miR-23b and miR-27b are oncogenic microRNAs in breast cancer: evidence from a CRISPR/Cas9 deletion study

BMC Cancer. 2019 Jun 28;19(1):642. doi: 10.1186/s12885-019-5839-2.


Background: Altered expression of microRNAs (miRNAs) is known to contribute to cancer progression. miR-23b and miR-27b, encoded within the same miRNA cluster, are reported to have both tumor suppressive and oncogenic activity across human cancers, including breast cancer.

Methods: To clarify this dichotomous role in breast cancer, miR-23b and miR-27b were knocked out using CRISPR/Cas9 gene knockout technology, and the role of endogenous miR-23b and miR-27b was examined in a breast cancer model system in vitro and in vivo.

Results: Characterization of the knockout cells in vitro demonstrated that miR-23b and miR-27b are indeed oncogenic miRNAs in MCF7 breast cancer cells. miR-23b and miR-27b knockout reduced tumor growth in xenograft nude mice fed a standard diet, supporting their oncogenic role in vivo. However, when xenograft mice were provided a fish-oil diet, miR-27b depletion, but not miR-23b depletion, compromised fish-oil-induced suppression of xenograft growth, indicating a context-dependent nature of miR-27b oncogenic activity.

Conclusions: Our results demonstrate that miR-23b and miR-27b are primarily oncogenic in MCF7 breast cancer cells and that miR-27b may have tumor suppressive activity under certain circumstances.

Keywords: Breast cancer; CRISPR/Cas9; microRNA.

MeSH terms

  • Animals
  • Breast Neoplasms / diet therapy
  • Breast Neoplasms / genetics*
  • Breast Neoplasms / pathology
  • CRISPR-Cas Systems
  • Cell Movement
  • Cell Proliferation
  • Cell Survival / drug effects
  • Dietary Supplements
  • Female
  • Fish Oils / administration & dosage
  • Fish Oils / pharmacology
  • Gene Expression Regulation, Neoplastic
  • Gene Knockout Techniques
  • Humans
  • MCF-7 Cells
  • Mice, Nude
  • MicroRNAs / genetics*
  • Xenograft Model Antitumor Assays


  • Fish Oils
  • MIRN23a microRNA, human
  • MIRN27 microRNA, human
  • MicroRNAs