Abstract 132: Investigating correlations of DARC under-expression (Duffy null phenotypes) with increased breast cancer lymph node metastasis

Abstract

Abstract DARC (aka Duffy), a chemokine receptor, is expressed on erythrocytes and endothelial cells in blood vessels. It has been linked to inhibition of tumor metastasis, and to regulation of plasma levels of some cytokines. The Duffy null (Fy-) phenotype, in which DARC is not expressed on red blood cells, is especially prevalent among people of West African descent. Little is known about how the presence or absence of DARC expression may affect breast cancer metastases and overall survival among African-American and European- American women. Our lab is investigating whether Fy- phenotypes could be associated with increased BrCa metastasis by genotyping the Fy- (null and weak) alleles and assessing DARC gene expression in breast and lymphoblast cells using qPCR and Immunofluorescence (IF). There are two isoforms of DARC, each with the Fy- SNP located in the promoter of one and the 5’UTR of the other. Due to this SNP, it is plausible that the alternate isoform is specific to these cell types and may still be expressed. Here we present data from the preliminary stages of this project; including characterizing Duffy alleles in our cell line models. We have genotyped the 3 known DARC polymorphisms that result in Fy- (and weak) erythrocyte phenotypes in breast cancer and lymphoblast cell lines. Specifically, we validated the genotype of HAPMAP lines from Yoruba, African-American, and CEPH-European descent for the -541T>C point mutation Fy- allele (rs2814778). Our breast cancer (BrCa) lines are derived from tumors of varying molecular subtypes, isolated from African-American women. We show that these BrCa lines are homozygous for the Fy- allele and yet still express the DARC protein. The specific isoform expressed in these cells (DARC-2) may not be the same as used to phenotype the Fy- status in erythrocytes (DARC-1). This suggests that a Fy- genotype may have some tissue specific expression of DARC-2 in epithelial cells. As well, we show that the levels of expression of the two DARC isoforms vary and are distinct among ancestral groups. We also show expression on the RNA level for individuals who have the duffy null genotype, which will be further validated. In conclusion, we hypothesize that Fy- status, as determined in endothelial and erythrocytes in people of African descent, may remove the metastatic protection of DARC. Also, alternate expression of DARC-2 on epithelial cells may increase the rate of metastases in the African population. Currently, we are analyzing clinical samples (blood and breast tissues) from local breast cancer patients for Fy- status and will determine if this correlates with metastatic disease. In addition, biochemical experiments will be conducted to determine whether DARC-related chemokines are in higher prevalence in the Fy- patients, how the isoforms differ in their affinity to the chemokine ligands, and whether this is associated with specific breast cancer subtypes. Citation Format: Andrea Walens, Brianna Bennett, Kauthar Mumin, Michael Lou, Rupali Hire, Michele Monteil, Melissa Davis. Investigating correlations of DARC under-expression (Duffy null phenotypes) with increased breast cancer lymph node metastasis. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 132. doi:10.1158/1538-7445.AM2014-132