Dimethyl itaconate selectively targets inflammatory and metabolic pathways in chronic lymphocytic leukemia.

Chronic lymphocytic leukemia (CLL) co-evolves with its own microenvironment where inflammatory stimuli including toll-like receptors (TLR) signaling can protect CLL cells from spontaneous and drug-induced apoptosis by upregulating IκBζ, an atypical co-transcription factor. To dissect IκBζ-centered signaling pathways, we performed a gene expression profile of primary leukemic cells expressing either high or low levels of IκBζ after stimulation, highlighting that IκBζ is not only an inflammatory gene but it may control metabolic rewiring of malignant cells thus pointing to a novel potential opportunity for therapy. We exploited the capacity of the dimethyl itaconate (DI), an anti-inflammatory electrophilic synthetic derivative of the metabolite Itaconate, to target IκBζ. CLL cells, murine leukemic splenocytes, and leukocytes from healthy donors were treated in vitro with DI that abolished metabolic activation and reduced cell viability of leukemic cells only, even in the presence of robust TLR prestimulation. RNA sequencing highlighted that in addition to the expected electrophilic stress signature observed after DI treatment, novel pathways emerged including the downregulation of distinct MHC class II complex genes. In conclusion, DI not only abrogated the proinflammatory effects of TLR stimulation but also targeted a specific metabolic vulnerability in CLL cells.

A fluorescent reporter model for the visualization and characterization of TDC.

TDC are hematopoietic cells that combine dendritic cell (DC) and conventional T-cell markers and functional properties. They were identified in secondary lymphoid organs (SLOs) of naïve mice as cells expressing CD11c, major histocompatibility molecules (MHC)-II, and the T-cell receptor (TCR). Despite thorough characterization, a physiological role for TDC remains to be determined. Unfortunately, using CD11c as a marker for TDC has the caveat of its upregulation on different cells, including T cells, upon activation. Here, we took advantage of Zbtb46-GFP reporter mice to explore the frequency and localization of TDC in different tissues at steady state and upon viral infection. RNA sequencing analysis confirmed that TDC sorted from Zbtb46-GFP mice have a gene signature that is distinct from conventional T cells and DC. In addition, this reporter model allowed for identification of TDC in situ not only in SLOs but also in the liver and lung of naïve mice. Interestingly, we found that TDC numbers in the SLOs increased upon viral infection, suggesting that TDC might play a role during viral infections. In conclusion, we propose a visualization strategy that might shed light on the physiological role of TDC in several pathological contexts, including infection and cancer.

ZFP423 regulates early patterning and multiciliogenesis in the hindbrain choroid plexus.

The choroid plexus (ChP) is a secretory tissue that produces cerebrospinal fluid (CSF) secreted into the ventricular system. It is a monolayer of secretory, multiciliated epithelial cells derived from neuroepithelial progenitors and overlying a stroma of mesenchymal cells of mesodermal origin. Zfp423, which encodes a Kruppel-type zinc-finger transcription factor essential for cerebellar development and mutated in rare cases of cerebellar vermis hypoplasia/Joubert syndrome and other ciliopathies, is expressed in the hindbrain roof plate, from which the IV ventricle ChP arises, and, later, in mesenchymal cells, which give rise to the stroma and leptomeninges. Mouse Zfp423 mutants display a marked reduction of the hindbrain ChP (hChP), which: (1) fails to express established markers of its secretory function and genes implicated in its development and maintenance (Lmx1a and Otx2); (2) shows a perturbed expression of signaling pathways previously unexplored in hChP patterning (Wnt3); and (3) displays a lack of multiciliated epithelial cells and a profound dysregulation of master genes of multiciliogenesis (Gmnc). Our results propose that Zfp423 is a master gene and one of the earliest known determinants of hChP development.

miR-17∼92 family clusters control iNKT cell ontogenesis via modulation of TGF-ß signaling.

