p66Shc/Notch-3 Interplay Controls Self-Renewal and Hypoxia Survival in Human Stem/Progenitor Cells of the Mammary Gland Expanded In Vitro as Mammospheres

Abstract

The comprehension of the basic biology of stem cells is expected to provide a useful insight into the pathogenesis of cancer. In particular, there is evidence that hypoxia promotes stem cell renewal in vitro as well as in vivo. It therefore seems reasonable that stem cell survival and hypoxia response are strictly connected at molecular level. We here report that the 66-kDa isoform of the SHC gene (p66Shc) is induced in a breast cancer cell line by the exposure to hypoxic environment and that it controls the expression of the stem cell regulatory gene Notch-3. Then, we show that p66Shc/Notch-3 interplay modulates self-renewal (by inducing the Notch-ligand Jagged-1) and hypoxia survival (by inducing the hypoxia-survival gene carbonic anhydrase IX) in mammary gland stem/progenitor cells, expanded in vitro as multicellular spheroids (mammospheres). We conclude that mechanisms that regulate stem cell renewal and hypoxia survival are integrated at the level of the p66Shc/Notch3 interplay. Because Notch-3, Jagged-1, and carbonic anhydrase IX are dysregulated in breast cancer, and because p66Shc is an aging-regulating gene, we envision that these data may help in understanding the relationship among aging, cancer, and stem cells. STEM CELLS 2007;25:807-815

JAG2 Induction in Hypoxic Tumor Cells Alters Notch Signaling and Enhances Endothelial Cell Tube Formation

“…Even though our results showed that JAG2 was responsible for a large fraction of the Notch activity under hypoxia, silencing of JAG2 did not result in complete inhibition of the hypoxic potentiation of Notch signaling. In light of the previous reports, the remaining elevation in Notch activity could be due to direct HIF-icN1 interactions or elevation of other Notch receptors (36).…”

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.…”

“…7 In MS, IL6 upregulates survival by promoting the Notch3/Jagged1 ligand/receptor system. 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.…”