Patient-derived xenografts (PDXs) can be improved by implantation of a humanized niche. Nevertheless, the overall complexity of the current protocols, as well as the use of specific biomaterials and procedures, limits the wider adoption of this approach. Here, we identify the essential minimum steps required to create the humanized scaffolds and achieve successful acute myeloid leukemia (AML) engraftment. We compared seven biomaterials, which included both published and custom-designed materials. The highest level of bone marrow niche was achieved with extracellular matrix gels and custom collagen fiber, both of which allowed for a simple non-surgical implantation. The biomaterial selection did not influence the following AML infiltration. Regarding xenotransplantation, standard intravenous administration produced the most robust engraftment, even for two out of four otherwise non-engrafting AML samples. In contrast, direct intra-scaffold xenotransplantation did not offer any advantage. In summary, we demonstrate that the combination of an injectable biomaterial for scaffold creation plus an intravenous route for AML xenotransplantation provide the most convenient and robust approach to produce AML PDX using a humanized niche.

• Keywords
• AML, T‐cell, collagen, mouse model, ossicles, patient‐derived xenografts,
• MeSH
• Leukemia, Myeloid, Acute * pathology   MeSH
• Biocompatible Materials * pharmacology   administration & dosage   MeSH
• Heterografts MeSH
• Humans MeSH
• Mice, SCID MeSH
• Mice MeSH
• Tissue Scaffolds * chemistry   MeSH
• Transplantation, Heterologous * MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Biocompatible Materials * MeSH

Several in vitro models have been developed to mimic chronic lymphocytic leukemia (CLL) proliferation in immune niches; however, they typically do not induce robust proliferation. We prepared a novel model based on mimicking T-cell signals in vitro and in patient-derived xenografts (PDXs). Six supportive cell lines were prepared by engineering HS5 stromal cells with stable expression of human CD40L, IL4, IL21, and their combinations. Co-culture with HS5 expressing CD40L and IL4 in combination led to mild CLL cell proliferation (median 7% at day 7), while the HS5 expressing CD40L, IL4, and IL21 led to unprecedented proliferation rate (median 44%). The co-cultures mimicked the gene expression fingerprint of lymph node CLL cells (MYC, NFκB, and E2F signatures) and revealed novel vulnerabilities in CLL-T-cell-induced proliferation. Drug testing in co-cultures revealed for the first time that pan-RAF inhibitors fully block CLL proliferation. The co-culture model can be downscaled to five microliter volume for large drug screening purposes or upscaled to CLL PDXs by HS5-CD40L-IL4 ± IL21 co-transplantation. Co-transplanting NSG mice with purified CLL cells and HS5-CD40L-IL4 or HS5-CD40L-IL4-IL21 cells on collagen-based scaffold led to 47% or 82% engraftment efficacy, respectively, with ~20% of PDXs being clonally related to CLL, potentially overcoming the need to co-transplant autologous T-cells in PDXs.

• MeSH
• Stromal Cells * metabolism   pathology   MeSH
• Leukemia, Lymphocytic, Chronic, B-Cell * pathology   genetics   drug therapy   MeSH
• Protein Kinase Inhibitors pharmacology   MeSH
• Interleukin-21 MeSH
• Interleukins genetics   metabolism   MeSH
• Coculture Techniques * MeSH
• Humans MeSH
• CD40 Ligand * metabolism   genetics   MeSH
• Mice MeSH
• Cell Proliferation * MeSH
• T-Lymphocytes immunology   metabolism   MeSH
• Xenograft Model Antitumor Assays MeSH
• Animals MeSH
• Check Tag
• Humans MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Names of Substances
• Protein Kinase Inhibitors MeSH
• Interleukin-21 MeSH
• Interleukins MeSH
• CD40 Ligand * MeSH