Discoidin domain receptor functions in physiological and pathological conditions

Amplification of DDR2 mediates sorafenib resistance through NF-κB/c-Rel signaling in hepatocellular carcinoma

Sorafenib was the first systemic therapy approved by the Food and Drug Administration to treat advanced hepatocellular carcinoma (HCC). However, sorafenib therapy is frequently accompanied by drug resistance. We aimed to explore the mechanisms of sorafenib resistance and provide feasible solutions to increase the response to sorafenib in patients with advanced HCC. The expression profile of discoidin domain receptor 2 (DDR2) in HCC tissues and cells was detected using quantitative real-time PCR (qPCR) and western blotting assays. The effects of DDR2 on sorafenib resistance were examined using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, colony formation, TdT-mediated dUTP nick end labeling, and flow cytometry assays. The effect of DDR2 on the nuclear factor kappa B (NF-κB) signaling pathway was evaluated by luciferase reporter, immunofluorescence, qPCR and flow cytometry assays. We demonstrated that DDR2 expression was dramatically upregulated in sorafenib-resistant HCC tissues relative to sensitive tissues. Downregulation of DDR2 sensitized HCC cell lines to sorafenib cytotoxicity. Further analysis showed that DDR2 could increase the nuclear location of REL proto-oncogene, a NF-κB subunit, to mediate NF-κB signaling. Blocking NF-κB signaling using the NF-κB signaling inhibitor, bardoxolone methyl, increased the response of HCC cells to sorafenib. Further analysis showed that DNA amplification of DDR2 is an important mechanism leading to DDR2 overexpression in HCC. Our results demonstrated that DDR2 is a potential therapeutic target in patients with HCC, and targeting DDR2 represents a promising approach to increase sorafenib sensitivity in patients with HCC.

Tyrosine kinases in the pathogenesis of tissue fibrosis in systemic sclerosis and potential therapeutic role of their inhibition

Systemic sclerosis (SSc) is an idiopathic autoimmune disease with a heterogeneous clinical phenotype ranging from limited cutaneous involvement to rapidly progressive diffuse SSc. The most severe SSc clinical and pathologic manifestations result from an uncontrolled fibrotic process involving the skin and various internal organs. The molecular mechanisms responsible for the initiation and progression of the SSc fibrotic process have not been fully elucidated. Recently it has been suggested that tyrosine protein kinases play a role. The implicated kinases include receptor-activated tyrosine kinases and nonreceptor tyrosine kinases. The receptor kinases are activated following specific binding of growth factors (platelet-derived growth factor, fibroblast growth factor, or vascular endothelial growth factor). Other receptor kinases are the discoidin domain receptors activated by binding of various collagens, the ephrin receptors that are activated by ephrins and the angiopoetin-Tie-2s receptors. The nonreceptor tyrosine kinases c-Abl, Src, Janus, and STATs have also been shown to participate in SSc-associated tissue fibrosis. Currently, there are no effective disease-modifying therapies for SSc-associated tissue fibrosis. Therefore, extensive investigation has been conducted to examine whether tyrosine kinase inhibitors (TKIs) may exert antifibrotic effects. Here, we review the role of receptor and nonreceptor tyrosine kinases in the pathogenesis of the frequently progressive cutaneous and systemic fibrotic alterations in SSc, and the potential of TKIs as SSc disease-modifying antifibrotic therapeutic agents.

Role of Discoidin Domain Receptor 2 in Craniofacial Bone Regeneration

Bone loss caused by trauma, neoplasia, congenital defects, or periodontal disease is a major cause of disability and human suffering. Skeletal progenitor cell-extracellular matrix interactions are critical for bone regeneration. Discoidin domain receptor 2 (DDR2), an understudied collagen receptor, plays an important role in skeletal development. Ddr2 loss-of-function mutations in humans and mice cause severe craniofacial and skeletal defects, including altered cranial shape, dwarfing, reduced trabecular and cortical bone, alveolar bone/periodontal defects, and altered dentition. However, the role of this collagen receptor in craniofacial regeneration has not been examined. To address this, calvarial subcritical-size defects were generated in wild-type (WT) and Ddr2-deficient mice. The complete bridging seen in WT controls at 4 wk postsurgery was not observed in Ddr2-deficient mice even after 12 wk. Quantitation of defect bone area by micro-computed tomography also revealed a 50% reduction in new bone volume in Ddr2-deficient mice. Ddr2 expression during calvarial bone regeneration was measured using Ddr2-LacZ knock-in mice. Expression was restricted to periosteal surfaces of uninjured calvarial bone and, after injury, was detected in select regions of the defect site by 3 d postsurgery and expanded during the healing process. The impaired bone healing associated with Ddr2 deficiency may be related to reduced osteoprogenitor or osteoblast cell proliferation and differentiation since knockdown/knockout of Ddr2 in a mesenchymal cell line and primary calvarial osteoblast cultures reduced osteoblast differentiation while Ddr2 overexpression was stimulatory. In conclusion, Ddr2 is required for cranial bone regeneration and may be a novel target for therapy.

Extracellular matrix and its therapeutic potential for cancer treatment

The extracellular matrix (ECM) is one of the major components of tumors that plays multiple crucial roles, including mechanical support, modulation of the microenvironment, and a source of signaling molecules. The quantity and cross-linking status of ECM components are major factors determining tissue stiffness. During tumorigenesis, the interplay between cancer cells and the tumor microenvironment (TME) often results in the stiffness of the ECM, leading to aberrant mechanotransduction and further malignant transformation. Therefore, a comprehensive understanding of ECM dysregulation in the TME would contribute to the discovery of promising therapeutic targets for cancer treatment. Herein, we summarized the knowledge concerning the following: (1) major ECM constituents and their functions in both normal and malignant conditions; (2) the interplay between cancer cells and the ECM in the TME; (3) key receptors for mechanotransduction and their alteration during carcinogenesis; and (4) the current therapeutic strategies targeting aberrant ECM for cancer treatment.

Vimentin regulates the assembly and function of matrix adhesions

The intermediate filament protein vimentin is a widely used phenotypic marker for identifying cells of the mesenchymal linkage such as fibroblasts and myofibroblasts, but the full repertoire of vimentin's functional attributes has not been fully explored. Here we consider how vimentin, in addition to its contributions to mechanical stabilization of cell structure, also helps to control the assembly of cell adhesions and migration through collagen matrices. While the assembly and function of matrix adhesions are critical for the differentiation of myofibroblasts and many other types of adherent cells, a potential mechanism that explains how vimentin affects the recruitment and abundance of centrally important proteins in cell adhesions has been elusive. Here we review recent data indicating that vimentin plays a central regulatory role in the assembly of focal adhesions which form in response to the attachment to collagen. We show that in particular, vimentin is a key organizer of the β1 integrin adhesive machinery, which affects cell migration through collagen. This review provides a comprehensive picture of the surprisingly broad array of processes and molecules with which vimentin interacts to affect cell function in the context of fibroblast and myofibroblast adhesion and migration on collagen.

The Yin and Yang of Discoidin Domain Receptors (DDRs): Implications in Tumor Growth and Metastasis Development

Simple Summary

The tumor microenvironment plays an important role in tumor development and metastasis. Collagens are major components of the extracellular matrix and can influence tumor development and metastasis by activating discoidin domain receptors (DDRs). This work shows the different roles of DDRs in various cancers and highlights the complexity of anti-DDR therapies in cancer treatment.

Abstract

The tumor microenvironment is a complex structure composed of the extracellular matrix (ECM) and nontumoral cells (notably cancer-associated fibroblasts (CAFs) and immune cells). Collagens are the main components of the ECM and they are extensively remodeled during tumor progression. Some collagens are ligands for the discoidin domain receptor tyrosine kinases, DDR1 and DDR2. DDRs are involved in different stages of tumor development and metastasis formation. In this review, we present the different roles of DDRs in these processes and discuss controversial findings. We conclude by describing emerging DDR inhibitory strategies, which could be used as new alternatives for the treatment of patients.

