Chondroitin sulfate proteoglycan 4 enhanced melanoma motility and growth requires a cysteine in the core protein transmembrane domain

Chondroitin Sulfate Proteoglycan 4 (CSPG4) as an Emerging Target for Immunotherapy to Treat Melanoma

Immunotherapies, including checkpoint inhibitor antibodies, have precipitated significant improvements in clinical outcomes for melanoma. However, approximately half of patients do not benefit from approved treatments. Additionally, apart from Tebentafusp, which is approved for the treatment of uveal melanoma, there is a lack of immunotherapies directly focused on melanoma cells. This is partly due to few available targets, especially those expressed on the cancer cell surface. Chondroitin sulfate proteoglycan 4 (CSPG4) is a cell surface molecule overexpressed in human melanoma, with restricted distribution and low expression in non-malignant tissues and involved in several cancer-promoting and dissemination pathways. Here, we summarize the current understanding of the expression and functional significance of CSPG4 in health and melanoma, and we outline immunotherapeutic strategies. These include monoclonal antibodies, antibody-drug conjugates (ADCs), chimeric-antigen receptor (CAR) T cells, and other strategies such as anti-idiotypic and mimotope vaccines to raise immune responses against CSPG4-expressing melanomas. Several showed promising functions in preclinical models of melanoma, yet few have reached clinical testing, and none are approved for therapeutic use. Obstacles preventing that progress include limited knowledge of CSPG4 function in human cancer and a lack of in vivo models that adequately represent patient immune responses and human melanoma biology. Despite several challenges, immunotherapy directed to CSPG4-expressing melanoma harbors significant potential to transform the treatment landscape.

Biomarkers Identification in the Microenvironment of Oral Squamous Cell Carcinoma: A Systematic Review of Proteomic Studies

An important determinant for oral squamous cell carcinoma (OSCC) onset and outcome is the composition of the tumor microenvironment (TME). Thus, the study of the interactions occurring among cancer cells, immune cells, and cancer-associated fibroblasts within the TME could facilitate the understanding of the mechanisms underlying OSCC development and progression, as well as of its sensitivity or resistance to the therapy. In this context, it must be highlighted that the characterization of TME proteins is enabled by proteomic methodologies, particularly mass spectrometry (MS). Aiming to identify TME protein markers employable for diagnosing and prognosticating OSCC, we have retrieved a total of 119 articles spanning 2001 to 2023, of which 17 have passed the selection process, satisfying all its criteria. We have found a total of 570 proteins detected by MS-based proteomics in the TME of OSCC; among them, 542 are identified by a single study, while 28 are cited by two or more studies. These 28 proteins participate in extracellular matrix remodeling and/or energy metabolism. Here, we propose them as markers that could be used to characterize the TME of OSCC for diagnostic/prognostic purposes. Noteworthy, most of the 28 individuated proteins share one feature: being modulated by the hypoxia that is present in the proliferating OSCC mass.

Chondroitin Sulfate Proteoglycan 4 Provides New Treatment Approach to Preventing Peritoneal Dissemination in Ovarian Cancer

Most epithelial ovarian cancer (EOC) patients are diagnosed with peritoneal dissemination. Cellular interactions are an important aspect of EOC cells when they detach from the primary site of the ovary. However, the mechanism remains underexplored. Our study aimed to reveal the role of chondroitin sulfate proteoglycan 4 (CSPG4) in EOC with a major focus on cell-cell interactions. We examined the expression of CSPG4 in clinical samples and cell lines of EOC. The proliferation, migration, and invasion abilities of the CSPG4 knockdown cells were assessed. We also assessed the role of CSPG4 in spheroid formation and peritoneal metastasis in an in vivo model using sh-CSPG4 EOC cell lines. Of the clinical samples, 23 (44.2%) samples expressed CSPG4. CSPG4 was associated with a worse prognosis in patients with advanced EOC. Among the EOC cell lines, aggressive cell lines, including ES2, expressed CSPG4. When CSPG4 was knocked down using siRNA or shRNA, the cell proliferation, migration, and invasion abilities were significantly decreased compared to the control cells. Proteomic analyses showed changes in the expression of proteins related to the cell movement pathways. Spheroid formation was significantly inhibited when CSPG4 was inhibited. The number of nodules and the tumor burden of the omentum were significantly decreased in the sh-CSPG4 mouse models. In the peritoneal wash fluid from mice injected with sh-CSPG4 EOC cells, significantly fewer spheroids were present. Reduced CSPG4 expression was observed in lymphoid enhancer-binding factor 1-inhibited cells. CSPG4 is associated with aggressive features of EOC and poor prognosis. CSPG4 could be a new treatment target for blocking peritoneal metastasis by inhibiting spheroid formation.

