cAMP stimulates expression of TGFβ receptor I (TβRI).

<p>(A) cAMP increases the expression of TβRI, but not of TβRII. Cells were treated as indicated in 2D or 3D cultures for 24 h and analyzed for the expression of TβRI, and TβRII by Q-RT-PCR. When transfected with Flag-Smad3 (Smad) or mock-transfected (Ctrl) cells were incubated overnight before forskolin or vector (mock) was added. (B) TβRI levels are higher in 3D-cultured compared to 2D-cultured cells. Cells were grown in 2D or 3D cultures for 24 h and analyzed for TβRI-RNA and TβRII-RNA levels. Each bar represents the mean value ± S.D. of three independent experiments. (C) cAMP-dependent induction of TβRI expression is rapid. Cells were incubated with forskolin (FSK) or mock-treated in 2D cultures for 3 or 6 h before RNA expression of TβRI was analyzed by Q-RT-PCR. (D) cAMP stimulates TβRI expression also in BT-20 and MCF-7 breast cancer cells. Cells were incubated with forskolin or mock-treated for 24 h and analyzed for TβRI expression by Q-RT-PCR. Each bar represents the mean value ± S.D. of three independent experiments. * p-value <0.05, *** p-value <0.005, **** p-value <0.001 (Student’s t-test).