Increased levels of gangliosides in the plasma and ascitic fluid of patients with advanced ovarian cancer

Serum Lipidome Profiling Reveals a Distinct Signature of Ovarian Cancer in Korean Women

BACKGROUND

Distinguishing ovarian cancer from other gynecological malignancies is crucial for patient survival yet hindered by non-specific symptoms and limited understanding of ovarian cancer pathogenesis. Accumulating evidence suggests a link between ovarian cancer and deregulated lipid metabolism. Most studies have small sample sizes, especially for early-stage cases, and lack racial/ethnic diversity, necessitating more inclusive research for improved ovarian cancer diagnosis and prevention.

METHODS

Here, we profiled the serum lipidome of 208 ovarian cancer, including 93 early-stage patients with ovarian cancer and 117 nonovarian cancer (other gynecological malignancies) patients of Korean descent. Serum samples were analyzed with a high-coverage liquid chromatography high-resolution mass spectrometry platform, and lipidome alterations were investigated via statistical and machine learning (ML) approaches.

RESULTS

We found that lipidome alterations unique to ovarian cancer were present in Korean women as early as when the cancer is localized, and those changes increase in magnitude as the diseases progresses. Analysis of relative lipid abundances revealed specific patterns for various lipid classes, with most classes showing decreased abundance in ovarian cancer in comparison with other gynecological diseases. ML methods selected a panel of 17 lipids that discriminated ovarian cancer from nonovarian cancer cases with an AUC value of 0.85 for an independent test set.

CONCLUSIONS

This study provides a systemic analysis of lipidome alterations in human ovarian cancer, specifically in Korean women.

IMPACT

Here, we show the potential of circulating lipids in distinguishing ovarian cancer from nonovarian cancer conditions.

Ganglioside analysis in body fluids by liquid-phase separation techniques hyphenated to mass spectrometry

The expression of gangliosides in central nervous system is a few times higher than in the extraneural tissue, a characteristic highlighting their major role at this level. Although in very low amounts, gangliosides are ubiquitously distributed in body fluids too, where, depending on many factors, including pathological states, their composition fluctuates, thus having diagnostic value. Ganglioside investigation in biological fluids, which, except for cerebrospinal fluid (CSF), may be sampled noninvasively, was for years impeded by the limited sensitivity of the analytical instrumentation available in glycomics. However, because the last decade has witnessed significant developments in biological mass spectrometry (MS) and the hyphenated separation techniques, marked by a major increase in sensitivity, reproducibility, and data reliability, ganglioside research started to be focused on biofluid analysis by separation techniques coupled to MS. In this context, our review presents the achievements in this emerging field of gangliosidomics, with a particular emphasis on modern liquid chromatography (LC), thin-layer chromatography, hydrophilic interaction LC, and ion mobility separation coupled to high-performance MS, as well as the results generated by these systems and allied experimental procedures in profiling and structural analysis of gangliosides in healthy or diseased body fluids, such as CSF, plasma/serum, and milk.

GD2 and GD3 gangliosides as diagnostic biomarkers for all stages and subtypes of epithelial ovarian cancer

Background

Ovarian cancer (OC) is the deadliest gynecological cancer, often diagnosed at advanced stages. A fast and accurate diagnostic method for early-stage OC is needed. The tumor marker gangliosides, GD2 and GD3, exhibit properties that make them ideal potential diagnostic biomarkers, but they have never before been quantified in OC. We investigated the diagnostic utility of GD2 and GD3 for diagnosis of all subtypes and stages of OC.

Methods

This retrospective study evaluated GD2 and GD3 expression in biobanked tissue and serum samples from patients with invasive epithelial OC, healthy donors, non-malignant gynecological conditions, and other cancers. GD2 and GD3 levels were evaluated in tissue samples by immunohistochemistry (n=299) and in two cohorts of serum samples by quantitative ELISA. A discovery cohort (n=379) showed feasibility of GD2 and GD3 quantitative ELISA for diagnosing OC, and a subsequent model cohort (n=200) was used to train and cross-validate a diagnostic model.

