Maximal adamantyl-substituted retinoid-related molecule-induced apoptosis requires NF-B noncanonical and canonical pathway activation

Abstract

NF-B transcription factors have a critical role in regulating cell survival and apoptosis. We have previously shown that 4-(3-Cl-(1-adamantyl)-4- hydroxyphenyl)-3-chlorocinnamic acid (3-Cl-AHPC), an adamantyl-substituted retinoid molecule, induced apoptosis and required NF-B activation in prostate and breast carcinoma cells. Here, we show that 3-Cl-AHPC activated both IB kinase (IKK)α and IKKΒ with subsequent activation of the canonical and noncanonical NF-B pathways in the human breast carcinoma and leukemia cell lines. 3-Cl-AHPC-mediated activation of the NF-B canonical pathway occurred within 6 h, whereas maximal activation of the NF-B noncanonical pathway required 48 h. Knockout of IKKα or IKKΒ expression in mouse embryonic fibroblast cells and knockdown of IKKα or IKKΒ in MDA-MB-468 cells resulted in the inhibition of 3-Cl-AHPC-mediated apoptosis, indicating that activation of canonical and noncanonical pathways are required for maximal 3-Cl-AHPC-mediated apoptosis. 3-Cl-AHPC activation of the noncanonical pathway was preceded by caspase-mediated decrease in the E3-ligase c-IAP1 with subsequent stabilization of NF-B-inducing kinase (NIK) expression, increased binding of NIK by TRAF3, activation of IKKα, and the resultant increased levels of RelB and p52. Increased expression of c-IAP1 blocked 3-Cl-AHPC-mediated stabilization of NIK levels and 3-Cl-AHPC-mediated apoptosis. Cdc37 expression was required for activation of IKKα and IKKΒ by 3-Cl-AHPC. These findings suggest that NF-B pathways have an important role in 3-Cl-AHPC-mediated apoptosis. © 2011 Macmillan Publishers Limited All rights reserved.