昼夜节律是生物体内具有自我调节功能、与日夜交替同步的以 24 小时为周期的一种生理节律系统，受生物钟基 因调控。生物钟基因在分子水平协调表达，控制和调节睡眠、觉醒、代谢、内分泌、细胞增殖分裂和凋亡以及免疫等各个 方面，使细胞、组织和器官的生命活动能够有序、协同，并呈现明显的昼夜节律。肿瘤发生的根本原因是机体在基因水平 上失去了对细胞生长的正常调控作用。昼夜节律与肿瘤之间的关系日益受到重视。通过对人体及动物的流行病学研究发现， 昼夜节律紊乱会增加包括乳腺癌、卵巢癌、肺癌、胰腺癌、前列腺癌、结直肠癌、子宫内膜癌、非霍奇金淋巴瘤、骨肉瘤、 白血病、头颈部鳞癌和肝癌等在内的常见恶性肿瘤发生几率。代谢节律紊乱会促进肿瘤的发展，并与抗肿瘤治疗的不良预 后及过早死亡相关。生物钟基因通过调控原癌基因、抑癌基因以及转录因子的表达，使其在肿瘤发生、发展和抑制方面发 挥直接或间接的作用。昼夜节律对肿瘤的发生、抑制相关作用的分子机制还有待于进一步的研究。生物钟基因与细胞周期 关系的阐明或许有助于我们更全面的了解肿瘤的发生、发展和散播转移机制，并可将其应用在肿瘤相关的治疗中以提高治 疗效果，在临床肿瘤的诊断、治疗及预后方面提供重要依据，具备良好的临床应用前景。

Circadian rhythm, regulated by clock control genes, is a sort of biological rhythm system which possess selfregulating function and accompany with day and night repeat on a near 24-hour basis. Circadian clock genes can control and regulate sleep, wake up, metabolism, endocrine, immune, cell proliferation and apoptosis in the molecular level, to make vital movement in tissues and cells cooperatively and orderly, as well as present distinct circadian rhythms. Organism lost regulating effect on cell growth in genetic level is the primary cause of cancer. The relationship between circadian rhythms and cancer is taken seriously recently. Epidemiologic studies in humans and animal models have revealed that development of common types of cancer such as breast cancer, ovarian cancer, lung cancer, pancreatic cancer, prostate cancer, colorectal cancer, endometrial cancer, non-hodgkin's lymphoma, osteosarcoma, leukemia, head and neck squamous carcinoma and liver cancer in vivo is closely associated with the loss of circadian homeostasis. Circadian clock genes can directly or indirectly affect oncogenesis, cancer progression, and suppression by regulate expression of tumor suppressor gene and oncogene and transcription factor. Further study on molecular mechanism between circadian rhythm and cancer development and suppression is necessary. To illustrate the relationship between circadian clock genes and cell cycle will help us understand the mechanism of tumorigenesis, transfer and spread, which will improve the clinical outcome, and provide important basis on clinical cancer diagnose, treatment and prognosis.