Table 1.
Main differences between dormant senescent and quiescent cancer cells and their roles in tumour relapse.
| Quiescent cancer cell | Senescent cancer cell | References | |
|---|---|---|---|
| Cell cycle arrest | Reversible: G0-G1 phase arrest | Irreversible: G1-G1 / S phase arrest / Cytokinetic block | 32,33,46,47,63,139 |
| Markers | None |
• p16INK4 expression / p53 activity • SASP factors • SA-β-gal staining • DNA damage-response • γH2AX foci and SAHF formation |
46,49,58 |
| Effectors | p27 | p53 (and p21) and / or p16INK4 mediated RB activation | 49–51 |
| Metabolic activity | Low (reduction in volume and size) | Very active (increased biomass leading to SASP production) | 33,51,56 |
| Role of immune system | Immune evasion | Attract immune cells by SASP secretion | 8,43,65,70 |
| Mechanisms of relapse | Re-enter cell cycle | Microenvironment modulation and immune cell recruitment via SASP | 21,30,44,68,70,100,101 |
| Structural changes | Chromatin compactation by methylation in H4K20 | SAHF formation and γH2AX foci / Lysosomal compartment expansion | 55,57,140 |
RB retinoblastoma protein, SA-β-gal senescence-associated β-galactosidase, SAHF senescence-associated heterochromatic foci, SASP senescence-associated secretory phenotype.