Discoidin domain receptor 2 (DDR2) promotes breast cancer cell metastasis and the mechanism implicates epithelial-mesenchymal transition programme under hypoxia

DDR2 expression in breast cancer is associated with blood vessel invasion, basal-like tumors, tumor associated macrophages, regulatory T cells, detection mode and prognosis

Discoidin Domain Receptor 2 (DDR2) is a receptor tyrosine kinase for collagen, stimulating epithelial-mesenchymal transition and stiffness in breast cancer. Here, we investigated levels of DDR2 in breast tumor cells in relation to vascular invasion, TIL subsets, macrophages, molecular tumor subtypes, modes of detection and prognosis. This retrospective, population-based series of invasive breast carcinomas from the Norwegian Screening Program in Vestfold County (Norway), period 2004-2009, included 200 screening patients and 82 cases detected in screening intervals. DDR2 was examined on core needle biopsies using a semi-quantitative, immunohistochemical staining index and dichotomized as low or high DDR2 expression. Counts of macrophages and TIL subsets were dichotomized based on immunohistochemistry using TMA. We also recorded blood or lymphatic vessel invasion (BVI or LVI) as present or absent by immunohistochemistry. High expression of DDR2 in tumor cells showed significant relation with high counts of CD163+ macrophages (p < 0.001) and FOXP3 TILs (p = 0.011), presence of BVI (p = 0.028), high tumor cell proliferation by Ki67 (p = 0.033), ER negativity (p = 0.001), triple-negative cases (p = 0.038), basal-like features (p < 0.001) as well as interval detection (p < 0.001). By multivariate analysis, high DDR2 expression was related to reduced recurrence-free survival (HR, 2.3, p = 0.017), when examined together with histologic grading, lymph node assessment, tumor diameter, BVI, and molecular tumor subtype. This study supports a link between high DDR2 expression, high counts of macrophages by CD163 (tumor associated) and regulatory T cells by FOXP3 together with the presence of BVI, possibly indicating increased tumor motility and intravasation in aggressive breast tumors.

DDR2 signaling and mechanosensing orchestrate neuroblastoma cell fate through different transcriptome mechanisms

The extracellular matrix (ECM) regulates carcinogenesis by interacting with cancer cells via cell surface receptors. Discoidin Domain Receptor 2 (DDR2) is a collagen-activated receptor implicated in cell survival, growth, and differentiation. Dysregulated DDR2 expression has been identified in various cancer types, making it as a promising therapeutic target. Additionally, cancer cells exhibit mechanosensing abilities, detecting changes in ECM stiffness, which is particularly important for carcinogenesis given the observed ECM stiffening in numerous cancer types. Despite these, whether collagen-activated DDR2 signaling and ECM stiffness-induced mechanosensing exert similar effects on cancer cell behavior and whether they operate through analogous mechanisms remain elusive. To address these questions, we performed bulk RNA sequencing (RNA-seq) on human SH-SY5Y neuroblastoma cells cultured on collagen-coated substrates. Our results show that DDR2 downregulation induces significant changes in the cell transcriptome, with changes in expression of 15% of the genome, specifically affecting the genes associated with cell division and differentiation. We validated the RNA-seq results by showing that DDR2 knockdown redirects the cell fate from proliferation to senescence. Like DDR2 knockdown, increasing substrate stiffness diminishes cell proliferation. Surprisingly, RNA-seq indicates that substrate stiffness has no detectable effect on the transcriptome. Furthermore, DDR2 knockdown influences cellular responses to substrate stiffness changes, highlighting a crosstalk between these two ECM-induced signaling pathways. Based on our results, we propose that the ECM could activate DDR2 signaling and mechanosensing in cancer cells to orchestrate their cell fate through distinct mechanisms, with or without involving gene expression, thus providing novel mechanistic insights into cancer progression.

DDR2-regulated arginase activity in ovarian cancer-associated fibroblasts promotes collagen production and tumor progression

Ovarian cancer has poor survival outcomes particularly for advanced stage, metastatic disease. Metastasis is promoted by interactions of stromal cells, such as cancer-associated fibroblasts (CAFs) in the tumor microenvironment (TME), with tumor cells. CAFs play a key role in tumor progression by remodeling the TME and extracellular matrix (ECM) to result in a more permissive environment for tumor progression. It has been shown that fibroblasts, in particular myofibroblasts, utilize metabolism to support ECM remodeling. However, the intricate mechanisms by which CAFs support collagen production and tumor progression are poorly understood. In this study, we show that the fibrillar collagen receptor, Discoidin Domain Receptor 2 (DDR2), promotes collagen production in human and mouse omental CAFs through arginase activity. CAFs with high DDR2 or arginase promote tumor colonization in the omentum. In addition, DDR2-depleted CAFs had decreased ornithine levels leading to decreased collagen production and polyamine levels compared to WT control CAFs. Tumor cell invasion was decreased in the presence CAF conditioned media (CM) depleted of DDR2 or arginase-1, and this invasion defect was rescued in the presence of CM from DDR2-depleted CAFs that constitutively overexpressed arginase-1. Similarly, the addition of exogenous polyamines to CM from DDR2-depleted CAFs led to increased tumor cell invasion. We detected SNAI1 protein at the promoter region of the arginase-1 gene, and DDR2-depleted CAFs had decreased levels of SNAI1 protein at the arginase-1 promoter region. Furthermore, high stromal arginase-1 expression correlated with poor survival in ovarian cancer patients. These findings highlight how DDR2 regulates collagen production by CAFs in the tumor microenvironment by controlling the transcription of arginase-1, and CAFs are a major source of arginase activity and L-arginine metabolites in ovarian cancer models.

DDR1/2 enhance KIT activation and imatinib resistance of primary and secondary KIT mutants in gastrointestinal stromal tumors

Gastrointestinal stromal tumors (GISTs) are predominantly initiated by KIT mutations. In this study, we observed that discoidin domain receptors 1 and 2 (DDR1 and DDR2) exhibited high expression in GISTs, were associated with KIT, and enhanced the activation of both wild-type KIT and primary KIT mutants. Inhibition of DDR1/2 led to a reduction in the activation of KIT and its downstream signaling molecules, ultimately impairing GIST cell survival and proliferation in vitro. Consequently, treatment of mice carrying germline KIT/V558A mutation with DDR1/2 inhibitor significantly impeded tumor growth, and the combined use of DDR1/2 inhibitor and imatinib, the first-line targeted therapeutic agent for GISTs, markedly enhanced tumor growth suppression. In addition, DDR1/2 inhibition resulted in decreased KIT expression, while KIT inhibition led to upregulation of DDR1/2 expression in GISTs. The presence of DDR1/2 also decreased the sensitivity of wild-type KIT or primary KIT mutants to imatinib, indicating a possible role for DDR1/2 in promoting GIST survival during KIT-targeted therapy. The development of drug-resistant secondary KIT mutations is a primary factor contributing to GIST recurrence following targeted therapy. Similar to primary KIT mutants, DDR1/2 can associate with and enhance the activation of secondary KIT mutants, further diminishing their sensitivity to imatinib. In summary, our data demonstrate that DDR1/2 contribute to KIT activation in GISTs and strengthen resistance to imatinib for both primary and secondary KIT mutants, providing a rationale for further exploration of DDR1/2 targeting in GIST treatment.

miR-199a-3p promotes gastric cancer progression by promoting its stemness potential via DDR2 mediation

BACKGROUND

Peritoneal metastasis (PM) is an independent prognostic factor in gastric cancer (GC), however, the underlying mechanisms of PM occurrence remain unclear.

