Myeloid p38 MAPK signaling in intestinal homeostasis, inflammation and tumorigenesis = Señalización por la MAPK p38 de células mieloides en la homeostasis, inflamación y tumorogénesis intestinal

[eng] Chronic inflammation is a hallmark of colon cancer, and patients with inflammatory bowel disease are prone to developing colon tumors. In recent years, many efforts have been devoted to characterize the interplay between inflammation, the tumor microenvironment and tumorigenesis. However, the molecular and cellular events involved in the pathogenesis of colitis-associated carcinogenesis are not fully understood. Myeloid cells play a key role in the tumor microenvironment, regulating tumor growth and therapeutic responses. One of the pathways that is often implicated in inflammatory diseases and cancer relies on the protein kinase p38. Specifically, p38 is a key regulator of epithelial cell homeostasis protecting against inflammation-associated colon tumorigenesis in mice. However, the contribution of myeloid p38 to colitis-associated tumorigenesis has been largely neglected. Therefore, the objective of this thesis is to investigate the role of myeloid p38 in intestinal mucosal repair and its implications in colorectal cancer by performing in vivo assays in mice. We further complemented the in vivo experiments using cellular models. We observed that mice with myeloid cell-specific downregulation of p38α generate less colon tumors in response to AOM/DSS treatment compared to wild-type mice. Our results extend previous findings indicating that myeloid p38 is a key mediator of inflammatory responses, and identify insulin-like growth factor-1 (IGF-1) as a novel effector downstream of p38 signaling in macrophages. To our knowledge, the regulation of IGF-1 by p38 in macrophages has not been described previously. IGF-1 is a natural growth hormone that is known to have also anti-inflammatory and pro-repair functions. We found that myeloid cells are a major source of IGF-1 in the large intestine, and genetic or pharmacological inhibition of IGF-1 suppresses inflammatory cell recruitment and reduces colitis-associated colon tumor burden. Ly6ChiCCR2+ monocytes are continuously generated in the bone marrow from hematopoietic stem cells and recruited to healthy and injured tissues, where they give rise to intestinal effector cells. Our studies demonstrate that Ly6ChiCCR2+ monocytes are reduced in p38-ΔMC mice and IGF-1-ΔMC mice compared to WT mice, even without any treatment. We believe this is important for the observed phenotype, given the key role of inflammatory monocytes in triggering the recruitment of other immune cells as well as in the initiation of the adaptive immune response. Our results indicate that suppression of p38 in myeloid cells ameliorates intestinal inflammation mainly through repression of inflammatory cell recruitment, which in turn results in reduced tumor burden. Several human and mouse studies have demonstrated that the regulation of inflammatory cytokines by p38 plays important roles in the pathogenesis of inflammatory diseases. In accordance, we observed that p38 in myeloid cells positively regulates key inflammatory mediators during intestinal inflammation. However, our results indicate that the decreased levels of inflammatory mediators and IGF-1 observed in DSS-treated p38-ΔMC mice correlates with a reduced number of infiltrated immune cells. Currently, the IGF-1 pathway is gaining tremendous interest due to its important role in cancer as well as inflammatory bowel disease, not only by modulating the innate and acquired immune system, but also through its multi-functional involvement in the tumor microenvironment. Our results suggest that targeted inhibition of the p38 pathway in myeloid cells could be therapeutically useful especially in tumors associated with chronic inflammation. Of note, IGF-1 is known to have mitogenic and anti-apoptotic functions, in addition to its role in inflammatory cell recruitment. Therefore, the targeting of extracellular effectors produced by myeloid cells that are implicated in disease pathogenesis such as IGF-1 might overcome the difficulty of targeting specific cell types

Myeloid p38α signaling promotes intestinal IGF‐1 production and inflammation‐associated tumorigenesis

Abstract The protein kinase p38α plays a key role in cell homeostasis, and p38α signaling in intestinal epithelial cells protects against colitis‐induced tumorigenesis. However, little is known on the contribution of p38α signaling in intestinal stromal cells. Here, we show that myeloid cell‐specific downregulation of p38α protects mice against inflammation‐associated colon tumorigenesis. The reduced tumorigenesis correlates with impaired detection in the colon of crucial chemokines for immune cell recruitment. We identify insulin‐like growth factor‐1 (IGF‐1) as a novel mediator of the p38α pathway in macrophages. Moreover, using genetic and pharmacological approaches, we confirm the implication of IGF‐1 produced by myeloid cells in colon inflammation and tumorigenesis. We also show a correlation between IGF‐1 pathway activation and the infiltration of myeloid cells with active p38α in colon samples from patients with ulcerative colitis or colon cancer. Altogether, our results uncover an important role for myeloid IGF‐1 downstream of p38α in colitis‐associated tumorigenesis and suggest the interest in evaluating IGF‐1 therapies for inflammation‐associated intestinal diseases, taking into consideration IGF‐1 signaling and immune cell infiltration in patient biopsies

