NF-κB-dependent Transcriptional Activation in Lung Carcinoma Cells by Farnesol Involves p65/RelA(Ser276) Phosphorylation via the MEK-MSK1 Signaling Pathway

Abstract

In this study, we demonstrate that treatment of human lung adenocarcinoma H460 cells with farnesol induces the expression of a number of immune response and inflammatory genes, including IL-6, CXCL3, IL-1alpha, and COX-2. This response was dependent on the activation of the NF-kappaB signaling pathway. Farnesol treatment reduces the level of IkappaBalpha and induces translocation of p65/RelA to the nucleus, its phosphorylation at Ser(276), and transactivation of NF-kappaB-dependent transcription. Moreover, overexpression of IkappaBalpha or treatment with the NF-kappaB inhibitor caffeic acid phenethyl ester greatly diminishes the induction of inflammatory gene expression by farnesol. We provide evidence indicating that the farnesol-induced phosphorylation of p65/RelA at Ser(276) is important for optimal transcriptional activity of NF-kappaB. The MEK1/2 inhibitor U0126 and knockdown of MEK1/2 expression with small interfering RNAs effectively blocked the phosphorylation of p65/RelA(Ser(276)) but not that of Ser(536), suggesting that this phosphorylation is dependent on the activation of the MEK1/2-ERK1/2 pathway. We further show that inhibition of MSK1, a kinase acting downstream of MEK1/2-ERK1/2, by H89 or knockdown of MSK1 expression also inhibited phosphorylation of p65/RelA(Ser(276)), suggesting that this phosphorylation is dependent on MSK1. Knockdown of MEK1/2 or MSK1 expression inhibits farnesol-induced expression of CXCL3, IL-1alpha, and COX-2 mRNA. Our results indicate that the induction of inflammatory genes by farnesol is mediated by the activation of the NF-kappaB pathway and involves MEK1/2-ERK1/2-MSK1-dependent phosphorylation of p65/RelA(Ser(276)). The activation of the NF-kappaB pathway by farnesol might be part of a prosurvival response during farnesol-induced ER stress.