Cancer-targeted IL-12 controls human rhabdomyosarcoma by senescence induction and myogenic differentiation.

Stimulating the immune system to attack cancer is a promising approach, even for the control of advanced cancers. Several cytokines that promote interferon-γ-dominated immune responses show antitumor activity, with interleukin 12 (IL-12) being of major importance. Here, we used an antibody-IL-12 fusion protein (NHS-IL12) that binds histones of necrotic cells to treat human sarcoma in humanized mice. Following sarcoma engraftment, NHS-IL12 therapy was combined with either engineered IL-7 (FcIL-7) or IL-2 (IL-2MAB602) for continuous cytokine bioavailability. NHS-IL12 strongly induced innate and adaptive antitumor immunity when combined with IL-7 or IL-2. NHS-IL12 therapy significantly improved survival of sarcoma-bearing mice and caused long-term remissions when combined with IL-2. NHS-IL12 induced pronounced cancer cell senescence, as documented by strong expression of senescence-associated p16INK4a and nuclear translocation of p-HP1γ, and permanent arrest of cancer cell proliferation. In addition, this cancer immunotherapy initiated the induction of myogenic differentiation, further promoting the hypothesis that efficient antitumor immunity includes mechanisms different from cytotoxicity for efficient cancer control in vivo.

Human Peripheral CD4(+) Vδ1(+) γδT Cells Can Develop into αßT Cells.

The lifelong generation of αßT cells enables us to continuously build immunity against pathogens and malignancies despite the loss of thymic function with age. Homeostatic proliferation of post-thymic naïve and memory T cells and their transition into effector and long-lived memory cells balance the decreasing output of naïve T cells, and recent research suggests that also αßT-cell development independent from the thymus may occur. However, the sites and mechanisms of extrathymic T-cell development are not yet understood in detail. γδT cells represent a small fraction of the overall T-cell pool, and are endowed with tremendous phenotypic and functional plasticity. γδT cells that express the Vδ1 gene segment are a minor population in human peripheral blood but predominate in epithelial (and inflamed) tissues. Here, we characterize a CD4(+) peripheral Vδ1(+) γδT-cell subpopulation that expresses stem-cell and progenitor markers and is able to develop into functional αßT cells ex vivo in a simple culture system and in vivo. The route taken by this process resembles thymic T-cell development. However, it involves the re-organization of the Vδ1(+) γδTCR into the αßTCR as a consequence of TCR-γ chain downregulation and the expression of surface Vδ1(+)Vß(+) TCR components, which we believe function as surrogate pre-TCR. This transdifferentiation process is readily detectable in vivo in inflamed tissue. Our study provides a conceptual framework for extrathymic T-cell development and opens up a new vista in immunology that requires adaptive immune responses in infection, autoimmunity, and cancer to be reconsidered.

Pre-differentiated human committed T-lymphoid progenitors promote peripheral T-cell re-constitution after stem cell transplantation in immunodeficient mice.

T-cell re-constitution after allogeneic stem cell transplantation (alloSCT) is often dampened by the slow differentiation of human peripheral blood CD34(+) (huCD34(+) ) hematopoietic stem cells (HSCs) into mature T cells. This process may be accelerated by the co-transfer of in vitro-pre-differentiated committed T/NK-lymphoid progenitors (CTLPs). Here, we analysed the developmental potential of huCD34(+) HSCs compared with CTLPs from a third-party donor in a murine NOD-scid IL2Rγ(null) model of humanised chimeric haematopoiesis. CTLPs (CD34(+) lin(-) CD45RA(+) CD7(+) ) could be generated in vitro within 10 days upon co-culture of huCD34(+) or cord blood CD34(+) (CB-CD34) HSCs on murine OP9/N-DLL-1 stroma cells but not in a novel 3-D cell-culture matrix with DLL-1(low) human stroma cells. In both in vitro systems, huCD34(+) and CB-CD34(+) HSCs did not give rise to mature T cells. Upon transfer into 6-wk-old immune-deficient mice, CTLPs alone did not engraft. However, transplantation of CTLPs together with huCD34(+) HSCs resulted in rapid T-cell engraftment in spleen, bone marrow and thymus at day 28. Strikingly, at this early time point mature T cells originated exclusively from CTLPs, whereas descendants of huCD34(+) HSCs still expressed a T-cell-precursor phenotype (CD7(+) CD5(+) CD1a(+/-) ). This strategy to enhance early T-cell re-constitution with ex vivo-pre-differentiated T-lymphoid progenitors could bridge the gap until full T-cell recovery in severely immunocompromised patients after allogeneic stem cell transplantation.