Results

GD2 and GD3 were expressed in tissues of all OC subtypes and FIGO stages but not in surrounding healthy tissue or other controls. In serum, GD2 and GD3 were elevated in patients with OC. A diagnostic model that included serum levels of GD2+GD3+age was superior to the standard of care (CA125, p<0.001) in diagnosing OC and early-stage (I/II) OC.

Conclusion

GD2 and GD3 expression was associated with high rates of selectivity and specificity for OC. A diagnostic model combining GD2 and GD3 quantification in serum had diagnostic power for all subtypes and all stages of OC, including early stage. Further research exploring the utility of GD2 and GD3 for diagnosis of OC is warranted.

Molecular, cellular and systemic aspects of epithelial ovarian cancer and its tumor microenvironment

Ovarian cancer encompasses a heterogeneous group of malignancies that involve the ovaries, fallopian tubes and the peritoneal cavity. Despite major advances made within the field of cancer, the majority of patients with ovarian cancer are still being diagnosed at an advanced stage of the disease due to lack of effective screening tools. The overall survival of these patients has, therefore, not substantially improved over the past decades. Most patients undergo debulking surgery and treatment with chemotherapy, but often micrometastases remain and acquire resistance to the therapy, eventually leading to disease recurrence. Here, we summarize the current knowledge in epithelial ovarian cancer development and metastatic progression. For the most common subtypes, we focus further on the properties and functions of the immunosuppressive tumor microenvironment, including the extracellular matrix. Current and future treatment modalities are discussed and finally we provide an overview of the different experimental models used to develop novel therapies.

The clinical role of glycobiology on ovarian cancer progression

Diverse carbohydrate (glycan) structures are located on lipids and proteins that cover the surface of human cells known as the glycocalyx. Research over many decades have illustrated that the glycan structures located in the glycocalyx change dramatically with cancer contributing to the early development and progression of tumors. New therapeutic and diagnostic applications for cancers based on targeting glycan changes are now in development and in early stage clinical trials. There is an abundance of research for ovarian cancer indicating that certain glycoproteins and glycolipids play major roles in the progression, recurrence, and chemoresistance of this disease. This review is focused on discussion of these biomarkers and how translational medicine for ovarian cancer can be further defined focusing on targeting glycans, glycoproteins, and glycan-mediated interactions.

Glycosphingolipids are mediators of cancer plasticity through independent signaling pathways

The molecular repertoire promoting cancer cell plasticity is not fully elucidated. Here, we propose that glycosphingolipids (GSLs), specifically the globo and ganglio series, correlate and promote the transition between epithelial and mesenchymal cells. The epithelial character of ovarian cancer remains stable throughout disease progression, and spatial glycosphingolipidomics reveals elevated globosides in the tumor compartment compared with the ganglioside-rich stroma. CRISPR-Cas9 knockin mediated truncation of endogenous E-cadherin induces epithelial-to-mesenchymal transition (EMT) and decreases globosides. The transcriptomics analysis identifies the ganglioside-synthesizing enzyme ST8SIA1 to be consistently elevated in mesenchymal-like samples, predicting poor outcome. Subsequent deletion of ST8SIA1 induces epithelial cell features through mTOR^S2448 phosphorylation, whereas loss of globosides in ΔA4GALT cells, resulting in EMT, is accompanied by increased ERK^Y202/T204 and AKT^S124. The GSL composition dynamics corroborate cancer cell plasticity, and further evidence suggests that mesenchymal cells are maintained through ganglioside-dependent, calcium-mediated mechanisms.

