Increased Matrix Rigidities Modulate Interleukin Gene Signatures in ER+ Breast Cancer

Metastases of breast cancer is a prevalent problem with over 25% of patients suffering with metastatic disease. Of the patients that present with metastatic disease, the majority are estrogen receptor positive (ER+) and have skeletal metastases. These skeletal metastases can cause several issues including pathological fractures, chronic pain, and hypercalcemia. Currently, there are not any cures for metastatic breast cancer in bone and only therapies to mediate the osteolysis caused by breast cancer. The bone microenvironment presents various physical forces that can act on the tumor cell that has been studied in ER- cells, however, the physical forces on ER+ tumor cells have not been widely evaluated. In this study, we explored the transcriptional changes that occur at different matrix rigidities associated with the bone microenvironment (bone marrow: 0.5 kPa to 32 kPa; cortical and trabecular bone – 2 x 107 kPa). We observed that lower stiffnesses contributed to increased gene signatures associated with interleukin signaling. Additionally, we observed that downstream estrogen signaling outputs were modified. These interesting findings give us insights on what may be changing when ER+ tumor cells encounter rigidities associated with the bone microenvironment. CytoSoft® Rigidity Plates were purchased from Advanced BioMatrix. The plate wells were coated with 4 ug/mL of fibronectin (Advanced Biomatrix) for 1 hour before use. MCF7s were cultured in phenol-red free DMEM (Gibco) and phenol-red free RPMI (Gibco), respectively, and supplemented with 10% charcoal-stripped fetal bovine serum and 1% penicillin-streptomycin. After 24 hours in culture, cells were plated at 0.2 x 106 on CytoSoft® Rigidity Plates which were purchased from Advanced BioMatrix. The plate wells were coated with 4 ug/mL of fibronectin (Advanced Biomatrix) for 1 hour before use. MCF7s were supplemented with 10 nM 17-B estradiol (Invitrogen) and cultured at 37 C for 48 hours at 5% CO2.