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

GD2 Expression in Medulloblastoma and Neuroblastoma for Personalized Immunotherapy: A Matter of Subtype

Neuroblastoma (NBL) and medulloblastoma (MB) are aggressive pediatric cancers which can benefit from therapies targeting gangliosides. Therefore, we compared the ganglioside profile of 9 MB and 14 NBL samples by thin layer chromatography and mass spectrometry. NBL had the highest expression of GD2 (median 0.54 nmol GD2/mg protein), and also expressed complex gangliosides. GD2-low samples expressed GD1a and were more differentiated. MB mainly expressed GD2 (median 0.032 nmol GD2/mg protein) or GM3. Four sonic hedgehog-activated (SHH) as well as one group 4 and one group 3 MBs were GD2-positive. Two group 3 MB samples were GD2-negative but GM3-positive. N-glycolyl neuraminic acid-containing GM3 was neither detected in NBL nor MB by mass spectrometry. Furthermore, a GD2-phenotype predicting two-gene signature (ST8SIA1 and B4GALNT1) was applied to RNA-Seq datasets, including 86 MBs and validated by qRT-PCR. The signature values were decreased in group 3 and wingless-activated (WNT) compared to SHH and group 4 MBs. These results suggest that while NBL is GD2-positive, only some MB patients can benefit from a GD2-directed therapy. The expression of genes involved in the ganglioside synthesis may allow the identification of GD2-positive MBs. Finally, the ganglioside profile may reflect the differentiation status in NBL and could help to define MB subtypes.

Preliminary Analysis of the Glycolipid Profile in Secondary Brain Tumors

Glycosphingolipids (GSLs) play numerous roles in cellular processes, including cell proliferation, apoptosis, inflammation, and cell signaling. Alteration of the GSLs metabolism leads to the accumulation of particular species of GSLs, which can lead to various pathologies, including carcinogenesis and metastasis; in essence, all neoplasms are characterized by the synthesis and aberrant organization of GSLs expressed on the cell surface. Secondary brain tumors make up the majority of intracranial cancers and generally present an unfavorable prognosis. In the present work, a native GSL mixture extracted and purified from a secondary brain tumor with primary pulmonary origin was obtained through extraction and purification and analyzed by MALDI TOF mass spectrometry. Research in the field of lipidomics could offer new data for the understanding of brain tropism and metastatic pathways, by studying the glycolipid molecules involved in the process of metastasis in general and in the production of brain metastases in particular. This could shed new light on the pattern of lipid glycosylation in secondary brain tumors, with a great impact on the effectiveness of cancer therapies, which could be adapted to the specific molecular pattern of the tumor.

Key role of a structural water molecule for the specificity of 14F7-An antitumor antibody targeting the NeuGc GM3 ganglioside

Tumor-associated glycolipids such as NeuGc GM3 are auspicious molecular targets in antineoplastic therapies and vaccine strategies. 14F7 is a monoclonal IgG1 with high clinical potential in cancer immunotherapy as it displays extraordinary specificity for NeuGc GM3, while it does not recognize the very similar, ubiquitous NeuAc GM3. Here we present the 2.3 Å crystal structure of the 14F7 antigen-binding domain (14F7 scFv) in complex with the NeuGc GM3 trisaccharide. Modeling analysis and previous mutagenesis data suggest that 14F7 may also bind to an alternative NeuGc GM3 conformation, not observed in the crystal structure. The most intriguing finding, however, was that a water molecule centrally placed in the complementarity-determining region directly mediates the specificity of 14F7 to NeuGc GM3. This has profound impact on the complexity of engineering in the binding site and provides an excellent example of the importance in understanding the water structure in antibody-antigen interactions.

Prognostic Significance of Tumor Tissue NeuGcGM3 Ganglioside Expression in Patients Receiving Racotumomab Immunotherapy

Expression of N-glycolyl GM3 (NeuGcGM3) ganglioside was detected in the tumor specimens of patients who were on Racotumomab anti-idiotype vaccine maintenance treatment, and prognostic significance as a biomarker was investigated. No statistically significant association was observed in the multivariate analysis between overall survival and tissue NeuGcGM3 IHC levels. Although numerically there was a difference favoring less intense IHC for better prognosis, this did not reach statistical power. However, there was a strong correlation between Racotumomab doses and overall survival (OS). Mean OS of the patient with more than 10 Racotumomab application was significantly longer than the patient who had less than 10 injections (70.7 months vs. 31.1 months, p < 0.001). We propose that, regardless of staining intensity, the presence of NeuGcGM3 in patient tissues might be an indicator of benefit in Racotumomab treatment.

