To test this, less aggressive luminal A breast cancer cells (estrogen receptor positive [ER+] T47D) and more aggressive basal breast cancer cells (ER− MDA-MB-231) were selected as prototypical examples of breast cancer cells from different subtypes that exhibit different phenotypic characteristics (epithelial vs. mesenchymal), and these cells were encapsulated within discrete environments to examine their response to individual and combinations of matrix cues. Here, ESR1 is linked to breast cancer.