PDCD1 and melanoma: Furthermore, the combined effect of anti-PD-1 antibody treatment and tumorous miR-21-3p overexpression on melanoma growth could be significantly blocked by the administration with liproxstatin-1 (figure 4B–F), indicating that the role of miR-21–3p overexpression in potentiating the efficacy of anti-PD-1 antibody depended on the induction of tumor cell ferroptosis.