Terminally sialylated and fucosylated complex N-glycans are involved in the malignant behavior of high-grade glioma.

Gliomas are the most common intracranial primary tumors, for which very few therapeutic options are available. The most malignant subtype is the glioblastoma, a disease associated with a 5-year survival rate lower than 5%. Given that research in glycobiology continues highlighting the role of glycans in tumor cell biology, it offers an interesting niche for the search of new therapeutic targets. In this study, we characterized aberrant glycosylation and its impact on cell biology over a broad panel of high- and low-grade glioma cell lines. Results show high expression of terminal Lewis glycans, mainly SLex, and overexpression of sialyl- and fucosyltransferases involved in their biosynthesis in high-grade glioma cell lines. Moreover, we report an association of complex multi-antennary N-glycans presenting ß1,6-GlcNAc branches with the high-grade glioma cells, which also overexpressed the gene responsible for these assemblies, MGAT5. In addition, downmodulation of N-glycosylation by treatment with the inhibitors Tunicamycin/Swainsonine or MGAT5 silencing decreased SLex expression, adhesion and migration in high-grade glioma cells. In contrast, no significant changes in these cell capacities were observed in low-grade glioma after treatment with the N-glycosylation inhibitors. Furthermore, inhibition of histone deacetylases by Trichostatin A provoked an increase in the expression of SLex and its biosynthetic related glycosyltransferases in low-grade glioma cells. Our results describe that aggressive glioma cells show high expression of Lewis glycans anchored to complex multi-antennary N-glycans. This glycophenotype plays a key role in malignant cell behavior and is regulated by histone acetylation dependent mechanisms.

Aberrant O-glycosylation modulates aggressiveness in neuroblastoma.

Neuroblastoma (NB) is the most common pediatric malignancy diagnosed before the first birthday in which MYCN oncogene amplification is associated with poor prognosis. Although aberrant glycosylation is an important actor in cell biology, little is known about its role in pediatric cancers such as NB. In this work we characterized the glycophenotype and the enzyme expression involved in glycans biosynthesis in five established human NB cell lines and in patient-derived primary tumors with different MYCN status. Our results show a high expression of Lewis glycan family both in MYCN-amplified cell lines and patient samples. Additionally, we report that MYCN-amplified cells overexpressed Core 2-initiating glycosyltransferase C2GNT1 in association with specific ST3Gals and FUTs, and showed increased binding to E- and P- selectins. Silencing of C2GNT1 expression in NB cells diminished expression of Lewis glycans, decreased the E- and P-selectin binding, and reduced cell adhesion, migration and proliferation in vitro. Treatment of MYCN-non-amplified cells with Trichostatin A (TSA), an histone deacetylase inhibitor, increased the expression of Lewis glycans and the enzymes involved in their biosynthesis. Our results demonstrate that MYCN-amplified NB cells overexpress Lewis family glycans, which belong to the Core 2 O-glycans group. Their expression plays a key role in the malignant behaviour of the NB cells and it is modulated by epigenetic mechanisms.

Antibody-dependent cell-mediated cytotoxicity induced by active immunotherapy based on racotumomab in non-small cell lung cancer patients.

Antitumor strategies based on positive modulation of the immune system currently represent therapeutic options with prominent acceptance for cancer patients' treatment due to its selectivity and higher tolerance compared to chemotherapy. Racotumomab is an anti-idiotype (anti-Id) monoclonal antibody (mAb) directed to NeuGc-containing gangliosides such as NeuGcGM3, a widely reported tumor-specific neoantigen in many human cancers. Racotumomab has been approved in Latin American countries as an active immunotherapy for advanced non-small cell lung cancer (NSCLC) treatment. In this work, we evaluated the induction of Ab-dependent cell-mediated cytotoxicity (ADCC) in NSCLC patients included in a phase III clinical trial, in response to vaccination with racotumomab. The development of anti-NeuGcGM3 antibodies (Abs) in serum samples of immunized patients was first evaluated using the NeuGcGM3-expressing X63 cells, showing that racotumomab vaccination developed antigen-specific Abs that are able to recognize NeuGcGM3 expressed in tumor cell membranes. ADCC response against NeuGcGM3-expressing X63 (target) was observed in racotumomab-treated- but not in control group patients. When target cells were depleted of gangliosides by treatment with a glucosylceramide synthase inhibitor, we observed a significant reduction of the ADCC activity developed by sera from racotumomab-vaccinated patients, suggesting a target-specific response. Our data demonstrate that anti-NeuGcGM3 Abs induced by racotumomab vaccination are able to mediate an antigen-specific ADCC response against tumor cells in NSCLC patients.

Comparability of Antibody-Mediated Cell Killing Activity Between a Proposed Biosimilar RTXM83 and the Originator Rituximab.

BACKGROUND: Biosimilars are described as biological products that resemble the structure of original biologic therapeutic products, with no clinically meaningful differences in terms of safety and effectiveness from the original. A wide range of biosimilars are under development or are already licensed in many countries. Biosimilars are earning acceptance and becoming a reality for immunotherapy treatments mainly based on the alternatives for the commercial anti-CD20 monoclonal antibody rituximab. The most important mechanism of action reported for this antibody is the induction of antibody-dependent cell cytotoxicity (ADCC), which is associated with the polymorphisms present at the 158 position in the IgG receptor FcγRIIIa. OBJECTIVE: The aim of the study was to validate the functional comparability between the proposed rituximab biosimilar RTXM83 and the original product. To achieve this we assessed the binding capacity and ADCC induction of this biosimilar, taking into account the different FcγRIIIa-158 polymorphisms. METHODS: Binding capacity was evaluated by flow cytometry using CD20 positive cells and a wide range of antibody concentrations. The FcγRIIIa-158 polymorphisms were analyzed by polymerase chain reaction (PCR) followed by allele-specific restriction enzyme digestion. ADCC was measured by a colorimetric lactate dehydrogenase-release assay, using effector cells from donors with different FcγRIIIa-158 polymorphisms. RESULTS: Binding capacity assay showed no differences between both products. Regarding ADCC, a similar relative potency was obtained between both antibodies, showing a higher response for the FcγRIIIa-158 valine/valine (V/V) polymorphism compared to the phenylalanine/phenylalanine (F/F), for both rituximab and RTXM83. CONCLUSION: Our data strongly suggest the biocomparability between the proposed biosimilar and the originator rituximab, in antibody recognition and ADCC activity. Additionally, our results suggest that donors with the FcγRIIIa-158V/V polymorphism induce a higher ADCC response, as has been reported.