Gangliosides as targets for immunotherapy for pancreatic adenocarcinoma

BR2 cell penetrating peptide effectively delivers anti-p21Ras scFv to tumor cells with ganglioside expression for therapy of ras-driven tumor

Purpose

Cell membrane penetrating peptide BR2 can bind with ganglioside and introduce foreign drugs into tumor cells. In this study, we employed BR2 to carry the broad-spectrum anti-p21Ras scFv prepared in our laboratory into ganglioside expressing tumor cells for therapy of ras-driven tumors.

Methods

BR2-p21Ras scFv gene was cloned to prokaryotic expression vector and expressed in E. coli BL21, then the fusion protein was purified with HisPur Ni-NTA. The immunoreactivity of the fusion protein with p21Ras was detected by ELISA and western blotting. The membrane-penetrating and immune co-localization with p21Ras of the fusion protein were determined by immunofluorescence. The antitumor activity was investigated using MTT, wound healing, colone formation, and apoptosis assays in vitro.

Results

BR2-p21Ras scFv fusion protein was successfully expressed and purified. We found that the fusion protein could specifically penetrate into human tumor cell lines which express ganglioside including human neuroblastoma cell line SK-N-SH, human colon cancer cell line HCT116 and human glioma cell line U251. After entering tumor cells the fusion protein bonded specifically with p21Ras. In vitro experiments revealed that it could significantly inhibit the proliferation, migration, and colone formation of HCT116, SK-N-SH, and U251 cells and promote the apoptosis of these tumor cells.

Conclusions

BR2-p21Ras scFv can penetrate ganglioside expressing tumor cells and inhibit the growth of ras-driven tumor by binding with p21Ras, and producing an inhibitory effect. It is suggested that BR2-p21Ras scFv is a potential ras-driven tumor therapeutic antibody.

Correlation between metabolomic profile constituents and feline pancreatic lipase immunoreactivity

Background

Feline pancreatic lipase immunoreactivity (fPLI) is commonly used to diagnose pancreatitis in cats (FP). Untargeted metabolomics has been extensively applied in human and veterinary medicine, but no metabolomic studies regarding FP have been conducted.

Objectives

To identify metabolites significantly associated with increased fPLI.

Animals

Forty‐nine client‐owned cats: 11 clinically healthy and 38 with various clinical conditions.

Methods

Analytical cross‐sectional study with convenience sampling. A panel of 630 metabolites belonging to 26 biochemical classes was quantified in plasma using a commercial metabolomic assay. The correlation between plasma metabolite concentrations and serum fPLI was evaluated using Spearman's rank correlation coefficient (R_s) with Bonferroni correction. Multivariable analysis then was performed to control for glomerular filtration rate, liver damage, and blood glucose concentration. The accuracy of selected metabolites in discriminating between cats with normal (≤3.5 μg/L) and increased (>5.3 μg/L) fPLI was estimated using the area under the receiver operating characteristic curve (AUROC).

Results

Four hundred and seven of 630 metabolites (64.6%) were quantified in all cats. When controlled for potential confounders only 3 sphingolipids were significantly positively correlated with fPLI: 2 cerebrosides: HexCer(d18:1/24:0); (R_s = .56), and HexCer(d18:1/24:1); (R_s = .58) and 1 sphingomyelin: SM C18:0 (R_s = .55). Their AUROCs in identifying cats with increased fPLI were 82% (95% confidence interval [CI 95%], 70%‐94%), 84% (CI 95%, 72%‐96%), and 78% (CI 95%, 65%‐92%), respectively.

Conclusions and Clinical Importance

Selected sphingolipids are moderately positively correlated with fPLI and appear to have fair to moderate diagnostic accuracy in discriminating between cats with normal and increased fPLI.