Generating Selective Leads for Mer Kinase Inhibitors-Example of a Comprehensive Lead-Generation Strategy

Mer is a member of the TAM (Tyro3, Axl, Mer) kinase family that has been associated with cancer progression, metastasis, and drug resistance. Their essential function in immune homeostasis has prompted an interest in their role as modulators of antitumor immune response in the tumor microenvironment. Here we illustrate the outcomes of an extensive lead-generation campaign for identification of Mer inhibitors, focusing on the results from concurrent, orthogonal high-throughput screening approaches. Data mining, HT (high-throughput), and DECL (DNA-encoded chemical library) screens offered means to evaluate large numbers of compounds. We discuss campaign strategy and screening outcomes, and exemplify series resulting from prioritization of hits that were identified. Concurrent execution of HT and DECL screening successfully yielded a large number of potent, selective, and novel starting points, covering a range of selectivity profiles across the TAM family members and modes of kinase binding, and offered excellent start points for lead development.

Complex roles of discoidin domain receptor tyrosine kinases in cancer

Discoidin domain receptors, DDR1 and DDR2 are members of the receptor tyrosine kinase (RTK) family that serves as a non-integrin collagen receptor and were initially identified as critical regulators of embryonic development and cellular homeostasis. In recent years, numerous studies have focused on the role of these receptors in disease development, in particular, cancer where they have been reported to augment ECM remodeling, invasion, drug resistance to facilitate tumor progression and metastasis. Interestingly, accumulating evidence also suggests that DDRs promote apoptosis and suppress tumor progression in various human cancers due to which their functions in cancer remain ill-defined and presents a case of an interesting therapeutic target. The present review has discussed the role of DDRs in tumorigenesis and the metastasis.

A guide to the composition and functions of the extracellular matrix

Extracellular matrix (ECM) is a dynamic 3-dimensional network of macromolecules that provides structural support for the cells and tissues. Accumulated knowledge clearly demonstrated over the last decade that ECM plays key regulatory roles since it orchestrates cell signaling, functions, properties and morphology. Extracellularly secreted as well as cell-bound factors are among the major members of the ECM family. Proteins/glycoproteins, such as collagens, elastin, laminins and tenascins, proteoglycans and glycosaminoglycans, hyaluronan, and their cell receptors such as CD44 and integrins, responsible for cell adhesion, comprise a well-organized functional network with significant roles in health and disease. On the other hand, enzymes such as matrix metalloproteinases and specific glycosidases including heparanase and hyaluronidases contribute to matrix remodeling and affect human health. Several cell processes and functions, among them cell proliferation and survival, migration, differentiation, autophagy, angiogenesis, and immunity regulation are affected by certain matrix components. Structural alterations have been also well associated with disease progression. This guide on the composition and functions of the ECM gives a broad overview of the matrisome, the major ECM macromolecules, and their interaction networks within the ECM and with the cell surface, summarizes their main structural features and their roles in tissue organization and cell functions, and emphasizes the importance of specific ECM constituents in disease development and progression as well as the advances in molecular targeting of ECM to design new therapeutic strategies.

Knockdown of AKT3 Activates HER2 and DDR Kinases in Bone-Seeking Breast Cancer Cells, Promotes Metastasis In Vivo and Attenuates the TGFβ/CTGF Axis

Bone metastases frequently occur in breast cancer patients and lack appropriate treatment options. Hence, understanding the molecular mechanisms involved in the multistep process of breast cancer bone metastasis and tumor-induced osteolysis is of paramount interest. The serine/threonine kinase AKT plays a crucial role in breast cancer bone metastasis but the effect of individual AKT isoforms remains unclear. Therefore, AKT isoform-specific knockdowns were generated on the bone-seeking MDA-MB-231 BO subline and the effect on proliferation, migration, invasion, and chemotaxis was analyzed by live-cell imaging. Kinome profiling and Western blot analysis of the TGFβ/CTGF axis were conducted and metastasis was evaluated by intracardiac inoculation of tumor cells into NOD scid gamma (NSG) mice. MDA-MB-231 BO cells exhibited an elevated AKT3 kinase activity in vitro and responded to combined treatment with AKT- and mTOR-inhibitors. Knockdown of AKT3 significantly increased migration, invasion, and chemotaxis in vitro and metastasis to bone but did not significantly enhance osteolysis. Furthermore, knockdown of AKT3 increased the activity and phosphorylation of pro-metastatic HER2 and DDR1/2 but lowered protein levels of CTGF after TGFβ-stimulation, an axis involved in tumor-induced osteolysis. We demonstrated that AKT3 plays a crucial role in bone-seeking breast cancer cells by promoting metastatic potential without facilitating tumor-induced osteolysis.

Novel Regulators of the IGF System in Cancer

The insulin-like growth factor (IGF) system is a dynamic network of proteins, which includes cognate ligands, membrane receptors, ligand binding proteins and functional downstream effectors. It plays a critical role in regulating several important physiological processes including cell growth, metabolism and differentiation. Importantly, alterations in expression levels or activation of components of the IGF network are implicated in many pathological conditions including diabetes, obesity and cancer initiation and progression. In this review we will initially cover some general aspects of IGF action and regulation in cancer and then focus in particular on the role of transcriptional regulators and novel interacting proteins, which functionally contribute in fine tuning IGF1R signaling in several cancer models. A deeper understanding of the biological relevance of this network of IGF1R modulators might provide novel therapeutic opportunities to block this system in neoplasia.

Discoidin domain receptors orchestrate cancer progression: A focus on cancer therapies

Discoidin domain receptors (DDR), including DDR1 and DDR2, are special types of the transmembrane receptor tyrosine kinase superfamily. DDR are activated by binding to the triple-helical collagen and, in turn, DDR can activate signal transduction pathways that regulate cell-collagen interactions involved in multiple physiological and pathological processes such as cell proliferation, migration, apoptosis, and cytokine secretion. Recently, DDR have been found to contribute to various diseases, including cancer. In addition, aberrant expressions of DDR have been reported in various human cancers, which indicates that DDR1 and DDR2 could be new targets for cancer treatment. Considerable effort has been made to design DDR inhibitors and several molecules have shown therapeutic effects in pre-clinical models. In this article, we review the recent literature on the role of DDR in cancer progression, the development status of DDR inhibitors, and the clinical potential of targeting DDR in cancer therapies.

Prediction and mechanistic analysis of drug-induced liver injury (DILI) based on chemical structure

BACKGROUND

Drug-induced liver injury (DILI) is a major safety concern characterized by a complex and diverse pathogenesis. In order to identify DILI early in drug development, a better understanding of the injury and models with better predictivity are urgently needed. One approach in this regard are in silico models which aim at predicting the risk of DILI based on the compound structure. However, these models do not yet show sufficient predictive performance or interpretability to be useful for decision making by themselves, the former partially stemming from the underlying problem of labeling the in vivo DILI risk of compounds in a meaningful way for generating machine learning models.

RESULTS

As part of the Critical Assessment of Massive Data Analysis (CAMDA) "CMap Drug Safety Challenge" 2019 ( http://camda2019.bioinf.jku.at ), chemical structure-based models were generated using the binarized DILIrank annotations. Support Vector Machine (SVM) and Random Forest (RF) classifiers showed comparable performance to previously published models with a mean balanced accuracy over models generated using 5-fold LOCO-CV inside a 10-fold training scheme of 0.759 ± 0.027 when predicting an external test set. In the models which used predicted protein targets as compound descriptors, we identified the most information-rich proteins which agreed with the mechanisms of action and toxicity of nonsteroidal anti-inflammatory drugs (NSAIDs), one of the most important drug classes causing DILI, stress response via TP53 and biotransformation. In addition, we identified multiple proteins involved in xenobiotic metabolism which could be novel DILI-related off-targets, such as CLK1 and DYRK2. Moreover, we derived potential structural alerts for DILI with high precision, including furan and hydrazine derivatives; however, all derived alerts were present in approved drugs and were over specific indicating the need to consider quantitative variables such as dose.

