The topology of vitronectin: A complementary feature for neuroblastoma risk classification based on computer‐aided detection

Tumors are complex networks of constantly interacting elements: tumor cells, stromal cells, immune and stem cells, blood/lympathic vessels, nerve fibers and extracellular matrix components. These elements can influence their microenvironment through mechanical and physical signals to promote tumor cell growth. To get a better understanding of tumor biology, cooperation between multidisciplinary fields is needed. Diverse mathematic computations and algorithms have been designed to find prognostic targets and enhance diagnostic assessment. In this work, we use computational digital tools to study the topology of vitronectin, a glycoprotein of the extracellular matrix. Vitronectin is linked to angiogenesis and migration, two processes closely related to tumor cell spread. Here, we investigate whether the distribution of this molecule in the tumor stroma may confer mechanical properties affecting neuroblastoma aggressiveness. Combining image analysis and graph theory, we analyze different topological features that capture the organizational cues of vitronectin in histopathological images taken from human samples. We find that the Euler number and the branching of territorial vitronectin, two topological features, could allow for a more precise pretreatment risk stratification to guide treatment strategies in neuroblastoma patients. A large amount of recently synthesized VN would create migration tracks, pinpointed by both topological features, for malignant neuroblasts, so that dramatic change in the extracellular matrix would increase tumor aggressiveness and worsen patient outcomes

Unraveling the extracellular matrix-tumor cell interactions to aid better targeted therapies for neuroblastoma

Treatment in children with high-risk neuroblastoma remains largely unsuccessful due to the development of metastases and drug resistance. The biological complexity of these tumors and their microenvironment represent one of the many challenges to face. Matrix glycoproteins such as vitronectin act as bridge elements between extracellular matrix and tumor cells and can promote tumor cell spreading. In this study, we established through a clinical cohort and preclinical models that the interaction of vitronectin and its ligands, such as αv integrins, are related to the stiffness of the extracellular matrix in high-risk neuroblastoma. These marked alterations found in the matrix led us to specifically target tumor cells within these altered matrices by employing nanomedicine and combination therapy. Loading the conventional cytotoxic drug etoposide into nanoparticles significantly increased its efficacy in neuroblastoma cells. We noted high synergy between etoposide and cilengitide, a high-affinity cyclic pentapeptide αv integrin antagonist. The results of this study highlight the need to characterize cell-extracellular matrix interactions, to improve patient care in high-risk neuroblastoma

Interferon-gamma ameliorates experimental autoimmune encephalomyelitis by inducing homeostatic adaptation of microglia

Compelling evidence has shown that interferon (IFN)-γ has dual effects in multiple sclerosis and in its animal model of experimental autoimmune encephalomyelitis (EAE), with results supporting both a pathogenic and beneficial function. However, the mechanisms whereby IFN-γ may promote neuroprotection in EAE and its effects on central nervous system (CNS)-resident cells have remained an enigma for more than 30 years. In this study, the impact of IFN-γ at the peak of EAE, its effects on CNS infiltrating myeloid cells (MC) and microglia (MG), and the underlying cellular and molecular mechanisms were investigated. IFN-γ administration resulted in disease amelioration and attenuation of neuroinflammation associated with significantly lower frequencies of CNS CD11b+ myeloid cells and less infiltration of inflammatory cells and demyelination. A significant reduction in activated MG and enhanced resting MG was determined by flow cytometry and immunohistrochemistry. Primary MC/MG cultures obtained from the spinal cord of IFN-γ-treated EAE mice that were ex vivo re-stimulated with a low dose (1 ng/ml) of IFN-γ and neuroantigen, promoted a significantly higher induction of CD4+ regulatory T (Treg) cells associated with increased transforming growth factor (TGF)-β secretion. Additionally, IFN-γ-treated primary MC/MG cultures produced significantly lower nitrite in response to LPS challenge than control MC/MG. IFN-γ-treated EAE mice had a significantly higher frequency of CX3CR1high MC/MG and expressed lower levels of program death ligand 1 (PD-L1) than PBS-treated mice. Most CX3CR1highPD-L1lowCD11b+Ly6G- cells expressed MG markers (Tmem119, Sall2, and P2ry12), indicating that they represented an enriched MG subset (CX3CR1highPD-L1low MG). Amelioration of clinical symptoms and induction of CX3CR1highPD-L1low MG by IFN-γ were dependent on STAT-1. RNA-seq analyses revealed that in vivo treatment with IFN-γ promoted the induction of homeostatic CX3CR1highPD-L1low MG, upregulating the expression of genes associated with tolerogenic and anti-inflammatory roles and down-regulating pro-inflammatory genes. These analyses highlight the master role that IFN-γ plays in regulating microglial activity and provide new insights into the cellular and molecular mechanisms involved in the therapeutic activity of IFN-γ in EAE

Global loss of cellular m 6 A RNA methylation following infection with different SARS-CoV-2 variants

International audienceInsights into host–virus interactions during SARS-CoV-2 infection are needed to understand COVID-19 pathogenesis and may help to guide the design of novel antiviral therapeutics. N 6 -Methyladenosine modification (m 6 A), one of the most abundant cellular RNA modifications, regulates key processes in RNA metabolism during stress response. Gene expression profiles observed postinfection with different SARS-CoV-2 variants show changes in the expression of genes related to RNA catabolism, including m 6 A readers and erasers. We found that infection with SARS-CoV-2 variants causes a loss of m 6 A in cellular RNAs, whereas m 6 A is detected abundantly in viral RNA. METTL3, the m 6 A methyltransferase, shows an unusual cytoplasmic localization postinfection. The B.1.351 variant has a less-pronounced effect on METTL3 localization and loss of m 6 A than did the B.1 and B.1.1.7 variants. We also observed a loss of m 6 A upon SARS-CoV-2 infection in air/liquid interface cultures of human airway epithelia, confirming that m 6 A loss is characteristic of SARS-CoV-2-infected cells. Further, transcripts with m 6 A modification are preferentially down-regulated postinfection. Inhibition of the export protein XPO1 results in the restoration of METTL3 localization, recovery of m 6 A on cellular RNA, and increased mRNA expression. Stress granule formation, which is compromised by SARS-CoV-2 infection, is restored by XPO1 inhibition and accompanied by a reduced viral infection in vitro. Together, our study elucidates how SARS-CoV-2 inhibits the stress response and perturbs cellular gene expression in an m 6 A-dependent manner