CD4 and neoplasm: Antibody-mediated cell depletion experiments demonstrated that protection conferred by Trabectedin/α-PD-1 treatment was dependent on the CD4+ and CD8+ T cells as the antitumor effect of this combination treatment was heavily compromised in the absence of CD4+ or CD8+ T cells (Fig. 1f); NK cells play a minor role since removal of these cells slightly decreased the tumor protection.