Indoleamine-2,3-dioxygenase in an immunotherapy model for Ewing sarcoma.

BACKGROUND/AIM: Interleukin-2 (IL2) transgenic Ewing sarcoma cells reduce tumor growth in vivo and in vitro. In the present study we analyzed the expression of immune suppressive indoleamine-2,3-dioxygenase (IDO) in this model. MATERIALS AND METHODS: Expression of IDO was analyzed by polymerase chain reaction. The impact of the cluster of differentiation 137 (CD137)/CD137 ligand (CD137L) co-stimulatory system on expression of IDO and different cytokines was analyzed both in vivo and in vitro. RESULTS: Tumors that developed in vivo in the presence of IL2 transgenic tumor cells expressed IDO. The presence of CD137L transgenic tumor cells led to down-regulation of IDO. Further in-vitro analysis of this phenomenon indicated that IDO was expressed in tumor cells as a consequence of interferon-gamma produced by lymphocytes in response to IL2. Depending on the concentration of IL2, stimulation of CD137 increased or reduced cytokine production in lymphocytes. CONCLUSION: Our data indicate that the CD137/CD137L pathway can modulate the immune response against Ewing sarcoma cells.