Adipocyte-derived collagen VI affects early mammary tumor progression in vivo, demonstrating a critical interaction in the tumor/stroma microenvironment
J. Clin. Invest. Puneeth Iyengar, et al. 115:1163 doi:10.1172/JCI23424 [Go to this article.]

Figure 3
Collagen VI stabilizes β-catenin and cyclin D1. (A) Dose response to increasing concentrations of collagen VI protein. A Tcf/Lef luciferase reporter construct was transfected into MCF-7 cells. Collagen VI treatment was for 3 hours. (B) Collagen VI–mediated Tcf/Lef induction. Luciferase activity was analyzed after treatment with vehicle, collagen VI (30 μg/ml), or collagen I (30 μg/ml) for 3 hours. (C) Time course of induction of Tcf/Lef activity. Luciferase activity was analyzed at different time points after treatment with 30 μg/ml collagen VI. (D) β-Catenin stability after collagen exposure. MCF-7 cells were metabolically labeled and then chased in the presence of cycloheximide for 30 minutes, 1 hour, and 2 hours. The chase medium contained vehicle, collagen VI (30 μg/ml), or collagen I (30 μg/ml). β-Catenin and GDI-3 were immunoprecipitated and quantitated. The ratio of β-catenin at 2 hours compared to 30 minutes was plotted as an indicator of β-catenin stability (3 independent experiments). No txt, no treatment. (E) Cyclin D1 stability after collagen exposure. MCF-7 cells were exposed for 3 hours to vehicle, human collagen VI (30 μg/ml), or collagen I (30 μg/ml). Cells were then lysed and analyzed for cyclin D1 by Western blot analysis. (F) Collagen VI acts in part through NG2 in MCF-7 cells to stabilize cyclin D1. In the presence of increasing amounts of NG2 neutralizing antibody in the medium (+, 0.15 μg/ml; ++, 0.45 μg/ml; +++, 0.75 μg/ml; ++++, 1 μg/ml), cyclin D1 levels decrease in a dose-dependent manner. Results are shown as mean ± SEM. *P < 0.05.