Immunogenicity of membrane-bound gangliosides in viable whole-cell vaccines

Whole-Cell Cancer Vaccines Induce Large Antibody Responses to Carbohydrates and Glycoproteins

Whole-cell cancer vaccines are a promising strategy for treating cancer, but the characteristics of a favorable immune response are not fully understood. New insights could enable development of better vaccines, discovery of new antigens, and identification of biomarkers of efficacy. Using glyco-antigen microarrays, we demonstrate that GVAX Pancreas (a granulocyte macrophage colony-stimulating factor-modified whole-cell tumor vaccine) induces large immunoglobulin G and immunoglobulin M responses to many antigens, including tumor-associated carbohydrates, blood group antigens, α-Gal, and bovine fetuin. Antibody responses to α-Gal, a glycan found in fetal bovine serum (FBS) used to produce the vaccine, correlated inversely with overall survival and appear to compete with productive responses to the vaccine. H1299 lysate vaccine, produced with FBS, also induced responses to α-Gal and fetuin but not K562-GM, which is produced in serum-free medium. Our results provide new potential biomarkers to evaluate productive/unproductive immune responses and suggest that removal/reduction of FBS could improve the efficacy of whole-cell vaccines.

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.

Inhibitors of melanogenesis increase toxicity of cyclophosphamide and lymphocytes against melanoma cells

High mortality rate for metastatic melanoma is related to its resistant to the current methods of therapy. Melanogenesis is a metabolic pathway characteristic for normal and malignant melanocytes that can affect the behavior of melanoma cells or its surrounding environment. Human melanoma cells in which production of melanin pigment is dependent on tyrosine levels in medium were used for experiments. Peripheral blood mononuclear cells were derived from the buffy coats purchased from Lifeblood Biological Services. Cell pigmentation was evaluated macroscopically, and tyrosinase activity was measured spectrophotometrically. Cell proliferation and viability were measured using lactate dehydrogenase release MTT, [(3)H]-thymidine incorporation and DNA content analyses, and gene expression was measured by real time RT-PCR. Pigmented melanoma cells were significantly less sensitive to cyclophosphamide and to killing action of IL-2-activated peripheral blood lymphocytes. The inhibition of melanogenesis by either blocking tyrosinase catalytic site or chelating copper ions sensitized melanoma cells towards cytotoxic action of cyclophosphamide, and amplified immunotoxic activities of IL-2 activated lymphocytes. Exogenous L-DOPA inhibited lymphocyte proliferation producing the cell cycle arrest in G1/0 and dramatically inhibited the production of IL-1beta, TNF-alpha, IL-6 and IL-10. Thus, the active melanogenesis could not only impair the cytotoxic action of cyclophosphamid but also has potent immunosuppressive properties. This resistance to a chemotherapeutic agent or immunotoxic activity of lymphocytes could be reverted by the action of tyrosinase inhibitors. Thus, the inhibition of melanogenesis might represent a valid therapeutic target for the management of advanced melanotic melanomas.

Glycoimmunomics of human cancer: current concepts and future perspectives

Future strategies for the treatment of human cancer require a full appreciation of the intracellular and extracellular changes that accompany neoplastic transformation. The changes may involve a variety of micro- and macro-molecules, including, but not restricted to, peptides, proteins (with sugar and/or lipid moieties), oligosaccharides, glycolipids (neutral or acidic, e.g., gangliosides), ceramides, fatty acids and other lipids. Although several therapeutic approaches have been well developed in recent years, most of the reported studies focus on proteins and peptides. Glycoantigens and lipoantigens have been neglected. Elucidation of the profiles and properties of all molecules associated with tumor progression is required to develop a successful strategy to treat human cancer. This review describes the unique immunomics of tumor-associated glycoantigens and explains why the field of glycoimmunomics may yield clinically important biomarkers and treatments for the management of human cancer.

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.

