PDCD1 and lung carcinoma: In a study by Li et al. [175], in mice with lung cancer, high levels of IL-17 secretion were associated with resistance to PD-1-based therapies; additionally, it was discovered that blocking PD-1 in mice after neutralization of IL-17 as well as anti-PD-1 treatment reduced the size of cancerous tumors and increased the activity of T CD8+ cells [175].