Abstract 5071: The functional relevance of Atypical Chemokine Receptor 1 (ACKR1/DARC) genetic isoforms in breast cancer

Abstract

Abstract Chemokines and their receptors can interact to affect the host's anti-tumor response by influencing the migration of host immune cells indirectly via a chemokine gradient. The regulation and function of these receptors is paramount in ensuring an appropriate immune response to an inflammatory stimulus, especially in the case of cancer. One such receptor, Atypical Chemokine Receptor 1 (ACKR1/DARC), is a genetically diverse transmembrane GPCR that can buffer pro-inflammatory CXC- and CC- chemokine activity in circulation and within tissues, influencing leukocyte migration. While the basic immunological function of this receptor is known, the specific function of its two genetic isoforms, A and B, is not. These isoforms are produced by two alternative promoters and distinct mRNA splicing events. Isoform A is not split by introns, even in the untranslated regions, and offers homology to CXCL8. The alternative splice variant, Isoform B, does contain an intron, and follows the GT-AG splicing rule, including a novel exon coding for an additional 7 amino acids. This localizes to the N-terminus, making up part of the extracellular binding region of the receptor. We aim to determine if the two major ACKR1 isoforms have distinct functional abilities to bind or sequester pro-inflammatory chemokines in epithelial breast cell lines. By creating isoform specific overexpression and knockout constructs, and transiently transfecting the DNA into our subtype specific cell lines, we can use an ELISA assay to determine chemokine concentration in the media, and measure differences based on isoform specificity. Using immunofluorescence, we first show that ACKR1 and our two proinflammatory chemokines, CCL2 and CXCL8, are expressed on the surface of epithelial cells and colocalize. We then indicate that there is an isoform specific difference in chemokine concentration between different breast cancer subtypes, in addition to differences seen in overexpression and knockout cell lines. Determining the functionality of these two isoforms can help us better understand ACKR1's role in the immune system, and its potential role as a prognostic marker in breast cancer. Citation Format: Brittany D. Jenkins, Rachel N. Martini, Inasia Brown, Melissa B. Davis. The functional relevance of Atypical Chemokine Receptor 1 (ACKR1/DARC) genetic isoforms in breast cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 5071.