IDO1 and neoplasm: We show here that IDO1 expression in immune cells and stromal cells, but not in tumor cells, impairs the antitumor effect of the gDE7 vaccine and, more relevantly, we demonstrated that combination of melatonin and an IDO inhibitor augmented the antitumor therapeutic effects of gDE7 and increased the activation of E7-specific cytotoxic CD8+ T-cell responses.