乳腺癌（BC）骨转移主要表现为破骨，治疗选择有限。转移的BC细胞通过形成肿瘤基质来促进骨骼中的次生环境，有利于它们的定居和殖民。肿瘤微环境（TME）主要由癌细胞产生。骨TME是由多个细胞（包括改变了的骨细胞、肿瘤细胞、基质细胞和免疫细胞）构成的复杂网络。最近的研究发现突显了在肿瘤转移中，小型非编码微RNA（miRNA）在影响TME方面的重要性。TME驻留细胞产生的miRNA促进肿瘤与其微环境之间的相互作用，从而调控肿瘤的生物学过程。这些miRNA可以作为癌基因或肿瘤抑制基因。因此，在调控肿瘤细胞和相关基质细胞的表型方面，miRNA抑制剂和模拟物广泛应用于临床前试验中。本综述简要总结了直接或间接从TME驻留细胞中分泌的miRNA在促进肿瘤生长、进展和转移方面的功能作用的最新进展。这些信息有助于开发乳腺癌的新型靶向治疗方法。© 2023. The Author(s), under exclusive licence to The Japanese Breast Cancer Society.

Breast cancer (BC) bone metastasis is primarily osteolytic and has limited therapeutic options. Metastasized BC cells prime the secondary environment in bone by forming a tumor niche, which favors their homing and colonization. The tumor microenvironment (TME) is primarily generated by the cancer cells. Bone TME is an intricate network of multiple cells, including altered bone, tumor, stromal, and immune cells. Recent findings highlight the significance of small non-coding microRNAs (miRNAs) in influencing TME during tumor metastasis. MiRNAs from TME-resident cells facilitate the interaction between the tumor and its microenvironment, thereby regulating the biological processes of tumors. These miRNAs can serve as oncogenes or tumor suppressors. Hence, both miRNA inhibitors and mimics are extensively utilized in pre-clinical trials for modulating the phenotypes of tumor cells and associated stromal cells. This review briefly summarizes the recent developments on the functional role of miRNAs secreted directly or indirectly from the TME-resident cells in facilitating tumor growth, progression, and metastasis. This information would be beneficial in developing novel targeted therapies for BC.© 2023. The Author(s), under exclusive licence to The Japanese Breast Cancer Society.