Sphingolipids as multifaceted mediators in ovarian cancer

Ovarian cancer is the most lethal gynaecological malignancy. It is commonly diagnosed at advanced stage when it has metastasised to the abdominal cavity and treatment becomes very challenging. While current standard therapy involving debulking surgery and platinum + taxane-based chemotherapy is associated with high response rates initially, the large majority of patients relapse and ultimately succumb to chemotherapy-resistant disease. In order to improve survival novel strategies for early detection and therapeutics against treatment-refractory disease are urgently needed. A promising new target against ovarian cancer is the sphingolipid pathway which is commonly hijacked in cancer to support cell proliferation and survival and has been shown to promote chemoresistance and metastasis in a wide range of malignant neoplasms. In particular, the sphingosine kinase 1-sphingosine 1-phosphate receptor 1 axis has been shown to be altered in ovarian cancer in multiple ways and therefore represents an attractive therapeutic target. Here we review the roles of sphingolipids in ovarian cancer progression, metastasis and chemoresistance, highlighting novel strategies to target this pathway that represent potential avenues to improve patient survival.

Sialic Acid-Dependent Inhibition of T Cells by Exosomal Ganglioside GD3 in Ovarian Tumor Microenvironments

The tumor microenvironment is rendered immunosuppressive by a variety of cellular and acellular factors that represent potential cancer therapeutic targets. Although exosomes isolated from ovarian tumor ascites fluids have been previously reported to induce a rapid and reversible T cell arrest, the factors present on or within exosomes that contribute to immunosuppression have not been fully defined. In this study, we establish that GD3, a ganglioside expressed on the surface of exosomes isolated from human ovarian tumor ascites fluids, is causally linked to the functional arrest of T cells activated through their TCR. This arrest is inhibited by Ab blockade of exosomal GD3 or by the removal of GD3⁺ exosomes. Empty liposomes expressing GD3 on the surface also inhibit the activation of T cells, establishing that GD3 contributes to the functional arrest of T cells independent of factors present in exosomes. Finally, we demonstrate that the GD3-mediated arrest of the TCR activation is dependent upon sialic acid groups, because their enzymatic removal from exosomes or liposomes results in a loss of inhibitory capacity. Collectively, these data define GD3 as a potential immunotherapeutic target.

Ovarian cancer and the immune system - The role of targeted therapies

The majority of patients with epithelial ovarian cancer are diagnosed with advanced disease. While many of these patients will respond initially to chemotherapy, the majority will relapse and die of their disease. Targeted therapies that block or activate specific intracellular signaling pathways have been disappointing. In the past 15years, the role of the immune system in ovarian cancer has been investigated. Patients with a more robust immune response, as documented by the presence of lymphocytes infiltrating within their tumor, have increased survival and better response to chemotherapy. In addition, a strong immunosuppressive environment often accompanies ovarian cancer. Recent research has identified potential therapies that leverage the immune system to identify and destroy tumor cells that previously evaded immunosurveillance mechanisms. In this review, we discuss the role of the immune system in ovarian cancer and focus on specific pathways and molecules that show a potential for targeted therapy. We also review the ongoing clinical trials using targeted immunotherapy in ovarian cancer. The role of targeted immunotherapy in patients with ovarian cancer represents a field of growing research and clinical importance.

Challenges and future perspectives of T cell immunotherapy in cancer

Since the formulation of the tumour immunosurveillance theory, considerable focus has been on enhancing the effectiveness of host antitumour immunity, particularly with respect to T cells. A cancer evades or alters the host immune response by various ways to ensure its development and survival. These include modifications of the immune cell metabolism and T cell signalling. An inhibitory cytokine milieu in the tumour microenvironment also leads to immune suppression and tumour progression within a host. This review traces the development in the field and attempts to summarize the hurdles that the approach of adoptive T cell immunotherapy against cancer faces, and discusses the conditions that must be improved to allow effective eradication of cancer.

