Conventional type 1 dendritic cells (cDC1s 1 ) are thought to perform antigen cross-presentation required to prime CD8 T cells 2 , 3 , while cDC2 are considered specialized for priming CD4 T cells 4 , 5 . CD4 T cells are also thought to help CD8 T cell responses through a variety of mechanisms 6 – 11 , including a model in which CD4 T cells ‘license’ cDC1 for CD8 T cell priming 12 . However, this model has not been directly tested in vivo or in the setting of a help-dependent tumour rejection. Here, we generated an Xcr1 -Cre mouse strain to evaluate the cellular interactions that mediate tumour rejection in a model requiring CD4 and CD8 T cells. As expected, tumour rejection required cDC1, and expression of MHC-I by cDC1. Unexpectedly, early priming of CD4 T cell against tumour-derived antigens also required cDC1, which was not simply due to a role in antigen transport to lymph nodes for processing by cDC2, since selective deletion of MHC-II in cDC1 also prevented early CD4 T cell priming. Further, deletion of either MHC-II or CD40 in cDC1 impaired tumour rejection, consistent with a role for cognate CD4 T cell interactions and CD40 signaling in cDC1 licensing. Finally, CD40 signaling in cDC1 was critical not only for CD8 T cell priming, but also for initial CD4 T cell activation. Thus, in the setting of tumour-derived antigens, cDC1 function as an autonomous platform capable of antigen processing and priming for both CD4 and CD8 T cells and directly orchestrating their cross-talk required for optimal anti-tumour immunity.

During the process of cross presentation, viral or tumor-derived antigens are presented to CD8+ T cells by the Batf3-dependent CD8α+/XCR1+ classical dendritic cell (cDC1). We designed a functional CRISPR screen for novel regulators of cross presentation, and identified the BEACH-domain containing protein WDFY4 as essential for cross-presentation of cell-associated antigens by cDC1. WDFY4 was not, however, required for MHC class II presentation or for cross-presentation by monocyte-derived DCs. In contrast to Batf3−/− mice, Wdfy4−/− mice have normal lymphoid and non-lymphoid cDC1 populations that produce IL-12 and protect against Toxoplasma gondii infection. However similar to Batf3−/− mice, Wdfy4−/− mice fail to prime virus- specific CD8+ T cells in vivo or induce tumor rejection, revealing a critical role for cross-presentation in anti-viral and anti-tumor immunity.

Induction of the transcription factor Irf8 in the common dendritic cell progenitor (CDP) is required for classical type 1 dendritic cell (cDC1) fate specification, but the mechanisms controlling this induction are unclear. Here we identified Irf8 enhancers via chromatin profiling of DCs and used CRISPR/Cas9 genome editing to assess their roles in Irf8 regulation. An enhancer 32 kilobases downstream of the Irf8 transcriptional start site (+32 kb Irf8 ) that was active in mature cDC1s was required for the development of this lineage, but not for its specification. Instead, a +41 kb Irf8 enhancer previously thought to be active only in plasmacytoid DCs was found to also be transiently accessible in cDC1 progenitors, and deleting this enhancer prevented the induction of Irf8 in CDPs and abolished cDC1 specification. Thus, cryptic activation of the +41 kb Irf8 enhancer in DC progenitors is responsible for cDC1 fate specification.

Based on the concept that anticocaine antibodies could prevent inhaled cocaine from reaching its target receptors in the brain, an effective anticocaine vaccine could help reverse cocaine addiction. Leveraging the knowledge that E1(-)E3(-) adenovirus (Ad) gene transfer vectors are potent immunogens, we have developed a novel vaccine platform for addictive drugs by covalently linking a cocaine analog to the capsid proteins of noninfectious, disrupted Ad vector. The Ad-based anticocaine vaccine evokes high-titer anticocaine antibodies in mice sufficient to completely reverse, on a persistent basis, the hyperlocomotor activity induced by intravenous administration of cocaine.

