IgM anti-ganglioside antibodies induced by melanoma cell vaccine correlate with survival of melanoma patients

Harnessing Antibody Polyspecificity for Cancer Immunotherapy

Targeting the diverse glycan repertoire expressed on tumor cells is considered a viable therapeutic strategy to deal with tumor cell heterogeneity. Inherently polyspecific, natural, glycan-reactive antibodies are purported to be protective in thwarting infections and in cancer immunotherapy. Tumor-associated carbohydrate antigens (TACAs) are related to pathogen glycans, to which nascent or natural antibodies exist and IgM responses are elicited. To capture the polyspecific nature of anticarbohydrate responses, we have focused on the rational design of carbohydrate mimetic peptides (CMPs) cross-reactive with TACA reactive antibodies. In particular, we have focused on the development of CMPs that display reactivity to GD2 and Lewis Y (LeY) reactive monoclonal antibodies. They would serve as templates for pan-immunogens inducing biosimilar polyreactive antibodies. In the design, we relied on structural analyses of CMP's enhanced binding to the templates using molecular modeling. Glycan reactivity patterns of affinity CMP-purified human antibodies further refined specificity profiles in comparison with the immune response to the CMP in clinical trials. In this study, we further define the molecular characteristics for this mimicry by considering the polyspecificity of LeY and GD2 reactive antibodies binding to the lacto-ceramide core Galβ(1,4)Glcβ(1-1')Cer. Binding to this minimum building block can be capitalized on for cancer therapy and diagnostics and illustrates a new approach in designing cancer vaccines taking advantage of the latent polyspecificity of antibodies and the relevance of natural antibodies in antigen discovery and design.

A TLR4-TRIF-dependent signaling pathway is required for protective natural tumor-reactive IgM production by B1 cells

Metastatic cancer involving spread to the peritoneal cavity is referred to as peritoneal carcinomatosis and has a very poor prognosis. Our previous studies demonstrated a toll-like receptor 4 (TLR4) and C-type lectin receptor (CLR; Mincle/MCL) agonist pairing of monophosphoryl lipid A (MPL) and trehalose-6,6'-dicorynomycolate (TDCM) effectively inhibits peritoneal tumor growth and ascites development through a mechanism dependent upon B1a cell-produced natural IgM, complement, and phagocytes. In the current study, we investigated the requirement for TLR4 and Fc receptor common γ chain (FcRγ), required for Mincle/MCL signaling, in the MPL/TDCM-elicited response. MPL/TDCM significantly increased macrophages and Ly6Chi monocytes in the peritoneal cavity of both TLR4-/- and FcRγ-/- mice, suggesting redundancy in the signals required for monocyte/macrophage recruitment. However, B1 cell activation, antibody secreting cell differentiation, and tumor-reactive IgM production were defective in TLR4-/-, but not FcRγ-/- mice. TRIF was required for production of IgM reactive against tumor- and mucin-related antigens, but not phosphorylcholine, whereas TLR4 was required for production of both types of reactivities. Consistent with this, B1 cells lacking TLR4 or TRIF did not proliferate or differentiate into tumor-reactive IgM-producing cells in vitro and did not reconstitute MPL/TDCM-dependent protection against peritoneal carcinomatosis in CD19-/- mice. Our results indicate a TLR4/TRIF-dependent pathway is required by B1 cells for MPL/TDCM-elicited production of protective tumor-reactive natural IgM. The dependency on TRIF signaling for tumor-reactive, but not phosphorylcholine-reactive, IgM production reveals unexpected heterogeneity in TLR4-dependent regulation of natural IgM production, thereby highlighting important differences to consider when designing vaccines or therapies targeting these specificities.