NG2/CSPG4 attenuates motility in mandibular fibrochondrocytes under serum starvation conditions

The migration of mandibular fibrochondrocytes is important for the development of the mandible, the homeostasis of the mandibular cartilage, and for the capacity of the tissue to respond to injury. Mandibular fibrochondrocytes have to overcome formidable obstacles during migration including a dense and heterogeneous three-dimensional matrix. Guiding the direction of cell migration and commitment to a migratory phenotype in this microenvironment necessitates a multivalent response to chemotactic and extracellular matrix-mediated stimuli. One of the key matrix components in the cartilage of the temporomandibular joint is type VI collagen. Neuron/glial antigen 2 (NG2/CSPG4) is a transmembrane proteoglycan that binds with collagen VI and has been implicated in a wide range of cell behaviors including cell migration, motility, adhesion, and proliferation. While NG2/CSPG4 has been shown to be a key regulator of mandibular cartilage homeostasis, its role in the migration of mandibular fibrochondrocytes during normal and cell stress conditions has yet to be resolved. Here, we address this gap in knowledge by characterizing NG2/CSPG4-dependent migration in mandibular fibrochondrocytes using primary mandibular fibrochondrocytes isolated from control and full length NG2/CSPG4 knockout mice, in primary mandibular fibrochondrocytes isolated from NG2|DsRed reporter mice and in an immortalized mandibular fibrochondrocyte cell line with a mutated NG2/CSPG4 ectodomain. All three cells demonstrate similar results, with loss of the full length or truncated NG2/CSPG4 increasing the rate of cell migration in serum starvation/cell stress conditions. These findings clearly implicate NG2/CSPG4 as a key molecule in the regulation of cell migration in mandibular fibrochondrocytes in normal and cell stress conditions, underscoring the role of NG2/CSPG4 as a mechanosensitive signaling hub in the mandibular cartilage.

Modeling extracellular matrix through histo-molecular gradient in NSCLC for clinical decisions

Lung cancer still represents a global health problem, being the main type of tumor responsible for cancer deaths. In this context, the tumor microenvironment, and the extracellular matrix (ECM) pose as extremely relevant. Thus, this study aimed to explore the prognostic value of epithelial-to-mesenchymal transition (EMT), Wnt signaling, and ECM proteins expression in patients with non-small-cell lung carcinoma (NSCLC) with clinical stages I-IIIA. For that, we used 120 tissue sections from patients and evaluated the immunohistochemical, immunofluorescence, and transmission electron microscopy (TEM) to each of these markers. We also used in silico analysis to validate our data. We found a strong expression of E-cadherin and β-catenin, which reflects the differential ECM invasion process. Therefore, we also noticed a strong expression of chondroitin sulfate (CS) and collagens III and V. This suggests that, after EMT, the basal membrane (BM) enhanced the motility of invasive cells. EMT proteins were directly associated with WNT5A, and collagens III and V, which suggests that the WNT pathway drives them. On the other hand, heparan sulfate (HS) was associated with WNT3A and SPARC, while WNT1 was associated with CS. Interestingly, the association between WNT1 and Col IV suggested negative feedback of WNT1 along the BM. In our cohort, WNT3A, WNT5A, heparan sulfate and SPARC played an important role in the Cox regression model, influencing the overall survival (OS) of patients, be it directly or indirectly, with the SPARC expression stratifying the OS into two groups: 97 months for high expression; and 65 for low expression. In conclusion, the present study identified a set of proteins that may play a significant role in predicting the prognosis of NSCLC patients with clinical stages I-IIIA.

