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.
CITATION STYLE
Hannafon, B. N., Cai, A., Calloway, C. L., Xu, Y. F., Zhang, R., Fung, K. M., & Ding, W. Q. (2019). MiR-23b and miR-27b are oncogenic microRNAs in breast cancer: Evidence from a CRISPR/Cas9 deletion study. BMC Cancer, 19(1). https://doi.org/10.1186/s12885-019-5839-2
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