Upregulation of cell surface GD3 ganglioside phenotype is associated with human melanoma brain metastasis

Melanoma metastasis to the brain is one of the most frequent extracranial brain tumors. Cell surface gangliosides are elevated in melanoma metastasis; however, the metabolic regulatory mechanisms that govern these specific changes are poorly understood in melanoma particularly brain metastases (MBM) development. We found ganglioside GD3 levels significantly upregulated in MBM compared to lymph node metastasis (LNM) but not for other melanoma gangliosides. Moreover, we demonstrated an upregulation of ST8SIA1 (GD3 synthase) as melanoma progresses from melanocytes to MBM cells. Using RNA‐ISH on FFPE specimens, we evaluated ST8SIA1 expression in primary melanomas (PRM) (n = 23), LNM and visceral metastasis (n = 45), and MBM (n = 39). ST8SIA1 was significantly enhanced in MBM compared to all other specimens. ST8SIA1 expression was assessed in clinically well‐annotated melanoma patients from multicenters with AJCC stage III B‐D LNM (n = 58) with 14‐year follow‐up. High ST8SIA1 expression was significantly associated with poor overall survival (HR = 3.24; 95% CI, 1.19–8.86, P = 0.02). In a nude mouse human xenograft melanoma brain metastasis model, MBM variants had higher ST8SIA1 expression than their respective cutaneous melanoma variants. Elevated ST8SIA1 expression enhances levels of cell surface GD3, a phenotype that favors MBM development, hence associated with very poor prognosis. Functional assays demonstrated that ST8SIA1 overexpression enhanced cell proliferation and colony formation, whereby ST8SIA1 knockdown had opposite effects. Icaritin a plant‐derived phytoestrogen treatment significantly inhibited cell growth in high GD3‐positive MBM cells through targeting the canonical NFκB pathway. The study demonstrates GD3 phenotype associates with melanoma progression and poor outcome.

Activation of B-1 Cells Promotes Tumor Cell Killing in the Peritoneal Cavity

Metastatic cancer involving spread to the peritoneal cavity is referred to as peritoneal carcinomatosis and has a very poor prognosis. Activating the antitumor immune response in the characteristically immune-suppressive peritoneal environment presents a potential strategy to treat this disease. In this study, we show that a toll-like receptor (TLR) and C-type lectin receptor (CLR) agonist pairing of monophosphoryl lipid A (MPL) and trehalose-6,6'-dicorynomycolate (TDCM) effectively inhibits tumor growth and ascites development in a mouse model of aggressive mammary cancer-induced peritoneal carcinomatosis. MPL/TDCM treatment similarly inhibited peritoneal EL4 tumor growth and ascites development. These effects were not observed in mice lacking B cells or mice lacking CD19, which are deficient in B-1a cells, an innate-like B-cell population enriched in the peritoneal cavity. Remarkably, adoptive transfer of B-1a cells, but not splenic B cells from WT mice, restored MPL/TDCM-induced protection in mice with B-cell defects. Treatment induced B-1 cells to rapidly produce high levels of natural IgM reactive against tumor-associated carbohydrate antigens. Consistent with this, we found significant deposition of IgM and C3 on peritoneal tumor cells as early as 5 days post-treatment. Mice unable to secrete IgM or complement component C4 were not protected by MPL/TDCM treatment, indicating tumor killing was mediated by activation of the classical complement pathway. Collectively, our findings reveal an unsuspected role for B-1 cell-produced natural IgM in providing protection against tumor growth in the peritoneal cavity, thereby highlighting potential opportunities to develop novel therapeutic strategies for the prevention and treatment of peritoneal metastases. SIGNIFICANCE: This work identifies a critical antitumor role for innate-like B cells localized within the peritoneal cavity and demonstrates a novel strategy to activate their tumor-killing potential.See related commentary by Tripodo, p. 5.

Cytotoxic activity against human neuroblastoma and melanoma cells mediated by IgM antibodies derived from peripheral blood of healthy donors

A small percentage of healthy donors identified in the Western population carry antibodies in their peripheral blood which convey cytotoxic activity against certain human melanoma and neuroblastoma cell lines. We measured the cytotoxic activity of sera and plasmas from healthy donors on the human neuroblastoma cell line Kelly and various melanoma cell lines. Antibodies of IgM isotype, presumably belonging to the class of naturally occurring antibodies, exerted cytotoxic activity in a complement-dependent fashion. Apart from complement-dependent tumor cell lysis, we observed C3 opsonization in all tumor cell lines upon treatment with cytotoxic plasmas. Cell lines tested primarily expressed membrane complement regulatory proteins (mCRP) CD46, CD55 and CD59 to various extents. Blocking of mCRPs by monoclonal antibodies enhanced cell lysis and opsonization, though some melanoma cells remained resistant to complement attack. Epitopes recognized by cytotoxic antibodies were represented by gangliosides such as GD2 and GD3, as evidenced by cellular sialidase pretreatment and enhanced expression of distinct gangliosides. It remains to be clarified why only a small fraction of healthy persons carry these antitumor cytotoxic antibodies.

