Cultures of the ERα-positive cell line MCF7 growing in ERα-positive PDSs strengthened the previously observed associations described above between gene expression and clinico-pathological variables (Table 1, Supplementary Table S4), such as an increased expression of SNAI2 (p = 0.005) and ALDH1A3 (p = 0.014) in high grade cancer. The gene discussed is ESR1; the disease is cancer.