Anaplastic large cell lymphoma (ALCL) is a peripheral T-cell lymphoma presenting mostly in children and young adults. The natural progression of this disease is largely unknown as is the identity of its true cell of origin. Here we present a model of peripheral ALCL pathogenesis where the malignancy is initiated in early thymocytes, before T-cell receptor (TCR) β-rearrangement, which is bypassed in CD4/NPM–ALK transgenic mice following Notch1 expression. However, we find that a TCR is required for thymic egress and development of peripheral murine tumours, yet this TCR must be downregulated for T-cell lymphomagenesis. In keeping with this, clonal TCR rearrangements in human ALCL are predominantly in-frame, but often aberrant, with clonal TCRα but no comparable clonal TCRβ rearrangement, yielding events that would not normally be permissive for survival during thymic development. Children affected by ALCL may thus harbour thymic lymphoma-initiating cells capable of seeding relapse after chemotherapy.

The impact of ultrasmall nanoparticles (<10-nm diameter) on the immune system is poorly understood. Recently, ultrasmall silica nanoparticles (USSN), which have gained increasing attention for therapeutic applications, were shown to stimulate T lymphocytes directly and at relatively low-exposure doses. Delineating underlying mechanisms and associated cell signaling will hasten therapeutic translation and is reported herein. Using competitive binding assays and molecular modeling, we established that the T cell receptor (TCR):CD3 complex is required for USSN-induced T cell activation, and that direct receptor complex–particle interactions are permitted both sterically and electrostatically. Activation is not limited to αβ TCR-bearing T cells since those with γδ TCR showed similar responses, implying that USSN mediate their effect by binding to extracellular domains of the flanking CD3 regions of the TCR complex. We confirmed that USSN initiated the signaling pathway immediately downstream of the TCR with rapid phosphorylation of both ζ-chain–associated protein 70 and linker for activation of T cells protein. However, T cell proliferation or IL-2 secretion were only triggered by USSN when costimulatory anti-CD28 or phorbate esters were present, demonstrating that the specific impact of USSN is in initiation of the primary, nuclear factor of activated T cells-pathway signaling from the TCR complex. Hence, we have established that USSN are partial agonists for the TCR complex because of induction of the primary T cell activation signal. Their ability to bind the TCR complex rapidly, and then to dissolve into benign orthosilicic acid, makes them an appealing option for therapies targeted at transient TCR:CD3 receptor binding.

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Background: Anaplastic large cell lymphoma (ALCL) is a T cell lymphoma representing 10-15% of all childhood non Hodgkin lymphomas, whereby those positive for aberrant expression of Anaplastic Lymphoma kinase (ALK) account for 50-80% of cases. The oncogene Nucleophosmin 1 (NPM)-ALK is considered the main driver of pediatric ALCL identified in 83% of ALK+ cases. ALCL cells rarely express a T cell receptor (TCR), CD4 nor CD8 despite displaying an activated cytotoxic T cell phenotype (production of perforin and Granzyme B). Expression of NPM-ALK in mice from the T-cell specific CD4 promoter (which gives rise to expression throughout thymic development) gives rise to thymic lymphomas not mimicking human ALCL suggesting other events are required for peripheral T cell lymphoma development and/or expression of NPM-ALK at different stages of T cell progression: some theories have revolved around the possibility of an infectious aetiology, or subversion of the development of T cells within the thymus in the pathogenesis of ALCL. Objective: To assess the potential cell of origin of ALCL through lineage restriction of NPM-ALK to defined T cell lineages (CD4 or CD8) using TCR transgenic mice. Experimental procedure: Disease presentation following backcrossing of the CD4/NPM-ALK mouse to a clonal transgenic TCR OT1 (CD4/NPM-ALK/OTI) or OTII (CD4/NPM-ALK/OTII) genetic background in the presence and absence of RAG was monitored. The OTI and OTII transgenic mice express a transgenic TCR which is MHC class I restricted, with a CD8 or MHC class II with a CD4 developmental skew respectively. The TCR in these mice has been engineered to recognise ovalbumin peptides (ova). Results: CD4/NPM-ALK/OTI mice develop peripheral disease histopathologically mimicking human ALCL. Conversely, CD4/NPM-ALK/OTII mice develop cortical thymic lymphomas similar to the parental CD4/NPM-ALK strain and mostly of a CD4 single positive T cell phenotype (64%). Intriguingly, the peripheral T cell tumours that develop in the CD4/NPM-ALK/OTI mice do not express the transgenic OTI TCR (or endogenously rearranged TCR). Additionally, haemopoietic tumors only occur on a RAG competent genetic background or in the absence of ova stimulation even though TCR transgene expressing T cells are detected in the periphery of these mice (CD4/NPM-ALK/OTI + MHV-ova administration or CD4/NPM-ALK/OTI/RAG-/-). Conclusions: These data represent the first murine model resembling human ALCL and suggest that restriction of NPM-ALK to the CD8 T cell lineage results in a disease more closely resembling human ALCL. Furthermore, our data suggest that in the periphery, signaling though the TCR may be pejorative towards peripheral lymphoma development. Citation Format: Tim Malcolm, Camilla J. Fairbairn, Katherine Hughes, Lukas Kenner, Amos Burke, Suzanne Turner. Assessing the origins of anaplastic large cell lymphoma in murine models via forced lineage specificity of NPM-ALK expression in T cells. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 671.

