Discoidin domain receptor 2 (DDR2) regulates body size and fat metabolism in mice

Lipid metabolism reprogramming in head and neck cancer

Lipid metabolism reprogramming is one of the most prominent metabolic anomalies in cancer, wherein cancer cells undergo dysregulation of lipid metabolism to acquire adequate energy, cell membrane building blocks, as well as signaling molecules essential for cell proliferation, survival, invasion, and metastasis. These adaptations enable cancer cells to effectively respond to challenges posed by the tumor microenvironment, leading to cancer therapy resistance and poor cancer prognosis. Head and neck cancer, ranking as the seventh most prevalent cancer, exhibits numerous abnormalities in lipid metabolism. Nevertheless, the precise role of lipid metabolic rewiring in head and neck cancer remains unclear. In line with the LIPID MAPS Lipid Classification System and cancer risk factors, the present review delves into the dysregulated molecules and pathways participating in the process of lipid uptake, biosynthesis, transportation, and catabolism. We also present an overview of the latest advancements in understanding alterations in lipid metabolism and how they intersect with the carcinogenesis, development, treatment, and prognosis of head and neck cancer. By shedding light on the significance of metabolic therapy, we aspire to improve the overall prognosis and treatment outcomes of head and neck cancer patients.

Exploring the Cellular and Molecular Mechanism of Discoidin Domain Receptors (DDR1 and DDR2) in Bone Formation, Regeneration, and Its Associated Disease Conditions

The tyrosine kinase family receptor of discoidin domain receptors (DDR1 and DDR2) is known to be activated by extracellular matrix collagen catalytic binding protein receptors. They play a remarkable role in cell proliferation, differentiation, migration, and cell survival. DDR1 of the DDR family regulates matrix-metalloproteinase, which causes extracellular matrix (ECM) remodeling and reconstruction during unbalanced homeostasis. Collagenous-rich DDR1 triggers the ECM of cartilage to regenerate the cartilage tissue in osteoarthritis (OA) and temporomandibular disorder (TMD). Moreover, DDR2 is prominently present in the fibroblasts, smooth muscle cells, myofibroblasts, and chondrocytes. It is crucial in generating and breaking collagen vital cellular activities like proliferation, differentiation, and adhesion mechanisms. However, the deficiency of DDR1 rather than DDR2 was detrimental in cases of OA and TMDs. DDR1 stimulated the ECM cartilage and improved bone regeneration. Based on the above information, we made an effort to outline the advancement of the utmost promising DDR1 and DDR2 regulation in bone and cartilage, also summarizing their structural, biological activity, and selectivity.

Ablation of myeloid discoidin domain receptor 2 exacerbates arthritis and high fat diet induced inflammation

Chronic systemic inflammation leads to sever disorders and diseases. It is of great importance to explore novel target for effective treatment. Discoidin domain receptor 2 (Ddr2) is a member of receptor tyrosine kinase (RTK) family and is implicated in skeletal and fat hemostasis. However, the role of Ddr2 in myeloid cells remains obscure. In this study, we conditionally deleted Ddr2 in myeloid lineage cells to generate cKO mice to investigate the role of Ddr2 in myeloid lineage cells. We found that cKO mice exhibited more severe inflammation both in collagen antibody-induced arthritis (CAIA) and high-fat diet (HFD)-induced obesity, indicating the protective role of Ddr2 against inflammation. Mechanistically, Ddr2 promotes macrophage repolarization from the M1 to M2 phenotype, and protect against systemic inflammation. Our study reveals for the first time that Ddr2 modulates macrophage repolarization and plays critical roles in macrophage-mediated inflammation, providing potential target for the intervention of inflammation and related diseases.