CONCLUSION

Using chemical structure-based descriptors such as structural fingerprints and predicted protein targets, DILI prediction models were built with a predictive performance comparable to previous literature. In addition, we derived insights on proteins and pathways statistically (and potentially causally) linked to DILI from these models and inferred new structural alerts related to this adverse endpoint.

Oxidative Stress, Glutathione Metabolism, and Liver Regeneration Pathways Are Activated in Hereditary Tyrosinemia Type 1 Mice upon Short-Term Nitisinone Discontinuation

Hereditary tyrosinemia type 1 (HT1) is an inherited condition in which the body is unable to break down the amino acid tyrosine due to mutations in the fumarylacetoacetate hydrolase (FAH) gene, coding for the final enzyme of the tyrosine degradation pathway. As a consequence, HT1 patients accumulate toxic tyrosine derivatives causing severe liver damage. Since its introduction, the drug nitisinone (NTBC) has offered a life-saving treatment that inhibits the upstream enzyme 4-hydroxyphenylpyruvate dioxygenase (HPD), thereby preventing production of downstream toxic metabolites. However, HT1 patients under NTBC therapy remain unable to degrade tyrosine. To control the disease and side-effects of the drug, HT1 patients need to take NTBC as an adjunct to a lifelong tyrosine and phenylalanine restricted diet. As a consequence of this strict therapeutic regime, drug compliance issues can arise with significant influence on patient health. In this study, we investigated the molecular impact of short-term NTBC therapy discontinuation on liver tissue of Fah-deficient mice. We found that after seven days of NTBC withdrawal, molecular pathways related to oxidative stress, glutathione metabolism, and liver regeneration were mostly affected. More specifically, NRF2-mediated oxidative stress response and several toxicological gene classes related to reactive oxygen species metabolism were significantly modulated. We observed that the expression of several key glutathione metabolism related genes including Slc7a11 and Ggt1 was highly increased after short-term NTBC therapy deprivation. This stress response was associated with the transcriptional activation of several markers of liver progenitor cells including Atf3, Cyr61, Ddr1, Epcam, Elovl7, and Glis3, indicating a concreted activation of liver regeneration early after NTBC withdrawal.

Discoidin domain receptor 1 activation links extracellular matrix to podocyte lipotoxicity in Alport syndrome

Background

Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase that is activated by collagens that is involved in the pathogenesis of fibrotic disorders. Interestingly, de novo production of the collagen type I (Col I) has been observed in Col4a3 knockout mice, a mouse model of Alport Syndrome (AS mice). Deletion of the DDR1 in AS mice was shown to improve survival and renal function. However, the mechanisms driving DDR1-dependent fibrosis remain largely unknown.

Methods

Podocyte pDDR1 levels, Collagen and cluster of differentiation 36 (CD36) expression was analyzed by Real-time PCR and Western blot. Lipid droplet accumulation and content was determined using Bodipy staining and enzymatic analysis. CD36 and DDR1 interaction was determined by co-immunoprecipitation. Creatinine, BUN, albuminuria, lipid content, and histological and morphological assessment of kidneys harvested from AS mice treated with Ezetimibe and/or Ramipril or vehicle was performed.

Findings

We demonstrate that Col I-mediated DDR1 activation induces CD36-mediated podocyte lipotoxic injury. We show that Ezetimibe interferes with the CD36/DDR1 interaction in vitro and prevents lipotoxicity in AS mice thus preserving renal function similarly to ramipril.

Interpretation

Our study suggests that Col I/DDR1-mediated lipotoxicity contributes to renal failure in AS and that targeting this pathway may represent a new therapeutic strategy for patients with AS and with chronic kidney diseases (CKD) associated with Col4 mutations.

Funding

This study is supported by the NIH grants R01DK117599, R01DK104753, R01CA227493, U54DK083912, UM1DK100846, U01DK116101, UL1TR000460 (Miami Clinical Translational Science Institute, National Center for Advancing Translational Sciences and the National Institute on Minority Health and Health Disparities), F32DK115109, Hoffmann-La Roche and Alport Syndrome Foundation.

Circ-PRKDC Facilitates the Progression of Colorectal Cancer Through miR-198/DDR1 Regulatory Axis

Background

Circular RNAs (circRNAs) play a crucial role in a variety of cancers, including colorectal cancer (CRC). This study aimed to explore the role of hsa_circ_0136666 (circ-PRKDC) in CRC and its potential mechanism.

Methods

The levels of circ-PRKDC, miR-198 and discoidin domain receptor 1 (DDR1) were measured using quantitative real-time polymerase chain reaction or Western blot. Cell viability was detected using cell counting kit-8 (CCK-8) assay. Cell apoptosis and cycle were evaluated via flow cytometry. Cell migration and invasion were examined using transwell assay. CyclinD1 protein level was determined via Western blot. The interaction among circ-PRKDC, miR-198 and DDR1 was confirmed by dual-luciferase reporter assay and RNA immunoprecipitation assay. Xenograft assay was performed to analyze tumor growth in vivo.

Results

Circ-PRKDC and DDR1 levels were increased, and miR-198 level was decreased in CRC tissues and cells. Circ-PRKDC depletion inhibited proliferation, migration and invasion, and expedited apoptosis and cell cycle arrest in SW480 and HCT116 cells. Silence of circ-PRKDC impeded CRC progression by sponging miR-198. Overexpression of miR-198 hindered CRC development via targeting DDR1. Moreover, circ-PRKDC silencing suppressed tumor growth in vivo.

Conclusion

Knockdown of circ-PRKDC inhibited CRC progression via modulating miR-198/DDR1 pathway.

The roles of collagen in chronic kidney disease and vascular calcification

The extracellular matrix component collagen is widely expressed in human tissues and participates in various cellular biological processes. The collagen amount generally remains stable due to intricate regulatory networks, but abnormalities can lead to several diseases. During the development of renal fibrosis and vascular calcification, the expression of collagen is significantly increased, which promotes phenotypic changes in intrinsic renal cells and vascular smooth muscle cells, thereby exacerbating disease progression. Reversing the overexpression of collagen substantially prevents or slows renal fibrosis and vascular calcification in a wide range of animal models, suggesting a novel target for treating patients with these diseases. Stem cell therapy seems to be an effective strategy to alleviate these two conditions. However, recent findings indicate that the natural pore structure of collagen fibers is sufficient to induce the inappropriate differentiation of stem cells and thereby exacerbate renal fibrosis and vascular calcification. A comprehensive understanding of the role of collagen in these diseases and its effect on stem cell biology will assist in improving the unmet requirements for treating patients with kidney disease.

Overexpression of DDR1 Promotes Migration, Invasion, Though EMT-Related Molecule Expression and COL4A1/DDR1/MMP-2 Signaling Axis

Purpose:

Discoidin domain receptor 1 (DDR1) belongs to a novel class of receptor tyrosine kinases. Previous evidence indicates that DDR1 overexpression promotes the aggressive growth of bladder cancer (BC) cells. This study aimed to investigate the molecular mechanisms by which DDR1 influences BC.

Methods:

DDR1 was transfected into human BC RT4 cells. DDR1, COL4A1, and MMP-2 expression in 30 BC tissues and paired adjacent tissues were examined by real-time polymerase chain reaction (RT-PCR) and immunohistochemistry. Transwell assays were conducted to determine cell migration and invasion. RT-PCR and western blot (WB) were also used to measure the DDR1, COL4A1, MMP-2, and EMT-related gene (ZEB1 and SLUG) expression in RT4 cells after DDR1 overexpression.