Chondroitin Sulfate Proteoglycan 4 as a Marker for Aggressive Squamous Cell Carcinoma

Chondroitin sulfate (CS) proteoglycan 4 (CSPG4) is a cell surface proteoglycan that is currently under investigation as a marker of cancer malignancy, and as a potential target of anticancer drug treatment. CSPG4 acts as a driver of tumourigenesis by regulating turnover of the extracellular matrix (ECM) to promote tumour cell invasion, migration as well as inflammation and angiogenesis. While CSPG4 has been widely studied in certain malignancies, such as melanoma, evidence is emerging from global gene expression studies, which suggests a role for CSPG4 in squamous cell carcinoma (SCC). While relatively treatable, lack of widely agreed upon diagnostic markers for SCCs is problematic, especially for clinicians managing certain patients, including those who are aged or infirm, as well as those with underlying conditions such as epidermolysis bullosa (EB), for which a delayed diagnosis is likely lethal. In this review, we have discussed the structure of CSPG4, and quantitatively analysed CSPG4 expression in the tissues and pathologies where it has been identified to determine the usefulness of CSPG4 expression as a diagnostic marker and therapeutic target in management of malignant SCC.

Loss of ABCA8B decreases myelination by reducing oligodendrocyte precursor cells in mice

The myelin sheath, which is wrapped around axons, is a lipid-enriched structure produced by mature oligodendrocytes. Disruption of the myelin sheath is observed in several neurological diseases, such as multiple sclerosis. A crucial component of myelin is sphingomyelin, levels of which can be increased by ABCA8, a member of the ATP-binding cassette transporter family. ABCA8 is highly expressed in the cerebellum, specifically in oligodendroglia. However, whether ABCA8 plays a role in myelination and mechanisms that would underlie this role remain unknown. Here, we found that the absence of Abca8b, a mouse ortholog of ABCA8, led to decreased numbers of cerebellar oligodendrocyte precursor cells (OPCs) and mature oligodendrocytes in mice. We show that in oligodendrocytes, ABCA8 interacts with chondroitin sulfate proteoglycan 4 (CSPG4), a molecule essential for OPC proliferation, migration, and myelination. In the absence of Abca8b, localization of CSPG4 to the plasma membrane was decreased, contributing to reduced cerebellar CSPG4 expression. Cerebellar CSPG4+ OPCs were also diminished, leading to decreased mature myelinating oligodendrocyte numbers and cerebellar myelination levels in Abca8b-/- mice. In addition, electron microscopy analyses showed that the number of nonmyelinated cerebellar axons was increased, whereas cerebellar myelin thickness (g-ratio), myelin sheath periodicity, and axonal diameter were all decreased, indicative of disordered myelin ultrastructure. In line with disrupted cerebellar myelination, Abca8b-/- mice showed lower cerebellar conduction velocity and disturbed locomotion. In summary, ABCA8 modulates cerebellar myelination, in part through functional regulation of the ABCA8-interacting protein CSPG4. Our findings suggest that ABCA8 disruption may contribute to the pathophysiology of myelin disorders.

