Hypoxic culture induces expression of sialin, a sialic acid transporter, and cancer-associated gangliosides containing non-human sialic acid on human cancer cells

Selectin Ligands Sialyl-Lewis a and Sialyl-Lewis x in Gastrointestinal Cancers

The tetrasaccharide structures Siaα2,3Galβ1,3(Fucα1,4)GlcNAc and Siaα2,3Galβ1,4(Fucα1,3)GlcNAc constitute the epitopes of the carbohydrate antigens sialyl-Lewis a (sLe^a) and sialyl-Lewis x (sLe^x), respectively, and are the minimal requirement for selectin binding to their counter-receptors. Interaction of sLe^x expressed on the cell surface of leucocytes with E-selectin on endothelial cells allows their arrest and promotes their extravasation. Similarly, the rolling of cancer cells ectopically expressing the selectin ligands on endothelial cells is potentially a crucial step favoring the metastatic process. In this review, we focus on the biosynthetic steps giving rise to selectin ligand expression in cell lines and native tissues of gastrointestinal origin, trying to understand whether and how they are deregulated in cancer. We also discuss the use of such molecules in the diagnosis of gastrointestinal cancers, particularly in light of recent data questioning the ability of colon cancers to express sLe^a and the possible use of circulating sLe^x in the early detection of pancreatic cancer. Finally, we reviewed the data dealing with the mechanisms that link selectin ligand expression in gastrointestinal cells to cancer malignancy. This promising research field seems to require additional data on native patient tissues to reach more definitive conclusions.

Harnessing cancer cell metabolism for theranostic applications using metabolic glycoengineering of sialic acid in breast cancer as a pioneering example

Abnormal cell surface display of sialic acids - a family of unusual 9-carbon sugars - is widely recognized as distinguishing feature of many types of cancer. Sialoglycans, however, typically cannot be identified with sufficiently high reproducibility and sensitivity to serve as clinically accepted biomarkers and similarly, almost all efforts to exploit cancer-specific differences in sialylation signatures for therapy remain in early stage development. In this report we provide an overview of important facets of glycosylation that contribute to cancer in general with a focus on breast cancer as an example of malignant disease characterized by aberrant sialylation. We then describe how cancer cells experience nutrient deprivation during oncogenesis and discuss how the resulting metabolic reprogramming, which endows breast cancer cells with the ability to obtain nutrients during scarcity, constitutes an "Achilles' heel" that we believe can be exploited by metabolic glycoengineering (MGE) strategies to develop new diagnostic methods and therapeutic approaches. In particular, we hypothesize that adaptations made by breast cancer cells that allow them to efficiently scavenge sialic acid during times of nutrient deprivation renders them vulnerable to MGE, which refers to the use of exogenously-supplied, non-natural monosaccharide analogues to modulate targeted aspects of glycosylation in living cells and animals. In specific, once non-natural sialosides are incorporated into the cancer "sialome" they can be exploited as epitopes for immunotherapy or as chemical tags for targeted delivery of imaging or therapeutic agents selectively to tumors.

Detection of Naturally Occurring Human Antibodies Against Gangliosides by ELISA

Gangliosides are sialic acid-containing glycolipids that have been considered attractive targets for cancer immunotherapy, based on the qualitative and quantitative changes they suffer during malignant transformation and due to their importance for tumor biology. Natural antibodies against gangliosides have been detected not only in cancer patients but also in healthy donors. The presence of these antibodies can be used as diagnostic or prognostic factor. However, these responses are difficult to detect because anti-ganglioside antibodies are usually of IgM isotype and low affinity. Enzyme Linked Immunosorbent Assay (ELISA) is an immunoassay based on the specific binding of antibodies to antigens bound to a solid phase. These antigens can be glycolipids like gangliosides. An enzyme linked to the last reactant allows the detection of specific binding through the development of color after the addition of a suitable substrate. ELISA combines the specificity of antibodies with the sensitivity of enzyme reactions. The ELISA method described herein can be used to detect antibody responses against gangliosides not only related to cancer but also to autoimmune diseases and infections, both in healthy donors, and patients, untreated or receiving specific immunotherapy.

Epigenetic regulation of glycosylation and the impact on chemo-resistance in breast and ovarian cancer

Glycosylation is one of the most fundamental posttranslational modifications in cellular biology and has been shown to be epigenetically regulated. Understanding this process is important as epigenetic therapies such as those using DNA methyltransferase inhibitors are undergoing clinical trials for the treatment of ovarian and breast cancer. Previous work has demonstrated that altered glycosylation patterns are associated with aggressive disease in women presenting with breast and ovarian cancer. Moreover, the tumor microenvironment of hypoxia results in globally altered DNA methylation and is associated with aggressive cancer phenotypes and chemo-resistance, a feature integral to many cancers. There is sparse knowledge on the impact of these therapies on glycosylation. Moreover, little is known about the efficacy of DNA methyltransferase inhibitors in hypoxic tumors. In this review, we interrogate the impact that hypoxia and epigenetic regulation has on cancer cell glycosylation in relation to resultant tumor cell aggressiveness and chemo-resistance.

On the trail of the glycan codes stored in cancer-related cell adhesion proteins

Changes in the profile of protein glycosylation are a hallmark of ongoing neoplastic transformation. A unique set of tumor-associated carbohydrate antigens expressed on the surface of malignant cells may serve as powerful diagnostic and therapeutic targets. Cell-surface proteins with altered glycosylation affect the growth, proliferation and survival of those cells, and contribute to their acquisition of the ability to migrate and invade. They may also facilitate tumor-induced immunosuppression and the formation of distant metastases. Deciphering the information encoded in these particular glycan portions of glycoconjugates may shed light on the mechanisms of cancer progression and metastasis. A majority of the related review papers have focused on overall changes in the patterns of cell-surface glycans in various cancers, without pinpointing the molecular carriers of these glycan structures. The present review highlights the ways in which particular tumor-associated glycan(s) coupled with a given membrane-bound protein influence neoplastic cell behavior during the development and progression of cancer. We focus on altered glycosylated cell-adhesion molecules belonging to the cadherin, integrin and immunoglobulin-like superfamilies, examined in the context of molecular interactions.

