Table 2. Environmentally regulated in vitro modeling studies of breast cancer dormancy.
Recovery: Return to a proliferative state upon adding a proliferation trigger or removing the dormancy stimulus. Other gene expression: Dormancy marked by gene expression profiles not included in typical proliferation, p38/ERK activity, and cell cycle arrest analysis. Dormant line: An established cell line previously associated with dormancy was used as an inherent indicator of dormancy. FHL2, four-and-a-half LIM domains 2 protein; hFOB, human fetal osteoblasts; hMSC, human mesenchymal stem cells; ECM, extracellular matrix; HA, hyaluronic acid; 4NG1, G1-arrested cells that are tetraploid; IP-10, interferon-γ–inducible protein 10; PEG, polyethylene glycol; EphB6, ephrin receptor B6; CoCl2, cobalt(II) chloride; HIF-1-α, hypoxia-inducible factor 1-α; TGF-β1, transforming growth factor–β1; MEK1/2, mitogen-activated protein kinase kinases 1 and 2.
| Environmental control approach | Environmental control subgroups | Cellular or tumor dormancy | 2D or 3D culture | Breast cancer cell lines | Organotypic target | Dormancy markers | Summary | Reference (year) |
|---|---|---|---|---|---|---|---|---|
| Physical | Stiffness | Tumor | 3D | MDA-MB-231, MCF7 | N/A | Low/no proliferation, recovery, low Ki67, cell cycle arrest, other gene expression | Stiff 3D encapsulation gel increases dormancy via FHL2 and p21 nuclear localization. | (122) (2023) |
| Coculture, biochemical | Indirect coculture, bone marrow cell coculture, individual signaling molecule | Tumor | 3D | T47D, BT474 | Bone marrow | Low/no proliferation, recovery, low Ki67 | Soluble factors from bone marrow niche cells can either promote dormancy (hFOB) or proliferation (hMSC). | (68) (2023) |
| Biochemical, physical | ECM composition, serum deprivation, 2D versus 3D | Cellular | Both | MDA-MB-231, MCF7, D2.0R, D2A1, HCC1954, HCC1143 | N/A, bone marrow | Low/no proliferation, recovery, low Ki67, p38/ERK activity | Live cell lineage tracing helps to evaluate cellular dormancy in vitro, including differences in 2D and 3D and different culture environments. | (59) (2023) |
| Physical | Stiffness, suspension, cell spheroid size | Tumor | Both | MDA-MB-231Br, BT474Br3 | Brain | Low/no proliferation, low Ki67, p38/ERK activity | Spheroids on soft HA substrates are more dormant than suspended spheroids. | (130) (2023) |
| Physical | Viscoelasticity | Cellular | 2D | MCF7 | N/A | Cell cycle arrest, low Ki67 | Breast cancer cell dormancy and senescence are highly sensitive to changes in substrate viscoelasticity. | (127) (2022) |
| Biochemical | ECM composition | Tumor | 3D | MCF7 | N/A | Low/no proliferation, recovery, p38/ERK activity | 3D encapsulation culture without degradability or integrin-binding sites promotes dormancy in MCF7 cells. | (98) (2022) |
| Coculture, biochemical | Indirect coculture, brain cell coculture, vascularization, ECM composition, serum deprivation | Tumor | 3D | MDA-MB-231, T4-2 | Brain | Low/no proliferation, low Ki67 | Astrocyte-produced laminin-211 supports dormancy of brain metastatic breast cancer cells. | (80) (2022) |
| Biochemical, physical | Serum deprivation, 2D versus 3D | Tumor | Both | D2.0R, D2.A1, ZR-75-1 | Liver | Low/no proliferation, recovery, low Ki67, cell cycle arrest, other gene expression | Dormant, nonsenescent breast cancer cells in 3D encapsulation or serum deprivation have a large fraction of 4NG1 cells. | (106) (2021) |
| Coculture, biochemical | Liver cell coculture, individual signaling molecule, serum deprivation | Tumor | 3D | MDA-MB-231 | Liver | Low/no proliferation | IP-10 indirectly drives activation of breast cancer cells from dormancy via signaling from cocultured hepatocytes. | (78) (2021) |
| Biochemical, physical | Serum deprivation, confinement | Cellular | 3D | MDA-MB-231, MCF7, MDA-MB-468 | N/A | Recovery, low Ki67, p38/ERK activity, cell cycle arrest, other gene expression | Single-cell encapsulation in an agarose coating and silica-PEG gel causes breast cancer cell dormancy. | (107) (2021) |
| Biochemical | ECM composition | Both | 3D | MDA-MB-231, BoM-1833, LM2-4175, BrM2A-831 | N/A, bone marrow, lung, brain | Low/no proliferation, recovery, p38/ERK activity | In specific hydrogel formulations, different organotropic breast cancer cell lines enter into tumor-level or cellular dormancy states. | (99) (2021) |