Invariant natural killer T cells (iNKT) cells are T lymphocytes displaying innate effector functions, acquired through a distinct thymic developmental program regulated by microRNAs (miRNAs). Deleting miRNAs by Dicer ablation (Dicer KO) in thymocytes selectively impairs iNKT cell survival and functional differentiation. To unravel this miRNA-dependent program, we systemically identified transcripts that were differentially expressed between WT and Dicer KO iNKT cells at different differentiation stages and predicted to be targeted by the iNKT cell-specific miRNAs. TGF-ß receptor II (TGF-ßRII), critically implicated in iNKT cell differentiation, was found up-regulated in iNKT Dicer KO cells together with enhanced TGF-ß signaling. miRNA members of the miR-17∼92 family clusters were predicted to target Tgfbr2 mRNA upon iNKT cell development. iNKT cells lacking all three miR-17∼92 family clusters (miR-17∼92, miR-106a∼363, miR-106b∼25) phenocopied both increased TGF-ßRII expression and signaling, and defective effector differentiation, displayed by iNKT Dicer KO cells. Consistently, genetic ablation of TGF-ß signaling in the absence of miRNAs rescued iNKT cell differentiation. These results elucidate the global impact of miRNAs on the iNKT cell developmental program and uncover the targeting of a lineage-specific cytokine signaling by miRNAs as a mechanism regulating innate-like T-cell development and effector differentiation.

A novel function for FOXP3 in humans: intrinsic regulation of conventional T cells.

The role of forkhead box P3 (FOXP3) is well-established in T-regulatory cells, but the function of transient FOXP3 expression in activated human conventional T (Tconv) cells is unknown. In the present study, we used 2 approaches to determine the role of FOXP3 in human Tconv cells. First, we obtained Tconv clones from a female subject who is hemizygous for a null mutation in FOXP3, allowing the comparison of autologous T-cell clones that do or do not express FOXP3. Second, we knocked down activation-induced FOXP3 in Tconv cells from healthy donors with small interfering RNAagainst FOXP3. We found that FOXP3-deficient Tconv cells proliferate more and produce more cytokines than wild-type Tconv cells and have differential expression of 274 genes. We also investigated the role of FOXP3 in Th1 and Th17 cells and found that the expression of activation-induced FOXP3 was higher and more sustained in Th17 cells compared with Th1 cells. Knocking down FOXP3 expression in Th17 cells significantly increased the production of IFN-γ and decreased the expression of CCR4, but had no effect on IL-17 expression. These data reveal a novel function of FOXP3 in Tconv cells and suggest that expression of this protein is important in the function of multiple CD4(+) T-cell lineages.

Amino acid starvation induces reactivation of silenced transgenes and latent HIV-1 provirus via down-regulation of histone deacetylase 4 (HDAC4).

The epigenetic silencing of exogenous transcriptional units integrated into the genome represents a critical problem both for long-term gene therapy efficacy and for the eradication of latent viral infections. We report here that limitation of essential amino acids, such as methionine and cysteine, causes selective up-regulation of exogenous transgene expression in mammalian cells. Prolonged amino acid deprivation led to significant and reversible increase in the expression levels of stably integrated transgenes transcribed by means of viral or human promoters in HeLa cells. This phenomenon was mediated by epigenetic chromatin modifications, because histone deacetylase (HDAC) inhibitors reproduced starvation-induced transgene up-regulation, and transcriptome analysis, ChIP, and pharmacological and RNAi approaches revealed that a specific class II HDAC, namely HDAC4, plays a critical role in maintaining the silencing of exogenous transgenes. This mechanism was also operational in cells chronically infected with HIV-1, the etiological agent of AIDS, in a latency state. Indeed, both amino acid starvation and pharmacological inhibition of HDAC4 promoted reactivation of HIV-1 transcription and reverse transcriptase activity production in HDAC4(+) ACH-2 T-lymphocytic cells but not in HDAC4(-) U1 promonocytic cells. Thus, amino acid deprivation leads to transcriptional derepression of silenced transgenes, including integrated plasmids and retroviruses, by a process involving inactivation or down-regulation of HDAC4. These findings suggest that selective targeting of HDAC4 might represent a unique strategy for modulating the expression of therapeutic viral vectors, as well as that of integrated HIV-1 proviruses in latent reservoirs without significant cytotoxicity.

Disrupting pro-survival and inflammatory pathways with dimethyl fumarate sensitizes chronic lymphocytic leukemia to cell death.

