Ubiquitin proteasome system research in gastrointestinal cancer

Table 1 The roles of ubiquitin proteasome system members in gastrointestinal cancer

Enzyme	Esophageal cancer			Gastric cancer			Colorectal cancer
	P1	S2	C3	P1	S2	C3	P1	S2	C3
E2 enzyme	UBCH10	UBE2D3		UBCH10			UBCH10
	UBE2L3						UBE2Q2
	UCP						UBE2I
E3 enzyme	CHIP	FBX4	MDM2	AMFR	CHFR	CBLB	FBXL20	CHIP	FBXW7
	FBXO31	FBXL19		CUL1	CHIP	COP1	HUWE1	NEDD4L
	PACT	FBXW7		MDM2	FBXO31	NEDD4	UHRF1	NRDP1
	Smurf2			MKRN1	FBXW7		UHRF2	RNF43
	Skp2			RBX1	NEDD4L		Skp2
	UHRF1				RNF180
					ZNRF3
DUBs	UCH37	UCHL1			UCHL1		OTUB1	USP33	UCHL1
	USP9X	USP7			USP10		USP11	USP44
	USP22						USP22
							USP28

¹Tumor promoter role;

²Tumor suppressor role;

³Controversial role. AMFR: Autocrine motility factor receptor; CBLB: Cbl proto-oncogene B; CHFR: Checkpoint with forkhead and ring finger domains; CHIP: C-terminal Hsp-interacting protein; COP1: Constitutive photomorphogenic 1; CUL1: Cullin 1; DUB: Deubiquitination enzymes; FBXO31: F-box protein 31; FBX4: F-box protein 4; FBXL: F-box and leucine-rich repeat protein; FBXW7: F-box and WD repeat domain containing 7; HUWE1: HECT, UBA and WWE domain containing 1; MDM2: MDM2 proto-oncogene; MKRN1: Makorin ring finger protein 1; NEDD4: Neural precursor cell expressed, developmentally down-regulated 4; NEDD4L: Neural precursor cell expressed, developmentally down-regulated 4-like; NRDP1: Neuregulin receptor degradation protein-1; OTUB1: OTU deubiquitinase, ubiquitin aldehyde binding 1; PACT: p53-associated cellular protein-testes derived; RBX1: RING box protein-1; RNF: Ring finger protein; Smurf2: SMAD specific E3 ubiquitin protein ligase 2; Skp2: S-phase kinase-interacting protein 2; UBCH10: Ubiquitin-conjugating enzyme H10; UBE2L3: Ubiquitin-conjugating enzyme E2L3; UBE2D3: Ubiquitin-conjugating enzyme E2D3; UCP:E2-EPF ubiquitin carrier protein; UHRF: Ubiquitin-like with PHD and ring finger domains; UCH37: Ubiquitin carboxyl-terminal hydrolase 37; USP: Ubiquitin specific protease; UCHL1: Ubiquitin carboxyl-terminal hydrolase1; UBE2Q2: Ubiquitin-conjugating enzyme E2Q family member 2; UBE2I: Ubiquitin-conjugating enzyme E2I; ZNRF3: Zinc and ring finger 3.