CD274 and breast cancer: To investigate if different cancer microenvironments provided by the PDSs could trigger changes in immune modulating molecules in cancer cells, we analyzed the expression of the PD-1 ligands PD-L1 and PD-L2 genes in the breast cancer cell lines MCF-7 and MDA-MB-231, adapted and expanding in 110 and 84 breast cancer PDSs respectively (Experimental workflow in Fig. 1, Supplementary Table 1).