Notch-1 associates with IKKα and regulates IKK activity in cervical cancer cells

Notch-1 inhibits apoptosis in some transformed cells through incompletely understood mechanisms. Notch-1 can increase nuclear factor-kappa B (NF-kappa B) activity through a variety of mechanisms. Overexpression of cleaved Notch-1 in T-cell acute lymphoblastic leukemia cells activates NF-kappa B via interaction with the I kappa B kinase (IKK) signalosome. Concomitant activation of the Notch and NF-kappa B pathways has been described in a large series of cervical cancer specimens. Here, we show that wild-type, spontaneously expressed Notch-1 stimulates NF-kappa B activity in CaSki cervical cancer cells by associating with the IKK signalosome through IKK alpha. A significant fraction of tumor necrosis factor (TNF)-alpha-stimulated I kappa B kinase activity in CaSki cells is Notch-1-dependent. In addition, Notch-1 is found in the nucleus in association with IKK alpha at IKK alpha-stimulated promoters and is required for association of IKK alpha with these promoters under basal and TNF-alpha-stimulated conditions. Notch-1-IKK alpha complexes are found in normal human keratinocytes as well, suggesting that IKK regulation is a physiological function of Notch-1. Both Notch-1 and IKK alpha knockdown sensitize CaSki cells to cisplatin-induced apoptosis to equivalent extents. Our data indicate that Notch-1 regulates NF-kappa B in cervical cancer cells at least in part via cytoplasmic and nuclear IKK-mediated pathways.