Chemoresistance remains a major obstacle to successful cancer treatment and leads to poor prognosis of the patients, yet the underlying mechanisms have not been fully understood. MicroRNAs (miRNAs) are non-coding small RNAs of 19-22 nucleotides which could negatively regulate gene expressions mainly through 3'-untranslated region (3'UTR) binding of target mRNAs. MiR-200 family (miR-200a, miR-200b, miR-200c, miR-141, and miR-429) is a cluster of miRNAs highly correlated with epithelial-mesenchymal transition (EMT), wherein miR-200b is identified as a critical regulator of tumor invasion, metastasis, and chemosensitivity. Recent advances of miR-200b dysregulation in tumor chemoresistance were summarized. Possible mechanisms and reversion strategies were also addressed.
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