Cancer cachexia is a highly prevalent condition associated with poor quality of life and reduced survival
. Tumor-induced perturbations in the endocrine, immune and nervous systems drive anorexia and ...catabolic changes in adipose tissue and skeletal muscle, hallmarks of cancer cachexia
. However, the molecular mechanisms driving cachexia remain poorly defined, and there are currently no approved drugs for the condition. Elevation in circulating growth differentiation factor 15 (GDF15) correlates with cachexia and reduced survival in patients with cancer
, and a GDNF family receptor alpha like (GFRAL)-Ret proto-oncogene (RET) signaling complex in brainstem neurons that mediates GDF15-induced weight loss in mice has recently been described
. Here we report a therapeutic antagonistic monoclonal antibody, 3P10, that targets GFRAL and inhibits RET signaling by preventing the GDF15-driven interaction of RET with GFRAL on the cell surface. Treatment with 3P10 reverses excessive lipid oxidation in tumor-bearing mice and prevents cancer cachexia, even under calorie-restricted conditions. Mechanistically, activation of the GFRAL-RET pathway induces expression of genes involved in lipid metabolism in adipose tissues, and both peripheral chemical sympathectomy and loss of adipose triglyceride lipase protect mice from GDF15-induced weight loss. These data uncover a peripheral sympathetic axis by which GDF15 elicits a lipolytic response in adipose tissue independently of anorexia, leading to reduced adipose and muscle mass and function in tumor-bearing mice.
De-ubiquitinating enzyme BAP1 is mutated in a hereditary cancer syndrome with increased risk of mesothelioma and uveal melanoma. Somatic BAP1 mutations occur in various malignancies. We show that ...mouse Bap1 gene deletion is lethal during embryogenesis, but systemic or hematopoietic-restricted deletion in adults recapitulates features of human myelodysplastic syndrome (MDS). Knockin mice expressing BAP1 with a 3xFlag tag revealed that BAP1 interacts with host cell factor—1 (HCF-1), O-linked N-acetylglucosamine transferase (OGT), and the polycomb group proteins ASXL1 and ASXL2 in vivo. OGT and HCF-1 levels were decreased by Bap1 deletion, indicating a critical role for BAP1 in stabilizing these epigenetic regulators. Human ASXL1 is mutated frequently in chronic myelomonocytic leukemia (CMML) so an ASXL/BAP1 complex may suppress CMML. A BAP1 catalytic mutation found in a MDS patient implies that BAP1 loss of function has similar consequences in mice and humans.
Mice homozygous for mutations in Dact1 (also called Dapper or Frodo) phenocopy human malformations involving the spine, genitourinary system and distal digestive tract. We traced this phenotype to ...disrupted germ-layer morphogenesis at the primitive streak. Notably, heterozygous mutation of Vangl2, a transmembrane component of the planar cell polarity (PCP) pathway, rescued recessive Dact1 phenotypes, whereas loss of Dact1 reciprocally rescued semidominant Vangl2 phenotypes. We show that Dact1, an intracellular protein, forms a complex with Vangl2. In Dact1 mutants, Vangl2 was increased at the primitive streak, where cells ordinarily undergo an epithelial-mesenchymal transition. This is associated with abnormal E-cadherin distribution and changes in biochemical measures of the PCP pathway. We conclude that Dact1 contributes to morphogenesis at the primitive streak by regulating Vangl2 upstream of cell adhesion and the PCP pathway.
The T cell hyperproliferation and autoimmune phenotypes that manifest in mice lacking E3 ubiquitin ligases such as Cbl, ITCH, or GRAIL highlight the importance of ubiquitination for the maintenance ...of peripheral T cell tolerance. Less is known, however, about the deubiquitinating enzymes that regulate T cell proliferation and effector function. Here, we define a cell intrinsic role for the deubiquitinase Usp9X during proximal TCR signaling. Usp9X-deficient T cells were hypoproliferative, yet mice with T cell-specific Usp9x deletion had elevated numbers of antigen-experienced T cells and expanded PD-1 and OX40-expressing populations consistent with immune hyperactivity. Aged Usp9x KO mice developed lupus-like autoimmunity and lymphoproliferative disease, indicating that ubiquitin ligases and deubiquitinases maintain the delicate balance between effective immunity and self-tolerance.
Abstract
Melanoma is one of the most common cancers with a high rate of brain metastases, with up to 75% of cases showing brain metastases upon autopsy. BRAF mutations are common in melanoma and ...found in up to 50-55% of melanoma brain metastases. Despite the clinical success of BRAF/MEK inhibitors for the treatment of advanced melanoma, dabrafenib and vemurafenib have limited intracranial overall response rates of 42-50% and median progression-free survival of 3.6-5.5 months. This limited efficacy is in part attributed to minimal blood-brain barrier penetration of the current available inhibitors. The goal of this study was to characterize a novel MEK inhibitor KIN-7136 as a potential therapeutic agent for brain metastasis driven by aberrant BRAF-MEK signaling, such as BRAF-mutant melanoma, using in vitro assays and an in vivo model of metastasis. KIN-7136 showed improved rodent brain exposure compared to conventional agents; the brain-to-plasma concentration ratio (Kp) of KIN-7136 was >1.0, much higher than comparators binimetinib and mirdametinib. In vitro cell viability assays showed potent cytotoxic effects of KIN-7136, with IC50s ranging from 15.4 to 204.9 nM in models of MAPK dysregulation including A375 (melanoma, BRAFV600E), NCI-H2405 (lung adenocarcinoma, BRAFΔNVTAP), HMVII (melanoma, BRAFG469V), and LN001 (patient derived lung adenocarcinoma, KRASG12V). Western blotting for phospho-ERK confirmed KIN-7136-mediated on-target downstream suppression in the A375 cell line. In vivo, daily oral treatment with KIN-7136 was well tolerated and produced a significant extension of overall survival compared to the vehicle control (p=0.0289, log-rank test) in the A375 intracranial tumor model in athymic mice. These preclinical data confirm activity of KIN-7136 in BRAF-mutant melanoma brain metastases models and support further research to advance its clinical progression.
A variety of signals finely tune insulin secretion by pancreatic β cells to prevent both hyper-and hypoglycemic states. Here, we show that post-translational regulation of the transcription factors ...ETV1, ETV4, and ETV5 by the ubiquitin ligase COP1 (also called RFWD2) in β cells is critical for insulin secretion. Mice lacking COP1 in β cells developed diabetes due to insulin granule docking defects that were fully rescued by genetic deletion of Etv1, Etv4, and Etv5. Genes regulated by ETV1, ETV4, or ETV5 in the absence of mouse COP1 were enriched in human diabetes-associated genes, suggesting that they also influence human β-cell pathophysiology. In normal β cells, ETV4 was stabilized upon membrane depolarization and limited insulin secretion under hyperglycemic conditions. Collectively, our data reveal that ETVs negatively regulate insulin secretion for the maintenance of normoglycemia.
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•Loss of COP1 in β cells caused insulin secretion defects and hyperglycemia•Deletion of transcription factors ETV1, ETV4, and ETV5 rescued COP1 phenotypes•ETV-dependent genes were significantly enriched in human diabetes and obesity GWAS•ETV transcription factors limited insulin secretion under hyperglycemic conditions
In adult pancreatic β cells, the post-translational regulation of the transcription factors ETV1, ETV4, and ETV5 by the ubiquitin ligase COP1 is critical for insulin secretion and the maintenance of normal glucose homeostasis. Dysregulation of this axis leads to the mis-expression of several ETV-target genes that are linked to diabetes and obesity.
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