Expression of promyelocytic leukemia zinc finger (PLZF) protein directs the effector differentiation of invariant NKT (iNKT) cells and IL-4⁺ γδ NKT cells. In this study, we show that PLZF is also required for the development and function of IL-17⁺ γδ T cells. We observed that PLZF is expressed in fetal-derived invariant Vγ5⁺ and Vγ6⁺ γδ T cells, which secrete IFN-γ and IL-17, respectively. PLZF deficiency specifically affected the effector differentiation of Vγ6⁺ cells, leading to reduced numbers of mature CD27⁻CD44⁺ phenotype capable of secreting IL-17. Although PLZF was not required for Vγ5⁺ γδ T cells to develop, when these cells were reprogrammed into IL-17–secreting cells in Skint-1 mutant mice, they required PLZF for their effector maturation, similarly to Vγ6⁺ γδ T cells. The impaired effector differentiation of PLZF-deficient Vγ6⁺ γδ T cells was not due to increased apoptosis and it was related to reduced proliferation of immature CD27⁺CD44⁻ Vγ6⁺ γδ T cells, which was required for their differentiation into mature CD27⁻CD44⁺ IL-17–secreting cells. Thus, the present study identifies that PLZF function is not restricted to NKT or IL-4⁺ T cells, but it also controls the development of IL-17⁺ γδ T cells.

Histone deacetylase 6 (HDAC6) inhibition is associated with an increased pro-inflammatory tumor microenvironment and antitumoral immune responses. Here, we show that the HDAC6 inhibitor AVS100 (SS208) had an antitumoral effect in SM1 melanoma and CT26 colon cancer models and increased the efficacy of anti–programmed cell death protein 1 treatment, leading to complete remission in melanoma and increased response in colon cancer. AVS100 treatment increased pro-inflammatory tumor-infiltrating macrophages and CD8 effector T cells with an inflammatory and T cell effector gene signature. Acquired T cell immunity and long-term protection were evidenced as increased immunodominant T cell clones after AVS100 treatment. Last, AVS100 showed no mutagenicity, toxicity, or adverse effects in preclinical good laboratory practice studies, part of the package that has led to US Food and Drug Administration clearance of an investigational new drug application for initiating clinical trials. This would be a first-in-human combination therapy of pembrolizumab with HDAC6 inhibition for locally advanced or metastatic solid tumors.

NK effector cells expressing a CAR construct may be used to target T-lineage markers. In this work, we compared the activity of a NK-specific CAR-NK and a CAR-T framework when expressed on NK effector cells to target CD3 and CD5 in T-cell malignancies. Our results show that CD3-CAR-T is more active than CD5-CAR-T to eliminate malignant T cells in vitro, however, CD3-CAR-T were less efficient to eliminate tumor cells in vivo, while CD5-CAR-T had antitumor activity in a diffuse xenograft model. Lack of in vivo efficacy correlated with downregulation of CD3 levels in target T cells after coculture with CD3-CAR effector cells. The CAR-NK framework greatly improved the efficacy of CARs leading to increased degranulation, cytokine secretion and elimination of the tumor xenograft by CD5-CAR-NK effector cells. Finally, all CAR constructs were similarly effective to eliminate malignant T cells in vitro. Our results show that the NK-CAR framework improves the activity of CARs in NK cells and that CD5 would be a better target than CD3 for T-cell malignancies, as dynamic downregulation of target expression may affect in vivo efficacy.

Nur77 and Nurr1 are critical for proopiomelanocortin (POMC) regulation by corticotrophin releasing hormone (CRH) in corticotrophs. We analyze the regulation and activity of Nur77 by interleukin (IL)‐1 in AtT‐20 corticotrophic cells and its consequences on POMC regulation. IL‐1 induces Nur77 and not Nurr1 mRNA and shows an increased transcriptional activity on the NurRE site, an effect dependent of p38 protein kinase activity. A NurRE mutation abrogates POMC promoter transcription by IL‐1 and a stable AtT‐20 clone overexpressing a dominant negative form of Nur77 is unresponsive to IL‐1‐dependent POMC induction and adrenocorticotrophin (ACTH) secretion. These results demonstrate that Nur77 is essential for POMC stimulation by IL‐1 in corticotrophs.

Expression of the transcription factor Zbtb1 is required for normal lymphoid development. We report in the present study that Zbtb1 maintains genome integrity in immune progenitors, without which cells undergo increased DNA damage and p53-mediated apoptosis during replication and differentiation. Increased DNA damage in Zbtb1-mutant (ScanT) progenitors was due to increased sensitivity to replication stress, which was a consequence of inefficient activation of the S-phase checkpoint response. Increased p53-mediated apoptosis affected not only lymphoid but also myeloid development in competitive bone marrow chimeras, and prevention of apoptosis by transgenic Bcl2 expression and p53 deficiency rescued lymphoid as well as myeloid development from Zbtb1-mutant progenitors. Interestingly, however, protection from apoptosis rescued only the early stages of T cell development, and thymocytes remained arrested at the double-negative 3 developmental stage, indicating a strict requirement of Zbtb1 at later T cell developmental stages. Collectively, these results indicate that Zbtb1 prevents DNA damage in replicating immune progenitors, allowing the generation of B cells, T cells, and myeloid cells.