Sialic acids: biomarkers in endocrinal cancers

Sialylations are post translational modification of proteins and lipids that play important role in recognition, signaling, immunological response and cell-cell interaction. Improper sialylations due to altered sialyl transferases, sialidases, gene structure and expression, sialic acid metabolism however lead to diseases and thus sialic acids form an important biomarker in disease. In the endocrinal biology such improper sialylations including altered expression of sialylated moieties have been shown to be associated with disorders. Cancer still remains to be the major cause of global death and the cancer of the endocrine organs suffer from the dearth of appropriate markers for disease prediction at the early stage and monitoring. This review is aimed at evaluating the role of sialic acids as markers in endocrinal disorders with special reference to cancer of the endocrine organs. The current study is summarized under the following headings of altered sialylations in endocrinal cancer of the (i) ovary (ii) pancreas (iii) thyroid (iv) adrenal and (v) pituitary gland. Studies in expression of sialic acid in testis cancer are limited. The future scope of this review remains in the targeting of endocrinal cancer by targeting altered sialylation which is a common expression associated with endocrinal cancer.

Tumor-associated glycans and their role in gynecological cancers: accelerating translational research by novel high-throughput approaches

Glycans are important partners in many biological processes, including carcinogenesis. The rapidly developing field of functional glycomics becomes one of the frontiers of biology and biomedicine. Aberrant glycosylation of proteins and lipids occurs commonly during malignant transformation and leads to the expression of specific tumor-associated glycans. The appearance of aberrant glycans on carcinoma cells is typically associated with grade, invasion, metastasis and overall poor prognosis. Cancer-associated carbohydrates are mostly located on the surface of cancer cells and are therefore potential diagnostic biomarkers. Currently, there is increasing interest in cancer-associated aberrant glycosylation, with growing numbers of characteristic cancer targets being detected every day. Breast and ovarian cancer are the most common and lethal malignancies in women, respectively, and potential glycan biomarkers hold promise for early detection and targeted therapies. However, the acceleration of research and comprehensive multi-target investigation of cancer-specific glycans could only be successfully achieved with the help of a combination of novel high-throughput glycomic approaches.

Molecular identification of GD3 as a suppressor of the innate immune response in ovarian cancer

Tumors often display mechanisms to avoid or suppress immune recognition. One such mechanism is the shedding of gangliosides into the local tumor microenvironment, and a high concentration of circulating gangliosides is associated with poor prognosis. In this study, we identify ganglioside GD3, which was isolated from the polar lipid fraction of ovarian cancer-associated ascites, as an inhibitory factor that prevents innate immune activation of natural killer T (NKT) cells. Purified GD3 displayed a high affinity for both human and mouse CD1d, a molecule involved in the presentation of lipid antigens to T cells. Purified GD3, as well as substances within the ascites, bound to the CD1d antigenic-binding site and did not require additional processing for its inhibitory effect on NKT cells. Importantly, in vivo administration of GD3 inhibited α-galactosylceramide (α-GalCer)-induced NKT cell activation in a dose-dependent manner. These data therefore indicate that ovarian cancer tumors may use GD3 to inhibit the antitumor NKT cell response as an early mechanism of tumor immune evasion.

Tissue micro array analysis of ganglioside N-glycolyl GM3 expression and signal transducer and activator of transcription (STAT)-3 activation in relation to dendritic cell infiltration and microvessel density in non-small cell lung cancer

BACKGROUND

Tumor immune escape and angiogenesis contribute to tumor progression, and gangliosides and activation of signal transducer and activator of transcription (STAT)-3 are implicated in these processes. As both are considered as novel therapeutic targets, we assessed the possible association of ganglioside GM3 expression and STAT3 activation with suppression of dendritic cell (DC) activation and angiogenesis in non-small cell lung cancer (NSCLC).

METHODS

Immunohistochemistry was performed on a tissue array to determine N-glycolyl GM3 (GM3) and phosphorylated STAT3 (pSTAT3) expression in 176 primary NSCLC resections. Median values of GM3 and pSTAT3 expression were used as cut off. Microvessel density (MVD) was determined by CD34 staining and morphology. CD1a and CD83 were used to determine infiltrating immature and mature dendritic cells, respectively.