CD45 Phosphatase Inhibits STAT3 Transcription Factor Activity in Myeloid Cells and Promotes Tumor-Associated Macrophage Differentiation

Recruitment of monocytic myeloid-derived suppressor cells (MDSCs) and differentiation of tumor-associated macrophages (TAMs) are the major factors contributing to tumor progression and metastasis. We demonstrated that differentiation of TAMs in tumor site from monocytic precursors was controlled by downregulation of the activity of the transcription factor STAT3. Decreased STAT3 activity was caused by hypoxia and affected all myeloid cells but was not observed in tumor cells. Upregulation of CD45 tyrosine phosphatase activity in MDSCs exposed to hypoxia in tumor site was responsible for downregulation of STAT3. This effect was mediated by the disruption of CD45 protein dimerization regulated by sialic acid. Thus, STAT3 has a unique function in the tumor environment in controlling the differentiation of MDSC into TAM, and its regulatory pathway could be a potential target for therapy.

Large-Scale Glycomics of Livestock: Discovery of Highly Sensitive Serum Biomarkers Indicating an Environmental Stress Affecting Immune Responses and Productivity of Holstein Dairy Cows

Because various stresses strongly influence the food productivity of livestock, biomarkers to indicate unmeasurable environmental stress in domestic animals are of increasing importance. Thermal comfort is one of the basic principles of dairy cow welfare that enhances productivity. To discover sensitive biomarkers that monitor such environmental stresses in dairy cows, we herein performed, for the first time, large-scale glycomics on 336 lactating Holstein cow serum samples over 9 months between February and October. Glycoblotting combined with MALDI-TOF/MS and DMB/HPLC allowed for comprehensive glycomics of whole serum glycoproteins. The results obtained revealed seasonal alterations in serum N-glycan levels and their structural characteristics, such as an increase in high-mannose type N-glycans in spring, the occurrence of di/triantennary complex type N-glycans terminating with two or three Neu5Gc residues in summer and autumn, and N-glycans in winter dominantly displaying Neu5Ac. A multivariate analysis revealed a correlation between the serum expression levels of these season-specific glycoforms and productivity.

A Phase I Study of the Anti-Idiotype Vaccine Racotumomab in Neuroblastoma and Other Pediatric Refractory Malignancies

BACKGROUND

Pediatric neuroectodermal malignancies express N-glycolylated gangliosides including N-glycolyl GM3 (NeuGcGM3) as targets for immunotherapy.

PROCEDURE

We evaluated the toxicity and maximum tolerated dose and immunological response of racotumomab, an anti-idiotype vaccine targeting NeuGcGM3 through a Phase I study enrolling children with relapsed or resistant tumors expressing NeuGcGM3.

MATERIALS AND METHODS

Drug dose was escalated to three levels (0.15-0.25-0.4 mg) of racotumomab administered intradermally. Each drug level included three patients receiving a total of three doses, every 14 days. A confirmation cohort was added to the highest dose level. Antibody response was assessed upon study entry and at 4-week intervals for at least three immunological determinations for each patient.

RESULTS

Fourteen patients were enrolled (10 with neuroblastoma, one with retinoblastoma, one with Wilms' tumor, and two with brainstem glioma). Three patients completed the three drug levels and three were enrolled in the confirmation cohort. One patient died of tumor progression before completing the three applications. Racotumomab was well tolerated. The only side effect observed was grade 1-2 toxicity at the injection site. Racotumomab elicited an IgM and/or IgG antibody response directed against NGcGM3 in nine patients and IgM against racotumomab in 11 of 13 evaluable patients. The maximum tolerated dose was not reached and no dose-limiting toxicity was seen.

CONCLUSIONS

Racotumomab vaccination has a favorable toxicity profile up to a dose of 0.4 mg, and most patients elicited an immune response. Its activity as immunotherapy for neuroectodermal malignancies will be tested in further clinical trials.

Prognostic Significance of N-Glycolyl GM3 Ganglioside Expression in Non-Small Cell Lung Carcinoma Patients: New Evidences

The prognostic role of N-glycolyl GM3 ganglioside (NeuGcGM3) expression in non-small cell lung carcinoma (NSCLC) still remains controversial. In this study, the NeuGcGM3 expression was reevaluated using an increased number of NSCLC cases and the 14F7 Mab (a highly specific IgG1 raised against NeuGcGM3). An immunohistochemical score integrating the percentage of 14F7-positive cells and the intensity of reaction was applied to reassess the relationship between NeuGcGM3 expression, some clinicopathological features, and the overall survival (OS) of NSCLC patients. The double and the triple expression of NeuGcGM3 with the epidermal growth factor receptor (EGFR) and/or its ligand, the epidermal growth factor (EGF), were also evaluated. NeuGcGM3 expression correlates with both S-Phase fraction (p = 0.006) and proliferation index (p = 0.000). Additionally, NeuGcGM3 expression was associated with a poor OS of patients in both univariate (p = 0.020) and multivariate (p = 0.010) analysis. Moreover, the double and/or the triple positivity of tumors to NeuGcGM3, EGFR, and/or EGF permitted us to identify phenotypes of NSCLC with a more aggressive biological behavior. Our results are in agreement with the negative prognostic significance of NeuGcGM3 expression in NSCLC patients. However, standardization of techniques to determine the expression of NeuGcGM3 in NSCLC as well as the implementation of a universal scoring system is recommended.

Pathobiological implications of mucin glycans in cancer: Sweet poison and novel targets

Mucins are large glycoproteins expressed on the epithelia that provide a protective barrier against harsh insults from toxins and pathogenic microbes. These glycoproteins are classified primarily as being secreted and membrane-bound; both forms are involved in pathophysiological functions including inflammation and cancer. The high molecular weight of mucins is attributed to their large polypeptide backbone that is extensively covered by glycan moieties that modulate the function of mucins and, hence, play an important role in physiological functions. Deregulation of glycosylation machinery during malignant transformation results in altered mucin glycosylation. This review describes the functional implications and pathobiological significance of altered mucin glycosylation in cancer. Further, this review delineates various factors such as glycosyltransferases and tumor microenvironment that contribute to dysregulation of mucin glycosylation during cancer. Finally, this review discusses the scope of mucin glycan epitopes as potential diagnostic and therapeutic targets.

