Detection of IKKε by immunohistochemistry in primary breast cancer: association with EGFR expression and absence of lymph node metastasis

IKKe is an oncogenic kinase that was found amplified and overexpressed in a substantial percentage of human breast cancer cell lines and primary tumors using genomic and gene expression analyses. Molecular studies have provided the rational for a key implication of IKKe in breast cancer cells proliferation and invasiveness through the phosphorylation of several substrates. Here, we performed immunohistochemical detection of IKKe expression on tissue microarrays constituted of 154 characterized human breast cancer tumors. We further determined the association with multiple clinicopathological parameters and 5-years overall, disease-free and distant disease free survival. We observed expression of IKKe in 60.4% of the breast cancer tumors. IKKe expression status showed no association with a panel of markers used for molecular classification of the tumors, including ER/PR/HER2 status, or with the molecular subtypes. However, IKKe expression was inversely associated with lymph node metastasis status (p = 0.0032). Additionally, we identified a novel association between IKKe and EGFR expression (p = 0.0011). The unexpected observation of an inverse association between IKKe and lymph node metastasis advocates for larger scale immunohistochemical profiling of primary breast tumors to clarify the role of IKKe in metastasis. This study suggests that breast cancer tumors expressing EGFR and IKKe may be potential targets for drugs aiming at inhibiting IKKe activity or expression.