Another way to increase the number of PDX models from biopsies is a preselection of the tumor type (e.g. focusing only on highly malignant/aggressive cases) or ex vivo enrichment of tumor cells via tumor-surface antigen-based sorting/separation (such as EpCAM or cancer-initiating/stem cells), followed by co-implantation with non-malignant stromal cells. This evidence concerns the gene EPCAM and neoplasm.