Novel and emerging targeted-based cancer therapy agents and methods

After several decades of uncovering the cancer features and following the improvement of therapeutic agents, however cancer remains as one of the major reasons of mortality. Chemotherapy is one of the main treatment options and has significantly improved the overall survival of cancer patients, but chemotherapeutic agents are highly toxic for normal cells. Therefore, there is a great unmet medical need to develop new therapeutic principles and agents. Targeted-based cancer therapy (TBCT) agents and methods have revolutionized the cancer treatment efficacy. Monoclonal antibodies (mAbs) and small molecule inhibitors (SMIs) are among the most effective agents of TBCT. These drugs have improved the prognosis and survival of cancer patients; however, the therapeutic resistance has subdued the effects. Several mechanisms lead to drug resistance such as mutations in the drug targets, activation of compensatory pathways, and intrinsic or acquired resistance of cancer stem cells. Therefore, new modalities, improving current generation of inhibitors and mAbs, and optimizing the combinational therapy regimens are necessary to decrease the current obstacles in front of TBCT. Moreover, the success of new TBCT agents such as mAbs, SMIs, and immunomodulatory agents has sparked further therapeutic modalities with novel targets to inhibit. Due to the lack of cumulative information describing different agents and methods of TBCT, this review focuses on the most important agents and methods of TBCT that are currently under investigation.

Improvement of the immune efficacy of carbohydrate vaccines by chemical modification on the GM3 antigen

N-modified GM3 glycoconjugates improved the efficiency of the vaccination without the combination of metabolic oligosaccharide engineering technology.

Carbohydrate-mimetic peptides for pan anti-tumor responses

Molecular mimicry is fundamental to biology and transcends to many disciplines ranging from immune pathology to drug design. Structural characterization of molecular partners has provided insight into the origins and relative importance of complementarity in mimicry. Chemical complementarity is easy to understand; amino acid sequence similarity between peptides, for example, can lead to cross-reactivity triggering similar reactivity from their cognate receptors. However, conformational complementarity is difficult to decipher. Molecular mimicry of carbohydrates by peptides is often considered one of those. Extensive studies of innate and adaptive immune responses suggests the existence of carbohydrate mimicry, but the structural basis for this mimicry yields confounding details; peptides mimicking carbohydrates in some cases fail to exhibit both chemical and conformational mimicry. Deconvolution of these two types of complementarity in mimicry and its relationship to biological function can nevertheless lead to new therapeutics. Here, we discuss our experience examining the immunological aspects and implications of carbohydrate-peptide mimicry. Emphasis is placed on the rationale, the lessons learned from the methodologies to identify mimics, a perspective on the limitations of structural analysis, the biological consequences of mimicking tumor-associated carbohydrate antigens, and the notion of reverse engineering to develop carbohydrate-mimetic peptides in vaccine design strategies to induce responses to glycan antigens expressed on cancer cells.

Humoral response to a viral glycan correlates with survival on PROSTVAC-VF

Therapeutic cancer vaccines can be effective for treating patients, but clinical responses vary considerably from patient to patient. Early indicators of a favorable response are crucial for making individualized treatment decisions and advancing vaccine design, but no validated biomarkers are currently available. In this study, we used glycan microarrays to profile antiglycan antibody responses induced by PROSTVAC-VF, a poxvirus-based cancer vaccine currently in phase III clinical trials. Although the vaccine is designed to induce T-cell responses to prostate-specific antigen, we demonstrate that this vaccine also induces humoral responses to a carbohydrate on the poxvirus, the Forssman disaccharide (GalNAcα1-3GalNAcβ). These responses had a statistically significant correlation with overall survival in two independent sample sets (P = 0.015 and 0.008) comprising more than 100 patients. Additionally, anti-Forssman humoral responses correlated with clinical outcome in a separate study of PROSTVAC-VF combined with a radiopharmaceutical (Quadramet). Studies on control subjects demonstrated that the survival correlation was specific to the vaccine. The results provide evidence that antiglycan antibody responses may serve as early biomarkers of a favorable response to PROSTVAC-VF and offer unique insights for improving vaccine design.

