Expression of chemokine receptors on circulating tumor cells in patients with solid tumors

Background: The study was performed to investigate the expression of chemokine receptors (CR) on circulating tumor cells (CTC), which may be of importance for organ-specific metastases and cancer treatment since CR are potential drug-targets. Methods: Blood samples from patients with metastatic carcinoma (MC) or melanoma (MM) were enriched for CTC and expression of CR (CXCR4, CCR6, CCR7 and CCR9) was evaluated by flow cytometry. Results: CTC were detected in 49 of 68 patients (72%) [28 MC; 21 MM] with a median number of 3 CTC (range: 194)/10 mL of blood. CXCR4 was expressed on CTC in 82% (40/49) of patients [median number 1 CTC/10 mL blood; range 1-14] and CCR6 in 29 patients (59%; median 1, range: 1-14). In MM patients, CCR7 was expressed on CTC in 6 (29%) samples and CCR9 in 12 (57%). A positive correlation between surface expression of CR and organ-specific metastatic pattern was not observed. Conclusions: CR were expressed on CTC of patients with solid tumors. Along with our findings, the observation that CR could be involved in CTC proliferation and migration of tumor cells appoints CTC as potential CR-antagonist therapeutic target.