METHOD

The roles of DDR2 were investigated in GC and its potential relationship to PM, and orthotopic implants into nude mice were performed to assess the biological effects of DDR2 on PM.

RESULTS

Herein, DDR2 level is more significantly observed to elevate in PM lesion than the primary lesion. GC with DDR2-high expression evokes a worse overall survival (OS) in TCGA, similar results of the gloomy OS with high DDR2 levels are clarified via the stratifying stage of TNM. The conspicuously increased expression of DDR2 was found in GC cell lines, luciferase reporter assays verified that miR-199a-3p directly targeted DDR2 gene, which was correlated to tumor progression. We ulteriorly observed DDR2 participated in GC stemness maintenance via mediating pluripotency factor SOX2 expression and implicated in autophagy and DNA damage of cancer stem cells (CSCs). In particular, DDR2 dominated EMT programming through recruiting NFATc1-SOX2 complex to Snai1 in governing cell progression, controlling by DDR2-mTOR-SOX2 axis in SGC-7901 CSCs. Furthermore, DDR2 promoted the tumor peritoneal dissemination in gastric xenograft mouse model.

CONCLUSION

Phenotype screens and disseminated verifications incriminating in GC exposit the miR-199a-3p-DDR2-mTOR-SOX2 axis as a clinically actionable target for tumor PM progression. The herein-reported DDR2-based underlying axis in GC represents novel and potent tools for studying the mechanisms of PM.

DDR2 coordinates EMT and metabolic reprogramming as a shared effector of FOXQ1 and SNAI1

While multiple transcription factors (TFs) have been recognized to drive epithelial-mesenchymal transition (EMT) in cancer, their interdependence and context-dependent functions are poorly understood. In this study, we show that FOXQ1 and SNAI1 act as independent TFs within the EMT program with a shared ability to upregulate common EMT TFs without reciprocally impacting the expression of one another. Despite this independence, human mammary epithelial cells (HMLE) with ectopic expression of either FOXQ1 or SNAI1 share a common gene set that is enriched for a DDR2 coexpression signature. Further analysis identified DDR2 as the most upregulated receptor tyrosine kinase and a shared downstream effector of FOXQ1 and SNAI1 in triple-negative breast cancer (TNBC) cell lines. Alteration of DDR2 expression in either FOXQ1 or SNAI1 driven EMT models or in TNBC cells resulted in a profound change of cell motility without significantly impacting EMT marker expression, cell morphology, or the stem cell population. Lastly, we demonstrated that knockdown of DDR2 in the FOXQ1-driven EMT model and TNBC cell line significantly altered the global metabolic profile, including glutamine-glutamate and Aspartic acid recycling.

Whole Transcriptome Sequencing Reveals Cancer-Related, Prognostically Significant Transcripts and Tumor-Infiltrating Immunocytes in Mantle Cell Lymphoma

Mantle cell lymphoma (MCL) is an aggressive B-cell non-Hodgkin lymphoma (NHL) subtype characterized by overexpression of CCND1 and SOX11 genes. It is generally associated with clinically poor outcomes despite recent improvements in therapeutic approaches. The genes associated with the development and prognosis of MCL are still largely unknown. Through whole transcriptome sequencing (WTS), we identified mRNAs, lncRNAs, and alternative transcripts differentially expressed in MCL cases compared with reactive tonsil B-cell subsets. CCND1, VCAM1, and VWF mRNAs, as well as MIR100HG and ROR1-AS1 lncRNAs, were among the top 10 most significantly overexpressed, oncogenesis-related transcripts. Survival analyses with each of the top upregulated transcripts showed that MCL cases with high expression of VWF mRNA and low expression of FTX lncRNA were associated with poor overall survival. Similarly, high expression of MSTRG.153013.3, an overexpressed alternative transcript, was associated with shortened MCL survival. Known tumor suppressor candidates (e.g., PI3KIP1, UBXN) were significantly downregulated in MCL cases. Top differentially expressed protein-coding genes were enriched in signaling pathways related to invasion and metastasis. Survival analyses based on the abundance of tumor-infiltrating immunocytes estimated with CIBERSORTx showed that high ratios of CD8⁺ T-cells or resting NK cells and low ratios of eosinophils are associated with poor overall survival in diagnostic MCL cases. Integrative analysis of tumor-infiltrating CD8⁺ T-cell abundance and overexpressed oncogene candidates showed that MCL cases with high ratio CD8⁺ T-cells and low expression of FTX or PCA3 can potentially predict high-risk MCL patients. WTS results were cross-validated with qRT-PCR of selected transcripts as well as linear correlation analyses. In conclusion, expression levels of oncogenesis-associated transcripts and/or the ratios of microenvironmental immunocytes in MCL tumors may be used to improve prognostication, thereby leading to better patient management and outcomes.

Special issue "The advance of solid tumor research in China": Discoidin domain receptor 2 promotes colorectal cancer metastasis by regulating epithelial mesenchymal transition via activating AKT signaling

Tumor metastasis is one of the main reasons for the high mortality rate associated with colorectal cancer (CRC). However, its underlying mechanisms have not been fully understood. Here, we reported that the expression of discoidin domain receptor 2 (DDR2) was significantly upregulated in CRC tissues compared with that in normal adjacent tissues. The expression level of DDR2 was negatively associated with prognosis of CRC patients. Therefore, DDR2 may play an oncogenic role in CRC development. Furthermore, DDR2 induced epithelial mesenchymal transition in CRC cells and regulated their invasive and metastatic capacity in vitro and in vivo. Mechanistically, increased DDR2 expression level activated the AKT/GSK-3β/Slug signaling pathway. In conclusion, these findings showed that DDR2 promoted CRC metastasis and DDR2 inhibition might represent an effective therapeutic strategy for local advanced and metastatic CRC treatment. This article is protected by copyright. All rights reserved.

DDR2 Expression in Cancer-Associated Fibroblasts Promotes Ovarian Cancer Tumor Invasion and Metastasis through Periostin-ITGB1

Ovarian cancer has the highest mortality of all gynecologic malignancies. As such, there is a need to identify molecular mechanisms that underlie tumor metastasis in ovarian cancer. Increased expression of receptor tyrosine kinase, DDR2, has been associated with worse patient survival. Identifying downstream targets of DDR2 may allow specific modulation of ovarian cancer metastatic pathways. Additionally, stromal cells play a critical role in metastasis. The crosstalk between tumor and stromal cells can lead to tumor progression. We first identified that tumor cells co-cultured with DDR2-expressing fibroblasts had lower periostin expression when compared to tumor cells co-cultured with DDR2-depleted fibroblasts. We confirmed that DDR2 regulates POSTN expression in ovarian cancer-associated fibroblasts (CAFs). We found that mesothelial cell clearance and invasion by tumor cells were enhanced three-fold when DDR2 and POSTN-expressing CAFs were present compared to DDR2 and POSTN-depleted CAFs. Furthermore, DDR2-depleted and POSTN-overexpressing CAFs co-injected with ovarian tumor cells had increased tumor burden compared to mice injected with tumor cells and DDR2 and POSTN-depleted CAFs. Furthermore, we demonstrated that DDR2 regulates periostin expression through integrin B1 (ITGB1). Stromal DDR2 is highly correlated with stromal POSTN expression in ovarian cancer patient tumors. Thus, DDR2 expression in CAFs regulates the steps of ovarian cancer metastasis through periostin.

Co-expression of DDR2 and IFITM1 promotes breast cancer cell proliferation, migration and invasion and inhibits apoptosis

PURPOSE

To investigate the roles of DDR2 and IFITM1 in breast cancer (BC).

