(72a) Investigating Matrix Stiffness Mediated Dormancy in Brain Metastatic Breast Cancer Cells Using a Hyaluronic Acid Hydrogel Platform
We observed that BCCs cultured on soft (~ 0.4 kPa) HA hydrogel were largely EdU and Ki67 negative suggesting that they were dormant (non-proliferative) whereas, cells cultured on stiff (~ 4.5 kPa) HA hydrogel were proliferative as indicated by EdU as well as Ki67 positivity. In addition, we observed nuclear localization of p21 and p27 (proteins associated with cell cycle arrest/dormancy) in cells cultured on soft HA hydrogels in contrast to their cytoplasmic localization in cells cultured on stiff HA hydrogels. Further, we observed enhanced resistance to chemotherapy drugs such as Paclitaxel (Taxol) in BCCs cultured on soft HA hydrogels as compared to stiff HA hydrogels. When non-proliferative cells from the soft HA hydrogel were transferred onto the stiff HA hydrogel, they became proliferative, and vice versa, indicating that the stiffness mediated dormancy is reversible. Overall, these results indicate that the HA hydrogel stiffness mediates dormancy in BCCs. We further investigated the role of focal adhesion kinases (FAK) in stiffness mediated dormancy and observed that blocking FAK in cells cultured on stiff HA hydrogels resulted in decreased Ki-67 positivity, suggesting that FAK signaling, in part, mediates dormancy in BCCs. We are currently studying the differential gene expression in BCCs cultured on soft versus stiff HA hydrogels through RNA sequencing to investigate genes associated with dormant phenotype in BCCs cultured on soft HA hydrogels. Such a biomimetic HA hydrogel platform could be utilized to model breast cancer dormancy in vitro and may be adapted as a drug screening platform.