From "Serum Sickness" to "Xenosialitis": Past, Present, and Future Significance of the Non-human Sialic Acid Neu5Gc

The description of "serum sickness" more than a century ago in humans transfused with animal sera eventually led to identification of a class of human antibodies directed against glycans terminating in the common mammalian sialic acid N-Glycolylneuraminic acid (Neu5Gc), hereafter called "Neu5Gc-glycans." The detection of such glycans in malignant and fetal human tissues initially raised the possibility that it was an oncofetal antigen. However, "serum sickness" antibodies were also noted in various human disease states. These findings spurred further research on Neu5Gc, and the discovery that it is not synthesized in the human body due to a human-lineage specific genetic mutation in the enzyme CMAH. However, with more sensitive techniques Neu5Gc-glycans were detected in smaller quantities on certain human cell types, particularly epithelia and endothelia. The likely explanation is metabolic incorporation of Neu5Gc from dietary sources, especially red meat of mammalian origin. This incorporated Neu5Gc on glycans appears to be the first example of a "xeno-autoantigen," against which varying levels of "xeno-autoantibodies" are present in all humans. The resulting chronic inflammation or "xenosialitis" may have important implications in human health and disease, especially in conditions known to be aggravated by consumption of red meat. In this review, we will cover the early history of the discovery of "serum sickness" antibodies, the subsequent recognition that they were partly directed against Neu5Gc-glycans, the discovery of the genetic defect eliminating Neu5Gc production in humans, and the later recognition that this was not an oncofetal antigen but the first example of a "xeno-autoantigen." Further, we will present comments about implications for disease risks associated with red meat consumption such as cancer and atherosclerosis. We will also mention the potential utility of these anti-Neu5Gc-glycan antibodies in cancer immunotherapy and provide some suggestions and perspectives for the future. Other reviews in this special issue cover many other aspects of this unusual pathological process, for which there appears to be no other described precedent.

Gangliosides generalities and role in cancer therapies

Gangliosides are located in the plasma membrane; this confers them the ability to interact with other molecules in order to participate in important cellular processes. Some gangliosides presence or absence in the cell surface is associated with either normal condition or pathologies. Particularly in cancer, gangliosides play a critical role in pathological events like cellular malignancy, tumor formation, and metastasis, defining gangliosides as good candidates to be used as cellular markers. When specific gangliosides are exhibited, immunotherapy could be applied in order to inhibit tumorigenesis or induce an immunogenic response. Novel cancer treatments such as NGcGM3/VSSP vaccines, valproic acid, BMS-345541 inhibitor of GD2 and immunotherapies using 1E10 and 14F7 monoclonal antibodies are described. On this review, there will be studied the gangliosides that allowed developing biological techniques that can give immunogenicity to cancer cells

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.

Hypothesis: Hypoxia induces de novo synthesis of NeuGc gangliosides in humans through CMAH domain substitute

Immunotherapy is a growing field in cancer research. A privileged tumor-associated antigen that has received much attention is N-glycolyl (NeuGc) GM3. This ganglioside is present in several types of cancer, but is almost undetectable in human healthy tissues. However, its non-hydroxylated variant, NeuAc GM3, is abundant in all mammals. Due to a deletion in the human gene encoding the key enzyme for synthesis of NeuGc, humans, in contrast to other mammals, cannot synthesize NeuGc GM3. Therefore the presence of this ganglioside in human cancer cells represents an enigma. It has been shown that hypoxic conditions trigger the expression of NeuGc gangliosides, which not only serve as attractive targets for cancer therapy, but also as diagnostic and prognostic tumor marker. Here, we confirm hypoxia-induced expression of the NeuGc GM3 ganglioside also in HeLa cells and reveal several candidate proteins, in particular GM3 synthase and subunit B of respiratory complex II (SDHB), that may be involved in the generation of NeuGc GM3 by SILAC-based proteome analysis. These findings have the potential to significantly advance our understanding of how this enigmatic tumor-associated antigen is produced in humans, and also suggest a possible mechanism of action of anti-tumor antibodies that recognize hypoxia markers, such as 14F7.

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.

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.

Tissue Expression of Low and High Molecular Weight Cytokeratins in Lung Carcinoma Sections: Its Correlation with Some Clinic-Pathological Features

The tissue expression of low (LMW) and high (HMW) molecular weight cytokeratins and Ber-EP4 antigen in both small (SCLC) and non-small (NSCLC) cell lung carcinomas, as well as its correlation with a variety of clinic-pathological features, was evaluated. In general, 43/52 (82.7%) of NSCLC sections showed the expression of at least one type of cytokeratin while only 7/16 (43.7%) of SCLC were stained with both LMW cytokeratin and pan-cytokeratins antibodies. Remarkably, 18/52 (34.6%) of NSCLC were positive to both types of cytokeratins. However, none of SCLC showed this pattern of expression. In NSCLC patients, the increasing levels of HMW cytokeratins expression, as shown by 34βE12 antibody, correlated with the occurrence of disease recurrence (P=0.0057; Fisher’s exact test). Consequently, the expression of HMW cytokeratins was found to be associated with a poor 4-year overall survival of NSCLC patients (P=0.0315; Log rank test), not taking into account the histopathological classification of tumors. Similar results were obtained when 8-year overall survival was assessed (P=0.0103; Log rank test). Our results could suggest the assessment of HMW cytokeratins in a larger series of NSCLC samples in order to confirm the potential prognostic value of them.

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.

