Biomarkers for response to immune checkpoint inhibitors in gastrointestinal cancers

Table 2 Summary of biomarkers worthy of further development in gastrointestinal tumors

Classification	Biomarkers	Tumor type	Response to ICI	Ref.
Tumor-genome biomarkers	POLE-mutation	Endometrial carcinoma	Pos	[93]
	Neoantigen	Pulmonary adenocarcinoma	Pos	[94]
Liquid-biopsy biomarkers	LDH	Melanoma	Neg	[99]
	NLR	Advanced solid tumors	Neg	[100]
Epigenetic	TET1-mutation	Multiple tumor types	Pos	[105]
	miRNA	Non-small-cell lung cancer	Pos	[107]
Patient characteristic	Gender	NA	Male: Pos; Female: Neg	[81,82]
	Age	NA	Controversial1	[84,115]
	Intestinal microbiota	NA	Pos/Neg	[85-87]

¹Age as a marker remains controversial, and there are conflicting cases of relevant data.

POLE: Polymerase gene epsilon; LDH: Lactate dehydrogenase; NLR: Neutrophil-to-lymphocyte ratio; miRNA: Micro RNA; Pos positive: Neg negative; NA: Not applicable; ICI: Immune checkpoint inhibitor.