PDCD1 and neoplasm: To verify this, a preclinical transplanted tumor model was established via subcutaneous injection of B16F10 melanoma cells into the flank of C57BL/6 mice to evaluate the therapeutic effect of anti-PD-1 immunotherapy synergized with the overexpression of tumor miR-21–3p level obtained by the pretransfection with vector (figure 4A).