Generation and characterization of a IgG monoclonal antibody specific for GM3 (NeuGc) ganglioside by immunizing β3Gn-T5 knockout mice

A murine monoclonal antibody (MAb-1) specific for GM3 has been generated by immunizing β3Gn-T5 knockout mice with purified GM3 ganglioside. The binding specificity of MAb-1 (IgG₃ subclass) was established by an enzyme-linked immunosorbent assay (ELISA) and FACS and the antibody showed high binding specificity with GM3. Cell viability assay showed that MAb-1 significantly suppressed cell growth. Immunohistochemistry analysis revealed that MAb-1 was strongly expressed in human ovarian cancer tissues, whereas it was hardly expressed in normal tissues. Finally, antibody-dependent cellular cytotoxicity (ADCC) activities were determined by measuring lactate dehydrogenase (LDH) releasing assay and the results showed high ADCC activities in two representative ovarian cancer cell lines (OVHM and ID8). All of these data indicate that MAb-1 may be potentially used as a therapeutic antibody against ovarian cancers in clinical trials.

Mammalian sialyltransferase ST3Gal-II: its exchange sialylation catalytic properties allow labeling of sialyl residues in mucin-type sialylated glycoproteins and specific gangliosides

While glycosyltransferases are known to display unidirectional enzymatic activity, recent studies suggest that some can also catalyze readily reversible reactions. Recently, we found that mammalian sialyltransferase ST3Gal-II can catalyze the formation of CMP-NeuAc from 5'-CMP in the presence of a donor containing the NeuAcα2,3Galβ1,3GalNAc unit [Chandrasekaran, E. V., et al. (2008) Biochemistry 47, 320-330]. This study shows by using [9-(3)H]- or [(14)C]sialyl mucin core 2 compounds that ST3Gal-II exchanges sialyl residues between CMP-NeuAc and the NeuAcα2,3Galβ1,3GalNAc unit and also radiolabels sialyl residues in gangliosides GD1a and GT1b, but not GM1. Exchange sialylation proceeds with relative ease, which is evident from the following. (a) Radiolabeleling of fetuin was ~2-fold stronger than that of asialo fetuin when CMP- [9-(3)H]NeuAc was generated in situ from 5'-CMP and [9-(3)H]NeuAcα2,3Galβ1,3GalNAcβ1,3Galα-O-Me by ST3Gal-II. (b) ST3Gal-II exchanged radiolabels between [(14)C]sialyl fetuin and [9-(3)H]NeuAcα2,3Galβ1,3GalNAcβ1,3Galα-O-Me by generating CMP-[(14)C]- and -[9-(3)H]NeuAc through 5'-CMP; only 20.3% (14)C and 28.0% (3)H remained with the parent compounds after the sialyl exchange. The [9-(3)H]sialyl-tagged MN glycophorin A, human chorionic gonadotropin β subunit, GlyCAM-1, CD43, fetuin, porcine Cowper's gland mucin, bovine casein macroglycopeptide, human placental glycoproteins, and haptoglobin were analyzed by using Pronase digestion, mild alkaline borohydride treatment, Biogel P6, lectin agarose, and silica gel thin layer chromatography. Sulfated and sialylated O-glycans were found in GlyCAM-1 and human placental glycoproteins. This technique has the potential to serve as an important tool as it provides a natural tag for the chemical and functional characterization of O-glycan-bearing glycoproteins.

Shiga toxin receptor Gb3Cer/CD77: tumor-association and promising therapeutic target in pancreas and colon cancer

BACKGROUND

Despite progress in adjuvant chemotherapy in the recent decades, pancreatic and colon cancers remain common causes of death worldwide. Bacterial toxins, which specifically bind to cell surface-exposed glycosphingolipids, are a potential novel therapy. We determined the expression of globotriaosylceramide (Gb3Cer/CD77), the Shiga toxin receptor, in human pancreatic and colon adenocarcinomas.