Results:

COL4A1 and MMP-2 interacted with DDR1 in the PPI network. RT-PCR and immunohistochemistry results showed that both mRNA and protein levels of DDR1 and COL4A1 were significantly increased in BC tissue, while the expression of MMP-2 was increased only at the mRNA level (P < 0.05). Overexpression of DDR1 in RT4 cells significantly promoted their migratory and invasive capabilities in vitro (P < 0.05). Moreover, overexpression of DDR1 in RT4 cells increased the mRNA and protein expression of ZEB1, SLUG, COL4A1, and MMP-2 (P < 0.01). DDR1-mediated migration and invasion of RT4 cells were reversed after COL4A1-siRNA treatment.

Conclusion:

DDR1 may be a potential therapeutic target in BC patients.

Silencing of sinusoidal DDR1 reduces murine liver metastasis by colon carcinoma

Liver metastasis depends on the collagenous microenvironment generated by hepatic sinusoidal cells (SCs). DDR1 is an atypical collagen receptor linked to tumor progression, but whether SCs express DDR1 and its implication in liver metastasis remain unknown. Freshly isolated hepatic stellate cells (HSCs), Kupffer cells (KCs), and liver sinusoidal endothelial cells (LSECs), that conform the SCs, expressed functional DDR1. HSCs expressed the largest amounts. C26 colon carcinoma secretomes increased DDR1 phosphorylation in HSCs and KCs by collagen I. Inhibition of kinase activity by DDR1-IN-1 or mRNA silencing of DDR1 reduced HSCs secretion of MMP2/9 and chemoattractant and proliferative factors for LSECs and C26 cells. DDR1-IN-1 did not modify MMP2/9 in KCs or LSECs secretomes, but decreased the enhancement of C26 migration and proliferation induced by their secretomes. Gene array showed that DDR1 silencing downregulated HSCs genes for collagens, MMPs, interleukins and chemokines. Silencing of DDR1 before tumor inoculation reduced hepatic C26 metastasis in mice. Silenced livers bore less tumor foci than controls. Metastatic foci in DDR1 silenced mice were smaller and contained an altered stroma with fewer SCs, proliferating cells, collagen and MMPs than foci in control mice. In conclusion, hepatic DDR1 promotes C26 liver metastasis and favors the pro-metastatic response of SCs to the tumor.

Discoidin Domain Receptors in Melanoma: Potential Therapeutic Targets to Overcome MAPK Inhibitor Resistance

Melanoma is a highly malignant skin cancer with high propensity to metastasize and develop drug resistance, making it a difficult cancer to treat. Current therapies targeting BRAF (V600) mutations are initially effective, but eventually tumors overcome drug sensitivity and reoccur. This process is accomplished in part by reactivating alternate signaling networks that reinstate melanoma proliferative and survival capacity, mostly through reprogramming of receptor tyrosine kinase (RTK) signaling. Evidence indicates that the discoidin domain receptors (DDRs), a set of RTKs that signal in response to collagen, are part of the kinome network that confer drug resistance. We previously reported that DDR1 is expressed in melanomas, where it can promote tumor malignancy in mouse models of melanoma, and thus, DDR1 could be a promising target to overcome drug resistance. In this review, we summarize the current knowledge on DDRs in melanoma and their implication for therapy, with emphasis in resistance to MAPK inhibitors.

Two-step release of kinase autoinhibition in discoidin domain receptor 1

Discoidin domain receptor 1 (DDR1) is a collagen-activated receptor tyrosine kinase with important functions in organogenesis and tissue homeostasis. Aberrant DDR1 activity contributes to the progression of human diseases, including fibrosis and cancer. How DDR1 activity is regulated is poorly understood. We investigated the function of the long intracellular juxtamembrane (JM) region of human DDR1 and found that the kinase-proximal segment, JM4, is an important regulator of kinase activity. Crystal structure analysis revealed that JM4 forms a hairpin that penetrates the kinase active site, reinforcing autoinhibition by the activation loop. Using in vitro enzymology with soluble kinase constructs, we established that release from autoinhibition occurs in two distinct steps: rapid autophosphorylation of the JM4 tyrosines, Tyr569 and Tyr586, followed by slower autophosphorylation of activation loop tyrosines. Mutation of JM4 tyrosines abolished collagen-induced DDR1 activation in cells. The insights may be used to develop allosteric, DDR1-specific, kinase inhibitors.

A Complex and Evolutive Character: Two Face Aspects of ECM in Tumor Progression

Tumor microenvironment, including extracellular matrix (ECM) and stromal cells, is a key player during tumor development, from initiation, growth and progression to metastasis. During all of these steps, remodeling of matrix components occurs, changing its biochemical and physical properties. The global and basic cancer ECM model is that tumors are surrounded by activated stromal cells, that remodel physiological ECM to evolve into a stiffer and more crosslinked ECM than in normal conditions, thereby increasing invasive capacities of cancer cells. In this review, we show that this too simple model does not consider the complexity, specificity and heterogeneity of each organ and tumor. First, we describe the general ECM in context of cancer. Then, we go through five invasive and most frequent cancers from different origins (breast, liver, pancreas, colon, and skin), and show that each cancer has its own specific matrix, with different stromal cells, ECM components, biochemical properties and activated signaling pathways. Furthermore, in these five cancers, we describe the dual role of tumor ECM: as a protective barrier against tumor cell proliferation and invasion, and as a major player in tumor progression. Indeed, crosstalk between tumor and stromal cells induce changes in matrix organization by remodeling ECM through invadosome formation in order to degrade it, promoting tumor progression and cell invasion. To sum up, in this review, we highlight the specificities of matrix composition in five cancers and the necessity not to consider the ECM as one general and simple entity, but one complex, dynamic and specific entity for each cancer type and subtype.

Reciprocal Interplay Between Fibrillar Collagens and Collagen-Binding Integrins: Implications in Cancer Progression and Metastasis

Cancers are complex ecosystems composed of malignant cells embedded in an intricate microenvironment made of different non-transformed cell types and extracellular matrix (ECM) components. The tumor microenvironment is governed by constantly evolving cell-cell and cell-ECM interactions, which are now recognized as key actors in the genesis, progression and treatment of cancer lesions. The ECM is composed of a multitude of fibrous proteins, matricellular-associated proteins, and proteoglycans. This complex structure plays critical roles in cancer progression: it functions as the scaffold for tissues organization and provides biochemical and biomechanical signals that regulate key cancer hallmarks including cell growth, survival, migration, differentiation, angiogenesis, and immune response. Cells sense the biochemical and mechanical properties of the ECM through specialized transmembrane receptors that include integrins, discoidin domain receptors, and syndecans. Advanced stages of several carcinomas are characterized by a desmoplastic reaction characterized by an extensive deposition of fibrillar collagens in the microenvironment. This compact network of fibrillar collagens promotes cancer progression and metastasis, and is associated with low survival rates for cancer patients. In this review, we highlight how fibrillar collagens and their corresponding integrin receptors are modulated during cancer progression. We describe how the deposition and alignment of collagen fibers influence the tumor microenvironment and how fibrillar collagen-binding integrins expressed by cancer and stromal cells critically contribute in cancer hallmarks.

Inhibition of DDR1 enhances in vivo chemosensitivity in KRAS-mutant lung adenocarcinoma

Platinum-based chemotherapy in combination with immune-checkpoint inhibitors is the current standard of care for patients with advanced lung adenocarcinoma (LUAD). However, tumor progression evolves in most cases. Therefore, predictive biomarkers are needed for better patient stratification and for the identification of new therapeutic strategies, including enhancing the efficacy of chemotoxic agents. Here, we hypothesized that discoidin domain receptor 1 (DDR1) may be both a predictive factor for chemoresistance in patients with LUAD and a potential target positively selected in resistant cells. By using biopsies from patients with LUAD, KRAS-mutant LUAD cell lines, and in vivo genetically engineered KRAS-driven mouse models, we evaluated the role of DDR1 in the context of chemotherapy treatment. We found that DDR1 is upregulated during chemotherapy both in vitro and in vivo. Moreover, analysis of a cohort of patients with LUAD suggested that high DDR1 levels in pretreatment biopsies correlated with poor response to chemotherapy. Additionally, we showed that combining DDR1 inhibition with chemotherapy prompted a synergistic therapeutic effect and enhanced cell death of KRAS-mutant tumors in vivo. Collectively, this study suggests a potential role for DDR1 as both a predictive and prognostic biomarker, potentially improving the chemotherapy response of patients with LUAD.

