Abstract 943: RelA regulates CXCR5/CXCL13 transcription and associated immune response in breast cancer
Authors: Chowdhury Sougata Roy , Biswas Subir , Mandal Gunjan , Bhattacharyya Arindam 
Published: July 2017

Abstract
It is evident from research outcomes that metastases-associated deaths are predominant in breast cancer. Recent developments on early diagnosis using mammographic screening and the implementation of adjuvant therapies may have reduced breast cancer associated deaths in decent numbers, although new markers for prognosis are of utmost importance for patients with higher risk of developing metastases or recurrence.
Chemokines are the key messenger of cellular immune response and can be targeted to reduce the intratumoral regulatory T cells (Treg) for antitumor immunity. Targeting either specific immunomodulators and/or intervening molecular mechanisms is thought to be a potential therapeutic option. In our previous study, we have found that co-expression of CXCR5 and CXCL13 is significantly associated with epithelial to mesenchymal transition (EMT) of cells and lymph node metastasis (LNM) during breast cancer progression. In this study, we are aiming to investigate how the transcriptional regulation of this receptor-ligand pair directs the process of disease development. Interestingly, it was found that RelA (p65), a subunit of NFkB protein, promoted the transcription of both CXCR5 and CXCL13. The putative RelA binding sites were validated using sequential deletion of respective promoter regions of CXCR5 and CXCL13. We observed that expression of CXCR5 significantly (p&lt;0.05) increased with RelA and Nrf2 overexpression and CXCL13 co-stimulation in MDA-MB-231 cell line. RelA was also found to induce the expression of CXCL13 in T-47D and MDA-MB-231 cell line. Significantly, SNAIL, a key EMT regulatory element, was found to be highly expressed in RelA-transfected MDA-MB-231 cell line with or without CXCR5 and CXCL13 co-stimulation. We also observed CXCR5+ T follicular helper (Tfh) and Treg sub-population within the tumor microenvironment, although numbers varied with stages and molecular subtypes. In chemotaxis assay, CXCR5+ Treg cells were found to be predominant among migratory T-cell subsets against RelA overexpression and/or CXCL13 stimulation. Simultaneously, CCL2, a pro-inflammatory chemokine, induced macrophages to secrete CCL22, which in turn, might attract CXCR5+ Treg and Th2 cells into the tumor microenvironment. Study in 4T1-BALB/c breast cancer mouse model demonstrated significant (p&lt;0.05) increase in CXCR5 and CXCL13 expression levels upon immunostimulation.
The study may help to understand the prognosis value of CXCR5 and CXCL13 considering the impact of this receptor-ligand pair on the regulation of Tfh/Treg ratio, EMT and LNM. We believe that this investigation may lead to a comprehensive prediction of the tumor fate as well as to explore possible markers for breast cancer prognosis and future chemotherapy with more precision.
Citation Format: Sougata Roy Chowdhury, Subir Biswas, Gunjan Mandal, Arindam Bhattacharyya. RelA regulates CXCR5/CXCL13 transcription and associated immune response in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 943. doi:10.1158/1538-7445.AM2017-943