GM-CSF Protects Macrophages from DNA Damage by Inducing Differentiation

At inflammatory loci, pro-inflammatory activation of macrophages produces large amounts of reactive oxygen species (ROS) that induce DNA breaks and apoptosis. Given that M-CSF and GM-CSF induce two different pathways in macrophages, one for proliferation and the other for survival, in this study we wanted to determine if these growth factors are able to protect against the DNA damage produced during macrophage activation. In macrophages treated with DNA-damaging agents we found that GM-CSF protects better against DNA damage than M-CSF. Treatment with GM-CSF resulted in faster recovery of DNA damage than treatment with M-CSF. The number of apoptotic cells induced after DNA damage was higher in the presence of M-CSF. Protection against DNA damage by GM-CSF is not related to its higher capacity to induce proliferation. GM-CSF induces differentiation markers such as CD11c and MHCII, as well as the pro-survival Bcl-2A1 protein, which make macrophages more resistant to DNA damage

Genomic profiling of pediatric ALK-positive anaplastic large cell lymphoma:A children's cancer and leukaemia group study

Anaplastic lymphoma kinase (ALK)-positive anaplastic large cell lymphoma (ALCL) is a T-cell malignancy in which ALK expression is a consequence of the t(2;5) or a variant translocation involving Chromosome 2. For the most part, this disease presents in the pediatric population and most, but not all, patients are successfully treated. Although the t(2;5) product nucleophosmin-ALK has been extensively studied for its transforming properties, very little is known regarding cooperative genetic mutations that may contribute to lymphomagenesis and may predict survival outcome, specifically in a purely pediatric population. We set out to determine the frequency and positions of genomic imbalances in this relatively rare disease. We collected biopsy material from 15 UK-resident children with ALK-expressing ALCL. We performed array comparative genomic hybridization at a resolution of 1 MB using DNA isolated from tumor tissue. Some of the more common genomic gains were confirmed by quantitative PCR. Regions of genomic gain were far more common than losses and were most often detected on chromosomes 1-4, 5-12, 14, and 17, with Chromosome 11 being the most frequent site of genomic imbalances. Patients with 14 or fewer imbalances had a lower overall 3-year survival (87.5-40%, P = 0.14) as did patients with gains in the regions of DDB1 or BIRC5. A range of genomic imbalances exist in ALK-expressing ALCL of a pediatric origin, with a greater number associated with poorer overall survival.</p

Identity noise and adipogenic traits characterize dermal fibroblast aging

During aging, stromal functions are thought to be impaired, but little is known whether this stems from changes of fibroblasts. Using population- and single-cell transcriptomics, as well as long-term lineage tracing, we studied whether murine dermal fibroblasts are altered during physiological aging under different dietary regimes that affect longevity. We show that the identity of old fibroblasts becomes undefined, with the fibroblast states present in young skin no longer clearly demarcated. In addition, old fibroblasts not only reduce the expression of genes involved in the formation of the extracellular matrix, but also gain adipogenic traits, paradoxically becoming more similar to neonatal pro-adipogenic fibroblasts. These alterations are sensitive to systemic metabolic changes: long-term caloric restriction reversibly prevents them, whereas a high-fat diet potentiates them. Our results therefore highlight loss of cell identity and the acquisition of adipogenic traits as a mechanism underlying cellular aging, which is influenced by systemic metabolism.M.C.S. was supported by a Boehringer Ingelheim Fonds International PhD fellowship. IRB Barcelona is the recipient of a Severo Ochoa Award of Excellence from MINECO (Government of Spain). H.H. is a Miguel Servet (CP14/00229) researcher funded by the Spanish Institute of Health Carlos III (ISCIII). This work has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sk1odowska-Curie grant agreement No. H2020-MSCA-ITN-2015-675752 (SINGEK

Identity noise and adipogenic traits characterize dermal fibroblast aging

During aging, stromal functions are thought to be impaired, but little is known whether this stems from changes of fibroblasts. Using population- and single-cell transcriptomics, as well as long-term lineage tracing, we studied whether murine dermal fibroblasts are altered during physiological aging under different dietary regimes that affect longevity. We show that the identity of old fibroblasts becomes undefined, with the fibroblast states present in young skin no longer clearly demarcated. In addition, old fibroblasts not only reduce the expression of genes involved in the formation of the extracellular matrix, but also gain adipogenic traits, paradoxically becoming more similar to neonatal pro-adipogenic fibroblasts. These alterations are sensitive to systemic metabolic changes: long-term caloric restriction reversibly prevents them, whereas a high-fat diet potentiates them. Our results therefore highlight loss of cell identity and the acquisition of adipogenic traits as a mechanism underlying cellular aging, which is influenced by systemic metabolism.M.C.S. was supported by a Boehringer Ingelheim Fonds International PhD fellowship. IRB Barcelona is the recipient of a Severo Ochoa Award of Excellence from MINECO (Government of Spain). H.H. is a Miguel Servet (CP14/00229) researcher funded by the Spanish Institute of Health Carlos III (ISCIII). This work has received funding from the European Union’s Horizon 2020 research and innovation program under the Marie Sk1odowska-Curie grant agreement No. H2020-MSCA-ITN-2015-675752 (SINGEK