Targeting Discoidin Domain Receptor 1 (DDR1) Signaling and Its Crosstalk with β1-integrin Emerges as a Key Factor for Breast Cancer Chemosensitization upon Collagen Type 1 Binding

Collagen type 1 (COL1) is a ubiquitously existing extracellular matrix protein whose high density in breast tissue favors metastasis and chemoresistance. COL1-binding of MDA-MB-231 and MCF-7 breast cancer cells is mainly dependent on β₁-integrins (ITGB1). Here, we elucidate the signaling of chemoresistance in both cell lines and their ITGB1-knockdown mutants and elucidated MAPK pathway to be strongly upregulated upon COL1 binding. Notably, Discoidin Domain Receptor 1 (DDR1) was identified as another important COL1-sensor, which is permanently active but takes over the role of COL1-receptor maintaining MAPK activation in ITGB1-knockdown cells. Consequently, inhibition of DDR1 and ERK1/2 act synergistically, and sensitize the cells for cytostatic treatments using mitoxantrone, or doxorubicin, which was associated with an impaired ABCG2 drug efflux transporter activity. These data favor DDR1 as a promising target for cancer cell sensitization, most likely in combination with MAPK pathway inhibitors to circumvent COL1 induced transporter resistance axis. Since ITGB1-knockdown also induces upregulation of pEGFR in MDA-MB-231 cells, inhibitory approaches including EGFR inhibitors, such as gefitinib appear promising for pharmacological interference. These findings provide evidence for the highly dynamic adaptation of breast cancer cells in maintaining matrix binding to circumvent cytotoxicity and highlight DDR1 signaling as a target for sensitization approaches.

Coordinated regulation of cell survival and cell cycle pathways by DDR2-dependent SRF transcription factor in cardiac fibroblasts

Relative resistance to apoptosis and the ability to proliferate and produce a collagen-rich scar determine the critical role of cardiac fibroblasts in wound healing and tissue remodeling following myocardial injury. Identification of cardiac fibroblast-specific factors and mechanisms underlying these aspects of cardiac fibroblast function is therefore of considerable scientific and clinical interest. In the present study, gene knockdown and overexpression approaches and promoter binding assays showed that discoidin domain receptor 2 (DDR2), a mesenchymal cell-specific collagen receptor tyrosine kinase localized predominantly in fibroblasts in the heart, acts via ERK1/2 MAPK-activated serum response factor (SRF) transcription factor to enhance the expression of antiapoptotic cIAP2 in cardiac fibroblasts, conferring resistance against oxidative injury. Furthermore, DDR2 was found to act via ERK1/2 MAPK-activated SRF to transcriptionally upregulate Skp2 that in turn facilitated post-translational degradation of p27, the cyclin-dependent kinase inhibitor that causes cell cycle arrest, to promote G₁-S transition, as evidenced by Rb phosphorylation, increased proliferating cell nuclear antigen (PCNA) levels, and flow cytometry. DDR2-dependent ERK1/2 MAPK activation also suppressed forkhead box O 3a (FoxO3a)-mediated transcriptional induction of p27. Inhibition of the binding of collagen type I to DDR2 using WRG-28 indicated the obligate role of collagen type I in the activation of DDR2 and its regulatory role in cell survival and cell cycle protein expression. Notably, DDR2 levels positively correlated with SRF, cIAP2, and PCNA levels in cardiac fibroblasts from spontaneously hypertensive rats. To conclude, DDR2-mediated ERK1/2 MAPK activation facilitates coordinated regulation of cell survival and cell cycle progression in cardiac fibroblasts via SRF.NEW & NOTEWORTHY Relative resistance to apoptosis and the ability to proliferate and produce a collagen-rich scar enable cardiac fibroblasts to play a central role in myocardial response to injury. This study reports novel findings that mitogen-stimulated cardiac fibroblasts exploit a common regulatory mechanism involving collagen receptor (DDR2)-dependent activation of ERK1/2 MAPK and serum response factor to achieve coordinated regulation of apoptosis resistance and cell cycle progression, which could facilitate their survival and function in the injured myocardium.

Blockade of Discoidin Domain Receptor 2 as a Strategy for Reducing Inflammation and Joint Destruction in Rheumatoid Arthritis Via Altered Interleukin-15 and Dkk-1 Signaling in Fibroblast-Like Synoviocytes

OBJECTIVE

This study was undertaken to uncover the pathophysiologic role of discoidin domain receptor 2 (DDR-2), a putative fibrillar collagen receptor, in inflammation promotion and joint destruction in rheumatoid arthritis (RA).

METHODS

In synovial tissue from patients with RA and from mice with collagen antibody-induced arthritis (CAIA) (using Ddr2^-/- and DBA/1 mice), gene and protein expression levels of DDR-2, interleukin-15 (IL-15), and Dkk-1 were measured by quantitative reverse transcription-polymerase chain reaction, Western blotting, and immunohistochemistry. Gene knockdown of DDR2 in human RA fibroblast-like synoviocytes (FLS) was conducted via small interfering RNA. Interaction between the long noncoding RNA H19 and microRNA 103a (miR-103a) was assessed in RA FLS using RNA pulldown assays. Cellular localization of H19 was examined using fluorescence in situ hybridization assays. Chromatin immunoprecipitation and dual luciferase reporter assays were applied to verify H19 transcriptional and posttranscriptional regulation by miR-103a.

RESULTS

DDR2 messenger RNA (mRNA) expression was significantly associated with the levels of IL-15 and Dkk-1 mRNA in the synovial tissue of RA patients (r² = 0.2022-0.3293, all P < 0.05; n = 33) and with the serum levels of IL-15 and Dkk-1 in mice with CAIA (P < 0.05). In human RA FLS, activated DDR-2 induced the expression of H19 through c-Myc. Moreover, H19 directly interacted with and promoted the degradation of miR-103a.

CONCLUSION

These results indicate a novel role for activated DDR-2 in RA FLS, showing that DDR-2 is responsible for regulating the expression of IL-15 and Dkk-1 in RA FLS and is involved in the promotion of inflammation and joint destruction during pathophysiologic development of RA. Moreover, DDR-2 inhibition, acting through the H19-miR-103a axis, leads to reductions in the inflammatory reaction and severity of joint destruction in mice with CAIA, suggesting that inhibition of DDR-2 may be a potential therapeutic strategy for RA.

Draft genome sequences of Hirudo medicinalis and salivary transcriptome of three closely related medicinal leeches

BACKGROUND

Salivary cell secretion (SCS) plays a critical role in blood feeding by medicinal leeches, making them of use for certain medical purposes even today.

RESULTS

We annotated the Hirudo medicinalis genome and performed RNA-seq on salivary cells isolated from three closely related leech species, H. medicinalis, Hirudo orientalis, and Hirudo verbana. Differential expression analysis verified by proteomics identified salivary cell-specific gene expression, many of which encode previously unknown salivary components. However, the genes encoding known anticoagulants have been found to be expressed not only in salivary cells. The function-related analysis of the unique salivary cell genes enabled an update of the concept of interactions between salivary proteins and components of haemostasis.

CONCLUSIONS

Here we report a genome draft of Hirudo medicinalis and describe identification of novel salivary proteins and new homologs of genes encoding known anticoagulants in transcriptomes of three medicinal leech species. Our data provide new insights in genetics of blood-feeding lifestyle in leeches.