LncRNA CEBPA-DT promotes liver cancer metastasis through DDR2/β-catenin activation via interacting with hnRNPC

BACKGROUND

Hepatocellular carcinoma (HCC) is the world's third leading cause of cancer-related death; due to the fast growth and high prevalence of tumor recurrence, the prognosis of HCC patients remains dismal. Long non-coding RNA CEBPA-DT, a divergent transcript of the CCAAT Enhancer Binding Protein Alpha (CEBPA) gene, has been shown to participate in multiple tumor progression. However, no research has established its cancer-promoting mechanism in HCC yet.

METHODS

CEBPA-DT was identified in human HCC tissues through RNA sequencing. The expression level of CEBPA-DT was assessed by quantitative real-time PCR. The biological effects of CEBPA-DT were evaluated in vitro and in vivo through gain or loss of function experiments. RNA fluorescence in situ hybridization (FISH), RNA immunoprecipitation (RIP) and RNA pull-down assays were applied to investigate the downstream target of CEBPA-DT. Immunofluorescence, subcellular protein fractionation, western blot, and co-immunoprecipitation were performed to analyze the subcellular location of β-catenin and its interaction with Discoidin domain-containing receptor 2 (DDR2).

RESULTS

CEBPA-DT was upregulated in human HCC tissues with postoperative distant metastasis and intimately related to the worse prognosis of HCC patients. Silencing of CEBPA-DT inhibited the growth, migration and invasion of hepatoma cells in vitro and in vivo, while enhancement of CEBPA-DT played a contrasting role. Mechanistic investigations demonstrated that CEBPA-DT could bind to heterogeneous nuclear ribonucleoprotein C (hnRNPC), which facilitated cytoplasmic translocation of hnRNPC, enhanced the interaction between hnRNPC and DDR2 mRNA, subsequently promoted the expression of DDR2. Meanwhile, CEBPA-DT induced epithelial-mesenchymal transition (EMT) process through upregulation of Snail1 via facilitating nuclear translocation of β-catenin. Using DDR2 inhibitor, we revealed that the CEBPA-DT induced the interaction between DDR2 and β-catenin, thus promoting the nuclear translocation of β-catenin to activate transcription of Snail1, contributing to EMT and HCC metastasis.

CONCLUSIONS

Our results suggested that CEBPA-DT promoted HCC metastasis through DDR2/β-catenin mediated activation of Snail1 via interaction with hnRNPC, indicating that the CEBPA-DT-hnRNPC-DDR2/β-catenin axis may be used as a potential therapeutic target for HCC treatment.

Genetic and pharmacological tools to study the role of discoidin domain receptors in kidney disease

Following injury the kidney undergoes a repair process, which results in replacement of the injured tissue with little evidence of damage. However, repetitive injuries or inability of the kidney to stop the repair process result in abnormal deposition of extracellular matrix (ECM) components leading to fibrosis and organ dysfunction. The synthesis/degradation of ECM components is finely regulated by several factors, including discoidin domain receptors (DDRs). These are receptor tyrosine kinases that are activated by collagens. Upon activation, DDRs control several cell functions that, when exacerbated, contribute to kidney injury and fibrosis. DDRs are undetectable in healthy kidney, but become rapidly upregulated in several kidney fibrotic conditions, thus making them attractive anti-fibrotic targets. DDRs contribute to kidney injury and fibrosis by promoting apoptosis of injured kidney cells, stimulating the production of pro-inflammatory cytokines, and regulating the production of ECM components. They achieve these effects by activating canonical intracellular molecules or by directly interacting with nuclear chromatin and promoting the transcription of pro-fibrotic genes. The goal of this review is to highlight canonical and non-canonical mechanisms whereby DDRs contribute to kidney injury/fibrosis. This review will summarize key findings obtained using cells and mice lacking DDRs and it will discuss the discovery and development of targeted DDR small molecule- and antisense-based inhibitors. Understanding the molecular mechanisms whereby DDRs control kidney injury and fibrosis might enable us to not only develop more selective and potent inhibitors, but to also determine when DDR inhibition needs to be achieved to prevent and/or halt the development of kidney fibrosis.

