The biology of decorin in the tumor microenvironment

Decorin is a ubiquitous secreted small-leucine rich proteoglycan associated with all major collagen-rich matrices. Initially described for its roles in maintaining the structural integrity of various organs and in collagen fibrillogenesis, decorin has gained notoriety for its involvement in regulating physiological and pathological processes such as wound healing, inflammation, cell adhesion, and carcinogenesis. Decorin exerts these functions through its ability to bind with high affinity to multiple receptor tyrosine kinases (RTKs). In cancer, decorin has been described as a paracrine tumor repressor and anti-angiogenic molecule. However, a detailed description of its mechanism of action in the tumor microenvironment was unknown. Understanding the role of the tumor stroma in modulating the signaling of cancer cells, tumor angiogenesis, and metastatic spreading is critical and of clinical relevance. This thesis unscrambles the biology of decorin in the tumor microenvironment and describes a new double mechanism of action where decorin alters signaling cascades of both cancer cells and surrounding stromal cells via selective binding to different RTKs, ultimately elucidating its tumor suppressor activity. The key observations of my studies are: [1] the discovery that physical interaction of decorin with the Met receptor on cancer cells causes a protracted downregulation of β-catenin and its downstream effector Myc both at the transcriptional and post-translational levels (chapter 3); [2] the discovery that systemic delivery of soluble decorin in-vivo causes genotypic changes in the stroma of orthotopic breast carcinoma xenografts and the identification of Peg3 as a novel decorin-induced tumor suppressor in the tumor microenvironment (chapter 5); [3] the observation that decorin evokes autophagy in endothelial cells via binding to VEGFR2 and induction of Peg3 (chapter 6). Thus, here I define how decorin dually affects the tumor proper by suppressing Met activity and the tumor vasculature by inducing unrestrained autophagy. Decorin could tie the interplay between extracellular signaling and intracellular catabolic pathways that leads to angiostasis and tumor growth suppression and could be an innovative therapeutic alternative against cancer

Decorin protein core affects the global gene expression profile of the tumor microenvironment in a triple-negative orthotopic breast carcinoma xenograft model

Decorin, a member of the small leucine-rich proteoglycan gene family, exists and functions wholly within the tumor microenvironment to suppress tumorigenesis by directly targeting and antagonizing multiple receptor tyrosine kinases, such as the EGFR and Met. This leads to potent and sustained signal attenuation, growth arrest, and angiostasis. We thus sought to evaluate the tumoricidal benefits of systemic decorin on a triple-negative orthotopic breast carcinoma xenograft model. To this end, we employed a novel high-density mixed expression array capable of differentiating and simultaneously measuring gene signatures of both Mus musculus (stromal) and Homo sapiens (epithelial) tissue origins. We found that decorin protein core modulated the differential expression of 374 genes within the stromal compartment of the tumor xenograft. Further, our top gene ontology classes strongly suggests an unexpected and preferential role for decorin protein core to inhibit genes necessary for immunomodulatory responses while simultaneously inducing expression of those possessing cellular adhesion and tumor suppressive gene properties. Rigorous verification of the top scoring candidates led to the discovery of three genes heretofore unlinked to malignant breast cancer that were reproducibly found to be induced in several models of tumor stroma. Collectively, our data provide highly novel and unexpected stromal gene signatures as a direct function of systemic administration of decorin protein core and reveals a fundamental basis of action for decorin to modulate the tumor stroma as a biological mechanism for the ascribed anti-tumorigenic properties

Mechanisms of Progranulin Action and Regulation in Genitourinary Cancers.

The growth factor progranulin has emerged in recent years as a critical regulator of transformation in several cancer models, including breast cancer, glioblastomas, leukemias, and hepatocellular carcinomas. Several laboratories, including ours, have also demonstrated an important role of progranulin in several genitourinary cancers, including ovarian, endometrial, cervical, prostate, and bladder tumors, where progranulin acts as an autocrine growth factor thereby modulating motility and invasion of transformed cells. In this review, we will focus on the mechanisms of action and regulation of progranulin signaling in genitourinary cancers with a special emphasis on prostate and bladder tumors

A novel role for drebrin in regulating progranulin bioactivity in bladder cancer.