Sphingolipids: key regulators of apoptosis and pivotal players in cancer drug resistance

Drug resistance elicited by cancer cells still constitutes a huge problem that frequently impairs the efficacy of both conventional and novel molecular therapies. Chemotherapy usually acts to induce apoptosis in cancer cells; therefore, the investigation of apoptosis control and of the mechanisms used by cancer cells to evade apoptosis could be translated in an improvement of therapies. Among many tools acquired by cancer cells to this end, the de-regulated synthesis and metabolism of sphingolipids have been well documented. Sphingolipids are known to play many structural and signalling roles in cells, as they are involved in the control of growth, survival, adhesion, and motility. In particular, in order to increase survival, cancer cells: (a) counteract the accumulation of ceramide that is endowed with pro-apoptotic potential and is induced by many drugs; (b) increase the synthesis of sphingosine-1-phosphate and glucosylceramide that are pro-survivals signals; (c) modify the synthesis and the metabolism of complex glycosphingolipids, particularly increasing the levels of modified species of gangliosides such as 9-O acetylated GD3 (αNeu5Ac(2-8)αNeu5Ac(2-3)βGal(1-4)βGlc(1-1)Cer) or N-glycolyl GM3 (αNeu5Ac (2-3)βGal(1-4)βGlc(1-1)Cer) and de-N-acetyl GM3 (NeuNH(2)βGal(1-4)βGlc(1-1)Cer) endowed with anti-apoptotic roles and of globoside Gb3 related to a higher expression of the multidrug resistance gene MDR1. In light of this evidence, the employment of chemical or genetic approaches specifically targeting sphingolipid dysregulations appears a promising tool for the improvement of current chemotherapy efficacy.

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.

Immunoreactivity of the 14F7 Mab Raised against N-Glycolyl GM3 Ganglioside in Primary Lymphoid Tumors and Lymph Node Metastasis

The reactivity of the 14F7 Mab, a highly specific IgG1 against N-glycolyl GM3 ganglioside (NeuGcGM3) in normal tissues, lymphomas, lymph node metastasis, and other metastatic sites was assessed by immunohistochemistry. In addition, the effect of chemical fixation on the 14F7 Mab staining using monolayers of P3X63Ag.653 cells was also evaluated. Moreover, the ability of 14F7 to bind NeuGcGM3 ganglioside inducing complement-independent cytotoxicity by a flow cytometry-based assay was measured. The 14F7 Mab was reactive in unfixed, 4% paraformaldehyde, 4% formaldehyde, and acetone fixed cells. Postfixation with acetone did not alter the localization of NeuGcGM3, while the staining with 14F7 Mab was significantly eliminated in both cells fixed and postfixed with methanol but only partially reduced with ethanol. The staining with 14F7 Mab was evidenced in the 89.2%, 89.4%, and 88.9% of lymphomas, lymph node metastasis, and other metastatic sites, respectively, but not in normal tissues. The treatment with 14F7 Mab affected both morphology and membrane integrity of P3X63Ag.653 cells. This cytotoxic activity was dose-dependent and ranged from 24.0 to 84.7% (10-1000  μ g/mL) as compared to the negative control. Our data could support the possible use of NeuGcGM3 as target for both active and passive immunotherapy against malignancies expressing this molecule.

Anti-ganglioside antibodies induced in chickens by an alum-adsorbed anti-idiotype antibody targeting NeuGcGM3

Racotumomab is a murine anti-idiotype cancer vaccine targeting NeuGcGM3 on melanoma, breast, and lung cancer. In order to characterize the immunogenicity of alum-adsorbed racotumomab in a non-clinical setting, Leghorn chickens were immunized in dose levels ranging from 25 μg to 1600 μg. Racotumomab was administered subcutaneously in the birds' neck with three identical boosters and serum samples were collected before, during and after the immunization schedule. A strong antibody response was obtained across the evaluated dose range, confirming the immunogenicity of racotumomab even at dose levels as low as 25 μg. As previously observed when using Freund's adjuvant, alum-adsorbed racotumomab induced an idiotype-specific response in all the immunized birds and ganglioside-specific antibodies in 60–100% of the animals. In contrast to the rapid induction anti-idiotype response, detection of ganglioside-specific antibodies in responsive animals may require repeated boosting. Kinetics of anti-NeuGcGM3 antibody titers showed a slight decline 2 weeks after each booster, arguing in favor of repeated immunizations in order to maintain antibody titer. Interestingly, the intensity of the anti-NeuGcGM3 response paralleled that of anti-mucin antibodies and anti-tumor antibodies, suggesting that the in vitro detection of anti-ganglioside antibodies might be a surrogate for an in vivo activity of racotumomab. Taken together, these results suggest that Leghorn chicken immunization might become the means to test the biological activity of racotumomab intended for clinical use.

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.

Ganglioside biochemistry

Gangliosides are sialic acid-containing glycosphingolipids. They occur especially on the cellular surfaces of neuronal cells, where they form a complex pattern, but are also found in many other cell types. The paper provides a general overview on their structures, occurrence, and metabolism. Key functional, biochemical, and pathobiochemical aspects are summarized.

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.