Serum Soluble Interleukin-2 Receptor is Increased in Malnourished and Immunosuppressed Patients With Gastric and Colorectal Cancer: Possible Influence of Myeloid-Derived Suppressor Cells

BACKGROUND: Soluble IL-2 receptor (sIL-2R) is the circulating form of a membrane receptor localized on lymphoid and some tumor cells; its biological function is not completely understood. METHODS: Serum levels of sIL-2R in blood samples taken from 51 cancer patients (21 gastric and 30 colorectal) and 18 healthy volunteers were measured and found to be significantly higher in the patients. RESULTS: Concentrations were significantly inversely correlated to nutritional parameters, including total protein and short turnover proteins such as prealbumin, retinol binding protein and transferrin, as well as to the stimulation index, which is a classical parameter of cell-mediated immunity. Concentrations were significantly positively correlated to neutrophil count and inversely to lymphocyte count. Significantly elevated levels of circulating myeloid-derived suppressor cells (MDSCs) were found in patients; this was significantly correlated to sIL-2R levels. CONCLUSIONS: Increased production of sIL-2R correlated with systemic inflammation, nutritional impairment and inhibition of cell-mediated immunity, and thus may be involved in immunological mechanisms inducing cancer cachexia. The same factors also appear to relate closely to induction of MDSCs.