Detection methods of circulating tumor cells in cutaneous melanoma: a systematic review

The vast majority of melanoma-related deaths are due to disseminated malignancy. Many treated patients who are clinically disease-free will go on to relapse. Therefore, new prognostic tools must be developed to better assess metastatic potential and assist in patient management. Circulating tumor cells are a widely studied metastatic biomarker with promising prognostic utility, as the shedding of cells from the primary tumor into peripheral blood is a necessary step in disease dissemination. An assortment of technologies and techniques has been developed to isolate and detect circulating melanoma cells (CMCs), but a standardized method is yet to be established. It is the aim of this study to systematically review the diverse enrichment and detection methods of circulating tumor cells in cutaneous melanoma. A literature search yielded 351 articles, of which 74 were deemed eligible according to inclusion criteria, the primary requirement being the reporting of patient CMC positivity status stratified by the stage of melanoma. Pertinent studies were used to evaluate the advantages and disadvantages of each method. Additionally, we calculated the sensitivity and specificity of seven common melanoma-associated markers based on the available literature.

Early development of PAT-SM6 for the treatment of melanoma

Despite the recent development of novel therapies for patients with metastatic melanoma, this disease remains fatal in the majority of those who develop a relapse. Here, we report the preclinical and early clinical development of a novel IgM antibody PAT-SM6 that specifically binds to a cancer-specific isoform of glucose-regulated protein 78 (GRP78) and low-density lipoprotein. Finding a GRP78 cancer-specific form on the surface of cancer cells, but not normal cells in vivo, presents an opportunity for cancer-specific targeting. PAT-SM6 binding to the cell surface induces apoptosis in a variety of tumors, including melanoma. Recent studies show the specificity of PAT-SM6 binding to the surface of melanoma cells and primary tissue but not to normal tissue. They also confirm, for the first time, cell proliferation inhibition and apoptosis through classical apoptotic pathways as well as induction of lipid accumulation in melanoma cells. These in-vitro data are supported by positive in-vivo data using PAT-SM6 in a xenograft C8161 model. Furthermore, PAT-SM6 was well tolerated in pharmacokinetic/toxicology studies in monkeys. On the basis of these preclinical observations, a clinical study of PAT-SM6 was carried out in patients with 'in-transit' melanoma. Even with microdosing, histological analyses of tumor biopsies detected the presence of PAT-SM6 as well as apoptosis. Although there are many small molecules and monoclonal antibodies currently in clinical development for patients with melanoma, PAT-SM6 is the only therapeutic targeting the cancer-specific isoform of GRP78. These PAT-SM6 preclinical data and positive findings from the phase 1 safety study provide strong support for the further development of this novel antibody.

Tumor-Associated Glycans and Immune Surveillance

Changes in cell surface glycosylation are a hallmark of the transition from normal to inflamed and neoplastic tissue. Tumor-associated carbohydrate antigens (TACAs) challenge our understanding of immune tolerance, while functioning as immune targets that bridge innate immune surveillance and adaptive antitumor immunity in clinical applications. T-cells, being a part of the adaptive immune response, are the most popular component of the immune system considered for targeting tumor cells. However, for TACAs, T-cells take a back seat to antibodies and natural killer cells as first-line innate defense mechanisms. Here, we briefly highlight the rationale associated with the relative importance of the immune surveillance machinery that might be applicable for developing therapeutics.

Does a "thiol shield" protect tumors from natural IgM antibody, and, if so, how can it be suppressed?