Nutrient-deprived cancer cells preferentially use sialic acid to maintain cell surface glycosylation

Cancer is characterized by abnormal energy metabolism shaped by nutrient deprivation that malignant cells experience during various stages of tumor development. This study investigated the response of nutrient-deprived cancer cells and their non-malignant counterparts to sialic acid supplementation and found that cells utilize negligible amounts of this sugar for energy. Instead cells use sialic acid to maintain cell surface glycosylation through complementary mechanisms. First, levels of key metabolites (e.g., UDP-GlcNAc and CMP-Neu5Ac) required for glycan biosynthesis are maintained or enhanced upon Neu5Ac supplementation. In concert, sialyltransferase expression increased at both the mRNA and protein levels, which facilitated increased sialylation in biochemical assays that measure sialyltransferase activity as well as at the whole cell level. In the course of these experiments, several important differences emerged that differentiated the cancer cells from their normal counterparts including resistant to sialic acid-mediated energy depletion, consistently more robust sialic acid-mediated glycan display, and distinctive cell surface vs. internal vesicle display of newly-produced sialoglycans. Finally, the impact of sialic acid supplementation on specific markers implicated in cancer progression was demonstrated by measuring levels of expression and sialylation of EGFR1 and MUC1 as well as the corresponding function of sialic acid-supplemented cells in migration assays. These findings both provide fundamental insight into the biological basis of sialic acid supplementation of nutrient-deprived cancer cells and open the door to the development of diagnostic and prognostic tools.

Recombinant AAV-mediated in vivo long-term expression and antitumour activity of an anti-ganglioside GM3(Neu5Gc) antibody

The ganglioside GM3(Neu5Gc) has gained increasing attention as therapeutic target because of its selective expression in various human tumours, such as melanoma, breast and lung cancer. 14F7 is a mouse IgG1 with specific reactivity to GM3(Neu5Gc)-positive tumours. The therapeutic activity of 14F7 has also been demonstrated in vivo, through its repetitive passive administration in tumour-bearing animals. In this work we used an alternative strategy to deliver recombinant 14F7 in vivo and analysed the therapeutic efficacy of this approach. We engineered a recombinant adeno-associated vector to direct the expression of secretable recombinant 14F7 in BALB/c animals. A single administration of the rAAV induced efficient production and secretion of the antibody in the bloodstream, with an expression level reaching plateau at ∼3 weeks after injection and persisting for almost a year. Strikingly, upon challenge with GM3(Neu5Gc)-positive X63-AG8.653 myeloma cells, tumour development was significantly delayed in animals treated with rAAV-14F7 with respect to animals treated with a control rAAV codifying for an irrelevant antibody. Finally, no significant differences in survival proportion were detected in animals injected with rAAV-14F7 or treated by standard administration of repetitive doses of purified monoclonal antibody 14F7.

Cancer intelligence acquired (CIA): tumor glycosylation and sialylation codes dismantling antitumor defense

Aberrant glycosylation is a key feature of malignant transformation and reflects epigenetic and genetic anomalies among the multitude of molecules involved in glycan biosynthesis. Although glycan biosynthesis is not template bound, altered tumor glycosylation is not random, but associated with common glycosylation patterns. Evidence suggests that acquisition of distinct glycosylation patterns evolves from a 'microevolutionary' process conferring advantages in terms of tumor growth, tumor dissemination, and immune escape. Such glycosylation modifications also involve xeno- and hypersialylation. Xeno-autoantigens such as Neu5Gc-gangliosides provide potential targets for immunotherapy. Hypersialylation may display 'enhanced self' to escape immunosurveillance and involves several not mutually exclusive inhibitory pathways that all rely on protein-glycan interactions. A better understanding of tumor 'glycan codes' as deciphered by lectins, such as siglecs, selectins, C-type lectins and galectins, may lead to novel treatment strategies, not only in cancer, but also in autoimmune disease or transplantation.

Molecular recognition of gangliosides and their potential for cancer immunotherapies

Gangliosides are sialic-acid-containing glycosphingolipids expressed on all vertebrate cells. They are primarily positioned in the plasma membrane with the ceramide part anchored in the membrane and the glycan part exposed on the surface of the cell. These lipids have highly diverse structures, not the least with respect to their carbohydrate chains, with N-acetylneuraminic acid (NeuAc) and N-glycolylneuraminic acid (NeuGc) being the two most common sialic-acid residues in mammalian cells. Generally, human healthy tissue is deficient in NeuGc, but this molecule is expressed in tumors and in human fetal tissues, and was hence classified as an onco-fetal antigen. Gangliosides perform important functions through carbohydrate-specific interactions with proteins, for example, as receptors in cell–cell recognition, which can be exploited by viruses and other pathogens, and also by regulating signaling proteins, such as the epidermal growth factor receptor (EGFR) and the vascular endothelial growth factor receptor (VEGFR), through lateral interaction in the membrane. Through both mechanisms, tumor-associated gangliosides may affect malignant progression, which makes them attractive targets for cancer immunotherapies. In this review, we describe how proteins recognize gangliosides, focusing on the molecular recognition of gangliosides associated with cancer immunotherapy, and discuss the importance of these molecules in cancer research.

Pilot study of a novel combination of two therapeutic vaccines in advanced non-small-cell lung cancer patients

Cancer vaccines contain tumor antigens in a pro-inflammatory context with the purpose to generate potent antitumor immune responses. However, tumor cells develop different immunosuppressive mechanisms that limit the effectiveness of an anticancer immune response. Therefore, therapeutic vaccine treatment alone is usually not sufficient to generate tumor regression or survival improvement, especially in the advanced disease scenario in which most clinical studies have been conducted. Combining cancer vaccines with different anticancer therapies such as chemotherapy, radiotherapy and other immunotherapeutic agents has had different levels of success. However, the combination of cancer vaccines with different mechanisms of action has not been explored in clinical trials. To address this issue, the current review summarizes the main clinical and immunological results obtained with two different therapeutic vaccines used in advanced non-small-cell lung cancer patients, inducing an immune response against epidermal growth factor (CIMAvax-EGF) and NGcGM3 ganglioside (racotumomab). We also discuss preliminary findings obtained in a trial of combination of these two vaccines and future challenges with these therapies.

A randomized, multicenter, placebo-controlled clinical trial of racotumomab-alum vaccine as switch maintenance therapy in advanced non-small cell lung cancer patients

PURPOSE

Racotumomab-alum is an anti-idiotype vaccine targeting the NeuGcGM3 tumor-associated ganglioside. This clinical trial was conducted to provide a preliminary estimate of efficacy and safety of racotumomab as switch maintenance for patients with advanced non-small cell lung cancer (NSCLC).

EXPERIMENTAL DESIGN

Patients with stage IIIb/IV NSCLC who have at least stable disease after first-line chemotherapy were randomized 1:1 to racotumomab-alum (5 immunizations every 2 weeks and re-immunizations every 4 weeks) or placebo. Treatment was administered beyond progressive disease, until severe performance status worsening or toxicity. At progression, only five patients per group received further anticancer therapy. The primary endpoint was overall survival (OS).

