IDO2 and neoplasm: Indeed, previous studies have demonstrated that imatinib impaired Treg proliferation and function on one hand [38, 39], and, on the other hand, potentiated antitumor T cell responses in an gastrointestinal stromal tumor model through CD8+ T cell activation inducing Treg apoptosis within the tumor by depleting indoleamine 2,3-dioxygenase [40].