Circulating immune markers in advanced renal cell carcinoma during immunotherapy with interferon gamma

Circulating immune markers sICAM-1, sELAM-1, sMHC-I, beta 2-MG, sCD4 and sCD8 were evaluated prior to and during immunotherapy with biologically active doses of interferon gamma (IFN-gamma) in 16 patients with advanced renal cell carcinoma (RCC) over a period of 12 months. Compared to 20 healthy controls, significantly (P < 0.01) elevated baseline levels of circulating adhesion molecules sICAM-1 (mean 1166 vs 230 ng/ml) and sELAM-1 (70 vs 17 ng/ml) were found in all patients. Compared to responders (n = 2) or patients with stable disease (n = 2), progressive disease during therapy (n = 12) was associated with significantly (P < 0.05) higher mean concentrations of sICAM-1 (1574 vs 962 ng/ml) and sELAM-1 (86 vs 46 ng/ml). Pretherapeutic and intratherapeutic levels of sMHC-I among the RCC patients were significantly (P < 0.05) lower than among the controls (0.41 vs 0.8 ng/ml). sCD4 levels clearly showed the same tendency (24 vs 33 U/l). sCD8 baseline levels, by contrast, were significantly (P < 0.05) elevated (564 vs 336 U/l), reflecting either activation of the NK-cell subset or increased synthesis of CD8+ T-suppressor cells. Again, significantly (P < 0.05) higher intratherapeutic sCD8 concentrations were observable with progressive disease than with response to therapy or stable disease (721 vs 355 U/l). Interestingly, although the biologically active dose of IFN-gamma was defined by an increase in beta 2-MG release of at least 30% within 48 h after injection, none of the other markers showed any significant alteration following IFN-gamma administration, suggesting that IFN-gamma in vivo does not produce changes in circulating markers of activation that might be expected on the basis of its effects in vitro. The finding of significantly elevated concentrations of sICAM-1, sELAM-1 and sCD8 in the presence of low sCD4 and sMHC-I levels might be of clinical significance for indicating ongoing tumor progression.