Soluble immune checkpoints in cancer: production, function and biological significance

Table 3 Biomarkers for clinical outcomes under target therapy for cancer patients

Biomarker	Cancer	Number of patients	Treatment	Level changes during treatment	Outcomes	References
sPD-1	NSCLC	n = 38	Erlotinib	Uncertain	Higher treatment levels associated with prolonged progression-free and overall survival	[21]
sPD-L1	DLBCL	n = 288	High-dose chemotherapy + rituximab	Uncertain	High pre-treatment levels associated with poorer prognosis	[34]
	Malignant melanoma	n = 251	Ipilimumab (±bevacizumab or sargramostim), pembrolizumab	Uncertain	High pre-treatment levels associated with disease progression	[35]
	NSCLC	n = 39	Nivolumab	Uncertain	Lower basal plasma levels associated with better clinical benefit	[36]
sCTLA-4	Melanoma	n = 14	Ipilimumab	Not mentioned	Higher sCTLA4 in responders, associated with longer OS	[48]

Such studies supply information for the formulation of diagnostic tools. Uncertain means the levels may be as same as control or be higher or lower than control in the study; not mentioned means no data found in the study