Cripto‐1 overexpression leads to enhanced invasiveness and resistance to anoikis in human MCF‐7 breast cancer cells

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Abstract
Cripto‐1 (CR‐1) is an epidermal growth factor (EGF)‐CFC protein that has been shown to signal through nodal/Alk‐4, PI3K/Akt, and/or ras/raf/MEK/MAPK pathways in mammalian cells, and that is frequently expressed in human primary breast carcinomas. In the present study, the human estrogen receptor positive, MCF‐7 breast cancer cell line, that expresses low levels of endogenous CR‐1, was transfected with a CR‐1 expression vector. MCF‐7 CR‐1 cells expressed high levels of a 25 kDa recombinant CR‐1 protein that was not detected in MCF‐7 cells transfected with a control vector (MCF‐7 neo). Overexpression of CR‐1 did not induce an estrogen independent phenotype in MCF‐7 cells. In fact, MCF‐7 CR‐1 cells showed a response to exogenous estrogens that was similar to MCF‐7 neo cells, and failed to grow in immunosuppressed mice in absence of estrogen stimulation. However, MCF‐7 CR‐1 cells showed a rate of proliferation in serum free conditions, and an ability to form colonies in soft‐agar that were higher as compared with MCF‐7 neo cells. More importantly, overexpression of CR‐1 enhanced the resistance to anoikis and the invasion ability of MCF‐7 cells. MCF‐7 CR‐1 cells showed levels of activation of both Akt and Smad‐2 that were significantly higher as compared with MCF‐7 neo. These findings suggest that CR‐1 overexpression might be associated with the progression towards a more aggressive phenotype in breast carcinoma, through the activation of both Akt and Smad‐2 signalling pathways. J. Cell. Physiol. 198: 31–39, 2004.

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