Cyclooxygenase-2 regulates TGF?-induced cancer stemness in triple-negative breast cancer.

ABSTRACT: Triple negative breast cancer (TNBC), an aggressive subtype of breast cancer, display poor prognosis and exhibit resistance to conventional therapies, partly due to an enrichment in breast cancer stem cells (BCSCs). Here, we investigated the role of the cyclooxygenase-2 (COX-2), a downstream target of TGF?, in regulating BCSCs in TNBC. Bioinformatics analysis revealed that COX-2 is highly expressed in TNBC and that its expression correlated with poor survival outcome in basal subtype of breast cancer. We also found TGF?-mediated COX-2 expression to be Smad3-dependent and to be required for BCSC self-renewal and expansion in TNBCs. Knocking down COX-2 expression strikingly blocked TGF?-induced tumorsphere formation and TGF?-induced enrichment of the two stem-like cell populations, CD24^lowCD44^high and ALDH+ BCSCs. Blocking COX-2 activity, using a pharmacological inhibitor also prevented TGF?-induced BCSC self-renewal. Moreover, we found COX-2 to be required for TGF?-induced expression of mesenchymal and basal breast cancer markers. In particular, we found that TGF?-induced expression of fibronectin plays a central role in TGF?-mediated breast cancer stemness. Together, our results describe a novel role for COX-2 in mediating the TGF? effects on BCSC properties and imply that targeting the COX-2 pathway may prove useful for the treatment of TNBC by eliminating BCSCs.

SUBMITTER: Tian J 

PROVIDER: S-EPMC5215509 | biostudies-literature | 2017 Jan

REPOSITORIES: biostudies-literature