| Coculture, biochemical | Lung cell coculture, individual signaling molecule | Tumor | 2D | D2.0R | Lung | Dormant line, other gene expression | EphB6 supports the survival of dormant breast cancer cells in the lung. | (73) (2021) |
| Coculture | Lung cell coculture | Tumor | 2D | MCF7, D2.0R, T47D-DBM | Lung | Dormant line, other gene expression | RNA-seq analysis of lung cell coculture with breast cancer cells reveals an autophagy-independent lysosomal mechanism of dormant survival. | (72) (2021) |
| Coculture | Indirect coculture, bone marrow coculture | Cellular | 2D | MDA-MB-231, MDA-MB-468, T47D | Bone marrow | Cell cycle arrest, other gene expression | MSC extracellular vesicle secretome is primed by breast cancer cells, altering the potential for dormancy of breast cancer cells that receive the extracellular vesicles. | (83) (2021) |
| Biochemical | ECM composition | Tumor | 3D | MDA-MB-231 | N/A | Low/no proliferation, recovery | A dormancy-inducing environment promotes cellular resistance to doxorubicin. | (34) (2020) |
| Physical | Stiffness, suspension, cell spheroid size | Tumor | Both | MDA-MB-231BR | Brain | Low/no proliferation, recovery, low Ki67 | Hyaluronic hydrogel stiffness and cell cluster size determine breast cancer dormancy versus proliferation. | (120) (2020) |
| Biochemical, physical | ECM composition, network organization | Tumor | 3D | MDA-MB-231, T47D, BT474 | Bone marrow, lung | Low/no proliferation, recovery, other gene expression | T47D ER+ breast cancer cells are more dormancy-capable than MDA-MB-231 TNBC cells, with dormancy also affected by the encapsulating hydrogel properties. | (60) (2020) |
| Coculture, biochemical, physical | Indirect coculture, ECM composition, serum deprivation, network organization | Tumor | 2D | 23 Human cell lines* | N/A, bone marrow | Low/no proliferation, recovery, low Ki67, cell cycle arrest | Producing and organizing fibronectin helps breast cancer cells to survive serum deprivation–induced dormancy in vitro. | (23) (2020) |
| Physical | Stiffness, cell seeding density | Tumor | 2D | MDA-MB-231BR, BT474BR3 | Brain | Low/no proliferation, low Ki67, cell cycle arrest, other gene expression | Softer hyaluronic acid substrates support breast cancer dormancy, disrupted by higher cell seeding densities. | (121) (2020) |
| Biochemical | ECM composition | Tumor | 3D | MDA-MB-231 | N/A | Low/no proliferation, recovery | Changing integrin-binding site density and network structure yields different balances of dormancy and proliferation for breast cancer cells. | (100) (2019) |
| Coculture, biochemical, physical | Bone marrow cell coculture, vascularization, individual signaling molecule, 2D versus 3D | Tumor | Both | MDA-MB-231, BoM-1833 | Bone marrow | Low/no proliferation, p38/ERK activity | 3D coculture with endothelial cells, bone marrow stromal cells, and fetal osteoblasts kept MDA-MB-231 cells dormant but not bone-tropic metastatic variant BoM-1833. | (69) (2019) |
| Coculture | Indirect coculture | Tumor | Both | MCF7 | Bone marrow | Low/no proliferation, low Ki67, other gene expression | MSC-derived extracellular vesicles promote a slightly less active phenotype in MCF7s. | (82) (2018) |
| Biochemical, physical | Individual signaling molecule, hypoxia, 2D versus 3D, suspension | Tumor | Both | MDA-MB-231, MCF7 | N/A | Low/no proliferation, recovery, low Ki67, cell cycle arrest | CoCl2 mimics hypoxia by stabilizing HIF-1-α, resulting in comparable induction of dormancy in MCF7 and MDA-MB-231 cells as true hypoxia. | (105) (2018) |
| Coculture, biochemical | Bone marrow cell coculture, ECM composition, individual signaling molecule | Cellular | 2D | MCF7 | Bone marrow | Low/no proliferation, recovery | Inflammatory cytokines IL-6, IL-8, and TGF-β1 induce proliferation from dormant breast cancer cells. | (95) (2018) |
| Coculture, biochemical | Liver cell coculture, individual signaling molecule | Tumor | 3D | MDA-MB-231 | Liver | Low/no proliferation, recovery | Proteomic analysis identifies candidate biomarkers for dormant breast cancer cells in the liver. | (76) (2018) |
| Coculture, biochemical, physical | Indirect coculture, liver cell coculture, individual signaling molecule, serum deprivation, stiffness | Tumor | Both | MDA-MB-231, MCF7 | Liver | Low/no proliferation | Activated hepatic stellate cells express high levels of IL-8 that activate dormant breast cancer cells in the liver. | (79) (2018) |