Periostin interaction with discoidin domain receptor-1 (DDR1) promotes cartilage degeneration

Osteoarthritis (OA) is characterized by progressive loss of articular cartilage accompanied by the new bone formation and, often, a synovial proliferation that culminates in pain, loss of joint function, and disability. However, the cellular and molecular mechanisms of OA progression and the relative contributions of cartilage, bone, and synovium remain unclear. We recently found that the extracellular matrix (ECM) protein periostin (Postn, or osteoblast-specific factor, OSF-2) is expressed at high levels in human OA cartilage. Multiple groups have also reported elevated expression of Postn in several rodent models of OA. We have previously reported that in vitro Postn promotes collagen and proteoglycan degradation in human chondrocytes through AKT/β-catenin signaling and downstream activation of MMP-13 and ADAMTS4 expression. Here we show that Postn induces collagen and proteoglycan degradation in cartilage by signaling through discoidin domain receptor-1 (DDR1), a receptor tyrosine kinase. The genetic deficiency or pharmacological inhibition of DDR1 in mouse chondrocytes blocks Postn-induced MMP-13 expression. These data show that Postn is signaling though DDR1 is mechanistically involved in OA pathophysiology. Specific inhibitors of DDR1 may provide therapeutic opportunities to treat OA.

Discoidin Domain Receptor 1 (DDR1) Is Necessary for Tissue Homeostasis in Pancreatic Injury and Pathogenesis of Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDA) and chronic pancreatitis are characterized by a dense collagen-rich desmoplastic reaction. Discoidin domain receptor 1 (DDR1) is a receptor tyrosine kinase activated by collagens that can regulate cell proliferation, migration, adhesion, and remodeling of the extracellular matrix. To address the role of DDR1 in PDA, Ddr1-null (Ddr^-/-) mice were crossed with the Kras^G12D/+; Trp53^R172H/+; Ptf1a^Cre/+ (KPC) model of metastatic PDA. Ddr1^-/-; KPC mice progress to differentiated PDA but resist progression to poorly differentiated cancer compared with KPC control mice. Strikingly, severe pancreatic atrophy accompanied tumor progression in Ddr1^-/-; KPC mice. To further explore the effects of Ddr1 ablation, Ddr1^-/- mice were crossed with the Kras^G12D/+; Ptf1a^Cre/+ neoplasia model and subjected to cerulein-induced experimental pancreatitis. Similar to KPC mice, tissue atrophy was a hallmark of both neoplasia and pancreatitis models in the absence of Ddr1. Compared with controls, Ddr1^-/- models had increased acinar cell dropout and reduced proliferation with no difference in apoptotic cell death between control and Ddr1^-/- animals. In most models, organ atrophy was accompanied by increased fibrillar collagen deposition, suggesting a compensatory response in the absence of this collagen receptor. Overall, these data suggest that DDR1 regulates tissue homeostasis in the neoplastic and injured pancreas.

An overview of DNA-encoded libraries: A versatile tool for drug discovery

DNA-encoded libraries (DELs) are collections of small molecules covalently attached to amplifiable DNA tags carrying unique information about the structure of each library member. A combinatorial approach is used to construct the libraries with iterative DNA encoding steps, facilitating tracking of the synthetic history of the attached compounds by DNA sequencing. Various screening protocols have been developed which allow protein target binders to be selected out of pools containing up to billions of different small molecules. The versatile methodology has allowed identification of numerous biologically active compounds and is now increasingly being adopted as a tool for lead discovery campaigns and identification of chemical probes. A great focus in recent years has been on developing DNA compatible chemistries that expand the structural diversity of the small molecule library members in DELs. This chapter provides an overview of the challenges and accomplishments in DEL technology, reviewing the technological aspects of producing and screening DELs with a perspective on opportunities, limitations, and future directions.

3D Extracellular Matrix Mimics: Fundamental Concepts and Role of Materials Chemistry to Influence Stem Cell Fate

Synthetic 3D extracellular matrices (ECMs) find application in cell studies, regenerative medicine, and drug discovery. While cells cultured in a monolayer may exhibit unnatural behavior and develop very different phenotypes and genotypes than in vivo, great efforts in materials chemistry have been devoted to reproducing in vitro behavior in in vivo cell microenvironments. This requires fine-tuning the biochemical and structural actors in synthetic ECMs. This review will present the fundamentals of the ECM, cover the chemical and structural features of the scaffolds used to generate ECM mimics, discuss the nature of the signaling biomolecules required and exploited to generate bioresponsive cell microenvironments able to induce a specific cell fate, and highlight the synthetic strategies involved in creating functional 3D ECM mimics.

Meeting report – first discoidin domain receptors meeting

For the first time, a meeting dedicated to the tyrosine kinase receptors DDR1 and DDR2 took place in Bordeaux, a famous and historical city in the south of France. Over the course of 3 days, the meeting allowed 60 participants from 11 different countries to exchange ideas and their new findings about these unique collagen receptors, focusing on their role in various physiological and pathological conditions and addressing their mechanisms of regulation and signalling. The involvement of these receptors in different pathologies was also considered, with emphasis on cancer development and potential therapeutic applications. Here, we summarize the key elements of this meeting.

Targeted Drug Delivery via the Use of ECM-Mimetic Materials

The use of drug delivery vehicles to improve the efficacy of drugs and to target their action at effective concentrations over desired periods of time has been an active topic of research and clinical investigation for decades. Both synthetic and natural drug delivery materials have facilitated locally controlled as well as targeted drug delivery. Extracellular matrix (ECM) molecules have generated widespread interest as drug delivery materials owing to the various biological functions of ECM. Hydrogels created using ECM molecules can provide not only biochemical and structural support to cells, but also spatial and temporal control over the release of therapeutic agents, including small molecules, biomacromolecules, and cells. In addition, the modification of drug delivery carriers with ECM fragments used as cell-binding ligands has facilitated cell-targeted delivery and improved the therapeutic efficiency of drugs through interaction with highly expressed cellular receptors for ECM. The combination of ECM-derived hydrogels and ECM-derived ligand approaches shows synergistic effects, leading to a great promise for the delivery of intracellular drugs, which require specific endocytic pathways for maximal effectiveness. In this review, we provide an overview of cellular receptors that interact with ECM molecules and discuss examples of selected ECM components that have been applied for drug delivery in both local and systemic platforms. Finally, we highlight the potential impacts of utilizing the interaction between ECM components and cellular receptors for intracellular delivery, particularly in tissue regeneration applications.

Collagen Kinase Receptors as Potential Therapeutic Targets in Metastatic Colon Cancer

Colorectal cancer (CRC) is one of the leading causes of tumor-related death worldwide. While surgery can cure patients with early stage CRC, the 5-year survival rate is only 10% for patients with metastatic disease. Therefore, new anti-metastatic therapies are needed for this cancer. Metastatic spread defines the dissemination of cancer cells with tumor-initiating capacities from the primary tumor and their colonization of distinct organs, mainly the liver, for secondary tumor formation. Although the underlying mechanisms are not fully understood, components of the tumor microenvironment have gained strong interest. Among the known metastatic-promoting factors, collagens are extracellular matrix components that are deposited within the tumor, the tumor microenvironment, and at metastatic site(s), and are recognized to play essential roles during metastasis development. Here, we review recent findings on the metastatic role of the collagen receptors Discoidin Domain Receptors 1 and 2 (DDR1 and DDR2) in CRC and discuss the therapeutic value of targeting these receptor tyrosine kinases in this cancer.