METHODOLOGY/PRINCIPAL FINDINGS

Tissue lipid extracts of matched pairs of cancerous and adjacent normal tissue from 21 pancreatic and 16 colon cancer patients were investigated with thin-layer chromatography overlay assay combined with a novel mass spectrometry approach. Gb3Cer/CD77 was localized by immunofluorescence microscopy of cryosections from malignant and corresponding healthy tissue samples. 62% of pancreatic and 81% of colon adenocarcinomas showed increased Gb3Cer/CD77 expression, whereas 38% and 19% of malignant pancreas and colon tissue, respectively, did not, indicating an association of this marker with neoplastic transformation. Also, Gb3Cer/CD77 was associated with poor differentiation (G>2) in pancreatic cancer (P = 0.039). Mass spectrometric analysis evidenced enhanced expression of Gb3Cer/CD77 with long (C24) and short chain fatty acids (C16) in malignant tissues and pointed to the presence of hydroxylated fatty acid lipoforms, which are proposed to be important for receptor targeting. They could be detected in 86% of pancreatic and about 19% of colon adenocarcinomas. Immunohistology of tissue cryosections indicated tumor-association of these receptors.

CONCLUSIONS/SIGNIFICANCE

Enhanced expression of Gb3Cer/CD77 in most pancreatic and colon adenocarcinomas prompts consideration of Shiga toxin, its B-subunit or B-subunit-derivatives as novel therapeutic strategies for the treatment of these challenging malignancies.

Immunogenic gangliosides in human ovarian carcinoma

Ganglioside signatures of four poorly and three moderately differentiated ovarian epithelial cancer (OEC) cell lines reveal the presence of GM3, GM2, GD2, O-AcGD2, GD1a and GM1b. The expression of GM3, presence of GD1a and GM1b in the ascitic fluid and plasma, together with a positive correlation in the total-gangliosides levels between ascitic fluid and plasma of OEC patients support the earlier contention that the tumor-gangliosides may be released (or shed) into the tumor-microenvironment. The immunogenicity of OEC-gangliosides is determined by comparing anti-ganglioside-IgM titers in ascitic fluid (n = 14) and plasma (n = 23) of OEC-patients and age-matched healthy (n = 14). The titers were measured by ELISA. Strikingly, the level of anti-GD1a-IgM is significantly higher in ascitic fluid and plasma of patients than in the plasma of healthy volunteers. Paired sample analysis of ascitic fluid and plasma from the same patients confirmed the significant expression of anti-GD1a IgM in OEC patients, while no such difference was observed with other anti-ganglioside IgMs among different groups. The significance of the endogenous IgM response to GD1a may be to eliminate this immunosuppressive-ganglioside from the tumor-microenvironment.

Endogenous immune response to gangliosides in patients with confined prostate cancer

Our study investigated whether endogenous IgM antibodies to gangliosides occur in patients with early stages of prostate cancer (CaP) patients, after defining ganglioside profiles of CaP cell lines. Immune and resorcinol staining detected the presence of gangliosides GM3, GM2, GD3, GD2 and GD1a but not GM1a, GD1b or GT1b in the extracts of normal prostatic epithelial cells (PrEC) and neoplastic androgen-insensitive (PC-3, DU145) and -sensitive (LNCaP-FGC and LNCaP-FGC-10) CaP cells. Using a sensitive ELISA, developed and validated in our laboratory, the titers of IgM against 8 gangliosides from sera of patients with benign prostatic hyperplasia (BPH) (n = 11), organ-confined (T1/T2, n = 36) and unconfined (T3/T4, n = 27) CaP and age-matched healthy men (n = 11) were determined double-blinded. Using ANOVA and Fisher's least significant difference (LSD) methods, the log-titers among different groups were compared. CaP patients differed from healthy and BPH patients in increased titers against GD1a and decreased titers against GD3. Titers of antibodies to other gangliosides exhibited no difference between CaP patients and others. The specific augmentation of anti-GD1a IgM in patients with organ-confined CaP (stage T1/T2) but not in patients with unconfined CaP (stage T3/T4) or BPH or in healthy controls is striking. This finding together with identification of GD1a as a major ganglioside in CaP cell lines and with the accruing studies on the immunosuppressive nature of GD1a indicates that augmentation of anti-GD1a IgM in confined CaP may signify an early endogenous immune response to eliminate a "danger signal" from tumor microenvironment and circulation.