Targeting adipocytic discoidin domain receptor 2 impedes fat gain while increasing bone mass

Obesity is closely associated with low-bone-mass disorder. Discoidin domain receptor 2 (DDR2) plays essential roles in skeletal metabolism, and is probably involved in fat metabolism. To test the potential role of DDR2 in fat and fat-bone crosstalk, Ddr2 conditional knockout mice (Ddr2^Adipo) were generated in which Ddr2 gene is exclusively deleted in adipocytes by Adipoq Cre. We found that Ddr2^Adipo mice are protected from fat gain on high-fat diet, with significantly decreased adipocyte size. Ddr2^Adipo mice exhibit significantly increased bone mass and mechanical properties, with enhanced osteoblastogenesis and osteoclastogenesis. Marrow adipocyte is diminished in the bone marrow of Ddr2^Adipo mice, due to activation of lipolysis. Fatty acid in the bone marrow was reduced in Ddr2^Adipo mice. RNA-Seq analysis identified adenylate cyclase 5 (Adcy5) as downstream molecule of Ddr2. Mechanically, adipocytic Ddr2 modulates Adcy5-cAMP-PKA signaling, and Ddr2 deficiency stimulates lipolysis and supplies fatty acid for oxidation in osteoblasts, leading to the enhanced osteoblast differentiation and bone mass. Treatment of Adcy5 specific inhibitor abolishes the increased bone mass gain in Ddr2^Adipo mice. These observations establish, for the first time, that Ddr2 plays an essential role in the crosstalk between fat and bone. Targeting adipocytic Ddr2 may be a potential strategy for treating obesity and pathological bone loss simultaneously.

Comparative transcriptomic analysis of deep- and shallow-water barnacle species (Cirripedia, Poecilasmatidae) provides insights into deep-sea adaptation of sessile crustaceans

BACKGROUND

Barnacles are specialized marine organisms that differ from other crustaceans in possession of a calcareous shell, which is attached to submerged surfaces. Barnacles have a wide distribution, mostly in the intertidal zone and shallow waters, but a few species inhabit the deep-sea floor. It is of interest to investigate how such sessile crustaceans became adapted to extreme deep-sea environments. We sequenced the transcriptomes of a deep-sea barnacle, Glyptelasma gigas collected at a depth of 731 m from the northern area of the Zhongjiannan Basin, and a shallow-water coordinal relative, Octolasmis warwicki. The purpose of this study was to provide genetic resources for investigating adaptation mechanisms of deep-sea barnacles.

RESULTS

Totals of 62,470 and 51,585 unigenes were assembled for G. gigas and O. warwicki, respectively, and functional annotation of these unigenes was made using public databases. Comparison of the protein-coding genes between the deep- and shallow-water barnacles, and with those of four other shallow-water crustaceans, revealed 26 gene families that had experienced significant expansion in G. gigas. Functional annotation showed that these expanded genes were predominately related to DNA repair, signal transduction and carbohydrate metabolism. Base substitution analysis on the 11,611 single-copy orthologs between G. gigas and O. warwicki indicated that 25 of them were distinctly positive selected in the deep-sea barnacle, including genes related to transcription, DNA repair, ligand binding, ion channels and energy metabolism, potentially indicating their importance for survival of G. gigas in the deep-sea environment.

CONCLUSIONS

The barnacle G. gigas has adopted strategies of expansion of specific gene families and of positive selection of key genes to counteract the negative effects of high hydrostatic pressure, hypoxia, low temperature and food limitation on the deep-sea floor. These expanded gene families and genes under positive selection would tend to enhance the capacities of G. gigas for signal transduction, genetic information processing and energy metabolism, and facilitate networks for perceiving and responding physiologically to the environmental conditions in deep-sea habitats. In short, our results provide genomic evidence relating to deep-sea adaptation of G. gigas, which provide a basis for further biological studies of sessile crustaceans in the deep sea.