Discoidin Domain Receptors, DDR1b and DDR2, Promote Tumour Growth within Collagen but DDR1b Suppresses Experimental Lung Metastasis in HT1080 Xenografts

The Discoidin Domain Receptors (DDRs) constitute a unique set of receptor tyrosine kinases that signal in response to collagen. Using an inducible expression system in human HT1080 fibrosarcoma cells, we investigated the role of DDR1b and DDR2 on primary tumour growth and experimental lung metastases. Neither DDR1b nor DDR2 expression altered tumour growth at the primary site. However, implantation of DDR1b- or DDR2-expressing HT1080 cells with collagen I significantly accelerated tumour growth rate, an effect that could not be observed with collagen I in the absence of DDR induction. Interestingly, DDR1b, but not DDR2, completely hindered the ability of HT1080 cells to form lung colonies after intravenous inoculation, suggesting a differential role for DDR1b in primary tumour growth and lung colonization. Analyses of tumour extracts revealed specific alterations in Hippo pathway core components, as a function of DDR and collagen expression, that were associated with stimulation of tumour growth by DDRs and collagen I. Collectively, these findings identified divergent effects of DDRs on primary tumour growth and experimental lung metastasis in the HT1080 xenograft model and highlight the critical role of fibrillar collagen and DDRs in supporting the growth of tumours thriving within a collagen-rich stroma.

Research into the Causes of Venom-Induced Mortality and Morbidity Identifies New Therapeutic Opportunities

Snakebite primarily affects rural subsistent farming populations in underdeveloped and developing nations. The annual number of deaths (100,000) and physical disabilities (400,000) of snakebite victims is a societal tragedy that poses a significant added socioeconomic burden to the society. Antivenom therapy is the treatment of choice for snakebite but, as testified by the continuing high rates of mortality and morbidity, too many rural tropical snakebite victims fail to access effective treatment. Here, we advocate for more basic research to better understand the pathogenesis of systemic and local envenoming and describe how research outcomes can identify novel snakebite therapeutic strategies with the potential to be more accessible and affordable to victims than current treatment.

Dapagliflozin Inhibits Cell Adhesion to Collagen I and IV and Increases Ectodomain Proteolytic Cleavage of DDR1 by Increasing ADAM10 Activity

Dapagliflozin, empagliflozin, tofogliflozin, selective inhibitors of sodium-glucose cotransporter 2 (SGLT2), is used clinically to reduce circulation glucose levels in patients with type 2 diabetes mellitus by blocking the reabsorption of glucose by the kidneys. Dapagliflozin is metabolized and inactivated by UGT1A9. Empagliflozin is metabolized and inactivated by UGT1A9 and by other related isoforms UGT2B7, UGT1A3, and UGT1A8. Tofogliflozin is metabolized and inactivated by five different enzymes CYP2C18, CYP3A4, CYP3A5, CYP4A11, and CYP4F3. Dapagliflozin treatment of HCT116 cells, which express SGLT2 but not UGT1A9, results in the loss of cell adhesion, whereas HepG2 cells, which express both SGLT2 and UGT1A9, are resistant to the adhesion-related effects of dapagliflozin. PANC-1 and H1792 cells, which do not express either SGLT2 or UGT1A9, are also resistant to adhesion related effects of dapagliflozin. On the other hand, either empagliflozin or tofogliflozin treatment of HCT116, HepG2, PANC-1, and H1792 cells are resistant to the adhesion-related effects as observed in dapagliflozin treated HCT116 cells. Knockdown of UGT1A9 by shRNA in HepG2 cells increased dapagliflozin sensitivity, whereas the overexpression of UGT1A9 in HCT116 cells protected against dapagliflozin-dependent loos of cell adhesion. Dapagliflozin treatment had no effect on cellular interactions with fibronectin, vitronectin, or laminin, but it induced a loss of interaction with collagen I and IV. In parallel, dapagliflozin treatment reduced protein levels of the full-length discoidin domain receptor I (DDR1), concomitant with appearance of DDR1 cleavage products and ectodomain shedding of DDR1. In line with these observations, unmetabolized dapagliflozin increased ADAM10 activity. Dapagliflozin treatment also significantly reduced Y792 tyrosine phosphorylation of DDR1 leading to decrement of DDR1 function and detachment of cancer cells. Concomitant with these lines of results, we experienced that CEA in patients with colon cancer, which express SGLT2 but not UGT1A9, and type 2 diabetes mellitus treated by dapagliflozin in addition to chemotherapy was decreased (case 1). CEA in patients with colon cancer, which express SGLT2 but not UGT1A9, and type 2 diabetes mellitus was treated by dapagliflozin alone after radiation therapy was decreased but started to rise after cessation of dapagliflozin (case 2). CA19-9 in two of patients with pancreatic cancer and type 2 diabetes mellitus was resistant to the combination therapy of dapagliflozin and chemotherapy (case 3 and 4 respectively). PIVKAII in patients with liver cancer and type 2 diabetes mellitus, and CYFRA in patients with squamous lung cancer and type 2 diabetes mellitus was also resistant the combination therapy of dapagliflozin and chemotherapy (case 5 and 6 respectively). Taken together, these data suggest a potential role for dapagliflozin anticancer therapy against colon cancer cells that express SGLT2, but not UGT1A9.

Discoidin Domain Receptor 1 functionally interacts with the IGF-I system in bladder cancer

Bladder cancer is one of the most common and aggressive cancers and, regardless of the treatment, often recurs and metastasizes. Thus, a better understanding of the mechanisms regulating urothelial tumorigenesis is critical for the design and implementation of rational therapeutic strategies. We previously discovered that the IGF-IR axis is critical for bladder cancer cell motility and invasion, suggesting a possible role in bladder cancer progression. However, IGF-IR depletion in metastatic bladder cancer cells only partially inhibited anchorage-independent growth. Significantly, metastatic bladder cancer cells have decreased IGF-IR levels but overexpressed the insulin receptor isoform A (IR-A), suggesting that the latter may play a more prevalent role than the IGF-IR in bladder tumor progression. The collagen receptor DDR1 cross-talks with both the IGF-IR and IR in breast cancer, and previous data suggest a role of DDR1 in bladder cancer. Here, we show that DDR1 is expressed in invasive and metastatic, but not in papillary, non-invasive bladder cancer cells. DDR1 is phosphorylated upon stimulation with IGF-I, IGF-II, and insulin, co-precipitates with the IGF-IR, and the IR-A and transient DDR1 depletion severely inhibits IGF-I-induced motility. We further demonstrate that DDR1 interacts with Pyk2 and non-muscle myosin IIA in ligands-dependent fashion, suggesting that it may link the IGF-IR and IR-A to the regulation of F-actin cytoskeleton dynamics. Similarly to the IGF-IR, DDR1 is upregulated in bladder cancer tissues compared to healthy tissue controls. Thus, our findings provide the first characterization of the molecular cross-talk between DDR1 and the IGF-I system and could lead to the identification of novel targets for therapeutic intervention in bladder cancer. Moreover, the expression profiles of IGF-IR, IR-A, DDR1, and downstream effectors could serve as a novel biomarker signature with diagnostic and prognostic significance.

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We discovered that the collagen receptor DDR1 cross-talks with insulin growth factor I (IGF-I) signaling in bladder cancer

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DDR1 co-precipitates with the IGF-IR and the insulin receptor (IR), and is phosphorylated upon stimulation with IGF ligands

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This collagen receptor modulates IGF-I-evoked motility and anchorage-independent growth

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DDR1 complexes with Pyk2, myosin IIA, IGF-IR and/or IR and regulates actin dynamics

Landscape of Intercellular Crosstalk in Healthy and NASH Liver Revealed by Single-Cell Secretome Gene Analysis

Cell-cell communication via ligand-receptor signaling is a fundamental feature of complex organs. Despite this, the global landscape of intercellular signaling in mammalian liver has not been elucidated. Here we perform single-cell RNA sequencing on non-parenchymal cells isolated from healthy and NASH mouse livers. Secretome gene analysis revealed a highly connected network of intrahepatic signaling and disruption of vascular signaling in NASH. We uncovered the emergence of NASH-associated macrophages (NAMs), which are marked by high expression of triggering receptors expressed on myeloid cells 2 (Trem2), as a feature of mouse and human NASH that is linked to disease severity and highly responsive to pharmacological and dietary interventions. Finally, hepatic stellate cells (HSCs) serve as a hub of intrahepatic signaling via HSC-derived stellakines and their responsiveness to vasoactive hormones. These results provide unprecedented insights into the landscape of intercellular crosstalk and reprogramming of liver cells in health and disease.

