Robust patient-derived xenografts of MDS/MPN overlap syndromes capture the unique characteristics of CMML and JMML

Abstract

• Genetically accurate xenografts of CMML are achievable with near 100% frequency in NSGS mice.• Robust human engraftment and overt phenotypes of CMML and JMML xenografts here facilitate preclinical therapeutic evaluation in vivo.Chronic myelomonocytic leukemia (CMML) and juvenile myelomonocytic leukemia (JMML) are myelodysplastic syndrome (MDS)/myeloproliferative neoplasm (MPN) overlap disorders characterized by monocytosis, myelodysplasia, and a characteristic hypersensitivity to granulocyte-macrophage colony-stimulating factor (GM-CSF). Currently, there are no available disease-modifying therapies for CMML, nor are there preclinical models that fully recapitulate the unique features of CMML. Through use of immunocompromised mice with transgenic expression of human GM-CSF, interleukin-3, and stem cell factor in a NOD/SCID-IL2Rg null background (NSGS mice), we demonstrate remarkable engraftment of CMML and JMML providing the first examples of serially transplantable and genetically accurate models of CMML. Xenotransplantation of CD34 1 cells (n 5 8 patients) or unfractionated bone marrow (BM) or peripheral blood mononuclear cells (n 5 10) resulted in robust engraftment of CMML in BM, spleen, liver, and lung of recipients (n 5 82 total mice). Engrafted cells were myeloid-restricted and matched the immunophenotype, morphology, and genetic mutations of the corresponding patient. Similar levels of engraftment were seen upon serial transplantation of human CD34 1 cells in secondary NSGS recipients (2/5 patients, 6/11 mice), demonstrating the durability of CMML grafts and functionally validating CD34 1 cells as harboring the disease-initiating compartment in vivo.Successful engraftments of JMML primary samples were also achieved in all NSGS recipients (n 5 4 patients, n 5 12 mice). Engraftment of CMML and JMML resulted in overt phenotypic abnormalities and lethality in recipients, which facilitated evaluation of the JAK2/FLT3 inhibitor pacritinib in vivo. These data reveal that NSGS mice support the development of CMML and JMML disease-initiating and mature leukemic cells in vivo, allowing creation of genetically accurate preclinical models of these disorders. (Blood. 2017;130(4):397-407)

Effects of Corynebacterium bovis on Engraftment of Patient-derived Chronic-Myelomonocytic Leukemia Cells in NSGS Mice

“…Consequently, the CMML PDX mouse model is vital to understanding CMML pathogenesis and to developing improved therapeutic approaches. 31 Metrics indicative of effective human CMML PDX engraftment of NSGS mice include thrombocytopenia, splenomegaly, the presence of CMML infi ltrates in histopathologic sections of murine organs, and the presence of CD45 + cells in FACS-analyzed isolates of murine spleen, bone marrow, and peripheral blood. All of these CMML model metrics were signifi cantly decreased in the C. bovis PCRpositive cohort that we describe here.…”

“…30 In our prior report of this CMML mouse model, we demonstrated that sublethally irradiated NSGS mice are engrafted by CMML primary PDX as purified CD34 + cells, unfractionated bone marrow, or PBMC, resulting in splenomegaly, thrombocytopenia, and immunohistochemically localizable CMML infiltrates in the bone marrow, spleen, liver, and lung of engrafted NSGS mice and thus recapitulating the human condition. 31 This CMML PDX mouse model was found to be genetically and phenotypically accurate, with serially transplanted PDX cells in NSGS mice remaining similar to the original immunophenotype, morphology, and genetic mutations of the CMML patient. 31 This new mouse model permits the characterization of CMML disease pathogenesis and the testing of novel CMML therapeutics but is limited by the rarity of CMML patient specimens for NSGS mouse engraftment.…”

“…31 This CMML PDX mouse model was found to be genetically and phenotypically accurate, with serially transplanted PDX cells in NSGS mice remaining similar to the original immunophenotype, morphology, and genetic mutations of the CMML patient. 31 This new mouse model permits the characterization of CMML disease pathogenesis and the testing of novel CMML therapeutics but is limited by the rarity of CMML patient specimens for NSGS mouse engraftment. As a consequence, there is no room for error or tolerance for study invalidation…”

“…This method of CMML PDX modeling results in premoribund euthanasia of CMML PDX-recipient NSGS mice at approximately 30 to 120 d after injection and is preceded by thrombocytopenia in engrafted mice. 31 After euthanasia of CMML PDX-recipient NSGS mice, tissues including blood, spleen, liver, lung, femora, and tibiae were collected for analyses. Spleens were weighed.…”

CMML/JMML PDXs: as easy as 1, 2, NSG-SGM3

“…These morphologically, immunophenotypically, and genetically accurate models will pave the way for in vivo biological studies and preclinical testing of novel therapies. 1 …”