SignificanceHigh-affinity antibody responses involve selection of B cells in the germinal center (GC) by cognate interactions with T follicular helper (TFH) cells, which in turn must first be activated by classical dendritic cells (cDCs). We observe that Notch2-dependent cDC2s are required in vivo for induction of TFH cells, GC B cells, and specific antibody production in response to sheep red blood cell (SRBC) immunization. Notch2 signaling impacted a broad transcriptional program in cDC2s both at homeostasis and after SRBC immunization, although we have not identified a target gene that mediates TFH differentiation. Thus, Notch2 is a transcription factor that acts in cDCs and is selectively required for support of the GC reaction.

Histone lysine demethylases facilitate the activity of oncogenic transcription factors including possibly MYC. Here we show that multiple histone demethylases influence the viability and poor prognosis of neuroblastoma cells where MYC is often overexpressed. We also identified the approved small molecule antifungal agent ciclopirox as a novel pan-histone demethylase inhibitor. Ciclopirox targeted several histone demethylases including KDM4B implicated in MYC function. Accordingly, ciclopirox inhibited Myc signaling in parallel with mitochondrial oxidative phosphorylation, resulting in suppression of neuroblastoma cell viability and inhibition of tumor growth associated with an induction of differentiation. Our findings provide new insights into epigenetic regulation of MYC function and suggest a novel pharmacologic basis to target histone demethylases as an indirect MYC targeting approach for cancer therapy.

IMPORTANCE Little information is available regarding the minimum number of lymph nodes needed to accurately stage patients when performing a mesenteric lymphadenectomy for small-bowel neuroendocrine tumors. OBJECTIVES To determine the prognostic role of lymph node positivity and the ideal number of lymph nodes for accurately staging patients with small-bowel neuroendocrine tumors. DESIGN, SETTING, AND PARTICIPANTS This case series from the US Neuroendocrine Tumor Study Group, a collaboration among 8 US-based, academic tertiary care referral centers, obtained demographic, perioperative, and pathologic data from the group's database, Social Security Death Index, and publicly available obituaries. All patients in these institutions with small-bowel neuroendocrine tumors who underwent curative-intent surgical resection of a primary tumor between January 1, 2000, and December 31, 2015, were included (n = 199). Patients with duodenal or ampullary tumors, other nonneuroendocrine concurrent malignant neoplasms, mortality of fewer than 30 days after the surgical procedure, and distant metastatic disease were excluded. Data analysis was conducted from September 1, 2017, to December 1, 2017. MAIN OUTCOMES AND MEASURES Primary study outcome was recurrence-free survival. Hypothesis was generated after data collection and data entry into the US Neuroendocrine Tumor Study Group database. RESULTS Of the 199 patients included, 112 (56.3%) were male and 87 (43.7%) female with a mean (SD) age of 60.3 (12.5) years and a mean (SD) body mass index of 29.5 (6.0). One hundred fifty-four patients (77.4%) had lymph node-positive disease. No difference in 3-year recurrence-free survival was found between patients with lymph node-positive and lymph node-negative disease. Patients with 4 positive lymph nodes had a worse 3-year recurrence-free survival compared with those with 1 to 3 or 0 positive lymph nodes (81.6% vs 91.4% vs 92.1%; P = .01). When examining patients with fewer than 8 resected lymph nodes, no difference in 3-year recurrence-free survival was observed among patients with 4 or more, 1 to 3, or 0 positive lymph nodes (100% vs 93.8% vs 91.7%; P = .87). Retrieval of 8 or more lymph nodes, however, accurately discriminated patients with 4 or more, 1 to 3, or 0 positive lymph nodes (3-year recurrence-free survival: 79.9% vs 89.6% vs 92.9%; P = .05). CONCLUSIONS AND RELEVANCE The findings from this study suggest that, for patients undergoing curative-intent resection of small-bowel neuroendocrine tumors, accurate lymph node staging requires a minimum of 8 lymph nodes for examination, and 4 or more positive lymph nodes are associated with decreased 3-year recurrence-free survival compared with 1 to 3 or 0 positive lymph nodes; a thorough regional lymphadenectomy may be critical for accurate staging and management of this disease.

Durai et al. demonstrate that the less severe DC deficiency in Flt3–/– mice compared to Flt3l–/– mice is due to the enhanced sensitivity of Flt3–/– progenitors to compensatory cytokines that support DC development.