Host genotype and tumor phenotype of chemokine decoy receptors integrally affect breast cancer relapse

Abstract

Purpose: Chemokines may play vital roles in breast cancer progression and metastasis. The primary members of chemokine decoy receptors (CDR), DARC and D6, are expressed in breast tumors and lymphatic/hematogenous vessels. CDRs sequestrate the pro-malignant chemokines. We hypothesized that breast cancer patients carrying different levels of CDR expression in tumor and/or in host might have differing clinical outcomes.

Methods: This prospective observational study measured both expression and germline genotype of DARC and D6 in 463 primary breast cancer patients enrolled between 2004 and 2006. The endpoint was breast cancer relapse-free survival (RFS).

Results: There was a significant association between the co-expression of CDR (immunohistochemical expression of both DARC and D6) with RFS (hazard ratio [HR] of 0.32, 95% confidence interval [CI] 0.19 to 0.54). Furthermore, the co-genotype of two non-synonymous polymorphisms (with two major alleles of DARC-rs12075 and D6-rs2228468 versus the others) significantly related to relapse. Mechanistically, the variant-alleles of these two polymorphisms significantly decreased by 20-30% of CCL2/CCL5 (CDR ligands) levels relative to their major counterparts. Multivariate analysis highlighted that the co-expression and co-genotype of CDR were independent predictors of RFS, with HR of 0.46 (95% CI 0.27 to 0.80) and 0.56 (95% CI 0.37 to 0.85), respectively. The addition of host CDR genetic information to tumor-based factors (including co-expression of CDR) improved the relapse prediction ability (P = 0.02 of AUC comparison).

Conclusion: The host genotype and tumor phenotype of CDR integrally affect breast cancer relapse. Host-related factors should be considered for individualized prediction of prognosis.

Keywords: breast cancer; chemokine decoy receptor; genotype; metastasis; phenotype.

Figure 1. Flow chart of research

SNP, single nucleotide polymorphism; IHC, immunohistochemistry; CDR, chemokine decoy receptor.

Figure 2. Tumor expression of chemokine decoy receptors (CDR) and host genotype of CDR jointly affect breast cancer relapse

A. Effect of tumor phenotype of CDR on relapse-free survival (RFS). P for log rank = 7.5 × 10⁻⁶. The RFS curve was derived from the Kaplan-Meier estimate, and the survival differences between groups were compared by log-rank test. B. Effect of host genotype of CDR on RFS. P for log rank = 0.002 C. Joint effect of tumor phenotype and host genotype of CDR on RFS. P-values of the differences between high expression/minor genotype group and high expression/major genotype group, high expression/major genotype group and low expression/minor genotype group, and low expression/minor genotype group and low expression/major genotype group are 0.007, 0.354, and 0.047, respectively. High expression indicates co-expression of DARC and D6, otherwise low expression. Minor genotype indicates patients with at-least-one protective minor allele, otherwise major genotype. D. Chemokine levels in the supernatant of cells detected by ELISA after 24-hour incubation. For transient transfection, 1 μg pDARC-42G or -42A, 1 μg pD6-373S or -373Y, or the combination of 1 μg variant-type DARC-42A and 1 μg variant-type pD6-373Y were transfected. An empty expression vector was also used as a control. 72 hours after transfection, the levels of human CCL2 and CCL5 in cell supernatants were determined with a sandwich ELISA. Columns represent the mean of three independent experiments; bars, standard error; *, P < 0.05. E. ROC curves assessing the discriminatory performance of the CDR phenotype/genotype model and the CDR phenotype model for the prediction of disease relapse. P = 0.02 for AUC comparison.