Tumor-induced dysfunction in interleukin-2 production and interleukin-2 receptor signaling: a mechanism of immune escape

Cancer J Sci Am. 2000 Feb;6 Suppl 1:S81-7.

Abstract

Purpose: The development of an effective antitumor immune response is compromised in patients with renal cell carcinoma. Despite significant infiltration by T lymphocytes into renal tumors, no detectable induction of gene expression is associated with the generation of an antitumor immune response. Tumor-induced down-regulation of interleukin (IL)-2 expression may contribute to the impaired development of the T cell-mediated antitumor immune response. Within renal tumors, there is no detectable expression of IL-2 or the IL-2 receptor alpha chain, and only low levels of interferon gamma (IFN-gamma) mRNA are detected. Products in the tumor environment may suppress the expression of these genes, thus inhibiting production of type 1 helper T cell cytokines.

Methods: Peripheral blood lymphocytes obtained from healthy volunteers were exposed to supernatants from renal cell carcinoma explants, and the immunologic consequences of this were assessed using a variety of molecular assays.

Results: Soluble products from renal tumor explants can inhibit the production of IL-2 and IFN-gamma by peripheral blood lymphocytes and can suppress T-cell proliferation. Soluble products from renal cell carcinoma explants appear to block the nuclear translocation of nuclear factor kappa B (NFkappaB) proteins p50 and RelA without affecting cytoplasmic levels of these proteins. In some experiments, a reduction in the nuclear translocation of other transcription factors involved in IL-2 gene expression, including nuclear factor of activated T cells and accessory protein-1, was observed. Gangliosides isolated from tumor supernatants blocked the production of IL-2 and IFN-gamma in response to ionomycin plus phorbol myristate acetate stimulation. These gangliosides also inhibited stimulus-dependent activation and nuclear accumulation of NFkappaB. Coculture experiments demonstrated that renal cell carcinoma lines known to express gangliosides could inhibit the activation of NFkappaB in normal T cells and the Jurkat T-cell line. Supernatants from renal cell carcinoma explants and renal cell carcinoma cell lines can also suppress the proliferation of normal T cells, thus reproducing another defect observed in tumor-infiltrating lymphocytes. Supernatants from renal cell carcinoma tumors also appear to inhibit signaling through the IL-2 receptor. Although tumor supernatants had little effect on IL-2 receptor (alpha, beta or gamma) expression, they did block expression of JAK3, a key kinase involved in signaling through the IL-2 receptor pathway. Moreover, downstream events in IL-2 receptor signaling linked to JAK3 were impaired in T cells treated with tumor supernatants.

Conclusion: These findings suggest that soluble products from renal tumors may suppress T-cell responses by blocking both IL-2 production and normal IL-2 receptor signaling.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Carcinoma, Renal Cell / immunology*
  • Humans
  • Interferon-gamma / biosynthesis
  • Interleukin-2 / biosynthesis*
  • Kidney Neoplasms / immunology*
  • Lymphocyte Activation
  • NF-kappa B / metabolism
  • Receptors, Interleukin-2 / physiology*
  • T-Lymphocytes / immunology
  • Tumor Cells, Cultured

Substances

  • Interleukin-2
  • NF-kappa B
  • Receptors, Interleukin-2
  • Interferon-gamma