We recently established a critical role for the growth factor progranulin in bladder cancer insofar as progranulin promotes urothelial cancer cell motility and contributes, as an autocrine growth factor, to the transformed phenotype by modulating invasion and anchorage-independent growth. In addition, progranulin expression is upregulated in invasive bladder cancer tissues compared to normal controls. However, the molecular mechanisms of progranulin action in bladder cancer have not been fully elucidated. In this study, we searched for novel progranulin-interacting proteins using pull-down assays with recombinant progranulin and proteomics. We discovered that drebrin, an F-actin binding protein, bound progranulin in urothelial cancer cells. We characterized drebrin function in urothelial cancer cell lines and showed that drebrin is critical for progranulin-dependent activation of the Akt and MAPK pathways and modulates motility, invasion and anchorage-independent growth. In addition, drebrin regulates tumor formation in vivo and its expression is upregulated in bladder cancer tissues compared to normal tissue controls. Our data are translationally relevant as indicate that drebrin exerts an essential functional role in the regulation of progranulin action and may constitute a novel target for therapeutic intervention in bladder tumors. In addition, drebrin may serve as novel biomarker for bladder cancer

Complexity of Progranulin Mechanisms of Action in Mesothelioma

Background: Mesothelioma is an aggressive disease with limited therapeutic options. The growth factor progranulin plays a critical role in several cancer models, where it regulates tumor initiation and progression. Recent data from our laboratories have demonstrated that progranulin and its receptor, EphA2, constitute an oncogenic pathway in bladder cancer by promoting motility, invasion and in vivo tumor formation. Progranulin and EphA2 are expressed in mesothelioma cells but their mechanisms of action are not well defined. In addition, there are no data establishing whether the progranulin/EphA2 axis is tumorigenic for mesothelioma cells. Methods: The expression of progranulin in various mesothelioma cell lines derived from all major mesothelioma subtypes was examined by western blots on cell lysates, conditioned media and ELISA assays. The biological roles of progranulin, EphA2, EGFR, RYK and FAK were assessed in vitro by immunoblots, human phospho-RTK antibody arrays, pharmacological (specific inhibitors) and genetic (siRNAs, shRNAs, CRISPR/Cas9) approaches, motility, invasion and adhesion assays. In vivo tumorigenesis was determined by xenograft models. Focal adhesion turnover was evaluated biochemically using focal adhesion assembly/disassembly assays and immunofluorescence analysis with focal adhesion-specific markers. Results: In the present study we show that progranulin is upregulated in various mesothelioma cell lines covering all mesothelioma subtypes and is an important regulator of motility, invasion, adhesion and in vivo tumor formation. However, our results indicate that EphA2 is not the major functional receptor for progranulin in mesothelioma cells, where progranulin activates a complex signaling network including EGFR and RYK. We further characterized progranulin mechanisms of action and demonstrated that progranulin, by modulating FAK activity, regulates the kinetic of focal adhesion disassembly, a critical step for cell motility. Conclusion: Collectively, our results highlight the complexity of progranulin oncogenic signaling in mesothelioma, where progranulin modulate functional cross-talks between multiple RTKs, thereby suggesting the need for combinatorial therapeutic approaches to improve treatments of this aggressive disease

Atypical Chemokine Receptor 3 Generates Guidance Cues for CXCL12-Mediated Endothelial Cell Migration

Chemokine receptor CXCR4, its ligand stromal cell-derived factor-1 (CXCL12) and the decoy receptor atypical chemokine receptor 3 (ACKR3, also named CXCR7), are involved in the guidance of migrating cells in different anatomical districts. Here, we investigated the role of the ACKR3 zebrafish ortholog ackr3b in the vascularization process during embryonic development. Bioinformatics and functional analyses confirmed that ackr3b is a CXCL12-binding ortholog of human ACKR3. ackr3b is transcribed in the endoderm of zebrafish embryos during epiboly and is expressed in a wide range of tissues during somitogenesis, including central nervous system and somites. Between 18 somite and 26 h-post fertilization stages, the broad somitic expression of ackr3b becomes restricted to the basal part of the somites. After ackr3b knockdown, intersomitic vessels (ISVs) lose the correct direction of migration and are characterized by the presence of aberrant sprouts and ectopic filopodia protrusions, showing downregulation of the tip/stalk cell marker hlx1. In addition, ackr3b morphants show significant alterations of lateral dorsal aortae formation. In keeping with a role for ackr3b in endothelial cell guidance, CXCL12 gradient generated by ACKR3 expression in CHO cell transfectants guides human endothelial cell migration in an in vitro cell co-culture chemotaxis assay. Our results demonstrate that ackr3b plays a non-redundant role in the guidance of sprouting endothelial cells during vascular development in zebrafish. Moreover, ACKR3 scavenging activity generates guidance cues for the directional migration of CXCR4-expressing human endothelial cells in response to CXCL12

EphA2 is a functional receptor for the growth factor progranulin.

