Posttraumatic stress disorder (PTSD), a chronic disorder resulting from severe trauma, has been linked to immunologic dysregulation. Gene expression profiling has emerged as a promising tool for understanding the pathophysiology of PTSD. However, to date, all but one gene expression study was based on whole blood or unsorted peripheral blood mononuclear cell (PBMC), a complex tissue consisting of several populations of cells. The objective of this study was to utilize RNA sequencing to simultaneously profile the gene expression of four immune cell subpopulations (CD4T, CD8T, B cells, and monocytes) in 39 World Trade Center responders (20 with and 19 without PTSD) to determine which immune subsets play a role in the transcriptomic changes found in whole blood. Transcriptome-wide analyses identified cell-specific and shared differentially expressed genes across the four cell types.FKBP5 and PI4KAP1genes were consistently upregulated across all cell types. Notably,RESTandSEPT4, genes linked to neurodegeneration, were among the top differentially expressed genes in monocytes. Pathway analyses identified differentially expressed gene sets involved in mast cell activation and regulation in CD4T, interferon-beta production in CD8T, and neutrophil-related gene sets in monocytes. These findings suggest that gene expression indicative of immune dysregulation is common across several immune cell populations in PTSD. Furthermore, given notable differences between cell subpopulations in gene expression associated with PTSD, the results also indicate that it may be valuable to analyze different cell populations separately. Monocytes may constitute a key cell type to target in research on gene expression profile of PTSD.

Protein recoding by RNA editing is required for normal health and evolutionary adaptation. However, de novo induction of RNA editing in response to environmental factors is an uncommon phenomenon. While APOBEC3A edits many mRNAs in monocytes and macrophages in response to hypoxia and interferons, the physiological significance of such editing is unclear. Here, we show that the related cytidine deaminase, APOBEC3G, induces site-specific C-to-U RNA editing in natural killer cells, lymphoma cell lines, and, to a lesser extent, CD8-positive T cells upon cellular crowding and hypoxia. In contrast to expectations from its anti-HIV-1 function, the highest expression of APOBEC3G is shown to be in cytotoxic lymphocytes. RNA-seq analysis of natural killer cells subjected to cellular crowding and hypoxia reveals widespread C-to-U mRNA editing that is enriched for genes involved in mRNA translation and ribosome function. APOBEC3G promotes Warburg-like metabolic remodeling in HuT78 T cells under similar conditions. Hypoxia-induced RNA editing by APOBEC3G can be mimicked by the inhibition of mitochondrial respiration and occurs independently of HIF-1α. APOBEC3G is an endogenous RNA editing enzyme in primary natural killer cells and lymphoma cell lines. This RNA editing is induced by cellular crowding and mitochondrial respiratory inhibition to promote adaptation to hypoxic stress.

Alterations in myelopoiesis are common across various tumor types, resulting in immature populations termed myeloid-derived suppressor cells (MDSCs). MDSC burden correlates with poorer clinical outcomes, credited to their ability to suppress antitumor immunity. MDSCs consist of two major subsets, monocytic and polymorphonuclear (PMN). Intriguingly, the latter subset predominates in many patients and tumor models, although the mechanisms favoring PMN-MDSC responses remain poorly understood. Ordinarily, lineage-restricted transcription factors regulate myelopoiesis that collectively dictate cell fate. One integral player is IFN regulatory factor (IRF)–8, which promotes monocyte/dendritic cell differentiation while limiting granulocyte development. We recently showed that IRF8 inversely controls MDSC burden in tumor models, particularly the PMN-MDSC subset. However, where IRF8 acts in the pathway of myeloid differentiation to influence PMN-MDSC production has remained unknown. In this study, we showed that: 1) tumor growth was associated with a selective expansion of newly defined IRF8lo granulocyte progenitors (GPs); 2) tumor-derived GPs had an increased ability to form PMN-MDSCs; 3) tumor-derived GPs shared gene expression patterns with IRF8−/− GPs, suggesting that IRF8 loss underlies GP expansion; and 4) enforced IRF8 overexpression in vivo selectively constrained tumor-induced GP expansion. These findings support the hypothesis that PMN-MDSCs result from selective expansion of IRF8lo GPs, and that strategies targeting IRF8 expression may limit their load to improve immunotherapy efficacy.

Pro-inflammatory M1 macrophage polarization is associated with microbicidal and antitumor responses. We recently described APOBEC3A-mediated cytosine-to-uracil (C > U) RNA editing during M1 polarization. However, the functional significance of this editing is unknown. Here we find that APOBEC3A-mediated cellular RNA editing can also be induced by influenza or Maraba virus infections in normal human macrophages, and by interferons in tumor-associated macrophages. Gene knockdown and RNA_Seq analyses show that APOBEC3A mediates C>U RNA editing of 209 exonic/UTR sites in 203 genes during M1 polarization. The highest level of nonsynonymous RNA editing alters a highly-conserved amino acid in THOC5, which encodes a nuclear mRNA export protein implicated in M-CSF-driven macrophage differentiation. Knockdown of APOBEC3A reduces IL6, IL23A and IL12B gene expression, CD86 surface protein expression, and TNF-α, IL-1β and IL-6 cytokine secretion, and increases glycolysis. These results show a key role of APOBEC3A cytidine deaminase in transcriptomic and functional polarization of M1 macrophages.

Recurrent ovarian cancer patients, especially those resistant to platinum, lack effective curative treatments. To address this, we conducted a phase 2 clinical trial (NCT02853318) combining pembrolizumab with bevacizumab, to increase T cell infiltration into the tumor, and oral cyclophosphamide, to reduce the number of regulatory T cells. The trial accrued 40 heavily pretreated recurrent ovarian cancer patients. The primary endpoint, progression free survival, was extended to a median of 10.2 months. The secondary endpoints demonstrated an objective response rate of 47.5%, and disease control in 30% of patients for over a year while maintaining a good quality of life. We performed comprehensive molecular, immune, microbiome, and metabolic profiling on samples of trial patients. Here, we show increased T and B cell clusters and distinct microbial patterns with amino acid and lipid metabolism are linked to exceptional clinical responses. This study suggests the immune milieu and host-microbiome can be leveraged to improve antitumor response in future immunotherapy trials.