Microenvironmental signals strongly influence chronic lymphocytic leukemia (CLL) cells through the activation of distinct membrane receptors, such as B-cell receptors, and inflammatory receptors, such as Toll-like receptors (TLRs). Inflammatory pathways downstream of these receptors lead to NF-κB activation, thus protecting leukemic cells from apoptosis. Dimethyl fumarate (DMF) is an anti-inflammatory and immunoregulatory drug used to treat patients with multiple sclerosis and psoriasis in which it blocks aberrant NF-κB pathways and impacts the NRF2 antioxidant circuit. Our in vitro analysis demonstrated that increasing concentrations of DMF reduce ATP levels and lead to the apoptosis of CLL cells, including cell lines, splenocytes from Eµ-TCL1-transgenic mice, and primary leukemic cells isolated from the peripheral blood of patients. DMF showed a synergistic effect in association with BTK inhibitors in CLL cells. DMF reduced glutathione levels and activated the NRF2 pathway; gene expression analysis suggested that DMF downregulated pathways related to NFKB and inflammation. In primary leukemic cells, DMF disrupted the TLR signaling pathways induced by CpG by reducing the mRNA expression of NFKBIZ, IL6, IL10 and TNFα. Our data suggest that DMF targets a vulnerability of CLL cells linked to their inflammatory pathways, without impacting healthy donor peripheral blood mononuclear cells.

Stool Microbiome Signature Associated with Response to Neoadjuvant Pembrolizumab in Patients with Muscle-invasive Bladder Cancer.

Neoadjuvant pembrolizumab has been shown to be a valid treatment for patients affected by muscle-invasive bladder cancer (MIBC), as demonstrated in the PURE-01 clinical trial (NCT02736266). Among the tumor-extrinsic factors influencing immunotherapy efficacy, extensive data highlighted that the microbiome is a central player in immune-mediated anticancer activity. This report aimed to investigate the composition and role of stool microbiome in patients enrolled in the PURE-01 clinical trial. An orthotopic animal model of bladder cancer (MB49-Luc) was used to support some of the findings from human data. An analysis of stool microbiome before pembrolizumab was conducted for 42 patients, of whom 23 showed a pathologic response. The information in the preclinical model of orthotopic bladder cancer treated with anti-PD-1 antibody or control isotype was validated. Linear discriminant analysis effect size and linear models were used to identify the bacterial taxa enriched in either responders or nonresponders. The identified taxa were also tested for their association with event-free survival (EFS). Survival at 31 d after tumor instillation was used as the study endpoint in the preclinical model. Responders and nonresponders emerged to differ in terms of enrichment for 16 bacterial taxa. Of these, the genus Sutterella was enriched in responders, while the species Ruminococcus bromii was enriched in nonresponders. The negative impact of R. bromii on anti-PD-1 antibody activity was also observed in the preclinical model. EFS and survival of the preclinical model showed a negative role of R. bromii. We found different stool bacterial taxa associated with the response or lack of response to neoadjuvant pembrolizumab. Moreover, we provided experimental data about the negative role of R. bromii on immunotherapy response. Further studies are needed to externally validate our findings and provide mechanistic insights about the host-pathogen interactions in MIBC. PATIENT SUMMARY: Using prepembrolizumab stool samples collected from patients enrolled in the PURE-01 clinical trials, we identified some bacterial taxa that were enriched in patients who either responded or did not respond to immunotherapy. Using an animal model of bladder cancer, we gathered further evidence of the negative impact of the Ruminococcus bromii on immunotherapy efficacy. Further studies are needed to confirm the current findings and test the utility of these bacteria as predictive markers of immunotherapy response.

Protein profiling reveals energy metabolism and cytoskeletal protein alterations in LMNA mutation carriers.