Decrease of human pancreatic cancer cell tumorigenicity by alpha1,3galactosyltransferase gene transfer

The enzyme alpha1,3galactosyltransferase synthesizes the alphaGal epitope, a carbohydrate structure (Galalpha1,3Galbeta1,4GlcNAc-R), on glycoconjugates in lower mammals. The enzyme is absent in humans but large amounts of natural antibodies that recognize alphaGal epitopes are present in human serum. It is likely that these antibodies contribute to the host defense and participate in the hyperacute rejection of xenograft. Previous studies indicated that the glycosyltransferase gene transfer into tumoral cells can modify the structure of glycoconjugates at the cell surface and, as a consequence, modulates the metastatic and tumorigenic behaviors of these cells. The aim of our study was to determine whether the expression of alphaGal epitope can modify the tumorigenicity of human pancreatic cancer cells. The expression of alphaGal epitopes in the human pancreatic cancer cell lines BxPC-3 and Panc-1 was obtained by selecting stable cell clones transfected with murine alpha1,3galactosyltransferase gene. The expression of the enzyme activity in BxPC-3 and Panc-1 cells resulted in the formation at the cell surface of alphaGal epitopes that are recognized by human anti-alphaGal antibodies. alphaGal epitope expression at the surface of pancreatic cancer cells was associated with the fixation of complement 1q to human anti-alphaGal antibodies. The alphaGal epitope expression also resulted in a delay in the tumoral development of BxPC-3 and Panc-1 cells in vivo after xenograft transplantation of nude mice. In addition to the impairment of the metastatic potential of murine tumor cell lines and the activation of immune response, our study provides evidence that the cell surface expression of alphaGal epitopes also modulates the tumorigenic behavior of human pancreatic cancer cells.

Serum total ganglioside level correlates with clinical course in melanoma patients after immunotherapy with therapeutic cancer vaccine

The authors tested the hypothesis that the therapeutic destruction of residual tumors may be reflected in the level of serum total gangliosides (sTG). The sTG level was evaluated in 17 patients with in-transit melanoma and 70 patients with resected regional node metastasis, who have received a polyvalent therapeutic melanoma cell vaccine. The treatment response was determined by regression of in-transit metastases or by overall survival after resection. sTG levels were measured, blinded, before and after immunotherapy. The mean sTG level of the in-transit melanoma patients increased from 18.57 +/- 3.18 mg/dL pretreatment to 23.7 +/- 5.5 mg/dL between weeks 2 and 16 after initiation of treatment (p(2) < 0.0001). By week 24, the level had returned to its prevaccine level in the seven clinical responders (18.1 +/- 2.3 mg/dL vs. 20.4 +/- 3.2 mg/dL; p(2) < 0.050) but remained higher than its prevaccine level in the 10 nonresponders (23.3 +/- 5.1 mg/dl vs. 17.2 +/- 2.7 mg/dL). Similarly, the sTG level of the patients with nodal metastases increased between weeks 2 and 16 after the first vaccine treatment; by week 24, it had returned to pretreatment level in patients who survived more than 56 weeks but remained significantly elevated (p(2) < 0.01) in patients who survived less than 56 weeks. The sTG level increased between weeks 2 and 16 in all vaccine recipients and returned to prevaccine level by week 24 in all who showed measurable regression of in-transit melanoma (7 of 17 patients) or improved overall survival (53 of 70 patients). The data suggest that sTG level could be a potential tool for assessing the response to immunotherapy in melanoma patients by week 24.

Serum anti-ganglioside IgM antibodies in soft tissue sarcoma: clinical prognostic implications

PURPOSE

Gangliosides are tumor-associated antigens with many biologic functions, including complex interactions with cytokines and other modulators of the immune system. Serum total ganglioside level may be an ideal surrogate marker to predict tumor burden and response to treatment. Antibodies produced against tumor gangliosides may help predict survival. The purpose of this study is to determine whether the serum total ganglioside levels might predict the tumor burden in patients with soft tissue sarcoma, and whether the augmented anti-ganglioside immunoglobulin M (IgM) response might reflect the clinical outcome of these patients.

METHODS

Serum TG levels were measured in the cryopreserved sera by estimating lipid-associated sialic acids from 97 patients before surgical resection of soft tissue sarcoma and from 39 age- and gender-matched healthy volunteers. All sera were analyzed for IgM titers (expressed natural log) by enzyme-linked immunosorbent assay against eight gangliosides (GM1, GM2, GM3, GD3, GD2, GD1a, GD1b, and GT1b). Cox regression was used for univariate and multivariate analyses of the variables affecting progression-free and overall survival.

