A Role for Human DNA Polymerase λ in Alternative Lengthening of Telomeres.

Telomerase negative cancer cell types use the Alternative Lengthening of Telomeres (ALT) pathway to elongate telomeres ends. Here, we show that silencing human DNA polymerase (Pol λ) in ALT cells represses ALT activity and induces telomeric stress. In addition, replication stress in the absence of Pol λ, strongly affects the survival of ALT cells. In vitro, Pol λ can promote annealing of even a single G-rich telomeric repeat to its complementary strand and use it to prime DNA synthesis. The noncoding telomeric repeat containing RNA TERRA and replication protein A negatively regulate this activity, while the Protection of Telomeres protein 1 (POT1)/TPP1 heterodimer stimulates Pol λ. Pol λ associates with telomeres and colocalizes with TPP1 in cells. In summary, our data suggest a role of Pol λ in the maintenance of telomeres by the ALT mechanism.

Tissue-Specific Immunopathology in Fatal COVID-19.

Rationale: In life-threatening coronavirus disease (COVID-19), corticosteroids reduce mortality, suggesting that immune responses have a causal role in death. Whether this deleterious inflammation is primarily a direct reaction to the presence of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) or an independent immunopathologic process is unknown.Objectives: To determine SARS-CoV-2 organotropism and organ-specific inflammatory responses and the relationships among viral presence, inflammation, and organ injury.Methods: Tissue was acquired from 11 detailed postmortem examinations. SARS-CoV-2 organotropism was mapped by using multiplex PCR and sequencing, with cellular resolution achieved by in situ viral S (spike) protein detection. Histologic evidence of inflammation was quantified from 37 anatomic sites, and the pulmonary immune response was characterized by using multiplex immunofluorescence.Measurements and Main Results: Multiple aberrant immune responses in fatal COVID-19 were found, principally involving the lung and reticuloendothelial system, and these were not clearly topologically associated with the virus. Inflammation and organ dysfunction did not map to the tissue and cellular distribution of SARS-CoV-2 RNA and protein between or within tissues. An arteritis was identified in the lung, which was further characterized as a monocyte/myeloid-rich vasculitis, and occurred together with an influx of macrophage/monocyte-lineage cells into the pulmonary parenchyma. In addition, stereotyped abnormal reticuloendothelial responses, including excessive reactive plasmacytosis and iron-laden macrophages, were present and dissociated from viral presence in lymphoid tissues.Conclusions: Tissue-specific immunopathology occurs in COVID-19, implicating a significant component of the immune-mediated, virus-independent immunopathologic process as a primary mechanism in severe disease. Our data highlight novel immunopathologic mechanisms and validate ongoing and future efforts to therapeutically target aberrant macrophage and plasma-cell responses as well as promote pathogen tolerance in COVID-19.

Monocyte-derived macrophages promote breast cancer bone metastasis outgrowth.

Bone metastasis is the major cause of death in breast cancer. The lack of effective treatment suggests that disease mechanisms are still largely unknown. As a key component of the tumor microenvironment, macrophages promote tumor progression and metastasis. In this study, we found that macrophages are abundant in human and mouse breast cancer bone metastases. Macrophage ablation significantly inhibited bone metastasis growth. Lineage tracking experiments indicated that these macrophages largely derive from Ly6C+CCR2+ inflammatory monocytes. Ablation of the chemokine receptor, CCR2, significantly inhibited bone metastasis outgrowth and prolonged survival. Immunophenotyping identified that bone metastasis-associated macrophages express high levels of CD204 and IL4R. Furthermore, monocyte/macrophage-restricted IL4R ablation significantly inhibited bone metastasis growth, and IL4R null mutant monocytes failed to promote bone metastasis outgrowth. Together, this study identified a subset of monocyte-derived macrophages that promote breast cancer bone metastasis in an IL4R-dependent manner. This suggests that IL4R and macrophage inhibition can have potential therapeutic benefit against breast cancer bone disease.

Multitarget CFTR Modulators Endowed with Multiple Beneficial Side Effects for Cystic Fibrosis Patients: Toward a Simplified Therapeutic Approach †.

Cystic fibrosis (CF) is a multiorgan disease caused by mutations of the cystic fibrosis transmembrane conductance regulator (CFTR). In addition to respiratory impairment due to mucus accumulation, viruses and bacteria trigger acute pulmonary exacerbations, accelerating disease progression and mortality rate. Treatment complexity increases with patients' age, and simplifying the therapeutic regimen represents one of the key priorities in CF. We have recently reported the discovery of multitarget compounds able to "kill two birds with one stone" by targeting F508del-CFTR and PI4KIIIß and thus acting simultaneously as CFTR correctors and broad-spectrum enterovirus (EV) inhibitors. Starting from these preliminary results, we report herein a hit-to-lead optimization and multidimensional structure-activity relationship (SAR) study that led to compound 23a. This compound showed good antiviral and F508del-CFTR correction potency, additivity/synergy with lumacaftor, and a promising in vitro absorption, distribution, metabolism, and excretion (ADME) profile. It was well tolerated in vivo with no sign of acute toxicity and histological alterations in key biodistribution organs.