Interaction of aryl hydrocarbon receptor and NF-κB subunit RelB in breast cancer is associated with interleukin-8 overexpression
Highlights
► AhR interacts with RelB in breast cancer. ► Overexpression of IL-8 in breast cancer is associated with AhR and RelB function. ► AhR and RelB mediate anti-apoptotic response.
Introduction
Recent reports have shown that the development of certain types of breast tumor is associated with inflammation and an inappropriate production of chemokines especially IL-8, which appears to be a critical phase in breast tumor metastasis [1], [2], [3]. Previous reports from our own group have demonstrated the critical role of the AhR in the transcriptional induction of IL-8 mediated by an activated AhR [4]. Interestingly, it was reported initially by David H. Sherr’s group that high levels of AhR expression is detected in chemical-induced mammary tumors in vivo in rats [5] as well as in several mouse and human cell lines exhibiting malignant phenotypes [6]. It was pointed out by the same group of scientists [7] that there is likelihood of the AhR contributing greatly to ongoing mammary tumor cell growth and apoptosis resistance while promoting transition to an invasive, metastatic phenotype in these cases. The above observations at the same time have raised some important questions: how does the overexpressed AhR contributes to those cellular changes, even in the absence of its ligands, how it coordinates its actions with signaling of growth factors and hormones, how it causes inflammatory responses in those cells, and how it contributes to malignant progression of those cells? Meanwhile there have been a number of recent discoveries regarding the physiological roles of the AhR itself (i.e. its natural biological activities that is not induced by exogenous ligands) mostly based on studies on AhR knockout mice [8], [9], [10] as well as the roles of AhR as one of the major coordinators of cellular stress responses, particularly inflammatory responses [11]. The role of AhR as a pro-survival factor conferring cells to acquire apoptosis resistance, even in the absence of any exogenously ligand of this receptor, has been reported in an ERα-negative MCF10AT1 breast cancer cells from our group [12]. These recent developments point to the possibility that the overexpression and activation of the AhR could play an important role in aiding the process of malignant transformation of those transformed mammary epithelial cells.
Despite the clear-cut demonstration of overexpression of AhR in DMBA-induced breast tumors in rats and mice, and a number of established human breast cancer cell lines [5], [6], data about a possible role of AhR in human primary breast tumor samples are scarce. Accordingly the major objective of this study has been to identify the type of breast tumors that overexpresses AhR as well as RelB and to gain insight into the mechanism of the AhR-dependent progression of those mammary epithelial cells leading to overexpression of IL-8 and the malignant phenotype.
Section snippets
Reagents and antibodies
Dimethylsulfoxide (Me2SO) and phorbol-12-myristate-13-acetate (TPA) were obtained from SIGMA (St. Louis, MO). [y-32P] ATP (6000 Ci/mmol) was purchased from ICN (Costa Mesa, CA). TCDD (>99% purity) was originally obtained from Dow Chemicals Co. (Midland, MI). Other molecular biological reagents were purchased from Qiagen (Valencia, CA) and Roche (Indianapolis, IN). Polyclonal RelA, CEBPβ (Santa Cruz Biotechnology, Santa Cruz, CA), NF-κB member RelB, p50 (Active Motif, Carlsbad, CA) and polyclonal
Western blot analysis of AhR and RelB in primary breast tissues
To analyze the expression level of AhR and RelB in primary breast tissue we performed Western blot analysis with whole cell protein from 6 pairs of breast tumor samples from the genotype of ERα-negative and ERα-positive samples. For this purpose we compared their protein expression of AhR and RelB in both the tumor sample (designated by T) and the matched normal breast tissue samples (designated as N) from each patient (Fig. 1A). A relatively high level of RelB and AhR protein was found in
Discussion
The initial observation that the AhR and RelB overexpressing breast tumors are found mainly among the ERα-negative type of tumors has already provided an important clue. A literature search for a similar sub-type of breast cancer overexpressing RelB showed that the case of inflammatory breast cancers [21] appears to fit best to this sub-type. In that work it has been demonstrated that overexpression of RelB and translocation of RelB into the nucleus of inflammatory breast cancer cases are found
Source of funding
This study has been supported by Research Grant FAS0703859 from the Susan G. Komen Foundation for the Cure, American Heart Association Western Affiliate 0765056Y and NIEHS Grant R21ES15846.
Conflict of interest statement
None declared.
Acknowledgments
We like to thank Laura Van Winkle and Jackie K. Chan (University of California Davis, CA) for technical assistance. We thank Ulrich Siebenlist (National Institute of Health, Bethesda, MD), David Sherr and Gail Sonenshein (Boston University, MA) for providing us with critical plasmids.
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2022, Seminars in Cancer BiologyCitation Excerpt :In that, it has been shown that activation of AhR by TCDD in human breast cancer cells, MCF-7 and MDA-MB-436, induced IL-8 expression and RelB resulting in decreased cell apoptosis and increased cell proliferation. This effect was further supported by activation of apoptosis in estrogen receptor α (ERα)-negative cell lines by the knockdown of AhR or RelB [96]. In human osteosarcoma MG-63 cell line, the activation of AhR by TCDD was associated with increased protein and mRNA levels of receptor activator of NF-κB ligand (RANKL) [97].