Targeting Serglycin Prevents Metastasis in Murine Mammary Carcinoma

Proteoglycans Determine the Dynamic Landscape of EMT and Cancer Cell Stemness

Proteoglycans (PGs) are pivotal components of extracellular matrices, involved in a variety of processes such as migration, invasion, morphogenesis, differentiation, drug resistance, and epithelial-to-mesenchymal transition (EMT). Cellular plasticity is a crucial intermediate phenotypic state acquired by cancer cells, which can modulate EMT and the generation of cancer stem cells (CSCs). PGs affect cell plasticity, stemness, and EMT, altering the cellular shape and functions. PGs control these functions, either by direct activation of signaling cascades, acting as co-receptors, or through regulation of the availability of biological compounds such as growth factors and cytokines. Differential expression of microRNAs is also associated with the expression of PGs and their interplay is implicated in the fine tuning of cancer cell phenotype and potential. This review summarizes the involvement of PGs in the regulation of EMT and stemness of cancer cells and highlights the molecular mechanisms.

Serglycin promotes proliferation, migration, and invasion via the JAK/STAT signaling pathway in osteosarcoma

BACKGROUND

Osteosarcoma (OS) is a common disease in the world, and its pathogenesis is still unclear. This study aims to identify the key genes that promote the proliferation, invasion, and metastasis of osteosarcoma cells.

METHOD

GSE124768 and GSE126209 were downloaded from the Gene Expression Omnibus (GEO) database. The gene ontology and enrichment pathway were analyzed by FunRich software. qPCR and Western blot were used to detect the gene expression. After gene knockdown, Transwell and wound healing assays were conducted on osteosarcoma cells to detect whether the genes were defined before enhancing the invasion of osteosarcoma.

RESULTS

Totally, 341 mRNAs were found to be regulated differentially in osteosarcoma cells compared to osteoblasts. In addition, the expression level of Serglycin (SRGN) in osteosarcoma cells was higher than that in human osteoblasts. The invasion and proliferation ability of osteosarcoma cells with upregulated Serglycin was significantly increased, and on the contrary, decreased after Serglycin knockdown. Moreover, we preliminarily found that Serglycin may associate with the JAK/STAT signaling pathway.

CONCLUSIONS

By using microarray and bioinformatics analyses, differently expressed mRNAs were identified and a complete gene network was constructed. To our knowledge, we describe for the first time Serglycin as a potential biomarker.

JAK/STAT inhibitor therapy partially rescues the lipodystrophic autoimmune phenotype in Clec16a KO mice

CLEC16A is implicated in multiple autoimmune diseases. We generated an inducible whole-body knockout (KO), Clec16a^ΔUBC mice to address the role of CLEC16A loss of function. KO mice exhibited loss of adipose tissue and severe weight loss in response to defective autophagic flux and exaggerated endoplasmic reticulum (ER) stress and robust cytokine storm. KO mice were glucose tolerant and displayed a state of systemic inflammation with elevated antibody levels, including IgM, IgA, Ig2b and IgG3, significantly reduced circulating insulin levels in the presence of normal food consumption. Metabolic analysis revealed disturbances in the lipid profile, white adipose decreasing concomitantly with enhanced inflammatory response, and energy wasting. Mechanistically, endoplasmic reticulum (ER) stress triggers excessive hormone sensitive lipases (HSL) mediated lipolysis which contributes to adipose inflammation via activation of JAK-STAT, stress kinases (ERK1/2, P38, JNK), and release of multiple proinflammatory mediators. Treatment with a JAK-STAT inhibitor (tofacitinib) partially rescued the inflammatory lipodystrophic phenotype and improved survival of Clec16a^ΔUBC mice by silencing cytokine release and modulating ER stress, lipolysis, mitophagy and autophagy. These results establish a mechanistic link between CLEC16A, lipid metabolism and the immune system perturbations. In summary, our Clec16a^ΔUBC mouse model highlights multifaceted roles of Clec16a in normal physiology, including a novel target for weight regulation and mutation-induced pathophysiology.

