Background
The presence of circulating tumor cells (CTCs) in the peripheral blood is a prerequisite for the formation of distant metastases. Transforming growth factor-βeta (TGF-β) and Chemokine (C-X-C Motif) Ligand-1 (CXCL1) are cytokines involved in the colonization of distant sites by CTCs in several pre-clinical animal models. However, their role is poorly-investigated in patients with metastatic cancer. Here, we investigated whether circulating levels of TGF-β and CXCL1 are predictors of CTC seeding in preferential distant sites in patients with metastatic breast cancer. Materials and
Conclusion
Our study shows that elevated circulating levels of TGF-β and CXCL1 are associated with a poor prognosis, and higher detection of CTCs and propensity of these cells to seed lung metastases in patients with breast cancer.
Methods
CTCs were isolated from the peripheral blood of 61 patients with metastatic breast cancer by immunomagnetic separation. Plasma samples were collected from the same patients and assayed for TGF-β and CXCL1 by enzyme-linked immunoassay.
Results
Patients were grouped in CK1+/- (N<10), CK2+ (N ≥ 10<50) and CK3+ (N ≥ 50), according to the number (N) of cytokeratin 7/8-positive CTCs: the highest number of CK7/8-positive CTCs was detected in patients with negative Human epidermal growth factor receptor-2 (HER-2/NEU) status (p<0.0001) antigen, identified by the monoclonal antibody Ki-67 (Ki-67) ≥ 15% (p=0.003), Carcinoma antigen 15-3 (CA-15.3) ≥ 40 U/ml (p=0.004) and those with lung metastases (p=0.01). We found that elevated plasma concentrations of TGF-β and CXCL1 are predictive for the detection of CTCs. In particular, patients with CK3+ CTCs and plasma concentrations of TGF-β and CXCL1 higher than the median value had a poor prognosis in comparison to patients with CK1+/- CTCs and TGF-β and CXCL1 concentrations below the median value.