Nuclear envelope-related muscular dystrophies, in particular those referred to as laminopathies, are relatively novel and unclear diseases, also considering the increasing number of mutations identified so far in genes of the nuclear envelope. As regard LMNA gene, only tentative relations between phenotype, type and localization of the mutations have been established in striated muscle diseases, while laminopathies affecting adipose tissue, peripheral nerves or progerioid syndromes could be linked to specific genetic variants. This study describes the biochemical phenotype of neuromuscular laminopathies in samples derived from LMNA mutant patients. Since it has been reported that nuclear alterations, due to LMNA defects, are present also in fibroblasts from Emery-Dreifuss muscular dystrophy and familial partial lipodystrophy patients, we analyzed 2D-maps of skin fibroblasts of patients carrying 12 different LMNA mutations spread along the entire gene. To recognize distinctive proteins underlying affected biochemical pathways, we compared them with fibroblasts from healthy controls and, more importantly, fibroblasts from patients with non-lamin related neuromuscular disorders. We found less abundance of cytoskeletal/structural proteins, confirming a dominant role for Lamin A/C in structural support of nuclear architecture. Interestingly, we also established significant changes in the expression of proteins involved in cellular energy production and oxidative stress response. To our knowledge, this is the first report where proteomics was applied to characterize ex-vivo cells from LMNA patients, suggesting that this may represent a new approach to better understand the molecular mechanisms of these rare diseases and facilitate the development of novel therapeutic treatments.

Toll-like receptor 9 signaling in chronic lymphocytic leukemia cell lines.

Chronic lymphocytic leukemia (CLL) is a prototypic neoplasia in which malignant cells strongly depend on microenvironmental stimulations in the lymphoid tissues where they accumulate; leukemic cells are exposed to interaction with bystander and accessory cells, as well as inflammatory soluble mediators. Cell lines are frequently used to model the pathobiology of this disease; however, they do not always recapitulate leukemic cell growth and response to stimulation, and no data are available on Toll-like receptors (TLR) signaling in CLL cell lines. To address this gap, we analyzed HG3, MEC2, and PCL12 cell lines, before and after CpG stimulation, by RNA-sequencing followed by bioinformatic analyses and validation experiments. We identified NFKBIZ mRNA and the corresponding IkBz protein as robust markers of TLR9 activation in both MEC2 and PCL12, but not in HG3 cells. Next, we compared our current results with previous results obtained with primary CLL patient samples and were able to conclude that MEC2 is most similar to the patients' cells in terms of global responsiveness to TLR stimulation; in particular, MEC2 better resembles the samples of patients, as it is characterized by high expression levels of IkBz, but with a lower number of genes regulated.

Alterations of the intestinal mucus layer correlate with dysbiosis and immune dysregulation in human Type 1 Diabetes.

BACKGROUND: In preclinical models of Type 1 Diabetes (T1D) the integrity of the gut barrier (GB) is instrumental to avoid dysregulated crosstalk between the commensal microbiota and immune cells and to prevent autoimmunity. The GB is composed of the intestinal epithelial barrier (IEB) and of the mucus layer containing mucins and antimicrobial peptides (AMPs) that are crucial to maintain immune tolerance. In preclinical models of T1D the alterations of the GB primarily affect the mucus layer. In human T1D increased gut permeability and IEB damage have been demonstrated but the integrity of the mucus layer was never assessed. METHODS: We evaluated GB integrity by measuring serological markers of IEB damage (serological levels of zonulin) and bacterial translocation such as lipopolysaccharide binding protein (LBP) and myeloid differentiation protein 2 (MD2), and mRNA expression of tight junction proteins, mucins and AMPs in intestinal tissue of T1D patients and healthy controls (HC). Simultaneously, we performed immunological profiling on intestinal tissue and 16S rRNA analysis on the mucus-associated gut microbiota (MAGM). FINDINGS: Our data show a GB damage with mucus layer alterations and reduced mRNA expression of several mucins (MUC2, MUC12, MUC13, MUC15, MUC20, MUC21) and AMPs (HD4 and HD5) in T1D patients. Mucus layer alterations correlated with reduced relative abundance of short chain fatty acids (SCFA)-producing bacteria such as Bifidobacterium dentium, Clostridium butyricum and Roseburia intestinalis that regulate mucin expression and intestinal immune homeostasis. In T1D patients we also found intestinal immune dysregulation with higher percentages of effector T cells such as T helper (Th) 1, Th17 and TNF-α+ T cells. INTERPRETATION: Our data show that mucus layer alterations are present in T1D subjects and associated with dysbiosis and immune dysregulation. FUNDING: Research Grants from the Juvenile Diabetes Foundation (Grant 1-INO-2018-640-A-N to MF and 2-SRA-2019-680-S-B to JD) and from the Italian Ministry of Health (Grant RF19-12370721 to MF).