Natural anti-tumor IgM antibodies are prevalent in the serum of cancer patients and normal subjects. Extensive research has been directed toward the ultimate goal of achieving a therapeutic effect from these antibodies either augmented by vaccination or by passive infusion. To date, the therapeutic effects have been limited. This thesis asserts that thiols within solid tumors reduce pentameric IgM to monomeric or other subunit form resulting in inactivation of its complement fixing and cross linking apoptosis inducing properties. A rationale for this normal physiological inactivation mechanism, possibly necessary for wound healing and pregnancy, is proposed along with therapeutic approaches, which would potentially suppress IgM inactivation.

Glycans as targets for therapeutic antitumor antibodies

Glycans represent a vast class of molecules that modify either proteins or lipids. They exert and regulate important and complex functions in both normal and cancer cell metabolism. As such, the most immunogenic glycans have been targeted in passive and active immunotherapy in human cancer for the past 25 years but it is only recently that techniques have become available to uncover novel glycan targets. The main focus of this review article is to highlight why and how monoclonal antibodies (mAbs) recognizing glycans, and in particular the glycans expressed on glycolipids, are being used in various strategies to target and kill cancer cells. The article reports on the historical use of mAbs and on very recent progress made in antitumor therapy using the anti-GD2 mAb and the antiganglioside mAbs, anti-N-glycolylneuraminic acid mAb and anti-Lewis mAb. Anti-GD2 is showing great promise in Phase III clinical trials in adjuvant treatment of neuroblastoma. Racotumomab, an anti-idiotypic mAb mimicking N-glycolylneuraminic acid-containing gangliosides, is currently being tested in a randomized, controlled Phase II/III clinical trial. This article also presents various strategies used by different groups to develop mAbs against these naturally poorly immunogenic glycans.

Association between circulating tumor cells and prognosis in patients with stage III melanoma with sentinel lymph node metastasis in a phase III international multicenter trial

PURPOSE

The outcomes of patients with melanoma who have sentinel lymph node (SLN) metastases can be highly variable, which has precluded establishment of consensus regarding treatment of the group. The detection of high-risk patients from this clinical setting may be helpful for determination of both prognosis and management. We report the utility of multimarker reverse-transcriptase quantitative polymerase chain reaction (RT-qPCR) detection of circulating tumor cells (CTCs) in patients with melanoma diagnosed with SLN metastases in a phase III, international, multicenter clinical trial.

PATIENTS AND METHODS

Blood specimens were collected from patients with melanoma (n = 331) who were clinically disease-free after complete lymphadenectomy (CLND) before entering onto a randomized adjuvant melanoma vaccine plus bacillus Calmette-Guérin (BCG) versus BCG placebo trial from 30 melanoma centers (United States and international). Blood was assessed using a verified multimarker RT-qPCR assay (MART-1, MAGE-A3, and GalNAc-T) of melanoma-associated proteins. Cox regression analyses were used to evaluate the prognostic significance of CTC status for disease recurrence and melanoma-specific survival (MSS).

RESULTS

Individual CTC biomarker detection ranged from 13.4% to 17.5%. There was no association of CTC status (zero to one positive biomarkers v two or more positive biomarkers) with known clinical or pathologic prognostic variables. However, two or more positive biomarkers was significantly associated with worse distant metastasis disease-free survival (hazard ratio [HR] = 2.13, P = .009) and reduced recurrence-free survival (HR = 1.70, P = .046) and MSS (HR = 1.88, P = .043) in a multivariable analysis.

CONCLUSION

CTC biomarker status is a prognostic factor for recurrence-free survival, distant metastasis disease-free survival, and MSS after CLND in patients with SLN metastasis. This multimarker RT-qPCR analysis may therefore be useful in discriminating patients who may benefit from aggressive adjuvant therapy or stratifying patients for adjuvant clinical trials.