METHODS

The expression of DDR2 and IFITM1 in BC tissues and cell lines was measured. DDR2 and/or IFITM1 were knocked down in BT20 and MDA-MB-231 cells, after which the viability, mobility and apoptosis of the cells were tested. Xenograft mouse models were established through subcutaneous tumor transplantation.

RESULTS

DDR2 and IFITM1 were highly expressed in invasive BC tissues and cell lines. Overexpression of DDR2 and/or IFITM1 was associated with poorer clinical outcomes and patient survival. Knockdown of DDR2 or IFITM1 suppressed the viability and invasiveness of BT20 and MDA-MB-231 cells and restrained the growth of xenograft tumors in nude mice. Simultaneous knockdown of IFITM1 and DDR2 surpassed knockdown of IFITM1 alone in suppressing BC development.

CONCLUSIONS

DDR2 and IFITM1 are co-expressed to facilitate the malignant behaviors of BC cells and promote the development of tumors.

Multiple roles for basement membrane proteins in cancer progression and EMT

Metastasis or the progression of malignancy poses a major challenge in cancer therapy and is the principal reason for increased mortality. The epithelial-Mesenchymal transition (EMT) of the Basement Membrane (BM) allows cells of epithelial phenotype to transform into a mesenchymal-like (quasi-mesenchymal) phenotype and metastasize via the lymphovascular system through a metastatic cascade by intravasation and extravasation. This helps in the progression of carcinoma from the primary site to distant organs. Collagen, laminin, and integrin are the prime components of BM and help in tumor cell metastasis, which makes them ideal cancer drug targets. Further, recent studies have shown that collagen, laminin, and integrin can be used as a biomarker for metastatic cells. In this review, we have summarized the current knowledge of such therapeutics, which are either currently in preclinical or clinical stages and could be promising cancer therapeutics. DATA AVAILABILITY: Not applicable.

Discoidin Domain Receptor 2 orchestrates melanoma resistance combining phenotype switching and proliferation

Combined therapy with anti-BRAF plus anti-MEK is currently used as first-line treatment of patients with metastatic melanomas harboring the somatic BRAF V600E mutation. However, the main issue with targeted therapy is the acquisition of tumor cell resistance. In a majority of resistant melanoma cells, the resistant process consists in epithelial-to-mesenchymal transition (EMT). This process called phenotype switching makes melanoma cells more invasive. Its signature is characterized by MITF low, AXL high, and actin cytoskeleton reorganization through RhoA activation. In parallel of this phenotype switching phase, the resistant cells exhibit an anarchic cell proliferation due to hyper-activation of the MAP kinase pathway. We show that a majority of human melanoma overexpress discoidin domain receptor 2 (DDR2) after treatment. The same result was found in resistant cell lines presenting phenotype switching compared to the corresponding sensitive cell lines. We demonstrate that DDR2 inhibition induces a decrease in AXL expression and reduces stress fiber formation in resistant melanoma cell lines. In this phenotype switching context, we report that DDR2 control cell and tumor proliferation through the MAP kinase pathway in resistant cells in vitro and in vivo. Therefore, inhibition of DDR2 could be a new and promising strategy for countering this resistance mechanism.

Discoidin Domain Receptor 2: A New Target in Cancer

BACKGROUND

Discoidin domain receptor is a new and unique type of receptor tyrosine kinases, which binds to collagen, the main compose of an extracellular matrix. DDR1 was identified to mediate cell aggregation, and dysregulation of DDR2 has also been shown to be involved in tumor pathogenesis, although its role in cancer development and progression remains controversial.

SUMMARY

Abnormal expression and mutations of DDR2 have been reported in several cancer types and its participation in different aspects of tumor progression, including proliferation, migration, invasion, metastasis, epithelial-mesenchymal transition, and chemotherapy resistance. Moreover, novel DDR2 inhibitors have been designed and indicate a therapeutic effect for the cancer treatment. Key Messages: In this review, we summarize the current knowledge on the role of DDR2 in cancer promotion and the potential therapeutic value of targeting DDR2.

Detection and analysis of long noncoding RNA expression profiles related to epithelial-mesenchymal transition in keloids

BACKGROUND

The role of epithelial-mesenchymal transition (EMT) in the pathogenesis of keloids is currently raising increasing attention. Long noncoding RNAs (lncRNAs) govern a variety of biological processes, such as EMT, and their dysregulation is involved in many diseases including keloid disease. The aim of this study was to identify differentially expressed EMT-related lncRNAs in keloid tissues versus normal tissues and to interpret their functions.

RESULTS

Eleven lncRNAs and 16 mRNAs associated with EMT were identified to have differential expression between keloid and normal skin tissues (fold change > 1.5, P < 0.05). Gene Ontology (GO) analysis showed that these differentially expressed mRNAs functioned in the extracellular matrix, protein binding, the positive regulation of cellular processes, the Set1C/COMPASS complex and histone acetyltransferase activity. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis demonstrated that these mRNAs are involved in pathways in cancer. The lncRNA, XLOC_000587 may promote cell proliferation and migration by enhancing the expression of ENAH, while AF268386 may facilitate the invasive growth of keloids by upregulating DDR2.

CONCLUSIONS

We characterized the differential expression profiles of EMT-related lncRNAs and mRNAs in keloids, which may contribute to preventing the occurrence and development of keloids by targeting the corresponding signaling pathways. These lncRNAs and mRNAs may provide biomarkers for keloid diagnosis and serve as potential targets for the treatment of this disease.

Collagen and Discoidin Domain Receptor 1 Partnership: A Multifaceted Role in the Regulation of Breast Carcinoma Cell Phenotype

Type I collagen, the major components of breast interstitial stroma, is able to regulate breast carcinoma cell behavior. Discoidin domain receptor 1 (DDR1) is a type I collagen receptor playing a key role in this process. In fact, collagen/DDR1 axis is able to trigger the downregulation of cell proliferation and the activation of BIK-mediated apoptosis pathway. The aim of this review is to discuss the role of two important factors that regulate these processes. The first factor is the level of DDR1 expression. DDR1 is highly expressed in epithelial-like breast carcinoma cells, but poorly in basal-like ones. Moreover, DDR1 undergoes cleavage by MT1-MMP, which is highly expressed in basal-like breast carcinoma cells. The second factor is type I collagen remodeling since DDR1 activation depends on its fibrillar organization. Collagen remodeling is involved in the regulation of cell proliferation and apoptosis through age- and proteolysis-related modifications.

The role of discoidin domain receptor 2 in the renal dysfunction of alport syndrome mouse model

Alport syndrome (AS) is a hereditary glomerular nephritis caused by mutation in one of the type IV collagen genes α3/α4/α5 that encode the heterotrimer COL4A3/4/5. Failure to form a heterotrimer due to mutation leads to the dysfunction of the glomerular basement membrane, and end-stage renal disease. Previous reports have suggested the involvement of the receptor tyrosine kinase discoidin domain receptor (DDR) 1 in the progression of AS pathology. However, due to the similarity between DDR1 and DDR2, the role of DDR2 in AS pathology is unclear. Here, we investigated the involvement of DDR2 in AS using the X-linked AS mouse model. Mice were treated subcutaneously with saline or antisense oligonucleotide (ASO; 5 mg/kg or 15 mg/kg per week) for 8 weeks. Renal function parameters and renal histology were analyzed, and the gene expressions of inflammatory cytokines were determined in renal tissues. The expression level of DDR2 was highly elevated in kidney tissues of AS mice. Knockdown of Ddr2 using Ddr2-specific ASO decreased the Ddr2 expression. However, the DDR2 ASO treatment did not improve the proteinuria or decrease the BUN level. DDR2 ASO also did not significantly ameliorate the renal injury, inflammation and fibrosis in AS mice. These results showed that Ddr2 knockdown by ASO had no notable effect on the progression of AS indicating that DDR2 may not be critically involved in AS pathology. This finding may provide useful information and further understanding of the role of DDRs in AS.

