Department of Physiology and Pathophysiology, School of Basic Medical Sciences, Fudan University, Shanghai, 200032, China.
Department of Surgery, Huashan Hospital, Fudan University, Shanghai, 200040, China.
Mol Biol Rep. 2022 Jan;49(1):373-384. doi: 10.1007/s11033-021-06883-z. Epub 2021 Nov 2.
To adapt to daily changes in the external environment, organisms have developed circadian rhythm systems with a period of approximately 24 h. Many studies have reported that both circadian rhythms and exosomes play important roles in the development and metastasis of tumors. However, whether circadian clock genes can affect the progression of tumors by regulating exosomes remains unclear.
In this study, we isolated exosomes from the supernatant of human colorectal cancer (CRC) cells, including SW480, SW620, and HCT116 cells, by differential centrifugation and characterized exosomes by transmission electron microscopy, nanoparticle tracking analysis, and Western blot analysis. Then, we found that exosomes derived from SW480, SW620 and HCT116 cells could promote the migration of HCT116 and human umbilical vein endothelial cells. Exosomes derived from SW620 cells showed increased stimulating effects when we increased the expression of BMAL1, a core circadian protein. In contrast, exosomes derived from SW480 and HCT116 cells showed decreased stimulating effects when we knocked down the expression of BMAL1. Furthermore, we discovered that BMAL1 promotes the release of exosomes by HCT116 and SW620 cells. In addition, by luciferase assay, we confirmed that BMAL1 transcriptionally regulates the expression of Rab27a, a key molecule related to the secretion of exosomes.
Our data reveal a new mechanism by which BMAL1 induces CRC metastasis by stimulating exosome secretion. This finding may help further clarify the role of circadian rhythm in the progression of CRC.
为了适应外部环境的日常变化，生物已经发展出了大约 24 小时周期的昼夜节律系统。许多研究报道称，昼夜节律和外泌体在肿瘤的发生和转移中都发挥着重要作用。然而，昼夜节律基因是否可以通过调节外泌体来影响肿瘤的进展尚不清楚。
在这项研究中，我们通过差速离心法从人结直肠癌细胞（包括 SW480、SW620 和 HCT116 细胞）的上清液中分离出外泌体，并通过透射电子显微镜、纳米颗粒跟踪分析和 Western blot 分析对其进行了表征。然后，我们发现 SW480、SW620 和 HCT116 细胞来源的外泌体可以促进 HCT116 和人脐静脉内皮细胞的迁移。当我们增加核心昼夜节律蛋白 BMAL1 的表达时，SW620 细胞来源的外泌体显示出增强的刺激作用。相比之下，当我们敲低 BMAL1 的表达时，SW480 和 HCT116 细胞来源的外泌体显示出减弱的刺激作用。此外，我们发现 BMAL1 通过 HCT116 和 SW620 细胞促进外泌体的释放。此外，通过荧光素酶测定，我们证实 BMAL1 转录调控与外泌体分泌相关的关键分子 Rab27a 的表达。
我们的数据揭示了一种新的机制，即 BMAL1 通过刺激外泌体的分泌来诱导 CRC 转移。这一发现可能有助于进一步阐明昼夜节律在 CRC 进展中的作用。