Over expression of CDK4 and MDM2 in a patient with recurrent ALK-negative mediastinal inflammatory myofibroblastic tumor: A case report

RATIONALE

The diagnosis of anaplastic lymphoma kinase (ALK)-negative inflammatory myofibroblastic tumors (IMT) remains challenging because of their morphological resemblance with spindle cell sarcoma with myofibroblastic characteristics.

PATIENT CONCERNS

A 69-year-old female patient presented with loco-regional recurrent IMT several times within 8 years after primary treatment and neck lymph node metastasis 3.5 years after last recurrence.

DIAGNOSIS

The primary, recurrence, and lymph node metastasis lesions were diagnosed as ALK-negative IMTs based on the histopathological features.

INTERVENTIONS

Biopsy samples were obtained during repeated surgeries and evaluated for genomic alterations during first and recurrent presentations. The evaluation was done using pathway-driven massive parallel sequencing, and genomic alterations between primary and recurrent tumors were compared.

OUTCOMES

Copy number gains and overexpression of mouse double minute 2 homolog (MDM2) and cyclin dependent kinase 4 (CDK4) were observed in the primary lesion, and additional gene amplification of Discoidin Domain Receptor Tyrosine Kinase 2 (DDR2), Succinate Dehydrogenase Complex II subunit C (SDHC), and thyroid stimulating hormone receptor (TSHR) Q720H were found in the recurrent tumors. Metastases to the neck lymph node were observed 3.5 years after recurrence.

LESSONS

Our results indicated genetic evolution in a microscopically benign condition and highlighted the importance of molecular characterization of fibro-inflammatory lesions of uncertain malignant potential.

Reprogramming of Energy Metabolism in Response to Radiotherapy in Head and Neck Squamous Cell Carcinoma

Head and neck cancer (HNC) is the sixth cause of cancer-related death worldwide. Head and neck squamous cells carcinoma (HNSCC) is the most frequent subtype of HNC. The development of HNSCC is associated to alcohol consumption, smoking or infection by high-risk human Papillomavirus (HR-HPV). Although the incidence of cancers associated with alcohol and tobacco has diminished, HNSCC associated with HR-HPV has significantly increased in recent years. However, HPV-positive HNSCC responds well to treatment, which includes surgery followed by radiation or chemoradiation therapy. Radiation therapy (RT) is based on ionizing radiation (IR) changing cell physiology. IR can directly interact with deoxyribonucleic acid (DNA) or produce reactive oxygen and nitrogen species (RONS), provoking DNA damage. When DNA damage is not repaired, programmed cell death (apoptosis and/or autophagy) is induced. However, cancer cells can acquire resistance to IR avoiding cell death, where reprogramming of energy metabolism has a critical role and is intimately connected with hypoxia, mitochondrial physiology, oxidative stress (OS) and autophagy. This review is focused on the reprogramming of energy metabolism in response to RT in HPV-positive and HPV-negative HNSCC, showing their differences in cellular metabolism management and the probable direction of treatments for each subtype of HNSCC.