RESULTS

One-hundred and seventy-six patients were randomized to racotumomab-alum (n = 87) and placebo (n = 89). Median OS was 8.23 and 6.80 months, respectively [HR, 0.63; 95% confidence interval (CI), 0.46-0.87; P = 0.004]. Median progression-free survival (PFS) in vaccinated patients was 5.33 versus 3.90 months for placebo (HR, 0.73; 95% CI 0.53-0.99; P = 0.039). The most common adverse events in the racotumomab-alum arm were burning and pain at the injection site, bone pain, and asthenia. A high antibody response of IgM and IgG isotype against the NeuGcGM3 ganglioside was obtained. Hyperimmune sera were able to specifically recognize and kill the NeuGcGM3-expressing L1210 cell line. Patients who developed anti-NeuGcGM3 antibodies capable to bind and kill ≥30% L1210 cells showed longer median survival times.

CONCLUSIONS

Switch maintenance with racotumomab-alum is an effective and a well-tolerated treatment option for patients with advanced NSCLC.

Involvement of a non-human sialic Acid in human cancer

Sialic acids are common monosaccharides that are widely expressed as outer terminal units on all vertebrate cell surfaces, and play fundamental roles in cell–cell and cell–microenvironment interactions. The predominant sialic acids on most mammalian cells are N-glycolylneuraminic acid (Neu5Gc) and N-acetylneuraminic acid (Neu5Ac). Neu5Gc is notable for its deficiency in humans due to a species-specific and species-universal inactivating deletion in the CMAH gene encoding the hydroxylase that converts CMP-Neu5Ac to CMP-Neu5Gc. However, Neu5Gc is metabolically incorporated into human tissues from dietary sources (particularly red meat), and detected at even higher levels in some human cancers. Early life exposure to Neu5Gc-containing foods in the presence of certain commensal bacteria that incorporate dietary Neu5Gc into lipooligosaccharides can lead to generation of antibodies that are also cross-reactive against Neu5Gc-containing glycans in human tissues (“xeno-autoantigens”). Such anti-Neu5Gc “xeno-autoantibodies” are found in all humans, although ranging widely in levels among individuals, and displaying diverse and variable specificities for the underlying glycan. Experimental evidence in a human-like Neu5Gc-deficient Cmah^−/−mouse model shows that inflammation due to “xenosialitis” caused by this antigen–antibody interaction can promote tumor progression, suggesting a likely mechanism for the well-known epidemiological link between red meat consumption and carcinoma risk. In this review, we discuss the history of this field, mechanisms of Neu5Gc incorporation into tissues, the origin and specificities of human anti-Neu5Gc antibodies, their use as possible cancer biomarkers, implications of xenosialitis in cancer initiation and progression, and current and future approaches toward immunotherapy that could take advantage of this unusual human-specific phenomenon.

Prognostic Role of 14F7 Mab Immunoreactivity against N-Glycolyl GM3 Ganglioside in Colon Cancer

Purpose. To assess the prognostic role of 14F7 Mab immunoreactivity, against N-Glycolyl GM3 ganglioside, in patients with colon cancer (CC) and to evaluate the relationship between its expression and clinicopathological features. Methods. Paraffin-embedded specimens were retrospectively collected from 50 patients with CC operated between 2004 and 2008. 14F7 Mab staining was determined by immunohistochemistry technique and its relation with survival and clinicopathologic features was evaluated. Results. The reactivity of 14F7 Mab was detected in all cases. Most cases had high level of immunostaining (70%) that showed statistical correlation with TNM stage (P = 0.025). In univariate survival analysis, level of 14F7 Mab immunoreactivity (P = 0.0078), TNM Stage (P = 0.0007) and lymphovascular invasion (0.027) were significant prognostic factors for overall survival. Among these variables, level of 14F7 Mab immunoreactivity (HR = 0.268; 95% CI  0.078–0.920; P = 0.036) and TNM stage (HR = 0.249; 95% CI 0.066–0.932; P = 0.039) were independent prognostic factors on multivariate analysis. Conclusions. This study is the first approach on the prognostic significance of 14F7 Mab immunoreactivity in patients with colon adenocarcinoma and this assessment might be used in the prognostic estimate of CC, although further studies will be required to validate these findings.

Hypoxia reduces the efficiency of elisidepsin by inhibiting hydroxylation and altering the structure of lipid rafts

The mechanism of action of elisidepsin (PM02734, Irvalec^®) is assumed to involve membrane permeabilization via attacking lipid rafts and hydroxylated lipids. Here we investigate the role of hypoxia in the mechanism of action of elisidepsin. Culturing under hypoxic conditions increased the half-maximal inhibitory concentration and decreased the drug’s binding to almost all cell lines which was reversed by incubation of cells with 2-hydroxy palmitic acid. The expression of fatty acid 2-hydroxylase was strongly correlated with the efficiency of the drug and inversely correlated with the effect of hypoxia. Number and brightness analysis and fluorescence anisotropy experiments showed that hypoxia decreased the clustering of lipid rafts and altered the structure of the plasma membrane. Although the binding of elisidepsin to the membrane is non-cooperative, its membrane permeabilizing effect is characterized by a Hill coefficient of ~3.3. The latter finding is in agreement with elisidepsin-induced clusters of lipid raft-anchored GFP visualized by confocal microscopy. We propose that the concentration of elisidepsin needs to reach a critical level in the membrane above which elisidepsin induces the disruption of the cell membrane. Testing for tumor hypoxia or the density of hydroxylated lipids could be an interesting strategy to increase the efficiency of elisidepsin.

Increasing the α 2, 6 sialylation of glycoproteins may contribute to metastatic spread and therapeutic resistance in colorectal cancer

Abnormal glycosylation due to dysregulated glycosyltransferases and glycosidases is a key phenomenon of many malignancies, including colorectal cancer (CRC). In particular, increased ST6 Gal I (β-galactoside α 2, 6 sialyltransferase) and subsequently elevated levels of cell-surface α 2, 6-linked sialic acids have been associated with metastasis and therapeutic failure in CRC. As many CRC patients experience metastasis to the liver or lung and fail to respond to curative therapies, intensive research efforts have sought to identify the molecular changes underlying CRC metastasis. ST6 Gal I has been shown to facilitate CRC metastasis, and we believe that additional investigations into the involvement of ST6 Gal I in CRC could facilitate the development of new diagnostic and therapeutic targets. This review summarizes how ST6 Gal I has been implicated in the altered expression of sialylated glycoproteins, which have been linked to CRC metastasis, radioresistance, and chemoresistance.