Recent Advances in the Role of Discoidin Domain Receptor Tyrosine Kinase 1 and Discoidin Domain Receptor Tyrosine Kinase 2 in Breast and Ovarian Cancer

Discoidin domain receptor tyrosine kinases (DDRs) are a class of receptor tyrosine kinases (RTKs), and their dysregulation is associated with multiple diseases (including cancer, chronic inflammatory conditions, and fibrosis). The DDR family members (DDR1a-e and DDR2) are widely expressed, with predominant expression of DDR1 in epithelial cells and DDR2 in mesenchymal cells. Structurally, DDRs consist of three regions (an extracellular ligand binding domain, a transmembrane domain, and an intracellular region containing a kinase domain), with their kinase activity induced by receptor-specific ligand binding. Collagen binding to DDRs stimulates DDR phosphorylation activating kinase activity, signaling to MAPK, integrin, TGF-β, insulin receptor, and Notch signaling pathways. Abnormal DDR expression is detected in a range of solid tumors (including breast, ovarian, cervical liver, gastric, colorectal, lung, and brain). During tumorigenesis, abnormal activation of DDRs leads to invasion and metastasis, via dysregulation of cell adhesion, migration, proliferation, secretion of cytokines, and extracellular matrix remodeling. Differential expression or mutation of DDRs correlates with pathological classification, clinical characteristics, treatment response, and prognosis. Here, we discuss the discovery, structural characteristics, organizational distribution, and DDR-dependent signaling. Importantly, we highlight the key role of DDRs in the development and progression of breast and ovarian cancer.

Expression and subcellular localization of Discoidin Domain Receptor 1 (DDR1) define prostate cancer aggressiveness

BACKGROUND

The Discoidin Domain Receptor 1 (DDR1) is one of the two members of a unique family of receptor tyrosine kinase receptors that signal in response to collagen, which has been implicated in cancer progression. Here, we examined the expression of DDR1 in prostate cancer (PCa), and assessed its potential value as a prognostic marker, as a function of grade, stage and other clinicopathologic parameters.

METHODS

We investigated the association between the expression level and subcellular localization of DDR1 protein and PCa aggressiveness by immunohistochemistry, using tissue microarrays (TMAs) encompassing 200 cases of PCa with various Gleason scores (GS) and pathologic stages with matched normal tissue, and a highly specific monoclonal antibody.

RESULTS

DDR1 was found to be localized in the membrane, cytoplasm, and nuclear compartments of both normal and cancerous prostate epithelial cells. Analyses of DDR1 expression in low GS (≤ 7[3 + 4]) vs high GS (≥ 7[4 + 3]) tissues showed no differences in nuclear or cytoplasmic DDR1in either cancerous or adjacent normal tissue cores. However, relative to normal-matched tissue, the percentage of cases with higher membranous DDR1 expression was significantly lower in high vs. low GS cancers. Although nuclear localization of DDR1 was consistently detected in our tissue samples and also in cultured human PCa and normal prostate-derived cell lines, its presence in that site could not be associated with disease aggressiveness. No associations between DDR1 expression and overall survival or biochemical recurrence were found in this cohort of patients.

CONCLUSION

The data obtained through multivariate logistic regression model analysis suggest that the level of membranous DDR1 expression status may represent a potential biomarker of utility for better determination of PCa aggressiveness.

The Journey of DDR1 and DDR2 Kinase Inhibitors as Rising Stars in the Fight Against Cancer

Discoidin domain receptor (DDR) is a collagen-activated receptor tyrosine kinase that plays critical roles in regulating essential cellular processes such as morphogenesis, differentiation, proliferation, adhesion, migration, invasion, and matrix remodeling. As a result, DDR dysregulation has been attributed to a variety of human cancer disorders, for instance, non-small-cell lung carcinoma (NSCLC), ovarian cancer, glioblastoma, and breast cancer, in addition to some inflammatory and neurodegenerative disorders. Since the target identification in the early 1990s to date, a lot of efforts have been devoted to the development of DDR inhibitors. From a medicinal chemistry perspective, we attempted to reveal the progress in the development of the most promising DDR1 and DDR2 small molecule inhibitors covering their design approaches, structure-activity relationship (SAR), biological activity, and selectivity.

Discoidin Domain Receptor 2 Mediates Lysophosphatidic Acid-Induced Ovarian Cancer Aggressiveness

Lysophosphatidic acid (LPA), a bioactive lipid produced extracellularly by autotaxin (ATX), has been known to induce various pathophysiological events, including cancer cell invasion and metastasis. Discoidin domain receptor 2 (DDR2) expression is upregulated in ovarian cancer tissues, and is closely associated with poor clinical outcomes in ovarian cancer patients. In the present study, we determined a critical role and signaling cascade for the expression of DDR2 in LPA-induced ovarian cancer cell invasion. We also found ectopic expression of ATX or stimulation of ovarian cancer cells with LPA-induced DDR2 expression. However, the silencing of DDR2 expression significantly inhibited ATX- and LPA-induced ovarian cancer cell invasion. In addition, treatment of the cells with pharmacological inhibitors of phosphoinositide 3-kinase (PI3K), Akt, and mTOR abrogated LPA-induced DDR2 expression. Moreover, we observed that HIF-1α, located downstream of the mTOR, is implicated in LPA-induced DDR2 expression and ovarian cancer cell invasion. Finally, we provide evidence that LPA-induced HIF-1α expression mediates Twist1 expression to upregulate DDR2 expression. Collectively, the present study demonstrates that ATX, and thereby LPA, induces DDR2 expression through the activation of the PI3K/Akt/mTOR/HIF-1α/Twist1 signaling axes, aggravating ovarian cancer cell invasion.

Multi-stage responsive peptide nanosensor: Anchoring EMT and mitochondria with enhanced fluorescence and boosting tumor apoptosis

Epithelial-mesenchymal transition (EMT) is closely related to tumor metastasis and invasion. Thereinto, mesenchymal tumor mitochondria are the critical target for tumor inhibition. Therefore, real-time in vivo monitoring of EMT as well as inhibiting mesenchymal tumor mitochondria is of great diagnosis and therapy significance. Herein, we construct a multi-stage recognition and morphological transformable self-assembly-peptide nano biosensor ^NDRP which can response the EMT marker and specifically damage the mesenchymal tumor cell in vivo. This nano-molar-affinity sensor is designed and screened with sensitive peptides containing a molecular switching which could be specifically triggered by the receptor to achieve the vesicle-to-fibril transformation in living system with enhanced fluorescent signal. ^NDRP nanosensor could target the tumor lesion in circulatory system, recognize mesenchymal tumor marker DDR2 (Discoidin domain receptor 2) in cellular level and specifically achieve mitochondria in subcellular level as well as damaged mitochondria which could be applied as a in vivo theranostic platform.

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.

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.

