The antiapoptotic effect of fibroblast growth factor-2 is mediated through nuclear factor-κB activation induced via interaction between Akt and IκB kinase-β in breast cancer cells

Fibroblast growth factor-2 (FGF-2) is known for its mitogenic and motogenic effects on breast cancer cells. Here, we demonstrate that FGF-2 is also a potent stimulator of breast cancer cell survival, as it counteracts the apoptotic activity of the C2 ceramide analogue and various chemotherapeutic agents (5-fluorouracil, camptothecin, etoposide) in MCF-7, T47-D and BT-20 cells. The use of pharmacological inhibitors (PD98059, wortmannin, LY294002, SN50) and transfection with negative dominants (IκBm, p110(PI3K (phosphoinositide 3-kinase))*ΔK, AktND) or small interfering RNA targeted against Akt indicated that PI3K/Akt and nuclear factor-κB (NF-κB), but not p42/p44 MAP-kinases, were required to stimulate FGF-2 antiapoptotic activity. The activation of NF-κB was dependent on PI3K/Akt, and using a combination of approaches based on immunoprecipitation, Western blotting and proteomics (two-dimensional electrophoresis and mass spectrometry), we identified the beta form of IκB kinase (IKKβ) as a target of Akt signaling. The selective disruption of IKKβ using small interfering RNA induced a potent inhibition of Akt-mediated activation of NF-κB and cell survival, indicating the functional involvement of IKKβ in FGF-2 antiapoptotic signaling. Together, these results demonstrate Akt/IKKβ interaction in NF-κB pathways, thereby emphasizing the potential of these proteins as therapeutic targets in breast cancer.