SLC17: a functionally diverse family of organic anion transporters

Molecular studies have determined that the SLC17 transporters, a family of nine proteins initially implicated in phosphate transport, mediate the transport of organic anions. While their role in phosphate transport remains uncertain, it is now clear that the transport of organic anions facilitated by this family of proteins is involved in diverse processes ranging from the vesicular storage of the neurotransmitters, to urate metabolism, to the degradation and metabolism of glycoproteins.

Hypoxia alters ocular drug transporter expression and activity in rat and calf models: implications for drug delivery

Chronic hypoxia, a key stimulus for neovascularization, has been implicated in the pathology of proliferative diabetic retinopathy, retinopathy of prematurity, and wet age related macular degeneration. The aim of the present study was to determine the effect of chronic hypoxia on drug transporter mRNA expression and activity in ocular barriers. Sprague-Dawley rats were exposed to hypobaric hypoxia (PB = 380 mmHg) for 6 weeks, and neonatal calves were maintained under hypobaric hypoxia (PB = 445 mmHg) for 2 weeks. Age matched controls for rats, and calves were maintained at ambient altitude and normoxia. The effect of hypoxia on transporter expression was analyzed by qRT-PCR analysis of transporter mRNA expression in hypoxic and control rat choroid-retina. The effect of hypoxia on the activity of PEPT, OCT, ATB(0+), and MCT transporters was evaluated using in vitro transport studies of model transporter substrates across calf cornea and sclera-choroid-RPE (SCRPE). Quantitative gene expression analysis of 84 transporters in rat choroid-retina showed that 29 transporter genes were up regulated or down regulated by ≥1.5-fold in hypoxia. Nine ATP binding cassette (ABC) families of efflux transporters including MRP3, MRP4, MRP5, MRP6, MRP7, Abca17, Abc2, Abc3, and RGD1562128 were up-regulated. For solute carrier family transporters, 11 transporters including SLC10a1, SLC16a3, SLC22a7, SLC22a8, SLC29a1, SLC29a2, SLC2a1, SLC3a2, SLC5a4, SLC7a11, and SLC7a4 were up regulated, while 4 transporters including SLC22a2, SLC22a9, SLC28a1, and SLC7a9 were down-regulated in hypoxia. Of the three aquaporin (Aqp) water channels, Aqp-9 was down-regulated, and Aqp-1 was up-regulated during hypoxia. Gene expression analysis showed down regulation of OCT-1, OCT-2, and ATB(0+) and up regulation of MCT-3 in hypoxic rat choroid-retina, without any effect on the expression of PEPT-1 and PEPT-2. Functional activity assays of PEPT, OCT, ATB(0+), and MCT transporters in calf ocular tissues showed that PEPT, OCT, and ATB(0+) functional activity was down-regulated, whereas MCT functional activity was up-regulated in hypoxic cornea and SCRPE. Gene expression analysis of these transporters in rat tissues was consistent with the functional transport assays except for PEPT transporters. Chronic hypoxia results in significant alterations in the mRNA expression and functional activity of solute transporters in ocular tissues.

Human antibodies reactive to NeuGcGM3 ganglioside have cytotoxic antitumor properties

N-glycolylated gangliosides are not naturally expressed in healthy human tissues but are overexpressed in several tumors. We demonstrate the existence of antibodies that bind (N-glycolylneuraminyl)-lactosylceramide (NeuGcGM3) and are detectable in the sera of 65 from the 100 donors (65%) tested by ELISA. From those 65 NeuGcGM3 antibody-positive donors, 35 had antibodies that were able to recognize and kill NeuGcGM3-expressing tumor cells by a complement-mediated mechanism. After complement inactivation, 11 of the 35 positive sera showed a direct cytotoxic effect on the tumor cells. This complement-independent cytotoxicity was dependent on the presence of antigen on the membrane and resembles an oncotic necrosis cell death. Both the levels of anti-NeuGcGM3 antibodies in the sera as well as the percentage of healthy donors with this immunity decreased with the age of the donor. In contrast to age and gender-matched healthy donors, we could only detect low reactivity against NeuGcGM3 in the sera of six out of 53 non-small cell lung cancer patients. These results suggest the existence of antibodies against NeuGcGM3 with antitumor immune surveillance functions, reinforcing the importance of N-glycolylated gangliosides as antitumor targets.

Implications on glycobiological aspects of tumor hypoxia in breast ductal carcinoma in situ

Breast carcinoma is one of the most common neoplasia and the first cause of women cancer related deaths worldwide. In the past few years with diagnostic increment, the number of patients diagnosed with ductal carcinoma in situ (DCIS) increased considerably and opened up new ways in research and new dilemmas in diagnostic and clinical practice. This work aimed to evaluate differences in Galectin-1 and Galectin-3 expression and lectins ligands profile on DCIS cells in hypoxic microenvironment. Lectin histochemistry and immunohistochemistry were performed with Concanavalin A, Wheat Germ Agglutinin, Peanut Agglutinin and Ulex europaeus Agglutinin lectins and with anti-Galectin-1 and anti-Galectin-3 antibodies. Lectin ligands were more recognized in hypoxic lesions by Concanavalin A (p = 0.0019), Wheat Germ Agglutinin (p < 0.001) and Ulex europaeus Agglutinin (p = 0.0014), but not by Peanut Agglutinin (p = 0.5779) when compared to non-hypoxic. Galectin-1 was not observed in all cases analyzed on both groups, differing from Galectin-3 that was overexpressed on cytoplasm of DCIS hypoxic group in relation to control group (p = 0.031). As far as we are concerned, this is the first paper that describes glycobiological alterations in breast cancer hypoxic environment in vivo that could be used to validate in vitro models on this aspect. Moreover, comedogenic/necrotic carcinomas were usually associated with poor-prognostic than others, and our results show that glycosylation may play an important role in this event.

