# Checkpoint (two meanings)

Source: https://onco.cc/terms/checkpoint/  
OnCo record `checkpoint` (Term). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

In cancer the word checkpoint means two unrelated things: a brake on immune cells that tumours press and checkpoint inhibitor drugs release, or a gate inside every dividing cell that stops it copying or splitting damaged DNA.

## Summary

Immune checkpoints are receptor-ligand pairs such as PD-1 with PD-L1, CTLA-4 with CD80 and CD86, LAG-3, TIM-3 and TIGIT that hold T cells and NK cells back; the drugs are antibodies that block them (or, for co-stimulatory receptors, agonists that press them). Cell-cycle checkpoints are the G1/S, G2/M and spindle assembly gates governed by cyclin D-CDK4/6 and RB, ATR-CHK1-WEE1, and MPS1, BUB1 and Aurora B, with the DNA-damage response behind them; the drugs are small molecules such as palbociclib, olaparib and azenosertib. The two families share a word and nothing else; OnCo keeps a hub for each, with every member, its partner, where it is expressed and the drugs against it.

## Fields

- Kind: Term
- Last checked: 2026-09-24
- Also known as: checkpoint; checkpoints; cell-cycle checkpoint; cell cycle checkpoint; cell-cycle checkpoints; checkpoint kinase; checkpoint kinases

## Connected records

- terms: [Cell cycle](https://onco.cc/terms/cell-cycle/), [Immune checkpoint](https://onco.cc/terms/immune-checkpoint/), [Immuno-oncology (IO) and checkpoint blockade](https://onco.cc/terms/immuno-oncology/), [Synthetic lethality](https://onco.cc/terms/synthetic-lethality/)
- technologies: [ATR and CHK1 inhibitors](https://onco.cc/technologies/atr-chk1-inhibitors/), [CDK4/6 inhibitors](https://onco.cc/technologies/cdk46-inhibitor/), [Immune checkpoint inhibitors](https://onco.cc/technologies/checkpoint-inhibitor/), [PARP inhibitors](https://onco.cc/technologies/parp-inhibitor/)
- targets: [Adenosine A2A receptor (ADORA2A)](https://onco.cc/targets/adora2a/), [ATM](https://onco.cc/targets/atm/), [ATR](https://onco.cc/targets/atr/), [AURKA](https://onco.cc/targets/aurka/), [AURKB](https://onco.cc/targets/aurkb/), [B7-H3](https://onco.cc/targets/b7h3/), [B7-H4 (VTCN1)](https://onco.cc/targets/b7h4/), [BTLA](https://onco.cc/targets/btla/), [BUB1](https://onco.cc/targets/bub1/), [CCND1](https://onco.cc/targets/ccnd1/), [CD112 (nectin-2)](https://onco.cc/targets/nectin2/), [CD137 (4-1BB, TNFRSF9)](https://onco.cc/targets/cd137/), [CD155 (PVR)](https://onco.cc/targets/pvr/), [CD24](https://onco.cc/targets/cd24/), [CD27](https://onco.cc/targets/cd27/), [CD28](https://onco.cc/targets/cd28/), [CD39 (ENTPD1)](https://onco.cc/targets/entpd1/), [CD40](https://onco.cc/targets/cd40/), [CD47](https://onco.cc/targets/cd47/), [CD73 / adenosine axis](https://onco.cc/targets/cd73-adenosine/), [CD80 (B7-1)](https://onco.cc/targets/cd80/), [CD86 (B7-2)](https://onco.cc/targets/cd86/), [CD96](https://onco.cc/targets/cd96/), [CDK4/6](https://onco.cc/targets/cdk4-6/), [CDKN2A](https://onco.cc/targets/cdkn2a/), [CEACAM1](https://onco.cc/targets/ceacam1/), [CHEK1](https://onco.cc/targets/chek1/), [CHEK2](https://onco.cc/targets/chek2/), [CTLA-4](https://onco.cc/targets/ctla4/), [FGL1](https://onco.cc/targets/fgl1/), [Galectin-9 (LGALS9)](https://onco.cc/targets/lgals9/), [GITR (TNFRSF18)](https://onco.cc/targets/tnfrsf18/), [HHLA2 (B7-H7)](https://onco.cc/targets/hhla2/), [HLA-DRA](https://onco.cc/targets/hla-dra/), [HLA-E](https://onco.cc/targets/hla-e/), [ICOS](https://onco.cc/targets/icos/), [IDO1](https://onco.cc/targets/ido1/), [Interleukin-10 (IL10)](https://onco.cc/targets/il10/), [KIR2DL1 (inhibitory KIR)](https://onco.cc/targets/kir2dl1/), [LAG-3](https://onco.cc/targets/lag3/), [LILRB1 (ILT2)](https://onco.cc/targets/lilrb1/), [LILRB2 (ILT4)](https://onco.cc/targets/lilrb2/), [MPS1 (TTK)](https://onco.cc/targets/ttk/), [NKG2A (KLRC1)](https://onco.cc/targets/klrc1/), [OX40 (TNFRSF4)](https://onco.cc/targets/tnfrsf4/), [PARP](https://onco.cc/targets/parp/), [PD-1](https://onco.cc/targets/pd1/), [PD-L1](https://onco.cc/targets/pdl1/), [PDCD1LG2](https://onco.cc/targets/pdcd1lg2/), [PLK1](https://onco.cc/targets/plk1/), [PVRIG (CD112R)](https://onco.cc/targets/pvrig/), [RB1](https://onco.cc/targets/rb1/), [Siglec-10](https://onco.cc/targets/siglec10/), [SIRPA](https://onco.cc/targets/sirpa/), [TDO2](https://onco.cc/targets/tdo2/), [TGFB1](https://onco.cc/targets/tgfb1/), [TIGIT](https://onco.cc/targets/tigit/), [TIM-3](https://onco.cc/targets/tim3/), [TNFRSF14](https://onco.cc/targets/tnfrsf14/), [TP53](https://onco.cc/targets/tp53/), [VISTA](https://onco.cc/targets/vista/), [WEE1](https://onco.cc/targets/wee1/)
- pathways: [Mitosis & the spindle assembly checkpoint](https://onco.cc/pathways/mitotic-spindle-checkpoint/), [p53 / RB / cell-cycle checkpoint](https://onco.cc/pathways/p53-cell-cycle/), [PD-1 / PD-L1 immune checkpoint & T-cell activation](https://onco.cc/pathways/pd1-checkpoint/)

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JSON: https://onco.cc/api/v1/entities/checkpoint.json