Harnessing the reverse cholesterol transport pathway to favor differentiation of monocyte-derived APCs and antitumor responses.

Lipid and cholesterol metabolism play a crucial role in tumor cell behavior and in shaping the tumor microenvironment. In particular, enzymatic and non-enzymatic cholesterol metabolism, and derived metabolites control dendritic cell (DC) functions, ultimately impacting tumor antigen presentation within and outside the tumor mass, dampening tumor immunity and immunotherapeutic attempts. The mechanisms accounting for such events remain largely to be defined. Here we perturbed (oxy)sterol metabolism genetically and pharmacologically and analyzed the tumor lipidome landscape in relation to the tumor-infiltrating immune cells. We report that perturbing the lipidome of tumor microenvironment by the expression of sulfotransferase 2B1b crucial in cholesterol and oxysterol sulfate synthesis, favored intratumoral representation of monocyte-derived antigen-presenting cells, including monocyte-DCs. We also found that treating mice with a newly developed antagonist of the oxysterol receptors Liver X Receptors (LXRs), promoted intratumoral monocyte-DC differentiation, delayed tumor growth and synergized with anti-PD-1 immunotherapy and adoptive T cell therapy. Of note, looking at LXR/cholesterol gene signature in melanoma patients treated with anti-PD-1-based immunotherapy predicted diverse clinical outcomes. Indeed, patients whose tumors were poorly infiltrated by monocytes/macrophages expressing LXR target genes showed improved survival over the course of therapy. Thus, our data support a role for (oxy)sterol metabolism in shaping monocyte-to-DC differentiation, and in tumor antigen presentation critical for responsiveness to immunotherapy. The identification of a new LXR antagonist opens new treatment avenues for cancer patients.

SIGIRR Downregulation and Interleukin-1 Signaling Intrinsic to Renal Cell Carcinoma.

Renal cell carcinoma is highly inflamed, and tumor cells are embedded into a microenvironment enriched with IL1. While inflammatory pathways are well characterized in the immune system, less is known about these same pathways in epithelial cells; it is unclear if and how innate immune signals directly impact on cancer cells, and if we could we manipulate these for therapeutic purposes. To address these questions, we first focused on the inflammatory receptors belonging to the IL1- and Toll-like receptor family including negative regulators in a small cohort of 12 clear cell RCC (ccRCC) patients' samples as compared to their coupled adjacent normal tissues. Our data demonstrated that renal epithelial cancer cells showed a specific and distinctive pattern of inflammatory receptor expression marked by a consistent downregulation of the inhibitory receptor SIGIRR mRNA. This repression was confirmed at the protein level in both cancer cell lines and primary tissues. When we analyzed in silico data of different kidney cancer histotypes, we identified the clear cell subtype as the one where SIGIRR was mostly downregulated; nonetheless, papillary and chromophobe tumor types also showed low levels as compared to their normal counterpart. RNA-sequencing analysis demonstrated that IL1 stimulation of the ccRCC cell line A498 triggered an intrinsic signature of inflammatory pathway activation characterized by the induction of distinct "pro-tumor" genes including several chemokines, the autocrine growth factor IL6, the atypical co-transcription factor NFKBIZ, and the checkpoint inhibitor PD-L1. When we looked for the macroareas most represented among the differentially expressed genes, additional clusters emerged including pathways involved in cell differentiation, angiogenesis, and wound healing. To note, SIGIRR overexpression in A498 cells dampened IL1 signaling as assessed by a reduced induction of NFKBIZ. Our results suggest that SIGIRR downregulation unleashes IL1 signaling intrinsic to tumor cells and that manipulating this pathway may be beneficial in ccRCC.

Big Data in Medicine, the Present and Hopefully the Future.

