Alessandra Fragale

Somatically acquired JAK1 mutations in adult acute lymphoblastic leukemia

Aberrant signal transduction contributes substantially to leukemogenesis. The Janus kinase 1 (JAK1) gene encodes a cytoplasmic tyrosine kinase that noncovalently associates with a variety of cytokine receptors and plays a nonredundant role in lymphoid cell precursor proliferation, survival, and differentiation. We report that somatic mutations in JAK1 occur in individuals with acute lymphoblastic leukemia (ALL). JAK1 mutations were more prevalent among adult subjects with the T cell precursor ALL, where they accounted for 18% of cases, and were associated with advanced age at diagnosis, poor response to therapy, and overall prognosis. All mutations were missense, and some were predicted to destabilize interdomain interactions controlling the activity of the kinase. Three mutations that were studied promoted JAK1 gain of function and conferred interleukin (IL)-3–independent growth in Ba/F3 cells and/or IL-9–independent resistance to dexamethasone-induced apoptosis in T cell lymphoma BW5147 cells. Such effects were associated with variably enhanced activation of multiple downstream signaling pathways. Leukemic cells with mutated JAK1 alleles shared a gene expression signature characterized by transcriptional up-regulation of genes positively controlled by JAK signaling. Our findings implicate dysregulated JAK1 function in ALL, particularly of T cell origin, and point to this kinase as a target for the development of novel antileukemic drugs.

Decreased Proliferation and Altered Differentiation in Osteoblasts from Genetically and Clinically Distinct Craniosynostotic Disorders

Craniosynostoses are a heterogeneous group of disorders characterized by premature fusion of cranial sutures. Mutations in fibroblast growth factor receptors (FGFRs) have been associated with a number of such conditions. Nevertheless, the cellular mechanism(s) involved remain unknown. We analyzed cell proliferation and differentiation in osteoblasts obtained from patients with three genetically and clinically distinct craniosynostoses: Pfeiffer syndrome carrying the FGFR2 C342R substitution, Apert syndrome with FGFR2 P253R change, and a nonsyndromic craniosynostosis without FGFR canonic mutations, as compared with control osteoblasts. Osteoblasts from craniosynostotic patients exhibited a lower proliferation rate than control osteoblasts. P253R and nonsyndromic craniosynostosis osteoblasts showed a marked differentiated phenotype, characterized by high alkaline phosphatase activity, increased mineralization and expression of noncollagenous matrix proteins, associated with high expression and activation of protein kinase Calpha and protein kinase Cepsilon isoenzymes. By contrast, the low proliferation rate of C342R osteoblasts was not associated with a differentiated phenotype. Although they showed higher alkaline phosphatase activity than control, C342R osteoblasts failed to mineralize and expressed low levels of osteopontin and osteonectin and high protein kinase Czeta levels. Stimulation of proliferation and inhibition of differentiation were observed in all cultures on FGF2 treatment. Our results suggest that an anticipated proliferative/differentiative switch, associated with alterations of the FGFR transduction pathways, could be the causative common feature in craniosynostosis and that mutations in distinct FGFR2 domains are associated with an in vitro heterogeneous differentiative phenotype.

IFN Regulatory Factor-1 Negatively Regulates CD4 + CD25 + Regulatory T Cell Differentiation by Repressing Foxp3 Expression

Regulatory T (Treg) cells are critical in inducing and maintaining tolerance. Despite progress in understanding the basis of immune tolerance, mechanisms and molecules involved in the generation of Treg cells remain poorly understood. IFN regulatory factor (IRF)-1 is a pleiotropic transcription factor implicated in the regulation of various immune processes. In this study, we report that IRF-1 negatively regulates CD4+CD25+ Treg cell development and function by specifically repressing Foxp3 expression. IRF-1-deficient (IRF-1−/−) mice showed a selective and marked increase of highly activated and differentiated CD4+CD25+Foxp3+ Treg cells in thymus and in all peripheral lymphoid organs. Furthermore, IRF-1−/− CD4+CD25− T cells showed extremely high bent to differentiate into CD4+CD25+Foxp3+ Treg cells, whereas restoring IRF-1 expression in IRF-1−/− CD4+CD25− T cells impaired their differentiation into CD25+Foxp3+ cells. Functionally, both isolated and TGF-β-induced CD4+CD25+ Treg cells from IRF-1−/− mice exhibited more increased suppressive activity than wild-type Treg cells. Such phenotype and functional characteristics were explained at a mechanistic level by the finding that IRF-1 binds a highly conserved IRF consensus element sequence (IRF-E) in the foxp3 gene promoter in vivo and negatively regulates its transcriptional activity. We conclude that IRF-1 is a key negative regulator of CD4+CD25+ Treg cells through direct repression of Foxp3 expression.