Carbohydrate vaccines as immunotherapy for cancer

Carbohydrates have established themselves as the most clinically relevant antigens of those tested and subsequently developed for vaccines against infectious diseases. However, in cancer patients, many of the defined carbohydrate antigens are really altered 'self' antigens and for unclear reasons, the body does not react to them immunologically. Although these self antigens have been found to be potentially suitable targets for immune recognition and killing, the development of vaccines for cancer treatment is actually more challenging compared with those for infectious diseases mainly because of the difficulty associated with breaking the body's immunological tolerance to the antigen. These antigens lack the inherent immunogenicity associated with bacterial antigens and, therefore, methods to enhance immunological recognition and induction of immunity in vivo are under investigation. These include defining the appropriate tumour-associated antigen, successfully synthesizing the antigen to mimic the original molecule, inducing an immune response, and subsequently enhancing the immunological reactivity so that all components can work together. This has been successfully accomplished with several glycolipid and glycoprotein antigens using carriers such as keyhole limpet haemocyanin (KLH) together with a saponin adjuvant, QS-21. Not only can high titre IgM and IgG antibodies be induced, which are specific for the antigen used for immunization, but the antibodies can mediate complement lysis. The approaches for synthesis, conjugation, clinical administration and immunological potential are discussed.

Gangliosides of organ-confined versus metastatic androgen-receptor-negative prostate cancer

Prior development of a unique androgen-receptor (AR)-negative cell line (HH870) from organ-confined (T2b) human prostate cancer (CaP) enabled comparison of the gangliosides associated with normal and neoplastic prostate epithelial cells, organ-confined versus metastatic (DU 145, PC-3), and AR-negative versus AR-positive CaP cell lines. Resorcinol-HCl and specific monoclonal antibodies were used to characterize gangliosides on 2D-chromatograms, and to visualize them on the cell surface with confocal-fluorescence microscopy. AR-negative cells expressed GM1b, GM2, GD2, GD1a, and GM3. GM1a, GD1b, and GT1b were undetectable. GM1b and GD1a were more prominent in AR-negative than in AR-positive cells. PC-3 and HH870 cells were unique in the expression of O-acetylGD2 (O-AcGD2) and two alpha2,3-sialidase-resistant, alkali-susceptible GMR17-reactive gangliosides. Expression of GD1a, GM1b, doublets of GD3, GD2, and O-AcGD2, and the presence of an additional alkali-labile-14.G2a-reactive ganglioside, two alkali-susceptible, and three alkali-resistant GMR17-reactive gangliosides makes HH870 a potential component of a polyvalent-vaccine for active-specific immunotherapy of CaP.

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.

Malignant melanoma

CONTEXT

The rapidly developing fields of melanoma research are revolutionizing the current concepts on melanoma etiology and pathogenesis and are introducing newer diagnostic techniques and potential therapeutic approaches.

OBJECTIVES

To present the most current concepts on the etiology and pathogenesis of melanoma and to introduce the recent diagnostic techniques and the potential therapeutic approaches.

METHODS

Data sources were reports on melanoma published in the English language literature and observations made using specimens available at Harvard University, Johns Hopkins Medical Center, Albany Medical College, Loyola University Medical Center, and University of Tennessee Health Science Center.

RESULTS

Studies on melanoma containing chromosomal or genetic evaluation were selected for further analysis. Current clinical and pathologic categories with the reported genetic abnormalities were related to the latest information on pigment biology. The data extracted were used to develop a conceptual framework on the pathogenesis of melanoma; the generated model was then evaluated and used to suggest potential therapeutic approaches.

CONCLUSIONS

(1) Melanoma is not genetically homogeneous, and the existing differences between the pathologic categories, particularly in areas such as type of growth phase (radial vs vertical growth), total vertical dimension, ulceration of primary tumor, and metastatic process, have profound prognostic and therapeutic implications. (2) Chromosomal aberrations and gene mutations are found in sporadic and familial melanomas; among the most important are those affecting the 9p21, which contains the p16 locus, a site known to be critical for normal progression of the cell cycle. Aberrant p16 expression is associated with more aggressive behavior. (3) Melanoma cells possess a remarkable repertoire of biosynthetic capacities represented by the production of hormones, growth factors, and their receptors that may sustain and accelerate tumor development and progression. For example, expression of the tumoral products alpha-melanocyte-stimulating hormone and adrenocorticotropic hormone is regulated in vitro by ultraviolet light, a known carcinogen. (4) Melanomas differ from other tumors in their intrinsic capability to express melanogenic enzymes with the corresponding structural proteins to actually synthesize melanin. Melanogenesis-related proteins are rapidly entering the clinical arena, being used not only as diagnostic markers, but also as potential targets for melanoma therapy.