NF-κB pathway inhibitors preferentially inhibit breast cancer stem-like cells

Abstract

Accumulating evidence indicates that breast cancer is caused by cancer stem cells and cure of breast cancer requires eradication of breast cancer stem cells. Previous studies with leukemia stem cells have shown that NF-κB pathway is important for leukemia stem cell survival. In this study, by using MCF7 sphere cells as model of breast cancer stem-like cells, we evaluated the effect of NF-κB pathway specific inhibitors on human breast cancer MCF7 sphere cells. Three inhibitors including parthenolide (PTL), pyrrolidinedithiocarbamate (PDTC) and its analog diethyldithiocarbamate (DETC) were found to preferentially inhibit MCF7 sphere cell proliferation. These compounds also showed preferential inhibition in term of proliferation and colony formation on MCF7 side population (SP) cells, a small fraction of MCF7 cells known to enrich in breast cancer stem-like cells. The preferential inhibition effect of these compounds was due to inhibition of the NF-κB activity in both MCF7 sphere and MCF7 cells, with higher inhibition effect on MCF7 sphere cells than on MCF7 cells. PDTC was further evaluated in vivo and showed significant tumor growth inhibition alone but had better tumor growth inhibition in combination with paclitaxel in the mouse xenograft model than either PDTC or paclitaxel alone. This study suggests that breast cancer stem-like cells could be selectively inhibited by targeting signaling pathways important for breast cancer stem-like cells.

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).…”

“…5,12,34 Here, we found that in breast CAF and in normal mammary gland fibroblasts (NF), NRs agonists downregulate NF-kBLuc and IL6Luc promoter activity (Figure 4a). In CAF, NRs agonists reduce the expression of a variety of inflammatory cytokines that promote MS formation, [5][6][7][8][9][10][11][12] namely IL6, IL8 and TNFa (Figure 4b). We then observed that supernatants of CAF treated with NRs agonists disclose a reduced capability to sustain MCF7-MS formation compared with controls ( Figure 4c).…”

“…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.…”

Sox2 expression in breast tumours and activation in breast cancer stem cells

“…This assay is used as a stem-like functional assay that allows the propagation of mammary epithelial and breast tumour cells in an undifferentiated state based on their ability to proliferate in suspension (Dontu et al, 2003;Ponti et al, 2005;Farnie et al, 2007) and has been used for cancer stem-like specific drug screening in MCF7 cells (Zhou et al, 2007;Ao et al, 2011). We did observe induction of Sox2 expression in mammospheres obtained from human breast tumour cell cultures, and from MCF7 and T47D cells.…”