The Role of Proteoglycans in Cancer Metastasis and Circulating Tumor Cell Analysis

Circulating tumor cells (CTCs) are accessible by liquid biopsies via an easy blood draw. They represent not only the primary tumor site, but also potential metastatic lesions, and could thus be an attractive supplement for cancer diagnostics. However, the analysis of rare CTCs in billions of normal blood cells is still technically challenging and novel specific CTC markers are needed. The formation of metastasis is a complex process supported by numerous molecular alterations, and thus novel CTC markers might be found by focusing on this process. One example of this is specific changes in the cancer cell glycocalyx, which is a network on the cell surface composed of carbohydrate structures. Proteoglycans are important glycocalyx components and consist of a protein core and covalently attached long glycosaminoglycan chains. A few CTC assays have already utilized proteoglycans for both enrichment and analysis of CTCs. Nonetheless, the biological function of proteoglycans on clinical CTCs has not been studied in detail so far. Therefore, the present review describes proteoglycan functions during the metastatic cascade to highlight their importance to CTCs. We also outline current approaches for CTC assays based on targeting proteoglycans by their protein cores or their glycosaminoglycan chains. Lastly, we briefly discuss important technical aspects, which should be considered for studying proteoglycans.

Proteoglycans in the Pathogenesis of Hormone-Dependent Cancers: Mediators and Effectors

Hormone-dependent cancers exhibit high morbidity and mortality. In spite of advances in therapy, the treatment of hormone-dependent cancers remains an unmet health need. The tumor microenvironment (TME) exhibits unique characteristics that differ among various tumor types. It is composed of cancerous, non-cancerous, stromal, and immune cells that are surrounded and supported by components of the extracellular matrix (ECM). Therefore, the interactions among cancer cells, stromal cells, and components of the ECM determine cancer progression and response to therapy. Proteoglycans (PGs), hybrid molecules consisting of a protein core to which sulfated glycosaminoglycan chains are bound, are significant components of the ECM that are implicated in all phases of tumorigenesis. These molecules, secreted by both the stroma and cancer cells, are crucial signaling mediators that modulate the vital cellular pathways implicated in gene expression, phenotypic versatility, and response to therapy in specific tumor types. A plethora of deregulated signaling pathways contributes to the growth, dissemination, and angiogenesis of hormone-dependent cancers. Specific inputs from the endocrine and immune systems are some of the characteristics of hormone-dependent cancer pathogenesis. Importantly, the mechanisms involved in various aspects of cancer progression are executed in the ECM niche of the TME, and the PG components crucially mediate these processes. Here, we comprehensively discuss the mechanisms through which PGs affect the multifaceted aspects of hormone-dependent cancer development and progression, including cancer metastasis, angiogenesis, immunobiology, autophagy, and response to therapy.

SRGN, a new identified shear-stress-responsive gene in endothelial cells

Endothelial cells (ECs) play an important role in the pathogenesis of cardiovascular disease, especially atherosclerosis (AS). The abnormal wall shear stress (WSS) which directly contacts with ECs is the key stimulating factor leading to AS. However, the underlying mechanism of ECs responding to WSS is still incompletely understood. This study aims to explore the novel mechano-sensitive genes and its potential mechanism in response to WSS in ECs by employing bioinformatics methods based on previously available high-throughput data from zebrafish embryos, both before and after blood flow formation. Six common differentially expressed genes (DEGs) (SRGN, SLC12A3, SLC25A4, PVALB1, ITGAE.2, zgc:198419) were selected out from two high-throughput datasets (GSE126617 and GSE20707) in the GEO database. Among them, SRGN was chosen for further verification through the in vitro shear stress loading experiments with human umbilical vein endothelial cells (HUVECs) and the in vivo partial ligation of carotid artery in mice. Our data indicated that low shear stress (LSS) could enhance the expression of SRGN via the PKA/CREB-dependent signaling pathway. The proportion of Ki67⁺ cells and the concentration of nitric oxide (NO) were high in SRGN high expression cells, suggesting that SRGN may be involved in the proliferation of HUVECs. Furthermore, in the partial ligation of the carotid artery mice model, we observed that the expression of SRGN was significantly increased in atherosclerotic plaques induced by abnormal shear stress. Taken together, this study demonstrated that SRGN is a key gene in the response of ECs to WSS and could be involved in AS.

Serglycin activates pro-tumorigenic signaling and controls glioblastoma cell stemness, differentiation and invasive potential

