Background: There remain a small number of patients with papillary thyroid cancer (PTC) who suffer recurrence, metastases, or death. While mutation of the BRAF gene, corresponding to the constitutively active BRAF V600E protein, has been associated with worse clinical outcomes in thyroid cancer, the reasons underlying this observation are presently unknown. Disruption of endogenous host immune surveillance and promotion of tumor immune escape is one mechanism by which BRAF V600E tumors may achieve more aggressive behavior. This study evaluated the relationship between BRAF V600E status and known strategies of tumor-mediated immune suppression. Methods: Tissue sections of PTC tumors from 33 patients were evaluated by immunohistochemistry for tumorexpressed suppressive ligands and enzymes and effector and suppressor populations of tumor-infiltrating immune cells. Presence of BRAF V600E was evaluated by direct DNA sequencing of PTC specimens and the results correlated with tumor-expressed molecules and tumor-infiltrating immune cell populations, as well as patient characteristics and pathologic findings. Results: BRAF V600E tumors more often express high levels of immunosuppressive ligands programmed death ligand 1 (53% vs. 12.5%) and human leukocyte antigen G (41% vs. 12.5%) compared to BRAF wild-type tumors. There was no association between indoleamine 2,3-dioxygenase 1 expression and BRAF V600E status. Furthermore, BRAF V600E tumors demonstrate both lower CD8 + effector to FoxP3 + regulatory T cell, and CD68 + pan-macrophage to CD163 + M2 macrophage ratios, indicating relative increases in suppressive T cell and macrophage components, respectively. Conclusions: Overall, BRAF V600E PTC tumors display a broadly immunosuppressive profile and evidence of disturbed host tumor immune surveillance that may contribute to the poorer outcomes observed in this subset of patients with thyroid cancer.

Purpose To evaluate Major Histocompatibility Complex (MHC) Class I expression on papillary thyroid cancer (PTC) and analyze changes in MHC expression and associated immune activation with current and experimental treatments for thyroid cancer using in vitro PTC cell lines. Experimental Design MHC Class I expression and assessment of tumor infiltrating leukocyte populations were evaluated by immunohistochemistry. PTC cell lines were analyzed for HLA-ABC expression by flow cytometry following tyrosine kinase inhibitor, interferon (IFN)-α or IFN-γ, or radiation treatment. Functional changes in antigenicity were assessed by co-culture of allogeneic donor peripheral blood leukocytes (PBL) with pre-treated or untreated PTC cell lines and measurement of T cell activation and cytokine production. Results Both MHC Class I and β2 microglobulin expression was reduced or absent in 76% of PTC specimens and was associated with reduced tumor infiltrating immune cells, including effector (CD3+, CD8+, CD16+) and suppressor (FoxP3+) populations. Treatment of PTC cell lines with the MEK1/2 inhibitor selumetinib or IFN increased HLA-ABC expression. This phenotypic change was associated with increased T cell activation (%CD25+ of CD3+) and interleukin 2 production by PBL co-cultured with treated PTC cell lines. Additive effects were seen with combination selumetinib and interferon treatment. Conclusions MHC Class I expression loss is frequent in human PTC specimens and represents a significant mechanism of immune escape. Increased antigenicity following selumetinib and IFN treatment warrants further study for immunotherapy of progressive PTC.

Purpose: Anaplastic lymphoma kinase (ALK)-negative, T-cell, anaplastic, non-Hodgkin lymphoma (T-ALCL) in patients with textured saline and silicone breast implants is a recently recognized clinical entity for which the etiology and optimal treatment remain unknown.Experimental Design: Using three newly established model cell lines from patient biopsy specimens, designated T-cell breast lymphoma (TLBR)-1 to -3, we characterized the phenotype and function of these tumors to identify mechanisms of cell survival and potential therapeutic targets.Results: Cytogenetics revealed chromosomal atypia with partial or complete trisomy and absence of the NPM-ALK (2;5) translocation. Phenotypic characterization showed strong positivity for CD30, CD71, T-cell CD2/5/7, and antigen presentation (HLA-DR, CD80, CD86) markers, and interleukin (IL)-2 (CD25, CD122) and IL-6 receptors. Studies of these model cell lines showed strong activation of STAT3 signaling, likely related to autocrine production of IL-6 and decreased SHP-1. STAT3 inhibition, directly or by recovery of SHP-1, and cyclophosphamide-Adriamycin-vincristine-prednisone (CHOP) chemotherapy reagents, effectively kill cells of all three TLBR models in vitro and may be pursued as therapies for patients with breast implant-associated T-ALCLs.Conclusions: The TLBR cell lines closely resemble the primary breast implant-associated lymphomas from which they were derived and as such provide valuable preclinical models to study their unique biology.

