Akt-dependent NF-κB activation is required for bile acids to rescue colon cancer cells from stress-induced apoptosis

J Shant, K Cheng, BS Marasa, JY Wang… - Experimental cell …, 2009 - Elsevier
J Shant, K Cheng, BS Marasa, JY Wang, JP Raufman
Experimental cell research, 2009Elsevier
Conjugated secondary bile acids promote human colon cancer cell proliferation by
activating EGF receptors (EGFR). We hypothesized that bile acid-induced EGFR activation
also mediates cell survival by downstream Akt-regulated activation of NF-κB.
Deoxycholyltaurine (DCT) treatment attenuated TNF-α-induced colon cancer cell apoptosis,
and stimulated rapid and sustained NF-κB nuclear translocation and transcriptional activity
(detected by NF-κB binding to an oligonucleotide consensus sequence and by activation of …
Conjugated secondary bile acids promote human colon cancer cell proliferation by activating EGF receptors (EGFR). We hypothesized that bile acid-induced EGFR activation also mediates cell survival by downstream Akt-regulated activation of NF-κB. Deoxycholyltaurine (DCT) treatment attenuated TNF-α-induced colon cancer cell apoptosis, and stimulated rapid and sustained NF-κB nuclear translocation and transcriptional activity (detected by NF-κB binding to an oligonucleotide consensus sequence and by activation of luciferase reporter gene constructs). Both DCT-induced NF-κB nuclear translocation and attenuation of TNF-α-stimulated apoptosis were dependent on EGFR activation. Inhibitors of nuclear translocation, proteosome activity, and IκBα kinase attenuated NF-κB transcriptional activity. Cell transfection with adenoviral vectors encoding a non-degradable IκBα ‘super-repressor’ blocked the actions of DCT on both NF-κB activation and TNF-α-induced apoptosis. Likewise, transfection with mutant akt and treatment with a chemical inhibitor of Akt attenuated effects of DCT on NF-κB transcriptional activity and TNF-α-induced apoptosis. Chemical inhibitors of Akt and NF-κB activation also attenuated DCT-induced rescue of H508 cells from ultraviolet radiation-induced apoptosis. Collectively, these observations indicate that, downstream of EGFR, bile acid-induced colon cancer cell survival is mediated by Akt-dependent NF-κB activation. These findings provide a mechanism whereby bile acids increase resistance of colon cancer to chemotherapy and radiation.
Elsevier