Fig. 3

Her2 overexpression inhibits let-7f via constitutive activation of ERK. a, The expression of let-7f in MCF-7 and MCF-7/Her2 cells was detected by real-time RT-PCR. b and c, The expression of Her2, β2-AR, and phosphorylated ERK in MCF-7 and SKBR3 cells was analyzed by Western blot (b) and the level of let-7f was detected by real-time RT-PCR (c). d and e, SKBR3 cells were transfected with the siRNA targeting Her2. The expression of Her2, β2-AR, and phosphorylated ERK was analyzed by Western blot (d) and the level of let-7f was detected by real-time RT-PCR (e). f, MCF-7/Her2 cells were pre-treated with 25 μM PD98059 or DMSO (as a solvent control) for 24 h and the expression of let-7f was analyzed. g and h, MCF-7/Her2 cells were pre-treated with 1 μM PD184352 (g) or 0.5 μM GDC0941 (h) for 2 h. The levels of phosphorylated ERK and AKT were analyzed by Western blot and the expression of let-7f was detected by real-time RT-PCR. i, MCF-7/Her2 cells were treated with 2.5 μM ISO and the expression of let-7f was analyzed by real-time RT-PCR. These experiments were repeated at least twice. *P < 0.05; **P < 0.01