Despite the functional role of serglycin as an intracellular proteoglycan, a variety of malignant cells depends on its expression and constitutive secretion to advance their aggressive behavior. Serglycin arose to be a biomarker for glioblastoma, which is the deadliest and most treatment-resistant form of brain tumor, but its role in this disease is not fully elucidated. In our study we suppressed the endogenous levels of serglycin in LN-18 glioblastoma cells to decipher its involvement in their malignant phenotype. Serglycin suppressed LN-18 (LN-18shSRGN) glioblastoma cells underwent astrocytic differentiation characterized by induced expression of GFAP, SPARCL-1 and SNAIL, with simultaneous loss of their stemness capacity. In particular, LN-18shSRGN cells presented decreased expression of glioma stem cell-related genes and ALDH1 activity, accompanied by reduced colony formation ability. Moreover, the suppression of serglycin in LN-18shSRGN cells retarded the proliferative and migratory rate, the invasive potential in vitro and the tumor burden in vivo. The lack of serglycin in LN-18shSRGN cells was followed by G2 arrest, with subsequent reduction of the expression of cell-cycle regulators. LN-18shSRGN cells also exhibited impaired expression and activity of proteolytic enzymes such as MMPs, TIMPs and uPA, both in vitro and in vivo. Moreover, suppression of serglycin in LN-18shSRGN cells eliminated the activation of pro-tumorigenic signal transduction. Of note, LN-18shSRGN cells displayed lower expression and secretion levels of IL-6, IL-8 and CXCR-2. Concomitant, serglycin suppressed LN-18shSRGN cells demonstrated repressed phosphorylation of ERK1/2, p38, SRC and STAT-3, which together with PI3K/AKT and IL-8/CXCR-2 signaling control LN-18 glioblastoma cell aggressiveness. Collectively, the absence of serglycin favors an astrocytic fate switch and a less aggressive phenotype, characterized by loss of pluripotency, block of the cell cycle, reduced ability for ECM proteolysis and pro-tumorigenic signaling attenuation.

Molecular principles of metastasis: a hallmark of cancer revisited

Metastasis is the hallmark of cancer that is responsible for the greatest number of cancer-related deaths. Yet, it remains poorly understood. The continuous evolution of cancer biology research and the emergence of new paradigms in the study of metastasis have revealed some of the molecular underpinnings of this dissemination process. The invading tumor cell, on its way to the target site, interacts with other proteins and cells. Recognition of these interactions improved the understanding of some of the biological principles of the metastatic cell that govern its mobility and plasticity. Communication with the tumor microenvironment allows invading cancer cells to overcome stromal challenges, settle, and colonize. These characteristics of cancer cells are driven by genetic and epigenetic modifications within the tumor cell itself and its microenvironment. Establishing the biological mechanisms of the metastatic process is crucial in finding open therapeutic windows for successful interventions. In this review, the authors explore the recent advancements in the field of metastasis and highlight the latest insights that contribute to shaping this hallmark of cancer.

Cancer Cell-derived Secretory Factors in Breast Cancer-associated Lung Metastasis: Their Mechanism and Future Prospects

In Breast cancer, Lung is the second most common site of metastasis after the bone. Various factors are responsible for Lung metastasis occurring secondary to Breast cancer. Cancer cellderived secretory factors are commonly known as 'Cancer Secretomes'. They exhibit a prompt role in the mechanism of Breast cancer lung metastasis. They are also major constituents of hostassociated tumor microenvironment. Through cross-talk between cancer cells and the extracellular matrix components, cancer cell-derived extracellular matrix components (CCECs) such as hyaluronan, collagens, laminin and fibronectin cause ECM remodeling at the primary site (breast) of cancer. However, at the secondary site (lung), tenascin C, periostin and lysyl oxidase, along with pro-metastatic molecules Coco and GALNT14, contribute to the formation of pre-metastatic niche (PMN) by promoting ECM remodeling and lung metastatic cells colonization. Cancer cell-derived secretory factors by inducing cancer cell proliferation at the primary site, their invasion through the tissues and vessels and early colonization of metastatic cells in the PMN, potentiate the mechanism of Lung metastasis in Breast cancer. On the basis of biochemical structure, these secretory factors are broadly classified into proteins and non-proteins. This is the first review that has highlighted the role of cancer cell-derived secretory factors in Breast cancer Lung metastasis (BCLM). It also enumerates various researches that have been conducted to date in breast cancer cell lines and animal models that depict the prompt role of various types of cancer cell-derived secretory factors involved in the process of Breast cancer lung metastasis. In the future, by therapeutically targeting these cancer driven molecules, this specific type of organ-tropic metastasis in breast cancer can be successfully treated.