Targeting CD38 in multiple myeloma has resulted in outstanding responses. CD38 is widely expressed on myeloma cells and other hematological malignancies. Not much is known about its expression on solid tumors and its role in the immune system. We have analysed a range of solid tumors for CD38 expression and distribution. To optimally target CD38, we have generated a novel antibody that is depleting CD38-high expressing cells, but also has immune modulatory properties. To dissect CD38 expression in solid tumors we exploited mRNA expression libraries, performed immune histochemistry (IHC) on tumor sections, and flow cytometry on patient tumor material. Bioinformatic analysis of the immune cell atlas revealed varying CD38 expression among all cancers analysed, and CD38 expression could be correlated with immune markers, e.g. Foxp3, PD-1/L1. IHC and flow cytometry confirmed CD38 expression across common cancer types, mostly confined to infiltrating lymphocyte and myeloid subsets. Expression on tumor cells was patient dependent. CD38 expression on immune cells was heterogenous and found on NK cells, T cells, suppressive myeloid cells, as well as regulatory T and B cells. Of note, high expression of CD38 was found to be correlated to a subset of exhausted T cells co-expressing PD-1 and other exhaustion markers. To target CD38 in solid tumors, we have screened a panel of CD38-binding antibodies. All antibodies have the potential to deplete CD38 positive tumor cells in vitro and in vivo. Additionally, their ability to influence effector T and NK cell activation has been evaluated. Among a panel of antibodies binding to distinct epitopes of CD38 and exerting unique functional properties, we have identified a fully human antibody, with strong capacity to deplete CD38-high cells in vitro and in vivo by varying killing mechanisms. This antibody was found to increase TCR-mediated signaling and proinflammatory cytokine secretion by human T cells, and further to enhance NK cell activation in vitro. Low dose injection to non-human primates resulted in increased expression of activation markers on both CD4 and CD8 T cells, while no T cell depletion was observed. Other selected antibodies comprise distinct modalities including strong to weak agonistic activity, differential killing properties, modulation of CD38 enzymatic activity, and offer a selection of candidates applicable for different treatment settings. In summary, we found heterogenous expression of CD38 in solid tumors, mostly confined to immune subsets. To target CD38, we present a potent anti-CD38 antibody with depleting effects on CD38-expressing cancer cells, as well as suppressive immune cells, and the capacity to increase the function of immune effector cells. This dual activity might allow to fully exploit the therapeutic potential of targeting CD38, not only in hematological malignancies but also in solid tumors. Citation Format: Nina Eissler, Simone Filosto, Jake Y. Henry, Michael F. Maguire, Kristina Witt, Andreas Lundqvist, Teresa Marafioti, Pascal Merchiers, Kevin Moulder, Beatriz Goyenechea, Haw Lu, Camilla Fairbairn, Sarah Windler, JD Aurellano, Omar Duramad, Dominic Smethurst, Sergio A. Quezada, Anne Goubier. A best in class anti-CD38 antibody with antitumor and immune-modulatory properties [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3812.