Tissue Reactivity of the 14F7 Mab Raised against N-Glycolyl GM3 Ganglioside in Tumors of Neuroectodermal, Mesodermal, and Epithelial Origin

The expression of N-glycolylneuraminic acid forming the structure of gangliosides and/or other glycoconjugates (Hanganutziu-Deicher antigen) in human has been considered as a tumor-associated antigen. Specifically, some reports of 14F7 Mab (a highly specific Mab raised against N-glycolyl GM3 ganglioside) reactivity in human tumors have been recently published. Nevertheless, tumors of epithelial origin have been mostly evaluated. The goal of the present paper was to evaluate the immunohistochemical recognition of 14F7 Mab in different human tumors of neuroectodermal, mesodermal, and epithelial origins using an immunoperoxidase staining method. Samples of fetal, normal, and reactive astrocytosis of the brain were also included in the study. In general, nontumoral tissues, as well as, low-grade brain tumors showed no or a limited immunoreaction with 14F7 Mab. Nevertheless, high-grade astrocytomas (III-IV) and neuroblastomas, as well as, sarcomas and thyroid carcinomas were mostly reactive with 14F7. No reaction was evidenced in medulloblastomas and ependymoblastomas. Our data suggest that the expression of N-glycolyl GM3 ganglioside could be related to the aggressive behavior of malignant cells, without depending on the tumor origin. Our data could also support the possible use of N-glycolyl GM3 as a target for both active and passive immunotherapies of malignancies expressing this molecule.

Anti-ganglioside anti-idiotypic vaccination: more than molecular mimicry

Surgery, chemotherapy, and radiation therapy are standard modalities for cancer treatment, but the effectiveness of these treatments has reached a plateau. Thus, other strategies are being explored to combine with the current treatment paradigms in order to reach better clinical results. One of these approaches is the active immunotherapy based on the induction of anti-tumor responses by anti-idiotypic vaccination. This approach arose from Jerne’s idiotypic network theory, which postulates that B lymphocytes forms a functional network, with a role in the establishment of the immune repertoires, in the regulation of natural antibody production and even in the establishment of natural tolerance. Due to the large potential diversity of the immunoglobulin variable regions, the idiotypes repertoire can mimic the universe of self and foreign epitopes, even those of non-protein nature, like gangliosides. Gangliosides are sialic acid-containing glycolipids that have been considered attractive targets for cancer immunotherapy, based on the qualitative and quantitative changes they suffer during malignant transformation and due to their importance for tumor biology. Although any idiotype could be able to mimic any antigen, only those related to antigens involved in functions relevant for organism homeostasis, and that in consequence has been fixed by evolution, would be able not only to mimic, but also to activate the idiotypic cascades related with the nominal antigen. The present review updates the results, failures and hopes, obtained with ganglioside mimicking anti-idiotypic antibodies and presents evidences of the existence of a natural response against gangliosides, suggesting that these glycolipids could be idiotypically relevant antigens.

Preclinical evaluation of racotumomab, an anti-idiotype monoclonal antibody to N-glycolyl-containing gangliosides, with or without chemotherapy in a mouse model of non-small cell lung cancer

N-glycolylneuraminic acid (NeuGc) is a sialic acid molecule usually found in mammalian cells as terminal constituents of different membrane glycoconjugates such as gangliosides. The NeuGcGM3 ganglioside has been described as a tumor antigen for non-small cell lung cancer (NSCLC) in humans. Racotumomab is an anti-NeuGc-containing gangliosides anti-idiotype monoclonal antibody (mAb) (formerly known as 1E10) that has received attention as a potential active immunotherapy for advanced lung cancer in clinical trials. In this work, we have examined the antitumor activity of racotumomab in combination or not with chemotherapy, using the 3LL Lewis lung carcinoma as a preclinical model of NSCLC in C57BL/6 mice. Vaccination with biweekly doses of racotumomab at 50-200 μg/dose formulated in aluminum hydroxide (racotumomab-alum vaccine) demonstrated a significant antitumor effect against the progression of lung tumor nodules. Racotumomab-alum vaccination exerted a comparable effect on lung disease to that of pemetrexed-based chemotherapy (100 mg/kg weekly). Interestingly, chemo-immunotherapy was highly effective against lung nodules and well-tolerated, although no significant synergistic effect was observed as compared to each treatment alone in the present model. We also obtained evidence on the role of the exogenous incorporation of NeuGc in the metastatic potential of 3LL cells. Our preclinical data provide support for the combination of chemotherapy with the anti-idiotype mAb racotumomab, and also reinforce the biological significance of NeuGc in lung cancer.

Detection of N-glycolyated gangliosides in non-small-cell lung cancer using GMR8 monoclonal antibody

Gangliosides are glycosphingolipids found on the cell surface. They act as recognition molecules or signal modulators and regulate cell proliferation and differentiation. N-glycolylneuraminic acid (NeuGc)-containing gangliosides have been detected in some neoplasms in humans, although they are usually absent in normal human tissues. Our aim was to evaluate the presence of NeuGc-containing gangliosides including GM3 (NeuGc) and assess their relationship with the prognosis of non-small-cell lung cancer (NSCLC). NeuGc-containing ganglioside expression in NSCLC tissues was analyzed immunohistochemically using the mouse monoclonal antibody GMR8, which is specific for gangliosides with NeuGc alpha 2,3Gal-terminal structures. On the basis of NeuGc-containing ganglioside expression, we performed survival analysis. We also investigated the differences in the effects of GM3 (N-acetylneuraminic acid [NeuAc]) and GM3 (NeuGc) on inhibition of epidermal growth factor receptor (EGFR) tyrosine kinase in A431 cells. As a result, the presence of NeuGc-containing gangliosides was evident in 86 of 93 (93.5%) NSCLC samples. The NSCLC patients with high NeuGc-containing ganglioside expression had a low overall survival rate and a significantly low progression-free survival rate. In the in vitro study, the inhibitory effect of GM3 on EGFR tyrosine kinase in A431 cells after exposure to GM3 (NeuGc) was lower than that after exposure to GM3 (NeuAc). In conclusion, NeuGc-containing gangliosides including GM3 (NeuGc) are widely expressed in NSCLC, and NeuGc-containing ganglioside expression is associated with patient survival. The difference in the effects of GM3 (NeuGc) and GM3 (NeuAc) on the inhibition of EGFR tyrosine kinase might contribute to improvement in the prognosis of NSCLC patients.