IRF-1 deficiency skews the differentiation of dendritic cells toward plasmacytoid and tolerogenic features

Members of the IFN regulatory factors (IRFs) family are transcriptional regulators that play essential roles in the homeostasis and function of the immune system. Recent studies indicate a direct involvement of some members of the family in the development of different subsets of dendritic cells (DC). Here, we report that IRF‐1 is a potent modulator of the development and functional maturation of DC. IRF‐1‐deficient mice (IRF‐1−/−) exhibited a predominance of plasmacytoid DC and a selective reduction of conventional DC, especially the CD8α+ subset. IRF‐1−/− splenic DC were markedly impaired in their ability to produce proinflammatory cytokines such as IL‐12. By contrast, they expressed high levels of IL‐10, TGF‐β, and the tolerogenic enzyme indoleamine 2,3 dioxygenase. As a consequence, IRF‐1−/− DC were unable to undergo full maturation and retained plasmacytoid and tolerogenic characteristics following virus infection ex vivo and in vivo. Accordingly, DC from IRF‐1−/− mice were less efficient in stimulating the proliferation of allogeneic T cells and instead, induced an IL‐10‐mediated, suppressive activity in allogeneic CD4+CD25+ regulatory T cells. Together, these results indicate that IRF‐1 is a key regulator of DC differentiation and maturation, exerting a variety of effects on the functional activation and tolerogenic potential of these cells.

Mutations in ZBTB20 cause Primrose syndrome

Primrose syndrome and 3q13.31 microdeletion syndrome are clinically related disorders characterized by tall stature, macrocephaly, intellectual disability, disturbed behavior and unusual facial features, with diabetes, deafness, progressive muscle wasting and ectopic calcifications specifically occurring in the former. We report that missense mutations in ZBTB20, residing within the 3q13.31 microdeletion syndrome critical region, underlie Primrose syndrome. This finding establishes a genetic link between these disorders and delineates the impact of ZBTB20 dysregulation on development, growth and metabolism.

HIV-1, interferon and the interferon regulatory factor system: An interplay between induction, antiviral responses and viral evasion

Thirty years after the first isolation of the etiological agent of AIDS, the virus HIV-1 is still a major threat worldwide with millions of individuals currently infected. Although current combination therapies allow viral replication to be controlled, HIV-1 is not eradicated and persists in drug- and immune system-insensitive reservoirs and a cure is still lacking. Pathogens such as HIV-1 that cause chronic infections are able to adapt to the host in a manner that ensures long term residence and survival, via the evolution of numerous mechanisms that evade various aspects of the innate and adaptive immune response. One such mechanism is targeted to members of the interferon (IFN) regulatory factor (IRF) family of proteins. These transcription factors regulate a variety of biological processes including interferon induction, immune cell activation and downstream pattern recognition receptors (PRRs). HIV-1 renders IRFs harmless and hijacks them to its own advantage in order to facilitate its replication and evasion of immune responses. Type I interferon (IFN), the canonical antiviral innate response, can be induced in both acute and chronic HIV-1 infection in vivo, but in the majority of individuals this initial response is not protective and can contribute to disease progression. Type I IFN expression is largely inhibited in T cells and macrophages in order to successfully establish productive infection, whereas sustained IFN production by plasmacytoid dendritic cells is considered an important source of chronic immune activation, a hallmark to AIDS progression.

A multidisciplinary study using in vivo tumor models and microfluidic cell-on-chip approach to explore the cross-talk between cancer and immune cells

Abstract A full elucidation of events occurring inside the cancer microenvironment is fundamental for the optimization of more effective therapies. In the present study, the cross-talk between cancer and immune cells was examined by employing mice deficient (KO) in interferon regulatory factor (IRF)-8, a transcription factor essential for induction of competent immune responses. The in vivo results showed that IRF-8 KO mice were highly permissive to B16.F10 melanoma growth and metastasis due to failure of their immune cells to exert proper immunosurveillance. These events were found to be dependent on soluble factors released by cells of the immune system capable of shaping the malignant phenotype of melanoma cells. An on-chip model was then generated to further explore the reciprocal interactions between the B16.F10 and immune cells. B16.F10 and immune cells were co-cultured in a microfluidic device composed of three culturing chambers suitably inter-connected by an array of microchannels; mutual interactions were then followed using time-lapse microscopy. It was observed that WT immune cells migrated through the microchannels towards the B16.F10 cells, establishing tight interactions that in turn limited tumor spread. In contrast, IRF-8 KO immune cells poorly interacted with the melanoma cells, resulting in a more invasive behavior of the B16.F10 cells. These results suggest that IRF-8 expression plays a key role in the cross-talk between melanoma and immune cells, and under-score the value of cell-on-chip approaches as useful in vitro tools to reconstruct complex in vivo microenvironments on a microscale level to explore cell interactions such as those occurring within a cancer immunoenvironment.

