Table 1 Summary of circRNAs and their functions in the TME

mediating tumour immune surveillance

circRNAs

exogenous

-

probably activated antitumour immunity

RIG-I/ immunocytes

[65]

circRNAs

exosomes

-

probably regulated antitumour immunity

immunocytes

[58, 70, 72, 73]

circ-0020397

CRC

up

inhibited the activation and proliferation of T cells, and promoted the viability and invasion of CRC cells

miR-138/ PD-L1

[79]

circARSP91

HCC

up

enhanced the cytotoxicity of NK cell and upregulated NK-mediated immune responses

ULBP1

[92]

circ-0000977

PC

-

inhibited the killing ability of NK

miR-153 /HIF1α, ADAM10

[168]

promoting angiogenesis

circ0001429

bladder cancer

up

promoted cell metastasis and angiogenesis

miR-205-5p /VEGFA

[99]

circSCAF11

glioma

up

stimulated angiogenesis and tumourigenesis

miR-421/SP1/ VEGFA

[100]

circRNA cZNF292

glioma

up

promoted cell proliferation and angiogenesis

VEGFR-1/2, p-VEGFR-1/2 and EGFR

[101]

circRNA cZNF292

hepatoma

up

promoting cell proliferation, VM, and radioresistance

SOX9, Wnt/β-catenin

[103]

circ-SHKBP1I

GECs

up

stimulated angiogenesis

miR-544a/ FOXP1/ AGGF1 or miR-379/ FOXP2/ AGGF1

[20]

circ-0010729

HUVECs

up

promoted vascular endothelial cell proliferation

miR-186 /HIF1α

[104]

circ-002136

GECs

up

stimulated angiogenesis

FUS/circ-002136 /miR-138-5p /SOX13 feedback loop

[105]

circ-DICER1

GECs

up

promoted angiogenesis

MOV10/circ-DICER1 /miR-103a-3p (miR-382-5p) /ZIC4 Hsp90β/PI3K/Akt

[106]

inhibiting angiogenesis

circHIPK3

bladder cancer

down

inhibited cell migration, invasion, and angiogenesis

miR-558/ HPSE/ MMP-9 and VEGF

[107]

circSMARCA5

GBM

down

inhibited angiogenesis

VEGFA, SRSF1

circ-0003575

HUVECs

up

inhibiting angiogenesis

potential circRNA-miRNA-mRNA network

[110]

improving endothelial cell permeability

circRNA IARS

exosomes derived from PC cells

up

enhanced cell invasion, metastasis and endothelial cell permeability

miR-122/ RhoA/ F-actin

[112]

hypoxia

circDENND4C

breast cancer

up

promoted cell proliferation

-

circDENND4C

breast cancer

up

promoted cell glycolysis, migration, invasion and proliferation

miR-200b and miR-200c

[116]

circDENND2A

glioma

up

promoted cell migration and invasion

miR-625-5p

[169]

circ-0000977

PC

-

mediated immune escape

miR-153/ HIF1α

[168]

circ-0010729

HUVECs

up

enhanced cell proliferation, migration and suppressed apoptosis

miR-186/ HIF1α

[104]

circRNA cZNF292

hepatoma

up

promoted cell proliferation, VM, and radioresistance

SOX9, Wnt/β-catenin

[103]

causing ECM remodelling

circ-0000096

gastric cancer

down

affected cell growth and migration

VEGF, MMP-2 and MMP-9

[120]

circLMNB1

CRC

up

promoted cell dissemination, invasion and EMT

MMP-2 and MMP-9

[121]

circDENND4C

breast cancer

up

suppressed cell migration and invasion

MMP-2 and MMP-9

[116]

circ-0007334

PDAC

up

promoted cell invasion

miR-144-3p and miR-577/ COL1A1, MMP-7

[122]

circRNA cSMARCA5

HCC

down

inhibited cell proliferation and migration

miRNA-17-3p and miRNA-181b-5p/ TIMP-3

[124]

exosomes

circRNA IARS

exosomes derived from PC cells

up

promotedcell invasion and metastasis

miR-122

[112]

circ-DB

exosomes derived from adipocytes

up

promoted tumourigenesis and metastasis of HCC

miR-34a/ USP7/ cyclin A2

[135]

ciRS-133 (circ-0010522)

exosomes derived from GC cells

up

promoted white adipose browning in patients with gastric cancer

miR-133/ PRDM16

[119]