Leukocyte and brain DDR1 hypermethylation is altered in psychosis and is correlated with stress and inflammatory markers

Aim: To investigate DDR1 methylation in blood and brain DNA in psychosis and its relationship with stress markers. Materials & methods: Saliva cortisol, blood neutrophil and lymphocyte counts, leukocyte DNA and psychological variables were collected from 60 patients with nonaffective psychosis and 40 healthy controls (HC). Brain dorsolateral prefrontal cortex DNA from 35 patients with schizophrenia and 34 HC was studied. DDR1 methylation at 43 CpG sites was measured using the MassARRAY EpiTYPER platform. Results: We describe leukocyte DDR1 hypermethylation in patients with psychosis compared with HC; this hypermethylation is associated with psychological stress, neutrophil-to-lymphocyte ratios, and, in the dorsolateral prefrontal cortex, DDR1 methylation correlated with DDR1 isoform expression. Conclusion: We confirmed a relationship between stress and blood and brain DDR1 methylation in psychosis.

Discovery of VU6015929: A Selective Discoidin Domain Receptor 1/2 (DDR1/2) Inhibitor to Explore the Role of DDR1 in Antifibrotic Therapy

Herein, we report the discovery of a potent and selective dual DDR1/2 inhibitor, 7e (VU6015929), displaying low cytotoxicity, good kinome selectivity, and possessing an acceptable in vitro DMPK profile with good rodent in vivo pharmacokinetics. VU6015929 potently blocks collagen-induced DDR1 activation and collagen-IV production, suggesting DDR1 inhibition as an exciting target for antifibrotic therapy.

DDR1 autophosphorylation is a result of aggregation into dense clusters

The collagen receptor DDR1 is a receptor tyrosine kinase that promotes progression of a wide range of human disorders. Little is known about how ligand binding triggers DDR1 kinase activity. We previously reported that collagen induces DDR1 activation through lateral dimer association and phosphorylation between dimers, a process that requires specific transmembrane association. Here we demonstrate ligand-induced DDR1 clustering by widefield and super-resolution imaging and provide evidence for a mechanism whereby DDR1 kinase activity is determined by its molecular density. Ligand binding resulted in initial DDR1 reorganisation into morphologically distinct clusters with unphosphorylated DDR1. Further compaction over time led to clusters with highly aggregated and phosphorylated DDR1. Ligand-induced DDR1 clustering was abolished by transmembrane mutations but did not require kinase activity. Our results significantly advance our understanding of the molecular events underpinning ligand-induced DDR1 kinase activity and provide an explanation for the unusually slow DDR1 activation kinetics.

Collagen Induces a More Proliferative, Migratory and Chemoresistant Phenotype in Head and Neck Cancer via DDR1

Head and neck squamous cell carcinoma (HNSCC) is the sixth most common cancer worldwide and includes squamous cell carcinomas of the oropharynx and oral cavity. Patient prognosis has remained poor for decades and molecular targeted therapies are not in routine use. Here we showed that the overall expression of collagen subunit genes was higher in cancer-associated fibroblasts (CAFs) than normal fibroblasts. Focusing on collagen8A1 and collagen11A1, we showed that collagen is produced by both CAFs and tumour cells, indicating that HNSCCs are collagen-rich environments. We then focused on discoidin domain receptor 1 (DDR1), a collagen-activated receptor tyrosine kinase, and showed that it is over-expressed in HNSCC tissues. Further, we demonstrated that collagen promoted the proliferation and migration of HNSCC cells and attenuated the apoptotic response to cisplatin. Knockdown of DDR1 in HNSCC cells demonstrated that these tumour-promoting effects of collagen are mediated by DDR1. Our data suggest that specific inhibitors of DDR1 might provide novel therapeutic opportunities to treat HNSCC.

Loss of Discoidin Domain Receptor 1 Predisposes Mice to Periodontal Breakdown

The discoidin domain receptors, DDR1 and DDR2, are nonintegrin collagen receptors and tyrosine kinases. DDRs regulate cell functions, and their extracellular domains affect collagen fibrillogenesis and mineralization. Based on the collagenous nature of dentoalveolar tissues, we hypothesized that DDR1 plays an important role in dentoalveolar development and function. Radiography, micro-computed tomography (micro-CT), histology, histomorphometry, in situ hybridization (ISH), immunohistochemistry (IHC), and transmission electron microscopy (TEM) were used to analyze Ddr1 knockout (Ddr1^-/-) mice and wild-type (WT) controls at 1, 2, and 9 mo, and ISH and quantitative polymerase chain reaction (qPCR) were employed to assess Ddr1/DDR1 messenger RNA expression in mouse and human tissues. Radiographic images showed normal molars but abnormal mandibular condyles, as well as alveolar bone loss in Ddr1^-/- mice versus WT controls at 9 mo. Histological, histomorphometric, micro-CT, and TEM analyses indicated no differences in enamel or dentin Ddr1^-/- versus WT molars. Total volumes (TVs) and bone volumes (BVs) of subchondral and ramus bone of Ddr1^-/- versus WT condyles were increased and bone volume fraction (BV/TV) was reduced at 1 and 9 mo. There were no differences in alveolar bone volume at 1 mo, but at 9 mo, severe periodontal defects and significant alveolar bone loss (14%; P < 0.0001) were evident in Ddr1^-/- versus WT mandibles. Histology, ISH, and IHC revealed disrupted junctional epithelium, connective tissue destruction, bacterial invasion, increased neutrophil infiltration, upregulation of cytokines including macrophage colony-stimulating factor, and 3-fold increased osteoclast numbers (P < 0.05) in Ddr1^-/- versus WT periodontia at 9 mo. In normal mouse tissues, ISH and qPCR revealed Ddr1 expression in basal cell layers of the oral epithelia and in immune cells. We confirmed a similar expression pattern in human oral epithelium by ISH and qPCR. We propose that DDR1 plays an important role in periodontal homeostasis and that absence of DDR1 predisposes mice to periodontal breakdown.

Heat shock protein 47 (HSP47) binds to discoidin domain-containing receptor 2 (DDR2) and regulates its protein stability

Cell-collagen interactions are crucial for cell migration and invasion during cancer development and progression. Heat shock protein 47 (HSP47) is an endoplasmic reticulum-resident molecular chaperone that facilitates collagen maturation and deposition. It has been previously shown that HSP47 expression in cancer cells is crucial for cancer invasiveness. However, exogenous collagen cannot rescue cell invasion in HSP47-silenced cancer cells, suggesting that other HSP47 targets contribute to cancer cell invasion. Here, we show that HSP47 expression is required for the stability and cell-surface expression of discoidin domain-containing receptor 2 (DDR2) in breast cancer tissues. HSP47 silencing reduced DDR2 protein stability, accompanied by suppressed cell migration and invasion. Co-immunoprecipitation results revealed that HSP47 binds to the DDR2 ectodomain. Using a photoconvertible technique and total internal reflection fluorescence microscopy, we further demonstrate that HSP47 expression significantly sustains the membrane localization of the DDR2 protein. These results suggest that binding of HSP47 to DDR2 increases DDR2 stability and regulates its membrane dynamics and thereby enhances cancer cell migration and invasion. Given that DDR2 has a crucial role in the epithelial-to-mesenchymal transition and cancer progression, targeting the HSP47-DDR2 interaction might be a potential strategy for inhibiting DDR2-dependent cancer progression.