Mitochondria-related core genes and TF-miRNA-hub mrDEGs network in breast cancer

Background: Mitochondria-nuclear cross-talk and mitochondrial retrograde regulation are involved in the genesis and development of breast cancer (BC). Therefore, mitochondria can be regarded as a promising target for BC therapeutic strategies. The present study aimed to construct regulatory network and seek the potential biomarkers of BC diagnosis and prognosis as well as the molecular therapeutic targets from the perspective of mitochondrial dysfunction. Methods: The microarray data of mitochondria-related encoding genes in BC cell lines were downloaded from GEO including GSE128610 and GSE72319. GSE128610 was treated as test set and validation sets consisted of GSE72319 and TCGA tissue samples, intending to identify mitochondria-related differentially expressed genes (mrDEGs). We performed enrichment analysis, PPI network, hub mrDEGs and overall survival analysis and constructed transcription factor (TF)-miRNA-hub mrDEGs network. Results: A total of 23 up-regulated and 71 down-regulated mrDEGs were identified and validated in BC cell lines and tissues. Enrichment analyses indicated that mrDEGs were associated with several cancer-related biological processes. Moreover, 9 hub mrDEGs were identified and validated in BC cell lines and tissues. Finally, 5 hub coregulated mrDEGs, 21 miRNAs and 117 TFs were used to construct TF-miRNA-hub mrDEGs network. MYC associated zinc finger protein (MAZ), heparin binding growth factor (HDGF) and Sp2 transcription factor (SP2) regulated 3 hub mrDEGs. Hsa-mir-21-5p, hsa-mir-1-3p, hsa-mir-218-5p, hsa-mir-26a-5p and hsa-mir-335-5p regulated 2 hub mrDEGs. Overall survival analysis suggested that the up-regulation of fibronectin 1 (FN1), as well as the down-regulation of discoidin domain receptor tyrosine kinase 2 (DDR2) correlated with unfavorable prognosis in BC. Conclusion: TF-miRNA-hub mrDEGs had instruction significance for the exploration of BC etiology. The hub mrDEGs such as FN1 and DDR2 were likely to regulate mitochondrial function and be novel biomarkers for BC diagnosis and prognosis as well as the therapeutic targets.

Expression of Class III Beta-Tubulin Is Associated with Invasive Potential and Poor Prognosis in Thyroid Carcinoma

Although American Thyroid Association guidelines offer a risk stratification scheme for thyroid cancer patients, there is a continuous need for more sophisticated biomarkers that can predict disease progression. In this study, we aim to evaluate the prognostic value of class III beta-tubulin (TUBB3) and uncover the relationship between TUBB3 and invasive potential in thyroid carcinoma. Immunohistochemistry (IHC) for TUBB3 and E-cadherin was performed on a total of 254 cases of thyroid cancer specimens. Tumor budding at the invasive margin was evaluated. In vitro functional studies were also performed; the protein and mRNA levels of TUBB3 were compared among the five cell types at baseline, with transwell invasion and after blocking of TUBB3 by shRNA. IHC revealed that the levels of TUBB3 were higher in conventional papillary carcinomas (cPTCs) and anaplastic thyroid carcinomas (ATCs). In univariate analysis, high tumor budding and TUBB3 expression were associated with inferior progression-free survival in cPTC. The results of a Western blot and RT-PCR agreed with the IHC finding. The results were further validated through data from The Cancer Genome Atlas database. Our results suggest that high expression of TUBB3 in thyroid carcinoma could predict invasive potential and possibly be linked with epithelial–mesenchymal transition.

Crosstalk between invadopodia and the extracellular matrix

The scaffold protein Tks5α is required for invadopodia-mediated cancer invasion both in vitro and in vivo. We have previously also revealed a role for Tks5 in tumor cell growth using three-dimensional (3D) culture model systems and mouse transplantation experiments. Here we use both 3D and high-density fibrillar collagen (HDFC) culture to demonstrate that native collagen-I, but not a form lacking the telopeptides, stimulated Tks5-dependent growth, which was dependent on the DDR collagen receptors. We used microenvironmental microarray (MEMA) technology to determine that laminin, fibronectin and tropoelastin also stimulated invadopodia formation. A Tks5α-specific monoclonal antibody revealed its expression both on microtubules and at invadopodia. High- and super-resolution microscopy of cells in and on collagen was then used to place Tks5α at the base of invadopodia, separated from much of the actin and cortactin, but coincident with both matrix metalloprotease and cathepsin proteolytic activity. Inhibition of the Src family kinases, cathepsins or metalloproteases all reduced invadopodia length but each had distinct effects on Tks5α localization. These studies highlight the crosstalk between invadopodia and extracellular matrix components, and reveal the invadopodium to be a spatially complex structure.

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.

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.

Emerging roles of ECM remodeling processes in cancer

Extracellular matrix (ECM) plays a central and dynamic role in the creation of tumor microenvironment. Herein we discuss the emerging biophysical and biochemical aspects of ECM buildup and proteolysis in cancer niche formation. Dysregulated ECM remodeling by cancer cells facilitate irreversible proteolysis and crosslinking, which in turn influence cell signaling, micro environmental cues, angiogenesis and tissue biomechanics. Further, we introduce the emerging roles of cancer microbiome in aberrant tumor ECM remodeling and membrane bound nano-sized vesicles called exosomes in creation of distant pre-metastatic niches. A detailed molecular and biophysical understanding of the ECM morphologies and its components such as key enzymes, structural and signaling molecules are critical in identifying the next generation of therapeutic and diagnostic targets in cancer.

Histone Arginine Methylation-Mediated Epigenetic Regulation of Discoidin Domain Receptor 2 Controls the Senescence of Human Bone Marrow Mesenchymal Stem Cells

The application of human bone marrow mesenchymal stem cells (hBM-MSCs) in cell-based clinical therapies is hindered by the limited number of cells remaining after the initial isolation process and by cellular senescence following in vitro expansion. Understanding the process of in vitro senescence in hBM-MSCs would enable the development of strategies to maintain their vitality after cell culture. Herein, we compared the gene expression profiles of human embryonic stem cells and human BM-MSCs from donors of different ages. We first found that the expression of discoidin domain receptor 2 (DDR2) in adult donor-derived hBM-MSCs was lower than it was in the young donor-derived hBM-MSCs. Moreover, in vitro cultured late-passage hBM-MSCs showed significant downregulation of DDR2 compared to their early-passage counterparts, and siRNA inhibition of DDR2 expression recapitulated features of senescence in early-passage hBM-MSCs. Further, we found through knockdown and overexpression approaches that coactivator-associated arginine methyltransferase 1 (CARM1) regulated the expression level of DDR2 and the senescence of hBM-MSCs. Finally, chromatin immunoprecipitation analysis confirmed direct binding of CARM1 to the DDR2 promoter region with a high level of H3R17 methylation in early-passage hBM-MSCs, and inhibition of CARM1-mediated histone arginine methylation decreased DDR2 expression and led to cellular senescence. Taken together, our findings suggest that DDR2 plays a major role in regulating the in vitro senescence of hBM-MSCs and that CARM1-mediated histone H3 methylation might be the upstream regulatory mechanism controlling this function of DDR2.

