Objective:To explore the action and mechanisms of miR‐487a on the sensitivity of xenograft mice induced by MCF‐7/MX cells to MX .Methods :The xenograft mice were constructed by inoculating subcutane‐ously MCF‐7/MX cells into the flank of nude mice .The expression of miR‐487a and breast cancer resistance protein (BCRP) in xenograft tumors induced by MCF‐7/MX cells after injecting miR‐487a agmir were examined by real‐time RT‐PCR and Western blot analysis .The sensitivity of xenograft mice induced by MCF‐7/MX cells to MX was ana‐lyzed by observing the changes of the tumor weight .Results:The intratumoral injections of miR‐487a agmir induced the increases of miR‐487a by 7 fold ,decreased the mRNA and protein expression of BCRP by 30% ,and significantly reduced the tumor weight of the xenograft mice .Concluslon:miR‐487a can inhibit the expression of BCRP and in‐crease the sensitivity of xenograft mice induced by MCF‐7/MX cells to MX .%目的：研究miR‐487a调控米托蒽醌（MX）耐药的乳腺癌耐药细胞MCF‐7／MX荷瘤鼠对MX敏感性的作用与机制。方法：通过裸鼠腋窝皮下接种MCF‐7／MX细胞构建荷瘤鼠模型；real‐time RT‐PCR、Western blot方法检测荷瘤鼠瘤体内注射miR‐487a agmir后对移植瘤内miR‐487a及BCRP表达的影响；并通过对荷瘤鼠尾静脉注射 M X后移植瘤体积和瘤重的检测，研究miR‐487a对MCF‐7／MX荷瘤鼠药物敏感性的影响。结果：在MCF‐7／MX细胞荷瘤鼠瘤体内注射miR‐487a agmir诱导miR‐487a表达增高约7倍；降低了移植瘤内的BCRP的mRNA和蛋白表达约30％；且显著降低了MX处理的MCF‐7／MX细胞荷瘤鼠移植瘤的重量，即增加了对MX的敏感性。结论：miR‐487a抑制了MCF‐7／MX细胞荷瘤鼠的BCRP表达，增加其对米托蒽醌的敏感性。
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