Racotumomab: an anti-idiotype vaccine related to N-glycolyl-containing gangliosides - preclinical and clinical data

Neu-glycolyl (NeuGc)-containing gangliosides are attractive targets for immunotherapy with anti-idiotype mAbs, because these glycolipids are not normal components of the cytoplasmic membrane in humans, but their expression has been demonstrated in several human malignant tumors. Racotumomab is an anti-idiotype mAb specific to P3 mAb, an antibody which reacts to NeuGc-containing gangliosides, sulfatides, and other antigens expressed in tumors. Preparations containing racotumomab were able to induce a strong anti-metastatic effect in tumor-bearing mice. Different Phase I clinical trials have been conducted in patients with advanced melanoma, breast cancer, and lung cancer. The results of these clinical trials demonstrated the low toxicity and the high immunogenicity of this vaccine. The induced antibodies recognized and directly killed tumor cells expressing NeuGcGM3. A Phase II/III multicenter, controlled, randomized, double blind clinical trial was conducted to evaluate the effect of aluminum hydroxide-precipitated racotumomab vaccine in overall survival in patients with advanced non-small cell lung cancer. The clinical results of this study showed a significant clinical benefit in the patients who were treated with the anti-idiotype vaccine.

Metabolism of vertebrate amino sugars with N-glycolyl groups: elucidating the intracellular fate of the non-human sialic acid N-glycolylneuraminic acid

The two major mammalian sialic acids are N-acetylneuraminic acid and N-glycolylneuraminic acid (Neu5Gc). The only known biosynthetic pathway generating Neu5Gc is the conversion of CMP-N-acetylneuraminic acid into CMP-Neu5Gc, which is catalyzed by the CMP-Neu5Ac hydroxylase enzyme. Given the irreversible nature of this reaction, there must be pathways for elimination or degradation of Neu5Gc, which would allow animal cells to adjust Neu5Gc levels to their needs. Although humans are incapable of synthesizing Neu5Gc due to an inactivated CMAH gene, exogenous Neu5Gc from dietary sources can be metabolically incorporated into tissues in the face of an anti-Neu5Gc antibody response. However, the metabolic turnover of Neu5Gc, which apparently prevents human cells from continued accumulation of this immunoreactive sialic acid, has not yet been elucidated. In this study, we show that pre-loaded Neu5Gc is eliminated from human cells over time, and we propose a conceivable Neu5Gc-degrading pathway based on the well studied metabolism of N-acetylhexosamines. We demonstrate that murine tissue cytosolic extracts harbor the enzymatic machinery to sequentially convert Neu5Gc into N-glycolylmannosamine, N-glycolylglucosamine, and N-glycolylglucosamine 6-phosphate, whereupon irreversible de-N-glycolylation of the latter results in the ubiquitous metabolites glycolate and glucosamine 6-phosphate. We substantiate this finding by demonstrating activity of recombinant human enzymes in vitro and by studying the fate of radiolabeled pathway intermediates in cultured human cells, suggesting that this pathway likely occurs in vivo. Finally, we demonstrate that the proposed degradative pathway is partially reversible, showing that N-glycolylmannosamine and N-glycolylglucosamine (but not glycolate) can serve as precursors for biosynthesis of endogenous Neu5Gc.

Metabolism of vertebrate amino sugars with N-glycolyl groups: mechanisms underlying gastrointestinal incorporation of the non-human sialic acid xeno-autoantigen N-glycolylneuraminic acid

Although N-acetyl groups are common in nature, N-glycolyl groups are rare. Mammals express two major sialic acids, N-acetylneuraminic acid and N-glycolylneuraminic acid (Neu5Gc). Although humans cannot produce Neu5Gc, it is detected in the epithelial lining of hollow organs, endothelial lining of the vasculature, fetal tissues, and carcinomas. This unexpected expression is hypothesized to result via metabolic incorporation of Neu5Gc from mammalian foods. This accumulation has relevance for diseases associated with such nutrients, via interaction with Neu5Gc-specific antibodies. Little is known about how ingested sialic acids in general and Neu5Gc in particular are metabolized in the gastrointestinal tract. We studied the gastrointestinal and systemic fate of Neu5Gc-containing glycoproteins (Neu5Gc-glycoproteins) or free Neu5Gc in the Neu5Gc-free Cmah(-/-) mouse model. Ingested free Neu5Gc showed rapid absorption into the circulation and urinary excretion. In contrast, ingestion of Neu5Gc-glycoproteins led to Neu5Gc incorporation into the small intestinal wall, appearance in circulation at a steady-state level for several hours, and metabolic incorporation into multiple peripheral tissue glycoproteins and glycolipids, thus conclusively proving that Neu5Gc can be metabolically incorporated from food. Feeding Neu5Gc-glycoproteins but not free Neu5Gc mimics the human condition, causing tissue incorporation into human-like sites in Cmah(-/-) fetal and adult tissues, as well as developing tumors. Thus, glycoproteins containing glycosidically linked Neu5Gc are the likely dietary source for human tissue accumulation, and not the free monosaccharide. This human-like model can be used to elucidate specific mechanisms of Neu5Gc delivery from the gut to tissues, as well as general mechanisms of metabolism of ingested sialic acids.

L1CAM from human melanoma carries a novel type of N-glycan with Galβ1-4Galβ1- motif. Involvement of N-linked glycans in migratory and invasive behaviour of melanoma cells

Dramatic changes in glycan biosynthesis during oncogenic transformation result in the emergence of marker glycans on the cell surface. We analysed the N-linked glycans of L1CAM from different stages of melanoma progression, using high-performance liquid chromatography combined with exoglycosidase sequencing, matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry, and lectin probes. L1CAM oligosaccharides are heavily sialylated, mainly digalactosylated, biantennary complex-type structures with galactose β1-4/3-linked to GlcNAc and with or without fucose α1-3/6-linked to GlcNAc. Hybrid, bisected hybrid, bisected triantennary and tetraantennary complex oligosaccharides, and β1-6-branched complex-type glycans with or without lactosamine extensions are expresses at lower abundance. We found that metastatic L1CAM possesses only α2-6-linked sialic acid and the loss of α2-3-linked sialic acid in L1CAM is a phenomenon observed during the transition of melanoma cells from VGP to a metastatic stage. Unexpectedly, we found a novel monoantennary complex-type oligosaccharide with a Galβ1-4Galβ1- epitope capped with sialic acid residues A1[3]G(4)2S2-3. To our knowledge this is the first report documenting the presence of this oligosaccharide in human cancer. The novel and unique N-glycan should be recognised as a new class of human melanoma marker. In functional tests we demonstrated that the presence of cell surface α2-3-linked sialic acid facilitates the migratory behaviour and increases the invasiveness of primary melanoma cells, and it enhances the motility of metastatic cells. The presence of cell surface α2-6-linked sialic acid enhances the invasive potential of both primary and metastatic melanoma cells. Complex-type oligosaccharides in L1CAM enhance the invasiveness of metastatic melanoma cells.