Randomly Distributed K14+ Breast Tumor Cells Polarize to the Leading Edge and Guide Collective Migration in Response to Chemical and Mechanical Environmental Cues

Collective cell migration is an adaptive, coordinated interactive process involving cell-cell and cell-extracellular matrix (ECM) microenvironmental interactions. A critical aspect of collective migration is the sensing and establishment of directional movement. It has been proposed that a subgroup of cells known as leader cells localize at the front edge of a collectively migrating cluster and are responsible for directing migration. However, it is unknown how and when leader cells arrive at the front edge and what environmental cues dictate leader cell development and behavior. Here, we addressed these questions by combining a microfluidic device design that mimics multiple tumor microenvironmental cues concurrently with biologically relevant primary, heterogeneous tumor cell organoids. Prior to migration, breast tumor leader cells (K14⁺) were present throughout a tumor organoid and migrated (polarized) to the leading edge in response to biochemical and biomechanical cues. Impairment of either CXCR4 (biochemical responsive) or the collagen receptor DDR2 (biomechanical responsive) abrogated polarization of leader cells and directed collective migration. This work demonstrates that K14⁺ leader cells utilize both chemical and mechanical cues from the microenvironment to polarize to the leading edge of collectively migrating tumors. SIGNIFICANCE: These findings demonstrate that pre-existing, randomly distributed leader cells within primary tumor organoids use CXCR4 and DDR2 to polarize to the leading edge and direct migration.

SALMON: Survival Analysis Learning With Multi-Omics Neural Networks on Breast Cancer

Improved cancer prognosis is a central goal for precision health medicine. Though many models can predict differential survival from data, there is a strong need for sophisticated algorithms that can aggregate and filter relevant predictors from increasingly complex data inputs. In turn, these models should provide deeper insight into which types of data are most relevant to improve prognosis. Deep Learning-based neural networks offer a potential solution for both problems because they are highly flexible and account for data complexity in a non-linear fashion. In this study, we implement Deep Learning-based networks to determine how gene expression data predicts Cox regression survival in breast cancer. We accomplish this through an algorithm called SALMON (Survival Analysis Learning with Multi-Omics Neural Networks), which aggregates and simplifies gene expression data and cancer biomarkers to enable prognosis prediction. The results revealed improved performance when more omics data were used in model construction. Rather than use raw gene expression values as model inputs, we innovatively use eigengene modules from the result of gene co-expression network analysis. The corresponding high impact co-expression modules and other omics data are identified by feature selection technique, then examined by conducting enrichment analysis and exploiting biological functions, escalated the interpretation of input feature from gene level to co-expression modules level. Our study shows the feasibility of discovering breast cancer related co-expression modules, sketch a blueprint of future endeavors on Deep Learning-based survival analysis. SALMON source code is available at https://github.com/huangzhii/SALMON/.

Non-redundant functions of EMT transcription factors

Epithelial-mesenchymal transition (EMT) is a crucial embryonic programme that is executed by various EMT transcription factors (EMT-TFs) and is aberrantly activated in cancer and other diseases. However, the causal role of EMT and EMT-TFs in different disease processes, especially cancer and metastasis, continues to be debated. In this Review, we identify and describe specific, non-redundant functions of the different EMT-TFs and discuss the reasons that may underlie disputes about EMT in cancer.

Different effects of long noncoding RNA NDRG1-OT1 fragments on NDRG1 transcription in breast cancer cells under hypoxia

Hypoxia plays a crucial role in the aggressiveness of solid tumors by driving multiple signaling pathways. Recently, long non-coding RNA (lncRNA) has been reported to promote or inhibit tumor aggressiveness by regulating gene expression. Previous studies in our laboratory found that the lncRNA NDRG1-OT1 is significantly up-regulated under hypoxia and inhibits its target gene NDRG1 at both the mRNA and protein levels. At the protein level, NDRG1-OT1 increases NDRG1 degradation via ubiquitin-mediated proteolysis. However, the repressive mechanism of NDRG1 at the RNA level is still unknown. Therefore, the purpose of this study was to study how NDRG1-OT1 transcriptionally regulates its target gene NDRG1. Luciferase reporter assays showed that NDRG1-OT1 decreased NDRG1 promoter activities. Mass spectrometry, bioinformatics tools, genetic manipulation, and immunoblotting were used to identify the interacting proteins. Surprisingly, different fragments of NDRG1-OT1 had opposite effects on NDRG1. The first quarter fragment (1-149 nt) of NDRG1-OT1 had no effect on the NDRG1 promoter; the second quarter fragment (150-263 nt) repressed NDRG1 by increasing the binding affinity of HNRNPA1; the third quarter fragment (264-392 nt) improved NDRG1 promoter activity by recruiting HIF-1α; the fourth quarter fragment (393-508 nt) down-regulated NDRG1 promoter activity via down-regulation of KHSRP under hypoxia. In summary, we have found a novel mechanism by which different fragments of the same lncRNA can cause opposite effects within the same target gene.

Multitasking discoidin domain receptors are involved in several and specific hallmarks of cancer

Discoidin domain receptors, DDR1 and DDR2, are two members of collagen receptor family that belong to tyrosine kinase receptor subgroup. Unlike other matrix receptor-like integrins, these collagen receptors have not been extensively studied. However, more and more studies are focusing on their involvement in cancer. These two receptors are present in several subcellular localizations such as intercellular junction or along type I collagen fibers. Consequently, they are involved in multiple cellular functions, for instance, cell cohesion, proliferation, adhesion, migration and invasion. Furthermore, various signaling pathways are associated with these multiple functions. In this review, we highlight and characterize hallmarks of cancer in which DDRs play crucial roles. We discuss recent data from studies that demonstrate the involvement of DDRs in tumor proliferation, cancer mutations, drug resistance, inflammation, neo-angiogenesis and metastasis. DDRs could be potential targets in cancer and we conclude this review by discussing the different ways to inhibits them.

Discoidin domain receptor 1 (DDR1) ablation promotes tissue fibrosis and hypoxia to induce aggressive basal-like breast cancers

Here, Takai et al. researched the function of discoidin domain receptor 1 (DDR1), a member of the subfamily of receptor tyrosine kinases activated by collagens that is overexpressed in breast and other carcinoma cells. Using bioinformatics analysis, breast cancer cell lines, and knockout mice, they demonstrate that DDR1 ablation leads to aggressive breast cancer, and their findings suggest that the absence of DDR1 provides a growth and adhesion advantage that favors the expansion of basal cells, potentiates fibrosis, and enhances necrosis/hypoxia and basal differentiation of transformed cells to increase their aggression and metastatic potential.

The discoidin domain receptor 1 (DDR1) is overexpressed in breast carcinoma cells. Low DDR1 expression is associated with worse relapse-free survival, reflecting its controversial role in cancer progression. We detected DDR1 on luminal cells but not on myoepithelial cells of DDR1^+/+ mice. We found that DDR1 loss compromises cell adhesion, consistent with data that older DDR1^−/− mammary glands had more basal/myoepithelial cells. Basal cells isolated from older mice exerted higher traction forces than the luminal cells, in agreement with increased mammary branches observed in older DDR1^−/− mice and higher branching by their isolated organoids. When we crossed DDR1^−/− mice with MMTV-PyMT mice, the PyMT/DDR1^−/− mammary tumors grew faster and had increased epithelial tension and matricellular fibrosis with a more basal phenotype and increased lung metastases. DDR1 deletion induced basal differentiation of CD90⁺CD24⁺ cancer cells, and the increase in basal cells correlated with tumor cell mitoses. K14⁺ basal cells, including K8⁺K14⁺ cells, were increased adjacent to necrotic fields. These data suggest that the absence of DDR1 provides a growth and adhesion advantage that favors the expansion of basal cells, potentiates fibrosis, and enhances necrosis/hypoxia and basal differentiation of transformed cells to increase their aggression and metastatic potential.

