Increased expression of P-glycoprotein and doxorubicin chemoresistance of metastatic breast cancer is regulated by miR-298

Am J Pathol. 2012 Jun;180(6):2490-503. doi: 10.1016/j.ajpath.2012.02.024. Epub 2012 Apr 19.


MicroRNAs (miRNAs) are short, noncoding RNA molecules that regulate the expression of a number of genes involved in cancer; therefore, they offer great diagnostic and therapeutic targets. We have developed doxorubicin-resistant and -sensitive metastatic human breast cancer cell lines (MDA-MB-231) to study the chemoresistant mechanisms regulated by miRNAs. We found that doxorubicin localized exclusively to the cytoplasm and was unable to reach the nuclei of resistant tumor cells because of the increased nuclear expression of MDR1/P-glycoprotein (P-gp). An miRNA array between doxorubicin-sensitive and -resistant breast cancer cells showed that reduced expression of miR-298 in doxorubicin-resistant human breast cancer cells was associated with increased expression of P-gp. In a transient transfection experiment, miR-298 directly bound to the MDR1 3' untranslated region and regulated the expression of firefly luciferase reporter in a dose-dependent manner. Overexpression of miR-298 down-regulated P-gp expression, increasing nuclear accumulation of doxorubicin and cytotoxicity in doxorubicin-resistant breast cancer cells. Furthermore, down-regulation of miR-298 increased P-gp expression and induced doxorubicin resistance in sensitive breast cancer cells. In summary, these results suggest that miR-298 directly modulates P-gp expression and is associated with the chemoresistant mechanisms of metastatic human breast cancer. Therefore, miR-298 has diagnostic and therapeutic potential for predicting doxorubicin chemoresistance in human breast cancer.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • 3' Untranslated Regions / genetics
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / genetics
  • ATP Binding Cassette Transporter, Subfamily B, Member 1 / metabolism*
  • Antibiotics, Antineoplastic / pharmacology*
  • Biological Transport / drug effects
  • Breast Neoplasms / drug therapy
  • Breast Neoplasms / genetics
  • Breast Neoplasms / metabolism*
  • Cell Death / drug effects
  • Dose-Response Relationship, Drug
  • Down-Regulation / physiology
  • Doxorubicin / pharmacology*
  • Drug Resistance, Neoplasm / genetics
  • Drug Resistance, Neoplasm / physiology
  • Drug Screening Assays, Antitumor
  • Female
  • Gene Expression Regulation, Neoplastic / physiology
  • Humans
  • MicroRNAs / physiology*
  • Neoplasm Metastasis
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism
  • RNA, Neoplasm / physiology
  • Tumor Cells, Cultured / drug effects


  • 3' Untranslated Regions
  • ATP Binding Cassette Transporter, Subfamily B, Member 1
  • Antibiotics, Antineoplastic
  • MIRN298 microRNA, human
  • MicroRNAs
  • Neoplasm Proteins
  • RNA, Neoplasm
  • Doxorubicin