Fibrinogen-like protein 1 (FGL1): the next immune checkpoint target

Table 1 Regulation of FGL1 expression in association with substance metabolism

Stimulating factor	Induced cell type	Signaling pathway	Phenotype	References
FGL1	3T3-L1 (adipocyte)	ERK1/2-C/EBPβ-PPARγ	FGL1-induced adipogenesis	[56]
	HepG2	ERK1/2	Impair insulin sensitivity	[52]
Hyperglycemia	HepG2	ERK1/2-NRF2-SOD1	Enhance antioxidative stress	[69]
		STAT3/HNF-1	Upregulate FGL1 expression
Hyperlipidemia (Palmitate)	Primary hepatocyte	C/EBPβ	Upregulate FGL1 expression	[68]
FGL1	C2C12 (myoblast)	JNK-p-JNK	Impair insulin sensitivity
Hepatectomy/IL-6	Hepatocyte	HNF-1/STAT3/AP-1	Activate the FGL1 and IGFBP-1 genes; restore metabolic homeostasis	[74, 78]

AP-1: activating protein-1; C/EBPβ: CCAAT/enhancer-binding protein β; ERK1/2: extracellular regulated protein kinases 1/2; HNF-1: hepatocyte nuclear factor-1; IGFBP-1: insulin-like growth factor binding protein 1; JNK: Jun N-terminal kinase; NRF2: nuclear factor erythroid-2-related factor 2; PPARγ: peroxisome proliferator-activated receptor gamma; SOD1: superoxide dismutase 1; STAT3: signal transducer and activator of transcription 3

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