TWIST1 induces expression of discoidin domain receptor 2 to promote ovarian cancer metastasis

The mesenchymal gene program has been shown to promote the metastatic progression of ovarian cancer; however, specific proteins induced by this program that lead to these metastatic behaviors have not been identified. Using patient derived tumor cells and established human ovarian tumor cell lines, we find that the Epithelial-to –Mesenchymal Transition inducing factor TWIST1 drives expression of Discoidin Domain Receptor 2 (DDR2), a receptor tyrosine kinase (RTK) that recognizes fibrillar collagen as ligand. The expression and action of DDR2 was critical for mesothelial cell clearance, invasion and migration in ovarian tumor cells. It does so, in part, by upregulating expression and activity of matrix remodeling enzymes that lead to increased cleavage of fibronectin and spreading of tumor cells. Additionally, DDR2 stabilizes SNAIL1, allowing for sustained mesenchymal phenotype. In patient derived ovarian cancer specimens, DDR2 expression correlated with enhanced invasiveness. DDR2 expression was associated with advanced stage ovarian tumors and metastases. In vivo studies demonstrated that the presence of DDR2 is critical for ovarian cancer metastasis. These findings indicate that the collagen receptor DDR2 is critical for multiple steps of ovarian cancer progression to metastasis, and thus, identifies DDR2 as a potential new target for the treatment of metastatic ovarian cancer.

The pronounced high expression of discoidin domain receptor 2 in human interstitial lung diseases

The most typical structural feature of human interstitial lung diseases (ILDs) is the accumulation of vast amounts of collagens within the lung interstitium. The membrane receptors that are responsible for recognising collagens and then transducing signals into the cells include four members of the integrin family (α1β1, α2β1, α10β1 and α11β1) and two members of the discoidin domain receptor family (DDR1 and DDR2). However, it remains unknown whether these six collagen receptors similarly contribute to the pathogenesis of fibrotic lung diseases.

Quantitative real-time PCR (qPCR) was utilised to assess the mRNA expression of the genes studied. Immunoblot experiments were performed to analyse the protein abundance and kinase activity of the gene products. The tissue location was determined by immunohistochemical staining.

qPCR data showed that DDR2 mRNA displays the most dramatic difference between idiopathic pulmonary fibrosis (IPF) patients and healthy groups. The outstanding increases in DDR2 proteins were also observed in some other types of ILD besides IPF. DDR2-expressing cells in ILD tissue sections were found to exhibit spindle or fibroblastic shapes.

Our investigation suggests that DDR2 might represent a major cell surface protein that mediates collagen-induced cellular effects in human ILD and, hence, is suitable for their diagnosis and therapy.

DDR2 is a major collagen-recognising receptor in human interstitial lung diseasehttp://ow.ly/Lhgh30gN603

Type I collagen aging impairs discoidin domain receptor 2-mediated tumor cell growth suppression

Tumor cells are confronted to a type I collagen rich environment which regulates cell proliferation and invasion. Biological aging has been associated with structural changes of type I collagen. Here, we address the effect of collagen aging on cell proliferation in a three-dimensional context (3D).

We provide evidence for an inhibitory effect of adult collagen, but not of the old one, on proliferation of human fibrosarcoma HT-1080 cells. This effect involves both the activation of the tyrosine kinase Discoidin Domain Receptor 2 (DDR2) and the tyrosine phosphatase SHP-2. DDR2 and SHP-2 were less activated in old collagen. DDR2 inhibition decreased SHP-2 phosphorylation in adult collagen and increased cell proliferation to a level similar to that observed in old collagen.

In the presence of old collagen, a high level of JAK2 and ERK1/2 phosphorylation was observed while expression of the cell cycle negative regulator p21^CIP1 was decreased. Inhibition of DDR2 kinase function also led to an increase in ERK1/2 phosphorylation and a decrease in p21^CIP1 expression. Similar signaling profile was observed when DDR2 was inhibited in adult collagen. Altogether, these data suggest that biological collagen aging could increase tumor cell proliferation by reducingthe activation of the key matrix sensor DDR2.

Collagen-derived proline promotes pancreatic ductal adenocarcinoma cell survival under nutrient limited conditions

Tissue architecture contributes to pancreatic ductal adenocarcinoma (PDAC) phenotypes. Cancer cells within PDAC form gland-like structures embedded in a collagen-rich meshwork where nutrients and oxygen are scarce. Altered metabolism is needed for tumour cells to survive in this environment, but the metabolic modifications that allow PDAC cells to endure these conditions are incompletely understood. Here we demonstrate that collagen serves as a proline reservoir for PDAC cells to use as a nutrient source when other fuels are limited. We show PDAC cells are able to take up collagen fragments, which can promote PDAC cell survival under nutrient limited conditions, and that collagen-derived proline contributes to PDAC cell metabolism. Finally, we show that proline oxidase (PRODH1) is required for PDAC cell proliferation in vitro and in vivo. Collectively, our results indicate that PDAC extracellular matrix represents a nutrient reservoir for tumour cells highlighting the metabolic flexibility of this cancer.

Cancer cells adapt their metabolism to survive limited nutrient availability. Here, the authors show that in conditions of limited glucose or glutamine availability, pancreatic ductal adenocarcinoma cells can use collagen-derived proline to foster the TCA cycle and allow cell survival both in vitro and in vivo.

Discoidin domain receptor 2 mediates collagen-induced activation of membrane-type 1 matrix metalloproteinase in human fibroblasts

Membrane-type 1 matrix metalloproteinase (MT1-MMP) is a membrane-bound MMP that is highly expressed in cells with invading capacity, including fibroblasts and invasive cancer cells. However, pathways of MT1-MMP up-regulation are not clearly understood. A potential physiological stimulus for MT1-MMP expression is fibrillar collagen, and it has been shown that it up-regulates both MT1-MMP gene and functions in various cell types. However, the mechanisms of collagen-mediated MT1-MMP activation and its physiological relevance are not known. In this study, we identified discoidin domain receptor 2 (DDR2) as a crucial receptor that mediates this process in human fibroblasts. Knocking down DDR2, but not the β1 integrin subunit, a common subunit for all collagen-binding integrins, inhibited the collagen-induced MT1-MMP-dependent activation of pro-MMP-2 and up-regulation of MT1-MMP at the gene and protein levels. Interestingly, DDR2 knockdown or pharmacological inhibition of DDR2 also inhibited the MT1-MMP-dependent cellular degradation of collagen film, suggesting that cell-surface collagen degradation by MT1-MMP involves DDR2-mediated collagen signaling. This DDR2-mediated mechanism is only present in non-transformed mesenchymal cells as collagen-induced MT1-MMP activation in HT1080 fibrosarcoma cells and MT1-MMP function in MDA-MB231 breast cancer cells were not affected by DDR kinase inhibition. DDR2 activation was found to be noticeably more effective when cells were stimulated by collagen without the non-helical telopeptide region compared with intact collagen fibrils. Furthermore, DDR2-dependent MT1-MMP activation by cartilage was found to be more efficient when the tissue was partially damaged. These data suggest that DDR2 is a microenvironment sensor that regulates fibroblast migration in a collagen-rich environment.

Biomarkers for EMT and MET in breast cancer: An update

Metastasis and recurrence are the leading cause of mortality due to breast cancer, but the underlying mechanisms are still poorly understood. Understanding the breast cancer metastasis mechanism is important for early diagnosis and treatment of breast cancer. The seeding and growth of breast cancer cells at sites distinct from the primary tumor is a complex and multistage process. Recently, it has been reported that the epithelial-mesenchymal transition (EMT) and the mesenchymal-epithelial transition (MET) are the main mechanisms for breast cancer metastasis. During EMT, carcinoma cells shed their differentiated epithelial characteristics, including cell-cell adhesion, polarity and lack of motility, and acquire mesenchymal traits, including motility and invasiveness. This review has summarized the studies of known EMT biomarkers in the context of breast cancer progression. These biomarkers include EMT-related genes, proteins, microRNAs and kinases. In general, the findings of these studies suggest that EMT markers are associated with the invasion and metastasis of breast cancer. Further studies on the link between EMT markers and breast cancer will contribute to identify biomarkers for predicting early breast cancer metastasis as well as to provide new ideas for the treatment of breast cancer.