The emergence of data coming from different venues, as several "omic" approaches, is providing already compelling evidence that the smart use of this information could provide invaluable information to prevent, diagnose and treat human diseases. However, the most daunting challenges remain ahead, as the explosive accumulation of data from additional perspectives, including social graphs, biosensors, and imaging, promise to deliver crucial information that could be exploited for the improvement of the entire human race, both in developed, and developing countries, optimizing health expenses and reaching also the less fortunate sections of the societies. And yet, formidable challenges remain, that pertain for the most part to the collection of the data, their organization, and most relevantly their integration. Here we provide few, pointed examples to the present relevance of these big data approaches in human health as well potential road maps toward the implementation of broader data collections and analyses.

The IL-1/IL-1 receptor axis and tumor cell released inflammasome adaptor ASC are key regulators of TSLP secretion by cancer associated fibroblasts in pancreatic cancer.

BACKGROUND: The thymic stromal lymphopoietin (TSLP), a key cytokine for development of Th2 immunity, is produced by cancer associated fibroblasts (CAFs) in pancreatic cancer where predominant tumor infiltrating Th2 over Th1 cells correlates with reduced patients' survival. Which cells and molecules are mostly relevant in driving TSLP secretion by CAFs in pancreatic cancer is not defined. METHODS: We performed in vitro, in vivo and ex-vivo analyses. For in vitro studies we used pancreatic cancer cell lines, primary CAFs cultures, and THP1 cells. TSLP secretion by CAFs was used as a read-out system to identify in vitro relevant tumor-derived inflammatory cytokines and molecules. For in vivo studies human pancreatic cancer cells and CAFs were orthotopically injected in immunodeficient mice. For ex-vivo studies immunohistochemistry was performed to detect ASC (apoptosis-associated speck-like protein containing a caspase recruitment domain) expression in surgical samples. Bioinformatics was applied to interrogate published data sets. RESULTS: We show in vitro that IL-1α and IL-1ß released by pancreatic cancer cells and tumor cell-conditioned macrophages are crucial for TSLP secretion by CAFs. Treatment of immunodeficient mice orthotopically injected with human IL-1 positive pancreatic cancer cells plus CAFs using the IL-1R antagonist anakinra significantly reduced TSLP expression in the tumor. Importantly, we found that pancreatic cancer cells release alarmins, among which ASC, able to induce IL-1ß secretion in macrophages. The relevance of ASC was confirmed ex-vivo by its expression in both tumor cells and tumor associated macrophages in pancreatic cancer surgical samples and survival data analyses showing statistically significant inverse correlation between ASC expression and survival in pancreatic cancer patients. CONCLUSIONS: Our findings indicate that tumor released IL-1α and IL-1ß and ASC are key regulators of TSLP secretion by CAFs and their targeting should ultimately dampen Th2 inflammation and improve overall survival in pancreatic cancer.

Immune signature drives leukemia escape and relapse after hematopoietic cell transplantation.

Transplantation of hematopoietic cells from a healthy individual (allogeneic hematopoietic cell transplantation (allo-HCT)) demonstrates that adoptive immunotherapy can cure blood cancers: still, post-transplantation relapses remain frequent. To explain their drivers, we analyzed the genomic and gene expression profiles of acute myeloid leukemia (AML) blasts purified from patients at serial time-points during their disease history. We identified a transcriptional signature specific for post-transplantation relapses and highly enriched in immune-related processes, including T cell costimulation and antigen presentation. In two independent patient cohorts we confirmed the deregulation of multiple costimulatory ligands on AML blasts at post-transplantation relapse (PD-L1, B7-H3, CD80, PVRL2), mirrored by concomitant changes in circulating donor T cells. Likewise, we documented the frequent loss of surface expression of HLA-DR, -DQ and -DP on leukemia cells, due to downregulation of the HLA class II regulator CIITA. We show that loss of HLA class II expression and upregulation of inhibitory checkpoint molecules represent alternative modalities to abolish AML recognition from donor-derived T cells, and can be counteracted by interferon-γ or checkpoint blockade, respectively. Our results demonstrate that the deregulation of pathways involved in T cell-mediated allorecognition is a distinctive feature and driver of AML relapses after allo-HCT, which can be rapidly translated into personalized therapies.

Amino acid deprivation triggers a novel GCN2-independent response leading to the transcriptional reactivation of non-native DNA sequences.