Recent advances in developing synthetic carbohydrate-based vaccines for cancer immunotherapies

Cancer cells can often be distinguished from healthy cells by the expression of unique carbohydrate sequences decorating the cell surface as a result of aberrant glycosyltransferase activity occurring within the cell; these unusual carbohydrates can be used as valuable immunological targets in modern vaccine designs to raise carbohydrate-specific antibodies. Many tumor antigens (e.g., GM2, Ley, globo H, sialyl Tn and TF) have been identified to date in a variety of cancers. Unfortunately, carbohydrates alone evoke poor immunogenicity, owing to their lack of ability in inducing T-cell-dependent immune responses. In order to enhance their immunogenicity and promote long-lasting immune responses, carbohydrates are often chemically modified to link to an immunogenic protein or peptide fragment for eliciting T-cell-dependent responses. This review will present a summary of efforts and advancements made to date on creating carbohydrate-based anticancer vaccines, and will include novel approaches to overcoming the poor immunogenicity of carbohydrate-based vaccines.

Immunoreactivity of the 14F7 Mab (Raised against N-Glycolyl GM3 Ganglioside) as a Positive Prognostic Factor in Non-Small-Cell Lung Cancer

Lung carcinoma is the leading cause of cancer-related mortality worldwide. Therefore, numerous studies are focusing on the assessment of other biological and molecular prognostic factors in these tumors. We evaluated the relationship between 14F7 Mab reactivity, pathological features, DNA-content and S-phase fraction (SPF), and their impact in the survival of NSCLC patients. Hematoxylin and eosin staining and immunohistochemistry optical microscopy assays as well as DNA content and SPF measuring using flow cytometry were performed. The 14F7 reactivity was widely observed in NSCLC sections, no depending of the clinicopathological characteristics. We also obtained differences in the intensity of reaction with 14F7 as well as in the SPF between diploid and aneuploid carcinomas. Patients with diploid tumors showing higher SPF and 14F7 reaction joint to a low mitotic index displayed higher survival rates. Our results are in agreement with the assumption of the possible positive prognostic value of 14F7 staining in NSCLC.

Detection of N-glycolyl GM3 ganglioside in neuroectodermal tumors by immunohistochemistry: an attractive vaccine target for aggressive pediatric cancer

The N-glycolylated ganglioside NeuGc-GM3 has been described in solid tumors such as breast carcinoma, nonsmall cell lung cancer, and melanoma, but is usually not detected in normal human cells. Our aim was to evaluate the presence of NeuGc-GM3 in pediatric neuroectodermal tumors by immunohistochemistry. Twenty-seven archival cases of neuroblastoma and Ewing sarcoma family of tumors (ESFT) were analyzed. Formalin-fixed, paraffin-embedded tumor samples were cut into 5 μm sections. The monoclonal antibody 14F7, a mouse IgG1 that specifically recognizes NeuGc-GM3, and a peroxidase-labeled polymer conjugated to secondary antibodies were used. Presence of NeuGc-GM3 was evident in 23 of 27 cases (85%), with an average of about 70% of positive tumors cells. Immunoreactivity was moderate to intense in most tumors, showing a diffuse cytoplasmic and membranous staining, although cases of ESFT demonstrated a fine granular cytoplasmic pattern. No significant differences were observed between neuroblastoma with and without NMYC oncogene amplification, suggesting that expression of NeuGc-GM3 is preserved in more aggressive cancers. Until now, the expression of N-glycolylated gangliosides in pediatric neuroectodermal tumors has not been investigated. The present study evidenced the expression of NeuGc-GM3 in a high proportion of neuroectodermal tumors, suggesting its potential utility as a specific target of immunotherapy.

Immunohistochemical Reactivity of the 14F7 Monoclonal Antibody Raised against N-Glycolyl GM3 Ganglioside in Some Benign and Malignant Skin Neoplasms

The evaluation of 14F7 Mab (anti-N-glycolyl GM3 ganglioside) immunorecognition in normal skin, cutaneous malignant melanoma (CMM), and in lymph node metastases (LNM) has been previously reported. In this work we extended the study to benign (BMN) and dysplastic (DMN) melanocytic nevi, basal (BCC), and squamous cell carcinoma (SCC). Immunohistochemical assays with 14F7 followed by a biotinylated link universal and streptavidin-AP in normal and pathological tissues were made. No reaction of 14F7 in normal skin (0/10) as well as a low reactivity in BMN (2/11) and DMN (1/7) was detected. A limited staining in BCC (2/13) and in SCC (4/8) was also evidenced, while 14F7 Mab were mostly reactive in CMM (28/28) and in LNM (6/7). These results suggest that 14F7 reactivity could be closely related with the more aggressive biological behavior of CMM and also support the use of NeuGcGM3 as target for both passive and active melanoma immunotherapy.

Anti-NeuGcGM3 antibodies, actively elicited by idiotypic vaccination in nonsmall cell lung cancer patients, induce tumor cell death by an oncosis-like mechanism

1E10 is a murine anti-idiotypic mAb specific for an idiotypic mAb that reacts with NeuGc-containing gangliosides, sulfatides, and Ags expressed in some human tumors. In melanoma, breast, and lung cancer patients, this anti-idiotypic Ab was able to induce a specific Ab response against N-glycosylated gangliosides, attractive targets for cancer immunotherapy as these glycolipids are not naturally expressed in humans. A clinical study with nonsmall cell lung cancer patients showed encouraging clinical benefits. Immunological studies performed in 20 of these patients suggested a correlation between the induction of Abs against NeuGcGM3 and longer survival times. The induced anti-NeuGcGM3 Abs recognized and directly killed tumor cells expressing the Ag, by a mechanism independent of complement activation. In the present work, we show that this cytotoxicity differs from apoptosis because it is temperature independent, no chromatin condensation or caspase 3 induction are detected, and the DNA fragmentation induced has a different pattern than the one characteristic for apoptosis. It is a very quick process and involves cytosqeleton reorganization. The Abs induce cellular swelling and the formation of big membrane lesions that allow the leakage of cytoplasm and the loss of the cell membrane integrity. All of these characteristics resemble a process of oncotic necrosis. To our knowledge, this is the first report of the active induction in cancer patients of NeuGcGM3-specific Abs able to induce complement independent oncotic necrosis to tumor cells. These results contribute to reinforcing the therapeutic potential of anti-idiotypic vaccines and the importance of NeuGcGM3 ganglioside as antitumor target.