DDR2 Induces Gastric Cancer Cell Activities via Activating mTORC2 Signaling and Is Associated with Clinicopathological Characteristics of Gastric Cancer

BACKGROUND/AIM

Epithelial-mesenchymal transition (EMT) plays a role in cancer progression. Previous studies have suggested that discoidin domain receptor 2 (DDR2) is related to tumor progression and EMT. However, the role of DDR2 in regulating gastric cancer (GC) metastasis and in EMT has not been elucidated. In this study, we aimed to determine DDR2 expression and its clinical relation in GC and to investigate the effects of DDR2 on EMT and its underlying mechanisms.

METHODS

DDR2 expression and the relation to patients' clinicopathological features were assayed by Western blot or immunohistochemical staining. The effects of DDR2 overexpression were investigated using in vivo tumorigenicity and xenograft models. The effects of DDR2 on EMT marker expression were assayed by Western blot and immunofluorescence. The possible role of the mTORC pathway in these processes was explored.

RESULTS

DDR2 showed high expression in GC tissues and cells. DDR2 expression was negatively correlated with E-cadherin expression and positively correlated with N-cadherin and vimentin expression. High DDR2 expression is correlated with unfavorable pathoclinical features such as multiple tumor locations and intestinal-type GC. In xenograft models, DDR2 overexpression promoted tumor formation. Furthermore, DDR2 expression impacted on the invasion and motility of GC cells, accompanied by changes in EMT marker expression. Finally, our results revealed that DDR2 facilitates GC cell invasion and EMT through mTORC2 activation and AKT phosphorylation.

CONCLUSION

DDR2 is upregulated and correlated with unfavorable clinical features of GC patients. DDR2 promotes tumor formation and invasion through facilitating EMT process via mTORC2 activation and AKT phosphorylation.

The Action of Discoidin Domain Receptor 2 in Basal Tumor Cells and Stromal Cancer-Associated Fibroblasts Is Critical for Breast Cancer Metastasis

High levels of collagen deposition in human and mouse breast tumors are associated with poor outcome due to increased local invasion and distant metastases. Using a genetic approach, we show that, in mice, the action of the fibrillar collagen receptor discoidin domain receptor 2 (DDR2) in both tumor and tumor-stromal cells is critical for breast cancer metastasis yet does not affect primary tumor growth. In tumor cells, DDR2 in basal epithelial cells regulates the collective invasion of tumor organoids. In stromal cancer-associated fibroblasts (CAFs), DDR2 is critical for extracellular matrix production and the organization of collagen fibers. The action of DDR2 in CAFs also enhances tumor cell collective invasion through a pathway distinct from the tumor-cell-intrinsic function of DDR2. This work identifies DDR2 as a potential therapeutic target that controls breast cancer metastases through its action in both tumor cells and tumor-stromal cells at the primary tumor site.

Discoidin Domain Receptors: Potential Actors and Targets in Cancer

The extracellular matrix critically controls cancer cell behavior by inducing several signaling pathways through cell membrane receptors. Besides conferring structural properties to tissues around the tumor, the extracellular matrix is able to regulate cell proliferation, survival, migration, and invasion. Among these receptors, the integrins family constitutes a major class of receptors that mediate cell interactions with extracellular matrix components. Twenty years ago, a new class of extracellular matrix receptors has been discovered. These tyrosine kinase receptors are the two discoidin domain receptors DDR1 and DDR2. DDR1 was first identified in the Dictyostelium discoideum and was shown to mediate cell aggregation. DDR2 shares highly conserved sequences with DDR1. Both receptors are activated upon binding to collagen, one of the most abundant proteins in extracellular matrix. While DDR2 can only be activated by fibrillar collagen, particularly types I and III, DDR1 is mostly activated by type I and IV collagens. In contrast with classical growth factor tyrosine kinase receptors which display a rapid and transient activation, DDR1 and DDR2 are unique in that they exhibit delayed and sustained receptor phosphorylation upon binding to collagen. Recent studies have reported differential expression and mutations of DDR1 and DDR2 in several cancer types and indicate clearly that these receptors have to be taken into account as new players in the different aspects of tumor progression, from non-malignant to highly malignant and invasive stages. This review will discuss the current knowledge on the role of DDR1 and DDR2 in malignant transformation, cell proliferation, epithelial to mesenchymal transition, migratory, and invasive processes, and finally the modulation of the response to chemotherapy. These new insights suggest that DDR1 and DDR2 are new potential targets in cancer therapy.

Efficacy and Interaction of Antioxidant Supplements as Adjuvant Therapy in Cancer Treatment: A Systematic Review

Oxidative stress is a key component in carcinogenesis. Although radiation produces reactive oxygen species, some anticancer agents such as alkylating agents, platinum and antitumor antibiotics exert cytotoxicity by generating free radicals. Nonenzymatic exogenous antioxidants such as vitamins, minerals, and polyphenols can quench ROS activity. However, whether antioxidants alter antitumor effects during radiotherapy and some types of chemotherapy remains unclear. In the present study, we reviewed antioxidants as an adjuvant therapy for cancer patients during chemotherapy or radiotherapy. Electronic literature searches were performed to select all randomized controlled clinical trials (RCTs) in which antioxidants were administered to cancer patients along with chemotherapy or radiotherapy. Articles or abstracts written in English were included. In total, 399 reports received primary screening. Duplicated articles and those meeting the exclusion criteria (not RCT, not human, and no oral administration) were excluded. Finally, 49 reports matching the inclusion criteria were included. It was difficult to determine whether antioxidants affect treatment outcomes or whether antioxidants ameliorate adverse effects induced by chemotherapy and radiotherapy. It is desirable to use an evidence-based method to select supplements best suited to cancer patients. Although there are many opinions about risks or benefits of antioxidant supplementation, we could mostly conclude that the harm caused by antioxidant supplementation remains unclear for patients during cancer therapy, except for smokers undergoing radiotherapy.

The tumor microenvironment: An irreplaceable element of tumor budding and epithelial-mesenchymal transition-mediated cancer metastasis

Tumor budding occurs at the invasive front of cancer; the tumor cells involved have metastatic and stemness features, indicating a poor prognosis. Tumor budding is partly responsible for cancer metastasis, and its initiation is based on the epithelial-mesenchymal transition (EMT) process. The EMT process involves the conversion of epithelial cells into migratory and invasive cells, and is a profound event in tumorigenesis. The EMT, associated with the formation of cancer stem cells (CSCs) and resistance to therapy, results from a combination of gene mutation, epigenetic regulation, and microenvironmental control. Tumor budding can be taken to represent the EMT in vivo. The EMT process is under the influence of the tumor microenvironment as well as tumor cells themselves. Here, we demonstrate that the tumor microenvironment dominates EMT development and impacts cancer metastasis, as well as promotes CSC formation and mediates drug resistance. In this review, we mainly discuss components of the microenvironment, such as the extracellular matrix (ECM), inflammatory cytokines, metabolic products, and hypoxia, that are involved in and impact on the acquisition of tumor-cell motility and dissemination, the EMT, metastatic tumor-cell formation, tumor budding and CSCs, and cancer metastasis, including subsequent chemo-resistance. From our point of view, the tumor microenvironment now constitutes a promising target for cancer therapy.