In a variety of species, reduced food intake, and in particular protein or amino acid (AA) restriction, extends lifespan and healthspan. However, the underlying epigenetic and/or transcriptional mechanisms are largely unknown, and dissection of specific pathways in cultured cells may contribute to filling this gap. We have previously shown that, in mammalian cells, deprivation of essential AAs (methionine/cysteine or tyrosine) leads to the transcriptional reactivation of integrated silenced transgenes, including plasmid and retroviral vectors and latent HIV-1 provirus, by a process involving epigenetic chromatic remodeling and histone acetylation. Here we show that the deprivation of methionine/cysteine also leads to the transcriptional upregulation of endogenous retroviruses, suggesting that essential AA starvation affects the expression not only of exogenous non-native DNA sequences, but also of endogenous anciently-integrated and silenced parasitic elements of the genome. Moreover, we show that the transgene reactivation response is highly conserved in different mammalian cell types, and it is reproducible with deprivation of most essential AAs. The General Control Non-derepressible 2 (GCN2) kinase and the downstream integrated stress response represent the best candidates mediating this process; however, by pharmacological approaches, RNA interference and genomic editing, we demonstrate that they are not implicated. Instead, the response requires MEK/ERK and/or JNK activity and is reproduced by ribosomal inhibitors, suggesting that it is triggered by a novel nutrient-sensing and signaling pathway, initiated by translational block at the ribosome, and independent of mTOR and GCN2. Overall, these findings point to a general transcriptional response to essential AA deprivation, which affects the expression of non-native genomic sequences, with relevant implications for the epigenetic/transcriptional effects of AA restriction in health and disease.

Early involvement of cellular stress and inflammatory signals in the pathogenesis of tubulointerstitial kidney disease due to UMOD mutations.

Autosomal dominant tubulointerstitial kidney disease (ADTKD) is an inherited disorder that causes progressive kidney damage and renal failure. Mutations in the UMOD gene, encoding uromodulin, lead to ADTKD-UMOD related. Uromodulin is a GPI-anchored protein exclusively produced by epithelial cells of the thick ascending limb of Henle's loop. It is released in the tubular lumen after proteolytic cleavage and represents the most abundant protein in human urine in physiological condition. We previously generated and characterized a transgenic mouse model expressing mutant uromodulin (Tg UmodC147W) that recapitulates the main features of ATDKD-UMOD. While several studies clearly demonstrated that mutated uromodulin accumulates in endoplasmic reticulum, the mechanisms that lead to renal damage are not fully understood. In our work, we used kidney transcriptional profiling to identify early events of pathogenesis in the kidneys of Tg UmodC147W mice. Our results demonstrate up-regulation of inflammation and fibrosis and down-regulation of lipid metabolism in young Tg UmodC147W mice, before any functional or histological evidence of kidney damage. We also show that pro-inflammatory signals precede fibrosis onset and are already present in the first week after birth. Early induction of inflammation is likely relevant for ADTKD-UMOD pathogenesis and related pathways can be envisaged as possible novel targets for therapeutic intervention.

Lentiviral vectors escape innate sensing but trigger p53 in human hematopoietic stem and progenitor cells.

Clinical application of lentiviral vector (LV)-based hematopoietic stem and progenitor cells (HSPC) gene therapy is rapidly becoming a reality. Nevertheless, LV-mediated signaling and its potential functional consequences on HSPC biology remain poorly understood. We unravel here a remarkably limited impact of LV on the HSPC transcriptional landscape. LV escaped innate immune sensing that instead led to robust IFN responses upon transduction with a gamma-retroviral vector. However, reverse-transcribed LV DNA did trigger p53 signaling, activated also by non-integrating Adeno-associated vector, ultimately leading to lower cell recovery ex vivo and engraftment in vivo These effects were more pronounced in the short-term repopulating cells while long-term HSC frequencies remained unaffected. Blocking LV-induced signaling partially rescued both apoptosis and engraftment, highlighting a novel strategy to further dampen the impact of ex vivo gene transfer on HSPC. Overall, our results shed light on viral vector sensing in HSPC and provide critical insight for the development of more stealth gene therapy strategies.