Chondroitin sulfate proteoglycan 4, a targetable oncoantigen that promotes ovarian cancer growth, invasion, cisplatin resistance and spheroid formation

Epithelial ovarian cancer (EOC) is a highly heterogeneous disease encompassing several distinct molecular subtypes and clinical entities. Despite the initial success of surgical debulking and adjuvant chemotherapy, recurrence with chemotherapy resistant tumors is common in patients with EOC and leads to poor overall survival. The extensive genetic and phenotypic heterogeneity associated with ovarian cancers has hindered the identification of effective prognostic and predictive biomarkers in EOC patients. In the current studies, we identify a tumor cell surface oncoantigen, chondroitin sulfate proteoglycan 4 (CSPG4), as an independent risk factor for decreased survival of patients with EOC. Our results show that CSPG4 promotes EOC cell invasion, cisplatin resistance and spheroid formation in vitro and tumor expansion in vivo. Mechanistically, spheroid formation and tumor cell invasion are due to CSPG4-stimulated expression of the mesenchymal transcription factor ZEB1. Furthermore, we have developed a novel monoclonal anti-CSGP4 antibody against the juxtamembrane domain of the core protein that limits CSPG4-stimulated ZEB1 expression, tumor cell invasion and promotes EOC apoptosis within spheroid cultures. We therefore propose that CSPG4 expression drives phenotypic heterogeneity and malignant progression in EOC tumors. These studies further demonstrate that CSPG4 expression levels are a potential diagnostic biomarker in EOC and indicate that targeting cells which express this oncoantigen could limit recurrence and improve outcomes in patients with EOC.

Expression of chondroitin sulfate proteoglycan 4 (CSPG4) in melanoma cells is downregulated upon inhibition of BRAF

Chondroitin sulfate proteoglycan 4 (CSPG4) is a multifunctional transmembrane proteoglycan involved in spreading, migration and invasion of melanoma. In addition to the activating BRAF V600E mutation, CSPG4 was shown to promote MAPK signaling by mediating the growth-factor induced activation of receptor tyrosine kinases. However, it remains elusive which factors regulate CSPG4 expression. Therefore, the aim of the present study was to examine whether BRAF and MEK inhibitors have an effect on the expression of CSPG4. We exposed a panel of BRAF-mutant CSPG4-positive or -negative melanoma cell lines to BRAF and MEK inhibitors. Protein levels of CSPG4 were analyzed by flow cytometry (FACS), immunofluorescence microscopy (IF), and western blotting. CSPG4 mRNA levels were determined by quantitative PCR (qPCR). The prolonged exposure of cells to BRAF and MEK inhibitors resulted in markedly reduced levels of the CSPG4 protein in permanent resistant melanoma cells as well as decreased levels of its mRNA. We did not observe increasing levels of CSPG4 shedding into the culture supernatants. In addition, patient-derived matched tumor samples following therapy with kinase inhibitors showed decreased numbers of CSPG4-positive cells as compared to pre-therapy tumor samples. Our results indicate that BRAF and MEK inhibition downregulates CSPG4 expression until the cells have developed permanent resistance. Our findings provide the basis for further investigation of the role of CSPG4 in the development of drug-resistance in melanoma cells.

Chondroitin Sulphate Proteoglycans in the Tumour Microenvironment

Proteoglycans are macromolecules that are essential for the development of cells, human diseases and malignancies. In particular, chondroitin sulphate proteoglycans (CSPGs) accumulate in tumour stroma and play a key role in tumour growth and invasion by driving multiple oncogenic pathways in tumour cells and promoting crucial interactions in the tumour microenvironment (TME). These pathways involve receptor tyrosine kinase (RTK) signalling via the mitogen-activated protein kinase (MAPK) cascade and integrin signalling via the activation of focal adhesion kinase (FAK), which sustains the activation of extracellular signal-regulated kinases 1/2 (ERK1/2).Human CSPG4 is a type I transmembrane protein that is associated with the growth and progression of human brain tumours. It regulates cell signalling and migration by interacting with components of the extracellular matrix, extracellular ligands, growth factor receptors, intracellular enzymes and structural proteins. Its overexpression by tumour cells, perivascular cells and precursor/progenitor cells in gliomas suggests that it plays a role in their origin, progression and neo-angiogenesis and its aberrant expression in tumour cells may be a promising biomarker to monitor malignant progression and patient survival.The aim of this chapter is to review and discuss the role of CSPG4 in the TME of human gliomas, including its potential as a druggable therapeutic target.