Discoidin Receptor 2 Controls Bone Formation and Marrow Adipogenesis

Cell-extracellular matrix (ECM) interactions play major roles in controlling progenitor cell fate and differentiation. The receptor tyrosine kinase, discoidin domain receptor 2 (DDR2), is an important mediator of interactions between cells and fibrillar collagens. DDR2 signals through both ERK1/2 and p38 MAP kinase, which stimulate osteoblast differentiation and bone formation. Here we show that DDR2 is critical for skeletal development and differentiation of marrow progenitor cells to osteoblasts while suppressing marrow adipogenesis. Smallie mice (Ddr2slie/slie ), which contain a nonfunctional Ddr2 allele, have multiple skeletal defects. A progressive decrease in tibial trabecular bone volume/total volume (BV/TV) was observed when wild-type (WT), Ddr2wt/slie , and Ddr2slie/slie mice were compared. These changes were associated with reduced trabecular number (Tb.N) and trabecular thickness (Tb.Th) and increased trabecular spacing (Tb.Sp) in both males and females, but reduced cortical thickness only in Ddr2slie/slie females. Bone changes were attributed to decreased bone formation rather than increased osteoclast activity. Significantly, marrow fat and adipocyte-specific mRNA expression were significantly elevated in Ddr2slie/slie animals. Additional skeletal defects include widened calvarial sutures and reduced vertebral trabecular bone. To examine the role of DDR2 signaling in cell differentiation, bone marrow stromal cells (BMSCs) were grown under osteogenic and adipogenic conditions. Ddr2slie/slie cells exhibited defective osteoblast differentiation and accelerated adipogenesis. Changes in differentiation were related to activity of runt-related transcription factor 2 (RUNX2) and PPARγ, transcription factors that are both controlled by MAPK-dependent phosphorylation. Specifically, the defective osteoblast differentiation in calvarial cells from Ddr2slie/slie mice was associated with reduced ERK/MAP kinase and RUNX2-S319 phosphorylation and could be rescued with a constitutively active phosphomimetic RUNX2 mutant. Also, DDR2 was shown to increase RUNX2-S319 phosphorylation and transcriptional activity while also increasing PPARγ-S112 phosphorylation, but reducing its activity. DDR2 is, therefore, important for maintenance of osteoblast activity and suppression of marrow adipogenesis in vivo and these actions are related to changes in MAPK-dependent RUNX2 and PPARγ phosphorylation. © 2016 American Society for Bone and Mineral Research.

A molecular classification of human mesenchymal stromal cells

Mesenchymal stromal cells (MSC) are widely used for the study of mesenchymal tissue repair, and increasingly adopted for cell therapy, despite the lack of consensus on the identity of these cells. In part this is due to the lack of specificity of MSC markers. Distinguishing MSC from other stromal cells such as fibroblasts is particularly difficult using standard analysis of surface proteins, and there is an urgent need for improved classification approaches. Transcriptome profiling is commonly used to describe and compare different cell types; however, efforts to identify specific markers of rare cellular subsets may be confounded by the small sample sizes of most studies. Consequently, it is difficult to derive reproducible, and therefore useful markers. We addressed the question of MSC classification with a large integrative analysis of many public MSC datasets. We derived a sparse classifier (The Rohart MSC test) that accurately distinguished MSC from non-MSC samples with >97% accuracy on an internal training set of 635 samples from 41 studies derived on 10 different microarray platforms. The classifier was validated on an external test set of 1,291 samples from 65 studies derived on 15 different platforms, with >95% accuracy. The genes that contribute to the MSC classifier formed a protein-interaction network that included known MSC markers. Further evidence of the relevance of this new MSC panel came from the high number of Mendelian disorders associated with mutations in more than 65% of the network. These result in mesenchymal defects, particularly impacting on skeletal growth and function. The Rohart MSC test is a simple in silico test that accurately discriminates MSC from fibroblasts, other adult stem/progenitor cell types or differentiated stromal cells. It has been implemented in the www.stemformatics.org resource, to assist researchers wishing to benchmark their own MSC datasets or data from the public domain. The code is available from the CRAN repository and all data used to generate the MSC test is available to download via the Gene Expression Omnibus or the Stemformatics resource.

Discoidin domain receptor functions in physiological and pathological conditions

The discoidin domain receptors, DDR1 and DDR2, are nonintegrin collagen receptors that are members of the receptor tyrosine kinase family. Both DDRs bind a number of different collagen types and play important roles in embryo development. Dysregulated DDR function is associated with progression of various human diseases, including fibrosis, arthritis, and cancer. By interacting with key components of the extracellular matrix and displaying distinct activation kinetics, the DDRs form a unique subfamily of receptor tyrosine kinases. DDR-facilitated cellular functions include cell migration, cell survival, proliferation, and differentiation, as well as remodeling of extracellular matrices. This review summarizes the current knowledge of DDR-ligand interactions, DDR-initiated signal pathways and the molecular mechanisms that regulate receptor function. Also discussed are the roles of DDRs in development and disease progression.