Moreover, liver tumours were less responsive to anti-PD-1 compared to subcutaneous tumours, and these subcutaneous tumours appeared less responsive to anti-PD-1 in the presence of liver tumours (while there was no difference in the presence of lung tumours), confirming that liver tumours constitute a site of resistance to immunotherapy, which negatively affects the response at distant sites of disease. The gene discussed is PDCD1; the disease is neoplasm.