NFKBIA deletion in triple-negative breast cancer.
1012 Background: While effective, target-directed therapies are available for ER-positive and HER2-amplified breast cancer, adjuvant therapeutic options for triple-negative breast cancer (TNBC) are limited in the absence of well-defined molecular targets. Constitutive activation of oncogenic nuclear factor kB (NFkB) has been associated with ER-negative or basal-like (BL) breast cancers, but the underlying mechanism of this activation remains undefined. We previously showed that deletion of the endogenous NFkB repressor gene NFKBIA associates with EGFR non-amplified glioblastoma multiforme and portends unfavorable clinical outcome (Bredel et al. NEJM 2011). Methods: We analyzed >5,000 human breast cancers for deletions, mutations and/or expression of NFKBIA. We studied tumor suppressor activity of NFKBIA and the effect of targeted NFkB inhibition in cell culture with various NFKBIA genotypes. We compared molecular results with outcomes of affected persons. Results: NFKBIA is often (10.8%) deleted but not mutated in breast cancer. NFKBIA deletions are significantly associated with TNBC (32.8%) and particularly frequent in the BL subtype (36.7%). Loss of NFKBIA exerts a haploinsufficient effect on NFKBIA expression and the transactivation of several NF-kB target genes with important roles in breast carcinogenesis. Restoration of NFKBIA expression or pharmacologic NFkB inhibition attenuates the malignant phenotype of cells cultured from TNBC with NFKBIA deletion. Deletion and low expression of NFKBIA are highly associated with unfavorable overall survival, independent of patient age, tumor stage, nodal status, and tumor subtype. Loss of NFKBIA expression portends significantly poorer disease-specific survival, recurrence-free survival, and distant metastasis-free survival. Moreover, NFKBIA expression is significantly associated with duration of metastasis-free survival in subgroups of patients with brain or lung metastases from breast cancer. Conclusions: NFKBIA is a new, prognostically relevant, molecular target in TNBC, which remains a clinically challenging subtype of breast cancer with limited treatment options.