Although the growth factor progranulin was discovered more than two decades ago, the functional receptor remains elusive. Here, we discovered that EphA2, a member of the large family of Ephrin receptor tyrosine kinases, is a functional signaling receptor for progranulin. Recombinant progranulin bound with high affinity to EphA2 in both solid phase and solution. Interaction of progranulin with EphA2 caused prolonged activation of the receptor, downstream stimulation of mitogen-activated protein kinase and Akt, and promotion of capillary morphogenesis. Furthermore, we found an autoregulatory mechanism of progranulin whereby a feed-forward loop occurred in an EphA2-dependent manner that was independent of the endocytic receptor sortilin. The discovery of a functional signaling receptor for progranulin offers a new avenue for understanding the underlying mode of action of progranulin in cancer progression, tumor angiogenesis, and perhaps neurodegenerative diseases

miR-21 Plays a Dual Role in Tumor Formation and Cytotoxic Response in Breast Tumors

Breast cancer (BrCa) relies on specific microRNAs to drive disease progression. Oncogenic miR-21 is upregulated in many cancers, including BrCa, and is associated with poor survival and treatment resistance. We sought to determine the role of miR-21 in BrCa tumor initiation, progression and treatment response. In a triple-negative BrCa model, radiation exposure increased miR-21 in both primary tumor and metastases. In vitro, miR-21 knockdown decreased survival in all BrCa subtypes in the presence of radiation. The role of miR-21 in BrCa initiation was evaluated by implanting wild-type miR-21 BrCa cells into genetically engineered mouse models where miR-21 was intact, heterozygous or globally ablated. Tumors were unable to grow in the mammary fat pads of miR-21−/− mice, and grew in ~50% of miR-21+/− and 100% in miR-21+/+ mice. The contribution of miR-21 to progression and metastases was tested by crossing miR-21−/− mice with mice that spontaneously develop BrCa. The global ablation of miR-21 significantly decreased the tumorigenesis and metastases of BrCa, while sensitizing tumors to radio-and chemotherapeutic agents via Fas/FasL-dependent apoptosis. Therefore, targeting miR-21 alone or in combination with various radio or cytotoxic therapies may represent novel and efficacious therapeutic modalities for the future treatment of BrCa patients

Home-based pulmonary rehabilitation in patients undergoing (chemo)radiation therapy for unresectable lung cancer: a prospective explorative study

Aims The prevention of pulmonary toxicity is an important goal for patient candidate to radiation therapy for lung cancer. There is a lack of evidence on the role of exercise training for patients with unresectable stage III lung cancer candidated to radical treatment. The aim of this study was to evaluate the feasibility of a home-based pulmonary rehabilitation (PR) program and to identify reliable tools in terms of respiratory function, exercise capacity and quality of life. Methods Patients' recruitment lasted from April 2020 till February 2022. The PR program was proposed concomitantly to radiation therapy to the first 20 patients (interventional group, IG), and the other 20 patients were identified as an observational group (OG). All patients were assessed at baseline (T0) and after 8 weeks (T2) with 6 minute walking test (6MWT), modified Borg Scale (mBORG), SF-36 questionnaire (SF-36) and pulmonary function test (PFT); after 4 weeks (T1), only SF-36 was administered. Results A decrease of 13.8 m in the walked-distance was registered in the OG between T0 and T2 (p = 0.083). Instead, an increase of 56.6 m in the distance walked was recorded in the IG between T0 and T2 (p <= 0.001). In the OG, the mBORG scores showed a negative trend. On the contrary, in the IG, these scores showed a slight improvement. In the OG, all the items of SF-36 scores decreased between T0 and T1. In the IG, an increased trend from T0 to T2 was observed for all the items of SF-36. No clinically significant variations were detected from baseline to T2 in both groups regarding PFT. Conclusion The 6MWT, mBORG and SF-36 resulted as useful tools to assess the role of a PR program. A significant gain in functional exercise capacity and a prevention of the physiological impairment of QoL during radio(chemo)therapy was registered