulation and DCIS therapy.