Irreversible Electroporation Combined with Checkpoint Blockade and TLR7 Stimulation Induces Antitumor Immunity in a Murine Pancreatic Cancer Model

Irreversible electroporation (IRE) is a nonthermal ablation technique that is used clinically in selected patients with locally advanced pancreatic cancer, but most patients develop recurrent distant metastatic disease. We hypothesize that IRE can induce an in situ vaccination effect by releasing tumor neoantigens in an inflammatory context. Using an immunocompetent mouse model, we demonstrated that IRE alone produced complete regression of subcutaneous tumors in approximately 20% to 30% of mice. IRE was not effective in immunodeficient mice. Mice with complete response to IRE demonstrated prophylactic immunity and remained tumor free when rechallenged with secondary tumors on the contralateral flank. CD8⁺ T cells from IRE-responsive mice were reactive against peptides representing model-inherent alloantigens and conferred protection against tumor challenge when adoptively transferred into immunocompromised, tumor-naïve mice. Combining IRE with intratumoral Toll-like receptor-7 (TLR7) agonist (1V270) and systemic anti-programmed death-1 receptor (PD)-1 checkpoint blockade resulted in improved treatment responses. This combination also resulted in elimination of untreated concomitant distant tumors (abscopal effects), an effect not seen with IRE alone. These results suggest that the systemic antitumor immune response triggered by IRE can be enhanced by stimulating the innate immune system with a TLR7 agonist and the adaptive immune system with anti-PD-1 checkpoint blockade simultaneously. Combinatorial approaches such as this may help overcome the immunosuppressive pancreatic cancer microenvironment.

Serglycin as part of IL-1β induced inflammation in human chondrocytes

Serglycin (SRGN) is an intracellular proteoglycan produced and secreted by several cell types. The increased expression of SRGN was associated with greater aggressiveness in cancer and inflammation. In this study, we demonstrated that SRGN is increased in human chondrocytes after IL-β stimulation. Furthermore, we found that secreted SRGN was able to bind the CD44 receptor thus participating in the extension of the inflammatory response. Using SRGN knockdown cells we observed a significantly decrease in specific inflammatory markers and NF-kB activation. Similar results were observed by blocking the CD44 receptor. These data provide further evidences for a direct involvement of SRGN in the mechanisms regulating the non-infectious chondrocytes damage, and the consequent joint inflammation and cartilage destruction in arthritis.

Tumorigenic functions of serglycin: Regulatory roles in epithelial to mesenchymal transition and oncogenic signaling

Numerous studies point out serglycin as an important regulator of tumorigenesis in a variety of malignancies. Serglycin expression correlates with the aggressive phenotype of tumor cells and serves as a poor prognostic indicator for disease progression. Although serglycin is considered as an intracellular proteoglycan, it is also secreted in the extracellular matrix by tumor cells affecting cell properties, oncogenic signaling and exosomes cargo. Serglycin directly interacts with CD44 and possibly other cell surface receptors including integrins, evoking cell adhesion and signaling. Serglycin also creates a pro-inflammatory and pro-angiogenic tumor microenvironment by regulating the secretion of proteolytic enzymes, IL-8, TGFβ2, CCL2, VEGF and HGF. Hence, serglycin activates multiple signaling cascades that drive angiogenesis, tumor cell growth, epithelial to mesenchymal transition, cancer cell stemness and metastasis. The interference with the tumorigenic functions of serglycin emerges as an attractive prospect to target malignancies.

Serglycin promotes breast cancer cell aggressiveness: Induction of epithelial to mesenchymal transition, proteolytic activity and IL-8 signaling

Serglycin is an intracellular proteoglycan that is expressed and constitutively secreted by numerous malignant cells, especially prominent in the highly-invasive, triple-negative MDA-MB-231 breast carcinoma cells. Notably, de novo expression of serglycin in low aggressive estrogen receptor α (ERα)-positive MCF7 breast cancer cells promotes an aggressive phenotype. In this study, we discovered that serglycin promoted epithelial to mesenchymal transition (EMT) in MCF7 cells as shown by increased expression of mesenchymal markers vimentin, fibronectin and EMT-related transcription factor Snail2. These phenotypic traits were also associated with the development of drug resistance toward various chemotherapy agents and induction of their proteolytic potential as shown by the increased expression of matrix metalloproteinases, including MMP-1, MMP-2, MMP-9, MT1-MMP and up-regulation of urokinase-type plasminogen activator. Knockdown of serglycin markedly reduced the expression of these proteolytic enzymes in MDA-MB-231 cells. In addition, serglycin expression was closely linked to a pro-inflammatory gene signature including the chemokine IL-8 in ERα-negative breast cancer cells and tumors. Notably, serglycin regulated the secretion of IL-8 in breast cancer cells independently of their ERα status and promoted their proliferation, migration and invasion by triggering IL-8/CXCR2 downstream signaling cascades including PI3K, Src and Rac activation. Thus, serglycin promotes the establishment of a pro-inflammatory milieu in breast cancer cells that evokes an invasive mesenchymal phenotype via autocrine activation of IL-8/CXCR2 signaling axis.

