Inducible T-cell receptor expression in precursor T cells for leukemia control

Abstract

Co-transplantation of hematopoietic stem cells with those engineered to express leukemia-reactive T cell receptors (TCRs) and differentiated ex vivo into precursor T cells (preTs) may reduce the risk of leukemia relapse. Since expression of potentially self-(leukemia-) reactive TCRs will lead to negative selection or provoke autoimmunity upon thymic maturation, we investigated a novel concept whereby TCR expression set under the control of an inducible promoter would allow timely controlled TCR expression. After in vivo maturation and gene induction, preTs developed potent anti-leukemia effects. Engineered preTs provided protection even after repeated leukemia challenges by giving rise to effector and central memory cells. Importantly, adoptive transfer of TCR-transduced allogeneic preTs mediated anti-leukemia effect without evoking graft-versus-host disease (GVHD). Earlier transgene induction forced CD8+ T cell development, was required to obtain a mature T cell subset of targeted specificity, allowed engineered T cells to efficiently pass positive selection and abrogated the endogenous T cell repertoire. Later induction favored CD4 differentiation and failed to produce a leukemia-reactive population emphasizing the dominant role of positive selection. Taken together, we provide new functional insights for the employment of TCR-engineered precursor cells as a controllable immunotherapeutic modality with significant anti-leukemia activity.

Obstacles Posed by the Tumor Microenvironment to T cell Activity: A Case for Synergistic Therapies

“…Blockade of inhibitory pathways that negatively regulate TCR signaling may prolong T cell function within the TME, but this may also sustain TCR signaling in the tumor-reactive T cells, possibly leading to more profound T cell exhaustion and/or dysfunction, and indeed it appears that such blockade may only transiently restore function (Pauken et al, 2016). However, T cell engineering should allow testing strategies that interrupt chronic TCR signaling within tumors, such as with regulated TCR expression under the control of conditional and tunable promoters (Benabdellah et al, 2016; Hoseini et al, 2015; Roybal et al, 2016), and may make it possible to prevent acquisition of irreversible T cell dysfunction. Given the heterogeneity and TME complexity across the landscape of solid tumors, much remains to be discovered about the relationship between cancer immunity and distinct TMEs.…”

Chimeric antigen receptor–induced BCL11B suppression propagates NK-like cell development

“…To track the development of CAR-expressing lymphoid progenitors in vivo, irradiated syngeneic C57BL/6 (B6) recipients were transplanted with 3 × 10 6 TCD-BM cells and adoptively transferred with 8 × 10 6 im1928z1-engineered lymphoid progenitors ( Figure 1D and Supplemental Figure 1D). Cotransplanted lymphoid progenitors have been shown to foster early repopulation of the thymus (8,11). The im1928z1-generated lymphoid progenitors did, however, completely fail to repopulate the thymus ( Figure 1E).…”

“…HSPCs transduced with a host HLA-restricted TCR and differentiated into lymphoid progenitors of the T cell lineage have been shown to mediate potent antileukemic activity upon cotransplantation with T cell-depleted BM (TCD-BM) (11). To evaluate the biological consequences of CAR expression in differentiating lymphoid progenitors both in vitro and in vivo, we cloned a previously published murine second-generation CAR directed against mouse CD19 containing a CD28 costimulatory domain and 1 functional ITAM within the CD3ζ signaling domain, termed im1928z1 ( Figure 1A; supplemental material available online with this article; https://doi.org/10.1172/ JCI126350DS1).…”

“…To evaluate the biological consequences of CAR expression in differentiating lymphoid progenitors both in vitro and in vivo, we cloned a previously published murine second-generation CAR directed against mouse CD19 containing a CD28 costimulatory domain and 1 functional ITAM within the CD3ζ signaling domain, termed im1928z1 ( Figure 1A; supplemental material available online with this article; https://doi.org/10.1172/ JCI126350DS1). CAR expression was set under the control of a tetracycline-inducible (Tet-On) T11 promoter to enable studying of the impact of time-dependent CAR expression (11,16). For inducible transgene expression, murine BM-derived Lineage -Sca-1 + c-Kit + (LSK) cells with an rtTA-M2 transactivator knockin were used.…”

“…They give rise to a functional T cell population being both tolerant and MHC restricted to the host even in MHC-mismatched recipients (8)(9)(10). TCRengineered lymphoid precursors with a host-restricted TCR lead to rapid thymic repopulation, and their progeny can mediate potent and long-lasting antileukemia effects (11).…”