Abstract 5631: Leukaemia and lymphoma patient-derived xenografts (PDX) engraft on humanized mice and respond to immune therapy with check point inhibitors
Authors: Stecklum Maria , Wulf-Goldenberg Annika , Siegert Antje , Brzezicha Bernadette , Sterner-Kock Anja , Walther Wolfgang , Hoffmann Jens 
Published: September 2020

Abstract
Background
The preclinical evaluation of novel immune therapies for cancer remains a challenge, as models require both, engraftment of human tumor cells and a matching human immune cell population. In previous experiments, we have demonstrated, that we can use either peripheral blood mononuclear cells (PBMC) or hematopoietic stem cells (HSC) to establish a humanized immune system on highly immunodeficient mice. In this study, we transplanted patient-derived xenografts (PDX) from leukaemia and lymphoma on these humanized mice. Further, we validated the models by evaluating treatments with checkpoint inhibitors Nivolumab (Nivo) and Ipilimumab (Ipi) or standard of care therapies.
Methods
HSC were transplanted i.v. on immunodeficient mice. Engraftment of human immune cells was monitored by FACS analysis of blood samples. Three lymphoma PDX and one acute myeloid leukaemia (AML) model were s.c. transplanted on humanized mice. To model systemic leukaemia, three AML models were transplanted i.v. on humanized mice. Engraftment of the PDX was compared to growth on non-humanized mice. After successful engraftment, mice were treated with Nivo, Ipi or in combination with standard therapies and irradiation.
Results
We confirmed successful engraftment of HSC in the humanized mice. Within 14 weeks after HSC inoculation, FACS analysis revealed an established functional human immune system with up to 20% T-cells, characterized by a high PD-1 expression. The s.c. transplanted leukaemia and lymphoma PDX engrafted on the humanized mice and tumor growth was measured with calipers. Engraftment of i.v. transplanted AML models was confirmed by FACS measurement of human CD33+ AML cells in the blood of the humanized mice. Treatment with Ipi or Nivo alone or in combination led to a minor growth delay. FACS analysis confirmed an increased percentage of activated T-cells in the blood and in the s.c. tumors. Response to checkpoint inhibitors was in correlation to PD-L1 expression on the lymphoma and AML cells. Combination of check point inhibitors with radiotherapy provided additive effects in our models.
Conclusions
We developed a humanized immune-PDX model for different blood cancers enabling appropriate preclinical translational research on tumor immune biology and the evaluation of new therapies and combinations, as well as the identification and validation of biomarkers for immune therapy. These novel model are currently optimized for the preclinical evaluation of new bispecific immune cell engagers (BITE) and cell therapies (CART).
Citation Format: Maria Stecklum, Annika Wulf-Goldenberg, Antje Siegert, Bernadette Brzezicha, Anja Sterner-Kock, Wolfgang Walther, Jens Hoffmann. Leukaemia and lymphoma patient-derived xenografts (PDX) engraft on humanized mice and respond to immune therapy with check point inhibitors [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5631.