Interleukin-8 Expression Is Regulated by Histone Deacetylases through the Nuclear Factor-κB Pathway in Breast Cancer

We have reported recently that the chemokine interleukin 8 (IL-8)/CXCL8 was overexpressed in invasive estrogen receptor (ER alpha)-negative breast cancer cells compared with ER alpha-positive breast cancer cells. We now demonstrate that histone deacetylases (HDACs) play an essential role in the regulation of IL-8 gene expression in ER alpha-positive MCF-7 breast cancer cells. Treatment of MCF-7 cells with the HDAC inhibitor trichostatin A (TSA) led to a strong up-regulation of IL-8 protein and RNA levels in MCF-7 cells. The up-regulation of IL-8 in MCF-7 cells was time- and concentration-dependent. Moreover, run-on and transfection experiments demonstrated that IL-8 induction by HDAC inhibitors was transcriptional and involved mainly the nuclear factor-kappa B (NF-kappa B) site of the IL-8 promoter. These observations are corroborated by an up-regulation of NF-kappa B activity in MCF-7 cells in the presence of TSA. In addition, blocking NF-kappa B pathway by adenoviral delivery of a dominant-negative I kappa B or I kappa B kinase complex 2 (IKK2) mutant abolished IL-8 gene induction by histone deacetylase inhibitors. HDAC inhibitors triggered IKK phosphorylation and up-regulated p65 nuclear translocation, although they decreased the protein levels of I kappa B alpha, which accounts for NF-kappa B activation. TSA increased binding of acetylated histone 3 to the IL-8 gene promoter. In summary, our results demonstrate that NF-kappa B pathway repression by HDAC is responsible for the low expression of IL-8 in ER alpha-positive breast cancer cells.