Combined A20 and tripartite motif-containing 44 as poor prognostic factors for breast cancer patients of the Japanese population

We previously reported that a strong immunoreactivity of tripartite motif-containing 44 (TRIM44) predicts the poor prognosis of patients with invasive breast cancer, and proposed that TRIM44 activates nuclear factor-κB (NF-κB) signaling as a causative mechanism. In the present study, we examined the clinicopathological roles of A20, which is known to be an NF-κB responsive gene, with TRIM44, in an updated cohort. Tissue samples of invasive breast cancer were obtained from 140 Japanese female breast cancer patients who underwent surgical treatment. Immunoreactivities of A20 and TRIM44 were analyzed using specific antibodies for each protein. A positive A20 immunoreactivity was significantly associated with a shorter disease-free survival (P = 0.043) and was positively correlated with TRIM44 immunoreactivity (P = 0.039). Combined use of the immunoreactivities for two proteins revealed that double-positive status for both A20 and TRIM44 immunoreactivities was associated with a shorter disease-free survival (P = 0.012) and was an independent factor for poor prognosis. These results indicate that a combined A20 and TRIM44 immunoreactivity predicted the prognosis of patients with invasive breast cancer. Moreover, the positive correlation between A20 and TRIM44 immunoreactivities suggested that the activation of NF-κB signaling by TRIM44 could occur in clinical breast cancer tissues.

COUP-TFII inhibits NFkappaB activation in endocrine-resistant breast cancer cells

Reduced COUP-TFII expression contributes to endocrine resistance in breast cancer cells. Endocrine-resistant breast cancer cells have higher NFkappa B (NFκB) activity and target gene expression. The goal of this study was to determine if COUP-TFII modulates NFκB activity. Endocrine-resistant LCC9 cells with low endogenous COUP-TFII displayed ∼5-fold higher basal NFκB activity than parental endocrine-sensitive MCF-7 breast cancer cells. Transient transfection of LCC9 cells with COUP-TFII inhibited NFκB activation and reduced NFκB target gene expression. COUP-TFII and NFκB were inversely correlated in breast cancer patient samples. Endogenous COUP-TFII coimmunoprecipitated with NFκB subunits RelB and NFκB1 in MCF-7 cells. COUP-TFII inhibited NFκB-DNA binding in vitro and impaired coactivator induced NFκB transactivation. LCC9 cells were growth-inhibited by an NFκB inhibitor and 4-hydroxytamoxifen compared to MCF-7 cells. Together these data indicate a novel role for COUP-TFII in suppression of NFκB activity and explain, in part, why decreased COUP-TFII expression results in an endocrine-resistant phenotype.

Tuning NF-κB activity: a touch of COMMD proteins

NF-κB is an important regulator of immunity and inflammation, and its activation pathway has been studied extensively. The mechanisms that downregulate the activity of NF-κB have also received a lot of attention, particularly since its activity needs to be terminated to prevent chronic inflammation and subsequent tissue damage. The COMMD family has been identified as a new group of proteins involved in NF-κB termination. All ten COMMD members share the structurally conserved carboxy-terminal motif, the COMM domain, and are ubiquitously expressed. They seem to play distinct and non-redundant roles in various physiological processes, including NF-κB signaling. In this review, we describe the mechanisms and proteins involved in the termination of canonical NF-κB signaling, with a specific focus on the role of the COMMD family in the down-modulation of NF-κB.