RESULTS

Serum TG levels were higher in soft tissue sarcoma patients than in healthy individuals (21.8 + 7.7 vs 16.1 + 2.7 mg/dL; P = 0.001). Larger tumors, high histologic grade, and more advanced stage of disease correlated with higher serum total ganglioside levels (P < 0.05). Anti-ganglioside titers to GM3, GD2, and GT1b were significantly higher in patients with soft tissue sarcoma, whereas anti-GD1a and GD1b titers were significantly higher in healthy subjects. The titers of antibodies against GM1, GM2, and GD3 in patients with soft tissue sarcoma were comparable to those of the healthy individuals. When compared with healthy controls, patients with low-grade tumors had higher titers of anti-GT1b, anti-GM3, and anti-GD2 antibodies, and patients with high-grade tumors had higher titers of anti-GT1b and anti-GD2 antibodies. These data suggest that the predominant gangliosides expressed by sarcomas may include GT1b and GD2. In addition, low-grade tumors may express an immunogenic species of GM3. On both univariate and multivariate analyses, augmented anti-GD1a IgM titers, age > 50 years, and retroperitoneal location were predictive of decreased overall survival, whereas augmented anti-GT1b titers were predictive of improved overall survival.

CONCLUSIONS

Serum TG level may be a useful marker of tumor burden and response to treatment for soft tissue sarcoma. Anti-GD1a and anti-GT1b IgM titers predicted survival and may be of therapeutic and prognostic value in the management of soft tissue sarcoma.

Cryosurgical ablation of liver tumors in colon cancer patients increases the serum total ganglioside level and then selectively augments antiganglioside IgM

Cryosurgical ablation (CSA) of tumors induces disruptive necrosis. Necrosis may release tumor gangliosides into circulation and they may augment serum antiganglioside antibodies depending on the nature of gangliosides released. The hypothesis is tested by determining the level of serum total gangliosides (STG) and their antibody titers in the sera of colon cancer patients with cryoablated liver tumors. As controls, we examined the sera of patients who underwent radiofrequency ablation (RFA) and regular surgery (RS), none of which cause disruptive necrosis. The STG level (expressed as lipid-bound sialic acids, LBSA) is higher (p(2)<0.001) in 35 patients (stage IV) than in 38 healthy case-controls (median 23.48 mg/dL, Q-range 7.1 vs 16.04 mg/dL, Q-range 4.5). The mean STG level increased significantly to 31.2+/-6.0mg/dL (p(2)<0.03) after CSA. Concomitantly, the IgM titer against colon cancer-associated gangliosides (GM(2), GD(1a), GT(1b)), increased significantly, but no increase was observed against normal tissue gangliosides (GM(3) or GM(1)). Also after RFA and RS, no such increase was observed either in the level of STG or in IgM titer against tumor gangliosides. The results suggest that CSA-induced necrosis might have acted as an adjuvant, because purified gangliosides without exogenous adjuvants even after repeated immunization failed to elicit antibody response. The post-CSA decline in the STG level correlated with the increase in the antibodies, suggesting a homeostatic role of the antibodies.

Serum total gangliosides and TA90-IC levels: novel immunologic markers in colorectal cancer

BACKGROUND

Because of the challenge in defining prognostic markers predictive of recurrence or progression, carcinoembryonic antigen (CEA) remains the most frequently used marker in colorectal cancer, despite its low sensitivity. We hypothesized that TA90-IC status and serum ganglioside levels might be useful markers and might be of prognostic significance in colorectal cancer.

METHODS

Serum samples from 68 patients undergoing surgical treatment for histologically proven colorectal cancer were analyzed for the presence of CEA, serum gangliosides, and TA90-IC. Forty-one patients had node-negative disease, whereas 27 patients had limited metastatic disease. The intent was curative resection, even for patients with metastatic disease. Cryopreserved serum specimens were analyzed in a blinded fashion for total serum ganglioside levels (by an assay that detects lipid-associated sialic acids), for CEA, and for TA90-IC (by a murine monoclonal antibody-based enzyme-linked immunosorbent assay). A positive value for TA90-IC levels was defined as an optical density (OD) of more than 0.410 at 405 nm.

