TNFalpha up‐regulates SLUG via the NF‐kappaB/HIF1alpha axis, which imparts breast cancer cells with a stem cell‐like phenotype

Abstract

Extracellular and intracellular mediators of inflammation, such as Tumor Necrosis Factor alpha (TNFα) and NF-kappaB (NF-κB), play major roles in breast cancer pathogenesis, progression and relapse. SLUG, a mediator of the epithelial-mesenchymal transition process, is over-expressed in CD44 + /CD24 − tumor initiating breast cancer cells and in basal-like carcinoma, a subtype of aggressive breast cancer endowed with a stem cell-like gene expression profile. Cancer stem cells also over-express members of the pro-inflammatory NF-κB network, but their functional relationship with SLUG expression in breast cancer cells remains unclear. Here, we show that TNFα treatment of human breast cancer cells up-regulates SLUG with a dependency on canonical NF-κB/HIF1α signaling, which is strongly enhanced by p53 inactivation. Moreover, SLUG up-regulation engenders breast cancer cells with stem cell-like properties including enhanced expression of CD44 and Jagged-1 in conjunction with ERα down-regulation, growth as mammospheres and extracellular matrix invasiveness. Our results reveal a molecular mechanism whereby TNFα, a major proinflammatory cytokine, imparts breast cancer cells with stem cell-like features, which are connected to increased tumor aggressiveness.

Nuclear receptors agonists exert opposing effects on the inflammation dependent survival of breast cancer stem cells

“…Then, we tested the impact of the three NRs agonists on MS formation capability, which is currently considered the gold standard assay to assess the breast CSC phenotype in vitro. [6][7][8][9][10][11]33 We found that all the three NRs agonists reduce the number of MCF7-MS, but not of MCF10-MS with respect to control, and that IIF is the most active molecule (Figure 1c and Supplementary Figure 2a). Moreover, we compared the activity of NRs agonists on MS from tumor mammary gland (T-MS) and normal tissue samples (N-MS) ( Table 1 We finally proved that both in normoxia and hypoxia, NRs agonists induce cytotoxic effects in MS (Supplementary Figure 3a) and upregulate their cognate receptors (Supplementary Figure 3b).…”

“…This phenomenon is paralleled by the hampering of pro-inflammatory NF-kB/IL6 axis and associates with the downregulation of MS regulatory genes (SLUG, Notch3, Jagged1). 6,7,9,10 We also report that, at variance with the other NRs agonists, the PPARa specific agonist WY exerts a promoting role on MS formation and on the accompanying pro-inflammatory phenotype.…”

“…3 Cells disclosing a CSCs phenotype can be expanded in vitro as multicellular spheroids, named mammospheres (MS), obtained from breast cancer surgical specimens and cell lines. [6][7][8][9][10][11] The activity of nuclear factor-kB (NF-kB) pathway has been recognized to be of pivotal importance in MS survival. [8][9][10][11] In MS from aggressive breast cancer the over-expression of interleukin-6 (IL6), an NF-kB controlled gene, has been reported.…”

“…6,7 Besides IL6, other pro-inflammatory cytokines, such as interleukin-8 (IL8) were found to contribute to breast CSCs activity and survival. 5,12 According to these findings, tumor necrosis factor-a (TNFa), a major NF-kB inducer, was shown to enhance MS formation, 8,9 by upregulating SLUG, an NF-kB controlled regulator of the breast CSC phenotype. 9,10 In hematopoietic and prostate CSCs, NF-kB upregulation has been reported.…”

“…5,12 According to these findings, tumor necrosis factor-a (TNFa), a major NF-kB inducer, was shown to enhance MS formation, 8,9 by upregulating SLUG, an NF-kB controlled regulator of the breast CSC phenotype. 9,10 In hematopoietic and prostate CSCs, NF-kB upregulation has been reported. 13,14 A kind of 'NF-kB activity addiction' has been therefore proposed to likely render CSCs more susceptible to NF-kB inhibitors than their normal counterparts.…”