A majority of breast cancer deaths occur due to metastasis of cancer cells to distant organs. In particular, brain metastasis is very aggressive with an extremely low survival rate. Breast cancer cells that metastasize to the brain can enter a state of dormancy, which allows them to evade death. The brain microenvironment provides biophysical, biochemical, and cellular cues, and plays an important role in determining the fate of dormant cancer cells. However, how these cues influence dormancy remains poorly understood. Herein, we employed hyaluronic acid (HA) hydrogels with a stiffness of ~0.4 kPa as an in vitro biomimetic platform to investigate the impact of biochemical cues, specifically alterations in RGD concentration, on dormancy versus proliferation in MDA‐MB‐231Br brain metastatic breast cancer cells. We applied varying concentrations of RGD peptide (0, 1, 2, or 4 mg/mL) to HA hydrogel surfaces and confirmed varying degrees of surface functionalization using a fluorescently labeled RGD peptide. Post functionalization, ~10,000 MDA‐MB‐231Br cells were seeded on top of the hydrogels and cultured for 5 days. We found that an increase in RGD concentration led to changes in cell morphology, with cells transitioning from a rounded to spindle‐like morphology as well as an increase in cell spreading area. Also, an increase in RGD concentration resulted in an increase in cell proliferation. Cellular dormancy was assessed using the ratio of phosphorylated extracellular signal‐regulated kinase 1/2 (p‐ERK) to phosphorylated p38 (p‐p38) positivity, which was significantly lower in hydrogels without RGD and in hydrogels with lowest RGD concentration compared to hydrogels functionalized with higher RGD concentration. We also demonstrated that the HA hydrogel‐induced cellular dormancy was reversible. Finally, we demonstrated the involvement of β1 integrin in mediating cell phenotype in our hydrogel platform. Overall, our results provide insight into the role of biochemical cues in regulating dormancy versus proliferation in brain metastatic breast cancer cells.
The principal cause of death in cancer patients is metastasis, which remains an unresolved problem. Conventionally, metastatic dissemination is linked to actomyosin‐driven cell locomotion. However, the locomotion of cancer cells often does not strictly line up with the measured actomyosin forces. Here, a complementary mechanism of metastatic locomotion powered by dynein‐generated forces is identified. These forces arise within a non‐stretchable microtubule network and drive persistent contact guidance of migrating cancer cells along the biomimetic collagen fibers. It is also shown that the dynein‐powered locomotion becomes indispensable during invasive 3D migration within a tissue‐like luminal network formed by spatially confining granular hydrogel scaffolds (GHS) made up of microscale hydrogel particles (microgels). These results indicate that the complementary motricity mediated by dynein is always necessary and, in certain instances, sufficient for disseminating metastatic breast cancer cells. These findings advance the fundamental understanding of cell locomotion mechanisms and expand the spectrum of clinical targets against metastasis.
more » « less- Award ID(s):
- 1942561
- PAR ID:
- 10472652
- Publisher / Repository:
- Wiley Blackwell (John Wiley & Sons)
- Date Published:
- Journal Name:
- Advanced Science
- Volume:
- 10
- Issue:
- 31
- ISSN:
- 2198-3844
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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Abstract Approximately 90% of breast cancer related mortalities are due to metastasis to distant organs. At the metastatic sites, cancer cells are capable of evading death by exhibiting cellular or mass dormancy. However, the mechanisms involved in attaining dormancy at the metastatic site are not well understood. This is partly due to the lack of experimental models to study metastatic site‐specific interactions, particularly in the context of brain metastatic breast cancer (BMBC). Herein, an in vitro hyaluronic acid (HA) hydrogel‐based model is developed to study mass dormancy in BMBC. HA hydrogels with a stiffness of ≈0.4 kPa are utilized to mimic the brain extracellular matrix. MDA‐MB‐231Br or BT474Br3 BMBC spheroids are prepared and cultured on top of HA hydrogels or in suspension for 7 days. HA hydrogel induced a near mass dormant state in spheroids by achieving a balance between proliferating and dead cells. In contrast, these spheroids displayed growth in suspension cultures. The ratio of %p‐ERK to %p‐p38 positive cells is significantly lower in HA hydrogels compared to suspension cultures. Further, it is demonstrated that hydrogel induced mass dormant state is reversible. Overall, such models provide useful tools to study dormancy in BMBC and could be employed for drug screening.
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Abstract Breast cancer brain metastasis marks the most advanced stage of breast cancer no longer considered curable with a median survival period of ∼4–16 months. Apart from the genetic susceptibility (subtype) of breast tumors, brain metastasis is also dictated by the biophysical/chemical interactions of tumor cells with native brain microenvironment, which remain obscure, primarily due to the lack of tunable biomimetic
in vitro models. To address this need, we utilized a biomimetic hyaluronic acid (HA) hydrogel platform to elucidate the impact of matrix stiffness on the behavior of MDA‐MB‐231Br cells, a brain metastasizing variant of the triple negative breast cancer line MDA‐MB‐231. We prepared HA hydrogels of varying stiffness (0.2–4.5 kPa) bracketing the brain relevant stiffness range to recapitulate the biophysical cues provided by brain extracellular matrix. In this system, we observed that the MDA‐MB‐231Br cell adhesion, spreading, proliferation, and migration significantly increased with the hydrogel stiffness. We also demonstrated that the stiffness based responses of these cells were mediated, in part, through the focal adhesion kinase‐phosphoinositide‐3 kinase pathway. This biomimetic material system with tunable stiffness provides an ideal platform to further the understanding of mechanoregulation associated with brain metastatic breast cancer cells. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 106A: 1832–1841, 2018. -
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JBMR Plus published by Wiley Periodicals, Inc. on behalf of American Society for Bone and Mineral Research.
