环形RNA（circRNAs）是非编码RNA（ncRNAs）的最近子类之一，在基因表达调控中发挥关键功能，并在恶性肿瘤中包括乳腺癌（BC）中具有重要作用。本研究旨在评估hsa_circ_0001445和hsa_circ_0020397在BC中的表达和作用，以及在这些环境中环RNA/miRNA/mRNA的潜在相互作用。使用定量实时聚合酶链反应（qRT-PCR）对50例乳腺肿瘤和50例肿瘤旁正常组织中的hsa_circ_0001445和hsa_circ_0020397的表达进行了调查。最后，利用生物信息学分析揭示了hsa_circ_0001445、hsa_circ_0020397-miRNA-mRNA潜在的调控网络。与其正常对照组相比，恶性组织中hsa_circ_0001445的表达显著下调（P=0.020），而hsa_circ_0020397呈上调模式（P<0.001）。此外，观察到hsa_circ_0001445的高表达与避免染发（P=0.034）和正常体重指数（BMI）（P=0.016）有显著相关性，而hsa_circ_0020397的过度表达与缺乏维生素D摄入（P=0.039）有重要关联。另一方面，hsa_circ_0001445的低表达与月经初潮年龄˂14岁显著相关（P=0.027）。我们的研究还揭示了这两个环RNA在竞争性内源RNA（ceRNA）网络中具有调控关键mRNA和miRNA的潜力能力。研究表明，hsa_circ_0001445和hsa_circ_0020397在BC发展中可能通过吸附某些调控ceRNA网络的miRNAs发挥了两个相反的作用。然而，它们的分子相互作用需要通过进一步的功能研究进行验证。© 2022作者。本文为开放获取文章，根据创作共用协议（https://creativecommons.org/licenses/by/4.0）在任何媒介中允许无限制使用、分发和复制，前提是原始作品被正确引用。

Circular RNAs (circRNAs), one of the recent subclasses of non-coding RNAs (ncRNAs), show pivotal functions in regulation of gene expression and have significant roles in malignancies including breast cancer (BC). This study was aimed to assess the hsa_circ_0001445 and hsa_circ_0020397 expression and role in BC, as well as the potential circRNA/miRNA/mRNA crosstalk in these contexts.The expression of hsa_circ_0001445 and hsa_circ_0020397 in 50 breast tumors and 50 normal tissues adjacent to the tumors was investigated using quantitative real-time polymerase chain reaction (qRT-PCR). Finally, bioinformatics analyses were used to uncover hsa_circ_0001445, hsa_circ_0020397-miRNA-mRNA potential regulatory networks.The hsa_circ_0001445 expression was considerably downregulated in malignant tissues compared to their normal counterparts (P=0.020), while the hsa_circ_0020397 showed an upregulated pattern (P<0.001). Additionally, it was observed that the higher expression of hsa_circ_0001445 was associated with hair dye avoidance (P=0.034) and normal body mass index (BMI) (P=0.016) while hsa_circ_0020397 over-expression had an important association with a lack of vitamin D consumption (P=0.039). On the other hand, lower expression of hsa_circ_0001445 was significantly associated with age at menarche ˂14 years (P=0.027). Our study also revealed that the two circRNAs have potential ability to regulate key mRNAs and miRNAs in competing endogenous RNA (ceRNA) networks.It is suggested that hsa_circ_0001445 and hsa_circ_0020397 with two opposite roles may be involved in BC development through sponging some miRNAs regulating ceRNA networks. However, their molecular interactions should be validated by further functional studies.© 2022 The Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.