Purpose: We reported that in renal cell carcinoma patients with active disease, T-cell reactions to the tumor-associated antigens MAGE-6 and EphA2 are highly skewed toward TH2-type cytokine responses [interleukin (IL) 5]. Herein, we determined whether tumor-derived products, including gangliosides isolated from renal cell carcinoma patients, participate in the down-regulation of type 1 T-cell responses.
Experimental design: T cells from healthy volunteers or renal cell carcinoma patients were cultured in the presence and absence of supernatants derived from renal cell carcinoma explants or with gangliosides isolated from those tumor supernatants. T cells were stimulated or not with either autologous dendritic cells pulsed with superantigen (Staphylococcus enterotoxin B) or with phorbol 12-myristate 13-acetate and ionomycin and then were assessed for type 1 or type 2 responses (cytokine production and gene expression) and apoptosis.
Results: Tumor supernatants efficiently inhibited the TH1-type responses [interferon (IFN) gamma] of T cells stimulated with either S. enterotoxin B or phorbol 12-myristate 13-acetate and ionomycin but had no inhibitory effect on activated T-cell production of type 2 cytokines (IL-4, IL-5, and IL-10). Likewise, IFN-gamma mRNA and protein production were inhibited when T cells were cocultured with either renal cell carcinoma supernatant-derived gangliosides or a commercial source of purified GD1a. It was also determined that gangliosides impair type 1 responses by inducing apoptosis of activated T cells.
Conclusions: We propose that renal cell carcinoma-derived tumor products such as gangliosides can induce a type 2 bias in antitumor immunity by initiating apoptosis in the IFN-gamma-producing type 1 effector cells. This represents a relevant mechanism by which renal cell carcinoma can inhibit protective antitumor immunity.