| Biochemical, physical | Serum deprivation, confinement | Cellular | 3D | MDA-MB-231, MCF7, MDA-MB-468, MCF10DCIS.COM | N/A | Recovery, low Ki67 | Nondegradable cell encapsulation induces dormancy. | (108) (2017) |
| Coculture | Vascularization | Tumor | 3D | MDA-MB-231 | N/A | Low/no proliferation, p38/ERK activity | Coculturing MDA-MB-231s with endothelial cells in a hyaluronic acid hydrogel increases dormancy markers. | (81) (2017) |
| Biochemical | Hypoxia | Tumor | 2D | MDA-MB-231, MCF7, MDA-MB-468, T47D | N/A | Low/no proliferation, recovery, p38/ERK activity, cell cycle arrest | Hypoxia induces cancer stem cell–like dormancy in hypoxia-surviving MDA-MB-231s. | (74) (2017) |
| Coculture, physical | Liver cell coculture, stiffness | Tumor | 3D | MDA-MB-231 | Liver | Low/no proliferation, low Ki67 | The liver microphysiological system has different effects on breast cancer cell dormancy with a polystyrene scaffold or a hydrogel scaffold. | (77) (2017) |
| Coculture | Indirect coculture, bone marrow cell coculture | Tumor | 2D | MDA-MB-231, MCF7, T47D, BT474 | Bone marrow | Low/no proliferation, p38/ERK activity | Conditioned media from specific bone marrow stromal cell types induce breast cancer dormancy. | (71) (2017) |
| Physical | Stiffness | Tumor | 3D | MDA-MB-231 | N/A | Low/no proliferation, recovery, low Ki67 | Encapsulation in stiff collagen gels promotes dormancy. | (47) (2017) |
| Coculture, biochemical | Bone marrow cell coculture, individual signaling molecule | Tumor | 3D | MCF7, MDA-MB-231BRMS1 | Bone marrow | Low/no proliferation | Dormant breast cancer cells in a bone cell coculture environment can be stimulated to proliferate by bone remodeling cytokines. | (1) (2015) |
| Coculture | Liver cell coculture | Tumor | 3D | MDA-MB-231, MCF7 | Liver | Low/no proliferation, low Ki67, cell cycle arrest | Liver niche cells promote breast cancer dormancy. | (75) (2014) |
| Biochemical, physical | ECM composition, individual signaling molecule, 2D versus 3D | Tumor | Both | D2.0R, D2A1 | N/A | Low/no proliferation, low Ki67, cell cycle arrest | Src family kinase inhibition keeps breast cancer cells dormant, and coinhibition of MEK1/2 causes dormant cell apoptosis. | (45) (2014) |
| Coculture | Indirect coculture, bone marrow cell coculture, vascularization | Tumor | 3D | MDA-MB-231, MCF7, BT474, T47D, SUM159, SUM149, MDA-MB-435, ZR-75-1, LM2-4175, BoM-1833 | Bone marrow | Low/no proliferation, recovery, low Ki67, other gene expression | 3D coculture with bone marrow cells can inhibit or support breast cancer cell proliferation. | (70) (2013) |
| Coculture, biochemical | Vascularization | Tumor | 3D | T4-2 | Bone marrow, lung | Low/no proliferation, low Ki67 | Mature endothelial cell–derived thrombospondin-1 supports breast cancer dormancy. | (5) (2013) |
| Biochemical | ECM composition | Tumor | 3D | D2.0R, D2A1 | N/A | Low/no proliferation, dormant line | Fibrotic enrichment of collagen I drives the transition from breast cancer dormancy to proliferation. | (37) (2010) |
| Biochemical | ECM composition, individual signaling molecule | Cellular | 2D | MCF7 | Bone marrow | Low/no proliferation | Basic fibroblast growth factor initiates two independent pathways to promote breast cancer cell dormancy. | (94) (2009) |
| Biochemical, physical | ECM composition, network organization | Tumor | 3D | MDA-MB-231, MCF7, D2.0R, D2A1, 4T1 | N/A | Low/no proliferation, low Ki67, cell cycle arrest | Integrin binding to produced fibronectin helps breast cancer cells to begin proliferating from a dormant state. | (91) (2008) |
| Biochemical | ECM composition, individual signaling molecule | Cellular | 2D | MCF7, T47D | Bone marrow | Low/no proliferation, p38/ERK activity | Flavopiridol disrupts the fibronectin-dependent pathway of dormant breast cancer cell survival. | (93) (2005) |
| Coculture, biochemical | Bone marrow cell coculture, ECM composition, individual signaling molecule | Cellular | 2D | MDA-MB-231, MCF7, T47D | Bone marrow | Low/no proliferation | Basic fibroblast growth factor and fibronectin support a dormant breast cancer cell population. | (92) (2004) |
*(23) initially compared 23 human breast cancer cell lines, including MDA-MB-231 and MCF7 for their ability to survive serum deprivation–induced dormancy before focusing on the behavior of HCC1954 cells.