Moreover, small cell lung cancer research revealed that the CDK7 inhibitor YKL-5-124 activated CXCL9 and that CXCL10 signalling may be a promising outcome of combining YKL-5-124 and anti-PD-1, confirming the pivotal function of CXCL9 in immunotherapy (43). Here, PDCD1 is linked to small cell lung carcinoma.