Extrachromosomal circular DNA (eccDNA) refers to a type of circular DNA that originate from but are likely independent of chromosomes. Due to technological advancements, eccDNAs have recently emerged as multifunctional molecules with numerous characteristics. The unique topological structure and genetic characteristics of eccDNAs shed new light on the monitoring, early diagnosis, treatment, and prediction of cancer. EccDNAs are commonly observed in both normal and cancer cells and function via different mechanisms in the stress response to exogenous and endogenous stimuli, aging, and carcinogenesis and in drug resistance during cancer treatment. The structural diversity of eccDNAs contributes to the function and numerical diversity of eccDNAs and thereby endows eccDNAs with powerful roles in evolution and in cancer initiation and progression by driving genetic plasticity and heterogeneity from extrachromosomal sites, which has been an ignored function in evolution in recent decades. EccDNAs show great potential in cancer, and we summarize the features, biogenesis, evaluated functions, functional mechanisms, related methods, and clinical utility of eccDNAs with a focus on their role in evolution and cancer.

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小染色体外环状DNA（eccDNA）：进化和癌症的主要功能

染色体外环状 DNA (eccDNA) 是指一种环状 DNA，其起源于但可能独立于染色体。由于技术进步，eccDNAs 最近已成为具有众多特征的多功能分子。eccDNAs独特的拓扑结构和遗传特征为癌症的监测、早期诊断、治疗和预测提供了新的启示。EccDNAs 常见于正常细胞和癌细胞中，并通过不同的机制在对外源性和内源性刺激的应激反应、衰老和致癌作用以及癌症治疗期间的耐药性中发挥作用。eccDNAs 的结构多样性有助于 eccDNAs 的功能和数量多样性，从而通过驱动染色体外位点的遗传可塑性和异质性赋予 eccDNAs 在进化和癌症起始和进展中的强大作用，这在近几十年的进化中一直被忽视. EccDNAs 在癌症中显示出巨大的潜力，我们总结了 eccDNAs 的特征、生物发生、评估的功能、功能机制、相关方法和临床应用，重点介绍了它们在进化和癌症中的作用。