Abstract
In acute lymphoblastic leukemia (ALL), conventional cell lines do not recapitulate the clonal diversity and microenvironment. Orthotopic patient-derived xenograft models (PDX) overcome these limitations and mimic the clinical situation, but molecular stability and engraftment patterns have not yet been thoroughly assessed. We herein describe and characterize the PDX generation in NSG mice. In vivo tumor cell proliferation, engraftment and location were monitored by flow cytometry and bioluminescence imaging. Leukemic cells were retransplanted for up to four passages, and comparative analyses of engraftment pattern, cellular morphology and genomic hotspot mutations were conducted. Ninety-four percent of all samples were successfully engrafted, and the xenograft velocity was dependent on the molecular subtype, outcome of the patient and transplantation passage. While BCR::ABL1 blasts were located in the spleen, KMT2A-positive cases had higher frequencies in the bone marrow. Molecular changes appeared in most model systems, with low allele frequency variants lost during primary engraftment. After the initial xenografting, however, the PDX models demonstrated high molecular stability. This protocol for reliable ALL engraftment demonstrates variability in the location and molecular signatures during serial transplantation. Thorough characterization of experimentally used PDX systems is indispensable for the correct analysis and valid data interpretation of preclinical PDX studies.
Highlights
More than 95% of all therapeutic agents in the oncology sector that demonstrate preclinical activity fail during clinical development
As the classical cell line models do not recapitulate the polyclonal landscape of the initial tumors and primary cells are very difficult to cultivate in vitro, patient-derived xenograft models (PDX) systems are indispensable for the evaluation of novel therapeutic approaches and other hematological issues
There are obvious changes in the molecular landscape between primary sample and PDX mice in the majority of the cases investigated, PDX model systems remain a crucial part of preclinical acute lymphoblastic leukemia (ALL) research
Summary
More than 95% of all therapeutic agents in the oncology sector that demonstrate preclinical activity fail during clinical development. This is, in most cases, due to a lack of efficacy [1,2,3]. To further replicate the tumor microenvironment, ALL cells can be maintained in coculture with irradiated human or murine stromal feeder cells [10,11,12]. This procedure is technically challenging but allows longer cultivation periods of several weeks up to months
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