RESULTS

Serum ganglioside levels were elevated more frequently than CEA concentrations (84% vs 44%). The combination of serum ganglioside and CEA values was more sensitive (88%) than CEA value alone (44%) in identifying patients with early-stage colorectal cancer. TA90-IC levels were elevated more frequently than CEA concentrations (56% vs 32%). The combination of TA90-IC and CEA values was more sensitive (72%) than CEA value alone (32%) in identifying patients with advanced-stage colorectal cancer. At an enzyme-linked immunosorbent assay cutoff level of 0.410, 15 (56%) patients had positive TA90-IC values. Fourteen patients alive with residual disease had a median OD TA90-IC level of 0.879, and only three patients had levels below the OD cutoff value of 0.410. Thirteen patients with no evidence of disease had a median level of 0.277, and only four patients had OD levels > or = 0.410. TA90-IC was significantly higher in the alive with residual disease patients than those rendered no evidence of disease (P = 0.02).

CONCLUSIONS

We speculate that a multiple-marker analysis that combines CEA values with serum ganglioside and TA90-IC values may be more sensitive than CEA value alone for detecting colorectal cancer. The potential prognostic significance of TA90-IC status in advanced disease warrants further investigation.

Targeting of G(D2)-positive tumor cells by human T lymphocytes engineered to express chimeric T-cell receptor genes

Genetic engineering of human T lymphocytes to express tumor antigen-specific chimeric immune receptors is an attractive means for providing large numbers of effector cells for adoptive immunotherapy while bypassing major mechanisms of tumor escape from immune recognition. We have applied this strategy to the targeting of a G(D2)-positive tumor, neuroblastoma, which is the commonest extracranial solid tumor of childhood. Chimeric immune receptors were generated by joining an extracellular antigen-binding domain derived from either of the 2 ganglioside G(D2)-specific antibodies sc7A4 and sc14.G2a to a cytoplasmic signaling domain. The variable domains of hybridoma antibody 14.G2a were cloned and selected using a phage display approach. Upon coincubation with G(D2)-expressing tumor cell targets, human T lymphocytes transduced with recombinant retroviruses encoding chimeric receptors based on sc14.G2a, but not sc7A4, secreted significant levels of cytokines in a pattern comparable to the cytokine response obtained by engagement of the CD3 receptor. T cells transduced with the sc14.G2a-based chimeric T-cell receptors also displayed specific lysis of G(D2)-positive neuroblastoma cells, which was blocked in the presence of monoclonal antibody 14.G2a. In the absence of nonspecific stimulation of transduced cells, their functionality declined over time and antigenic stimulation of the chimeric receptor alone did not induce commitment to proliferation. These results support the feasibility of redirecting human T lymphocytes to a tumor-associated ganglioside epitope but emphasize that successful chimeric receptor-mediated adoptive immunotherapy will require additional strategies that overcome functional inactivation of gene-modified primary T lymphocytes.

Interleukin-2 binds to ganglioside GD(1b)

We have developed a solid matrix immunoassay to determine the binding of interleukin-2 (IL-2) to specific gangliosides. The assay establishes that recombinant human IL-2 binds to ganglioside GD(1b) but not to any other gangliosides (GM(1), GM(2), GM(3), GD(1a), GD(2), GD(3), and GT(1b)). The binding varies with the ratio of GD1b and IL-2. This assay enables distinguishing the nature of the sugar moiety of the ganglioside recognized by IL-2 and establishes the dosimetry of the ganglioside-IL-2 interaction. Since rIL-2 is administered systematically into stage IV melanoma patients, we have examined 45 tumor biopsies for GD(1b) content. The incidence of GD(1b) in tumor biopsies is 51%. We postulate that GD(1b) associated on the tumor or in the circulation of cancer patients may bind to rIL-2 and prevent the availability of rIL-2 to augment antitumor-immune response.