RESULTS

94% and 71% of the NSCLC samples expressed GM3 and nuclear pSTAT3, respectively. Median overall survival was 40.0 months. Both low GM3 expression and high pSTAT3 expression were associated with a worse survival, which reached near significance for GM3 (P = 0.08). Microvessel density (MVD), determined by CD34 staining and morphology, was lower in NSCLC samples with high GM3 expression. CD1a+ cells (immature DCs) were more frequent in NSCLC tissues as compared to peritumoral lung tissue, while CD83+ cells (mature DCs) were more frequent in peritumoral lung tissue. CD83+ DCs were less frequent in NSCLC tissues with high GM3 expression.

CONCLUSION

GM3 and pSTAT3 are widely expressed in NSCLC. Based on CD83 expression, GM3, but not pSTAT3, appeared to be involved in tumor-induced DC suppression. pSTAT3 expression was not associated with MVD, while GM3 might play an anti-angiogenic role.

Ascites specific inhibition of CD1d-mediated activation of natural killer T cells

PURPOSE

Natural killer T (NKT) cells recognize lipid antigen presented by CD1 molecules. NKT cells can both directly, through cytotoxicity, and indirectly, through activation of other effector cells, mediate antitumor immunity. It has been shown, however, that tumor-associated lipids are frequently shed into the tumor microenvironment, which can mediate immunosuppressive activity. Given that ovarian cancer-associated ascites has been reported to have increased levels of gangliosides, we examined the effect of tumor-associated and other ascites on CD1d-mediated antigen presentation to NKT cells.

EXPERIMENTAL DESIGN

To investigate the effects of ascites on NKT cell activation, we pretreated CD1d-expressing cells with the ascites and measured their ability to stimulate cytokine production in NKT cells. To determine whether antigen processing or editing was necessary, CD1d-immunoglobulin-based artificial antigen presenting cells (aAPC) were also incubated with ascites. In addition, to examine specificity, we analyzed whether ascites fluid could influence the activation of classic CD8+ T cells.

RESULTS

Pretreatment of CD1d-expressing cells with ascites from the majority of patients inhibited the ability of the cells to stimulate/activate NKT cells in a dose-dependent manner. Ascites treatment also partially blocked the ability of alpha-galactosylceramide-loaded CD1d-immunoglobulin-based aAPC to activate NKT cells. In addition, our data show that treatment with ascites does not inhibit HLA-A2-mediated activation of classic CD8+ T cells.

CONCLUSIONS

Together, these data suggest that ovarian and other cancers may have developed immune evasion mechanisms specifically targeting the CD1/NKT cell system.

The immunoregulatory effects of gangliosides involve immune deviation favoring type-2 T cell responses

Gangliosides, sialic acid-containing glycosphingolipids present in most cell membranes, are thought to participate in the maintenance of immune privilege and tumor-induced immunosuppression. However, the mechanisms responsible for their immunomodulatory activity remain poorly understood. The purpose of this study was to investigate whether gangliosides are able to modulate the balance of type-1/type-2 T cell responses and to characterize the cellular mechanisms involved. The effects of different gangliosides on anti-CD3-stimulated murine splenocytes and purified T cells were studied. The presence of gangliosides during T cell activation reduced the expression of interferon-gamma (IFN-gamma) and enhanced that of interleukin (IL)-4, suggesting a shift toward a type-2 response. Intracellular cytokine staining demonstrated that gangliosides inhibited IFN-gamma production in CD4+, CD8+, and natural killer (NK)1.1+ cell populations and enhanced IL-4 in CD4+ T cells. The ganglioside-mediated enhancement in IL-4 production was independent of changes in endogenous IFN-gamma, did not occur with cells from CD1d-deficient mice, and was partially inhibited by anti-CD1d antibodies. The inhibitory effects on IFN-gamma were independent of endogenous IL-4 or the presence of NKT cells and were unaffected by anti-CD1d antibodies. These results suggest that gangliosides may modify the immunological environment by promoting immune deviation in favor of type-2 T cell responses.