ABSTRACT
Breast cancer is a major disease which threatens the health of women around the world.Breast cancer patients have acquired resistance to existing treatment methods become the current clinical problems.MicroRNA(miRNA) is an endogenous non-coding RNA that participates in the regulation of a variety of biological processes,including cell proliferation,invasion,metastasis,epithelial interstitial transformation and drug resistance.Acquired resistance includes a variety of complex mechanisms that can affect the expression of cell-associated proteins through the abnormal expression of specific microRNAs,the binding of antineoplastic agents to the corresponding target,and the pathways associated with apoptosis.This article will focus on the expression of abnormal microRNA in acquired drug resistance which was caused by endocrine therapy,chemotherapy and molecular targeted therapy of breast cancer.miRNAs are considered as promising biomarkers and targets for diagnosis,treatments for acquired drug resistance of breast cancer.