Serglycin as a potential biomarker for glioma: association of serglycin expression, extent of mast cell recruitment and glioblastoma progression

Serglycin is an intracellular proteoglycan with a unique ability to adopt highly divergent structures by glycosylation with variable types of glycosaminoglycans (GAGs) when expressed by different cell types. Serglycin is overexpressed in aggressive cancers suggesting its protumorigenic role. In this study, we explored the expression of serglycin in human glioma and its correlation with survival and immune cell infiltration. We demonstrate that serglycin is expressed in glioma and that increased expression predicts poor survival of patients. Analysis of serglycin expression in a large cohort of low- and high-grade human glioma samples reveals that its expression is grade dependent and is positively correlated with mast cell (MC) infiltration. Moreover, serglycin expression in patient-derived glioma cells is significantly increased upon MC co-culture. This is also accompanied by increased expression of CXCL12, CXCL10, as well as markers of cancer progression, including CD44, ZEB1 and vimentin.In conclusion, these findings indicate the importance of infiltrating MCs in glioma by modulating signaling cascades involving serglycin, CD44 and ZEB1. The present investigation reveals serglycin as a potential prognostic marker for glioma and demonstrates an association with the extent of MC recruitment and glioma progression, uncovering potential future therapeutic opportunities for patients.

Proteoglycans remodeling in cancer: Underlying molecular mechanisms

Extracellular matrix is a highly dynamic macromolecular network. Proteoglycans are major components of extracellular matrix playing key roles in its structural organization and cell signaling contributing to the control of numerous normal and pathological processes. As multifunctional molecules, proteoglycans participate in various cell functions during morphogenesis, wound healing, inflammation and tumorigenesis. Their interactions with matrix effectors, cell surface receptors and enzymes enable them with unique properties. In malignancy, extensive remodeling of tumor stroma is associated with marked alterations in proteoglycans' expression and structural variability. Proteoglycans exert diverse functions in tumor stroma in a cell-specific and context-specific manner and they mainly contribute to the formation of a permissive provisional matrix for tumor growth affecting tissue organization, cell-cell and cell-matrix interactions and tumor cell signaling. Proteoglycans also modulate cancer cell phenotype and properties, the development of drug resistance and tumor stroma angiogenesis. This review summarizes the proteoglycans remodeling and their novel biological roles in malignancies with particular emphasis to the underlying molecular mechanisms.

SRGN-TGFβ2 regulatory loop confers invasion and metastasis in triple-negative breast cancer

Patients with triple-negative breast cancers (TNBC) are at a high risk for a recurrent or metastatic disease, and the molecular mechanisms associated with this risk are unclear. Proteoglycan serglycin (SRGN) proteins are involved in tumor metastasis, but their role in TNBC has not yet been elucidated. This study investigates the SRGN gene expression and how it regulates TGFβ2 and the downstream signaling of TGFβ2 in TNBC cells and tissues. Our results show that SRGN mRNA and protein expression levels were significantly higher in TNBC cell lines and tumor tissues than that in non-TNBC cells and tissues. We inhibited SRGN expression and protein secretion using shRNA and we observed this inhibited the invasive motility of TNBC cancer cells in vitro and metastasis of TNBC cancer cells in vivo. SRGN protein treatment increased the expression and secretion of transforming growth factor-β2 (TGFβ2) by activating CD44/CREB1 signaling and promoted epithelial-to-mesenchymal transition in TNBC cells. Moreover, TGFβ2 treatment increased the mRNA and protein expression of the SRGN gene by activating Smad3 to target the SRGN relative promoter domain in TNBC cells. Our findings demonstrate that SRGN interacts with TGFβ2 which regulates TNBC metastasis via the autocrine and paracrine routes. SRGN could serve as a potential target for development of agents or therapeutics for the TNBC.

Tumor microenvironment: driving forces and potential therapeutic targets for breast cancer metastasis

Distant metastasis to specific target organs is responsible for over 90% of breast cancer-related deaths, but the underlying molecular mechanism is unclear. Mounting evidence suggests that the interplay between breast cancer cells and the target organ microenvironment is the key determinant of organ-specific metastasis of this lethal disease. Here, we highlight new findings and concepts concerning the emerging role of the tumor microenvironment in breast cancer metastasis; we also discuss potential therapeutic intervention strategies aimed at targeting components of the tumor microenvironment.