T- and NK-cell lymphomas (TCL) are a heterogenous group of lymphoid malignancies with poor prognosis. In contrast to B-cell and myeloid malignancies, there are few preclinical models of TCLs, which has hampered the development of effective therapeutics. Here we establish and characterize preclinical models of TCL. We identify multiple vulnerabilities that are targetable with currently available agents (e.g., inhibitors of JAK2 or IKZF1) and demonstrate proof-of-principle for biomarker-driven therapies using patient-derived xenografts (PDXs). We show that MDM2 and MDMX are targetable vulnerabilities within TP53-wild-type TCLs. ALRN-6924, a stapled peptide that blocks interactions between p53 and both MDM2 and MDMX has potent in vitro activity and superior in vivo activity across 8 different PDX models compared to the standard-of-care agent romidepsin. ALRN-6924 induced a complete remission in a patient with TP53-wild-type angioimmunoblastic T-cell lymphoma, demonstrating the potential for rapid translation of discoveries from subtype-specific preclinical models.

Although the mechanisms of cross-talk that regulate the hematopoietic and epithelial compartments of the thymus are well established, the interactions of these compartments with the thymic endothelium have been largely ignored. Current understanding of the thymic vasculature is based on studies of adult thymus. We show that the neonatal period represents a unique phase of thymic growth and differentiation, marked by endothelium that is organized as primitive, dense networks of capillaries dependent on vascular endothelial growth factor (VEGF). VEGF dependence in neonates is mediated by significantly higher levels of both VEGF production and endothelial VEGF receptor 2 (VEGF-R2) expression than in the adult thymus. VEGF is expressed locally in the neonatal thymus by immature, CD4 ؊ CD8 ؊ "double negative" (DN) thymocytes and thymic epithelium. Relative to adult thymus, the neonatal thymus has greater thymocyte proliferation, and a predominance of immature thymocytes and cortical thymic epithelial cells (cTECs). Inhibition of VEGF signaling during the neonatal period results in rapid loss of the dense capillaries in the thymus and a marked reduction in the number of thymocytes. These data demonstrate that, during the early postnatal period, VEGF mediates cross-talk between the thymocyte and endothelial compartments of the thymus. IntroductionThe anatomy of the adult thymus and the mechanisms of cross-talk between its hematopoietic and epithelial compartments have been extensively studied through a variety of murine genetic and transplantation models. 1 The thymic epithelial cells (TECs) of the medulla and cortex have specialized roles in directing thymocyte proliferation, differentiation, and survival through both membranebound and soluble molecules. In turn, TEC development and survival is influenced by the presence of thymocytes at specific stages of development, through as yet undefined molecular mechanisms. 2,3 The role of the third compartment of the thymus, the vascular endothelium, has been generally considered to be limited to its function as a conduit for the delivery of circulating, marrow-derived thymic precursor cells; little attention has been paid to possible mechanisms of cross-talk that may regulate the thymic vascular compartment and the role of the endothelium in thymic development.The anatomy of the blood vessels in the adult thymus that deliver circulating stem and progenitor cells is closely linked to the organization of the TEC compartment. 4 The architecture of the adult thymic vasculature is hierarchic, consisting of arterioles that enter the thymus at the corticomedullary junction (CMJ) and form capillaries that ascend into the cortex in a series of anastomoses. At the periphery of the cortex, the capillaries form a fine network of branching arcades that then curve back down to the medulla, where they merge into larger postcapillary venules. 4,5 Vascular endothelial growth factor (VEGF) is a potent mitogen that plays a role in angiogenesis, promoting the migration, growth, and survival of...