PDCD1 and neoplasm: The proportion of KI67 and PD-1 expressing CD4+ T cells was significantly increased in the combined inhibitor treatment group which is indicative of increased proliferation and potential engagement of the immune suppressive PD-1/PD-L1 checkpoint pathway in line with the significant increase of PD-L1 expression on the tumour (Supplementary Fig. 3d; Fig. 2f).