Introduction: Chemokines are a group of small proteins that play a part in angiogenesis, inflammation, tumor cell migration as well as lymphocyte and leukocyte recruitment, activation and chemotaxis. Fractalkine (CX3CL1) is a chemokine found on the surface of normal and malignant intestinal epithelial cells and also in the plasma in a soluble form. Its receptor, CX3CR1, is found on monocytes/macrophages, natural killer cells, and T cells. High tissue expression levels of fractalkine in colon cancers has been linked to better prognosis, presumably via recruitment of lymphocytes (tumor infiltrating lymphocytes) and immune cells to the tumor. Soluble fractalkine increases monocyte, NK cell, and T-cell chemotaxis and has also been shown to independently inhibit liver and lung metastases in the murine setting. Blood fractalkine levels have not been well studied thus far. It is possible that soluble fractalkine levels in the plasma may be altered in the cancer population and predictive of disease stage or prognosis. As the first step in evaluating soluble fractalkine as a cancer marker, plasma levels of this chemokine were determined in patients with cancer or benign colonic diseases.
Methods: Blood samples were taken preoperatively from 50 colorectal cancer patients and from 50 patients with benign colonic diseases. Plasma levels of soluble human Fractalkine were measured using a homemade ELISA kit in duplicate. Results are presented as mean ± SD. The Mann Whitney U-test and the students t-test were used (p-value < 0.05 was considered significant).
Results: The mean age of the patients was similar (Cancer 66.9, Benign 63.8). The majority of the benign disease patients had adenomas. The cancer stage breakdown was: Stage 1, 12; Stage 2, 17; Stage 3, 18, and Stage 4, 3 patients. Preoperative fractalkine values in cancer patients were significantly lower than those in benign patients (256.7±116.9 pg/ml vs 438.5±400.3 pg/ml respectively, p=0.005). No differences in fractalkine levels was noted between cancer stages.
Conclusion: Cancer patients were found to have significantly lower plasma fractalkine levels than benign disease patients, however, no correlation was found between cancer stage and blood levels. Additional study is needed to determine whether plasma levels return to normal after surgery and to further investigate the potential role of fractalkine as a tumor marker.