| Breast cancer progression is a multiple-step process which results from complex signaling pathways associated with cell proliferation, cell survival, cell cycle regulation, apoptosis and epithelial-mesenchymal transition. The Ras, PI3K and Akt survival signaling pathway components are activated in the premalignant 10AT cells, and higher activation levels were observed in the CA1h and CA1a tumor cells. Ras levels were increased by 3.5-, 12.0-, and 9.8-fold in the 10AT, CA1h and CA1a cells, respectively, relative to the 10A cells. PI3K activity was elevated by 2.4- and 2.5-fold in the CA1h and CA1a cells, relative to 10A cells, respectively. CA1h and CA1a are having a low cell proliferation rate, resulting from the dysregulated cell cycle progression. CA1a cells are vulnerable to serum-starvation-induced apoptosis. E-cadherin, the epithelial marker of EMT, is decreased by &sim25.0% in the CA1a cells, whereas the mesenchymal marker vimentin levels increases by 1.8-, 1.9-, and 2.2-fold in the 10AT, CA1h and CA1a cells, respectively. These data suggest that differential alterations in signaling occur in Breast cancer progression is a multiple-step process which results from complex signaling pathways associated with cell proliferation, cell survival, cell cycle regulation, apoptosis and epithelial-mesenchymal transition. The Ras, PI3K and Akt survival signaling pathway components are activated in the premalignant 10AT cells, and higher activation levels were observed in the CA1h and CA1a tumor cells. Ras levels were increased by 3.5-, 12.0-, and 9.8-fold in the 10AT, CA1h and CA1a cells, respectively, relative to the 10A cells. PI3K activity was elevated by 2.4- and 2.5-fold in the CA1h and CA1a cells, relative to 10A cells, respectively. CA1h and CA1a are having a low cell proliferation rate, resulting from the dysregulated cell cycle progression. CA1a cells are vulnerable to serum-starvation-induced apoptosis. E-cadherin, the epithelial marker of EMT, is decreased by &sim25.0% in the CA1a cells, whereas the mesenchymal marker vimentin levels increases by 1.8-, 1.9-, and 2.2-fold in the 10AT, CA1h and CA1a cells, respectively. These data suggest that differential alterations in signaling occur in tumorigenesis and that tumor cells originating from the same progenitor cells exhibit differential and heterogeneous characteristics in key regulatory signaling components.TGF-beta is an inflammatory cytokine that has been demonstrated to be involved in breast cancer progression. Thus, the TGF-beta signaling in the MCF10A benign, premalignant and tumor human breast epithelial cell lineage has been examined. TGF-beta phosphorylates Smad2/3 equally in the 10A, 10AT, CA1h and CA1a cells. TGF-beta activation of Smad3 is mediated through TbetaRI. TGF-beta also activates PI3K/Akt/mTOR signaling pathway. TGF-beta increases PI3K activity by &sim2.3- and 2.5-fold in the 10A and 10AT cells, with no TGF-beta response in the CA1h and CA1a cells. TGF-beta increases Akt phosphorylation in the 10A and 10AT cells by &sim2.5- and 2.6-fold for Akt Ser473 and by &sim9.0- and 4.9-fold for Akt Thr308, respectively. TGF-beta increases mTOR phosphorylation by &sim2.3- and 2.4-fold in the 10A and 10AT cells, respectively. TGF-beta activation of PI3K, Akt and mTOR is mediated through Ras, rather than through TbetaRI. How TGF-beta activates Ras remains unclear. Interestingly, Ras is required for both the basal and TGF-beta-induced Smad3 phosphorylation through its downstream target mTOR, but not through PI3K or Akt.To get higher efficacy, combinational treatment is required. Thus, the combinational effects of Akt inhibitor and mTOR inhibitor on cell proliferation, survival and cell cycle have been examined. Akt inhibitor A-443654 induces apoptosis in a dose-dependent manner, with CA1a cells more sensitive than the 10A cells. Combination with rapamycin synergizes the apoptotic effects of A-443654, which results in increased efficacy in inducing apoptosis in CA1a cells, but are well-tolerated by the 10A cells. |