Critical Role of IRF-8 in Negative Regulation of TLR3 Expression by Src Homology 2 Domain-Containing Protein Tyrosine Phosphatase-2 Activity in Human Myeloid Dendritic Cells

Despite extensive studies that unraveled ligands and signal transduction pathways triggered by TLRs, little is known about the regulation of TLR gene expression. TLR3 plays a crucial role in the recognition of viral pathogens and induction of immune responses by myeloid DCs. IFN regulatory factor (IRF)-8, a member of the IRF family, is a transcriptional regulator that plays essential roles in the development and function of myeloid lineage, affecting different subsets of myeloid DCs. In this study, we show that IRF-8 negatively controls TLR3 gene expression by suppressing IRF-1– and/or polyinosinic-polycytidylic acid-stimulated TLR3 expression in primary human monocyte-derived DCs (MDDCs). MDDCs expressed TLR3 increasingly during their differentiation from monocytes to DCs with a peak at day 5, when TLR3 expression was further enhanced upon stimulation with polyinosinic-polycytidylic acid and then was promptly downregulated. We found that both IRF-1 and IRF-8 bind the human TLR3 promoter during MDDC differentiation in vitro and in vivo but with different kinetic and functional effects. We demonstrate that IRF-8–induced repression of TLR3 is specifically mediated by ligand-activated Src homology 2 domain-containing protein tyrosine phosphatase association. Indeed, Src homology 2 domain-containing protein tyrosine phosphatase–dephosphorylated IRF-8 bound to the human TLR3 promoter competing with IRF-1 and quashing its activity by recruitment of histone deacetylase 3. Our findings identify IRF-8 as a key player in the control of intracellular viral dsRNA-induced responses and highlight a new mechanism for negative regulation of TLR3 expression that can be exploited to block excessive TLR activation.

3D Microfluidic model for evaluating immunotherapy efficacy by tracking dendritic cell behaviour toward tumor cells

Immunotherapy efficacy relies on the crosstalk within the tumor microenvironment between cancer and dendritic cells (DCs) resulting in the induction of a potent and effective antitumor response. DCs have the specific role of recognizing cancer cells, taking up tumor antigens (Ags) and then migrating to lymph nodes for Ag (cross)-presentation to naïve T cells. Interferon-α-conditioned DCs (IFN-DCs) exhibit marked phagocytic activity and the special ability of inducing Ag-specific T-cell response. Here, we have developed a novel microfluidic platform recreating tightly interconnected cancer and immune systems with specific 3D environmental properties, for tracking human DC behaviour toward tumor cells. By combining our microfluidic platform with advanced microscopy and a revised cell tracking analysis algorithm, it was possible to evaluate the guided efficient motion of IFN-DCs toward drug-treated cancer cells and the succeeding phagocytosis events. Overall, this platform allowed the dissection of IFN-DC-cancer cell interactions within 3D tumor spaces, with the discovery of major underlying factors such as CXCR4 involvement and underscored its potential as an innovative tool to assess the efficacy of immunotherapeutic approaches.

IFN-α potentiates the direct and immune-mediated antitumor effects of epigenetic drugs on both metastatic and stem cells of colorectal cancer

Epigenetic alterations, including dysregulated DNA methylation and histone modifications, govern the progression of colorectal cancer (CRC). Cancer cells exploit epigenetic regulation to control cellular pathways, including apoptotic and metastatic signals. Since aberrations in epigenome can be pharmacologically reversed by DNA methyltransferase and histone deacetylase inhibitors, epigenetics in combination with standard agents are currently envisaged as a new therapeutic frontier in cancer, expected to overcome drug resistance associated with current treatments. In this study, we challenged this idea and demonstrated that the combination of azacitidine and romidepsin with IFN-α owns a high therapeutic potential, targeting the most aggressive cellular components of CRC, such as metastatic cells and cancer stem cells (CSCs), via tight control of key survival and death pathways. Moreover, the antitumor efficacy of this novel pharmacological approach is associated with induction of signals of immunogenic cell death. Of note, a previously undisclosed key role of IFN-α in inducing both antiproliferative and pro-apoptotic effects on CSCs of CRC was also found. Overall, these findings open a new frontier on the suitability of IFN-α in association with epigenetics as a novel and promising therapeutic approach for CRC management.