Therapeutic targeting of Notch signaling and immune checkpoint blockade in a spontaneous, genetically heterogeneous mouse model of T-cell acute lymphoblastic leukemia.

Jie Gao,Gavin Thurston,Ying Huang,Michael Van Meter,Shumei Ren,Susana Hernandez Lopez,Guoying Chen,Qi Zhao,Jose Rojas,Frank Kuhnert,Cagan Gurer

doi:10.1242/dmm.040931

Abstract

ABSTRACTT-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic cancer derived from the malignant transformation of T-cell progenitors. Outcomes remain poor for T-ALL patients who have either primary resistance to standard-of-care chemotherapy or disease relapse. Notably, there are currently no targeted therapies available in T-ALL. This lack of next-generation therapies highlights the need for relevant preclinical disease modeling to identify and validate new targets and treatment approaches. Here, we adapted a spontaneously arising, genetically heterogeneous, thymic transplantation-based murine model of T-ALL, recapitulating key histopathological and genetic features of the human disease, to the preclinical testing of targeted and immune-directed therapies. Genetic engineering of the murine Notch1 locus aligned the spectrum of Notch1 mutations in the mouse model to that of human T-ALL and confirmed aberrant, recombination-activating gene (RAG)-mediated 5′ Notch1 recombination events as the preferred pathway in murine T-ALL development. Testing of Notch1-targeting therapeutic antibodies demonstrated T-ALL sensitivity to different classes of Notch1 blockers based on Notch1 mutational status. In contrast, genetic ablation of Notch3 did not impact T-ALL development. The T-ALL model was further applied to the testing of immunotherapeutic agents in fully immunocompetent, syngeneic mice. In line with recent clinical experience in T-cell malignancies, programmed cell death 1 (PD-1) blockade alone lacked anti-tumor activity against murine T-ALL tumors. Overall, the unique features of the spontaneous T-ALL model coupled with genetic manipulations and the application to therapeutic testing in immunocompetent backgrounds will be of great utility for the preclinical evaluation of novel therapies against T-ALL.

Highlights

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic tumor which arises from the malignant transformation of T-cell progenitors (Belver and Ferrando, 2016; Vadillo et al, 2018)
Generation and characterization of the thymustransplantation-based murine T-ALL model To set up the thymus-transplantation-based mouse T-ALL model, newborn wild-type B6.Ly5.1 thymus (CD45.1+) was implanted under the kidney capsule of T-cell-progenitor-deficient CD45.2+ Rag2−/− Ιl2rg−/− [double knockout (DKO)] mice, as described previously (Martins et al, 2014)
Heterodimerization (HD) domain mutations were present in 25%, similar to the Notch1 HDD mutation frequency of 33% in human T-ALL patients (Grabher et al, 2006), compared to 11% in wildtype Notch1 thymus-derived T-ALL (Fig. 2D). These findings suggest that the ablation of cryptic recombination-activating gene (RAG)-mediated 5′ recombination events in the murine Notch1 locus does change the range of Targeting of oncogenic Notch1 signaling NOTCH1 is a critical oncogenic driver in T-ALL, and activating NOTCH1 mutations are present in around 60% of T-ALL patient tumors (Radtke et al, 2004; Weng et al, 2004)

Summary

Introduction

T-cell acute lymphoblastic leukemia (T-ALL) is an aggressive hematologic tumor which arises from the malignant transformation of T-cell progenitors (Belver and Ferrando, 2016; Vadillo et al, 2018). There are currently no targeted therapies available, and current immunotherapies have so far not proven effective in T-ALL (Ishitsuka et al, 2018; Ratner et al, 2018). Overall, this lack of effective treatment options necessitates the discovery of new therapeutic strategies and a better understanding of the disease biology (Litzow and Ferrando, 2015; Van Vlierberghe and Ferrando, 2012)

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Results

Conclusion