Carbohydrate mimetic peptides augment carbohydrate-reactive immune responses in the absence of immune pathology

Among the most challenging of clinical targets for cancer immunotherapy are Tumor Associated Carbohydrate Antigens (TACAs). To augment immune responses to TACA we are developing carbohydrate mimetic peptides (CMPs) that are sufficiently potent to activate broad-spectrum anti-tumor reactivity. However, the activation of immune responses against terminal mono- and disaccharide constituents of TACA raises concerns regarding the balance between “tumor destruction” and “tissue damage”, as mono- and disaccharides are also expressed on normal tissue. To support the development of CMPs for clinical trial testing, we demonstrate in preclinical safety assessment studies in mice that vaccination with CMPs can enhance responses to TACAs without mediating tissue damage to normal cells expressing TACA. BALB/c mice were immunized with CMPs that mimic TACAs reactive with Griffonia simplicifolia lectin 1 (GS-I), and tissue reactivity of serum antibodies were compared with the tissue staining profile of GS-I. Tissues from CMP immunized mice were analyzed using hematoxylin and eosin stain, and Luxol-fast blue staining for myelination. Western blots of membranes from murine mammary 4T1 cells, syngeneic with BALB/c mice, were also compared using GS-I, immunized serum antibodies, and naive serum antibodies. CMP immunization enhanced glycan reactivities with no evidence of pathological autoimmunity in any immunized mice demonstrating that tissue damage is not an inevitable consequence of TACA reactive responses.

Immunoglobulin M as a vaccine adjuvant

Vaccines are effective in preventing disease by stimulating the immune system and sustaining an immune response towards eradication of pathogens and diseased cells. However, designing successful vaccines is not always straightforward. For a vaccine to be successful, antigen-presenting cells (APC) need to be stimulated, primarily by adjuvants, towards a sustained immune response through integration of the innate and adaptive (humoral and cellular) immune systems. Furthermore, there is an immediate need for safe and effective adjuvants. There has been significant progress in understanding the mechanisms on how vaccines work and the role of adjuvants, dendritic cells, and the toll-like receptor (TLR) pathway. Currently, different adjuvants are actively explored but the potential of the immunoglobulin M (IgM) as a vaccine adjuvant has been overlooked. This article hypothesizes how the IgM molecule could function as a vaccine adjuvant by acting as a "soluble" toll-like receptor (TLR) through the formation of an immune complex with antigen (Ag) and other components of the innate immune system. The complex should lead to sustained humoral and/or cell-mediated immune responses. Hypothetically, it is also possible that the Ag-IgM complex recruits other components of complement or other factors that can activate other members of the adaptive immune system. As it is now possible to produce commercial-scale quantities of monoclonal human IgM antibodies, understanding the role of the IgM in linking the innate and adaptive immune systems may lead to practical therapeutic applications.

Monitoring the systemic human memory B cell compartment of melanoma patients for anti-tumor IgG antibodies

Melanoma, a potentially lethal skin cancer, is widely thought to be immunogenic in nature. While there has been much focus on T cell-mediated immune responses, limited knowledge exists on the role of mature B cells. We describe an approach, including a cell-based ELISA, to evaluate mature IgG antibody responses to melanoma from human peripheral blood B cells. We observed a significant increase in antibody responses from melanoma patients (n = 10) to primary and metastatic melanoma cells compared to healthy volunteers (n = 10) (P<0.0001). Interestingly, we detected a significant reduction in antibody responses to melanoma with advancing disease stage in our patient cohort (n = 21) (P<0.0001). Overall, 28% of melanoma patient-derived B cell cultures (n = 1,800) compared to 2% of cultures from healthy controls (n = 600) produced antibodies that recognized melanoma cells. Lastly, a patient-derived melanoma-specific monoclonal antibody was selected for further study. This antibody effectively killed melanoma cells in vitro via antibody-mediated cellular cytotoxicity. These data demonstrate the presence of a mature systemic B cell response in melanoma patients, which is reduced with disease progression, adding to previous reports of tumor-reactive antibodies in patient sera, and suggesting the merit of future work to elucidate the clinical relevance of activating humoral immune responses to cancer.

Eliciting carbohydrate-specific immune response against sialosides: success and challenges

Chemoenzymatic synthesis has been shown to be a powerful adjunct to carbohydrate chemistry since it allows chemists to prepare a wide range of complex carbohydrate analogs in large amounts and with unparalleled efficiency. Here we summarize investigations conducted in our group into the synthesis and immunochemistry of tumor-associated gangliosides and the development of a chemoenzymatic route to α(2→8)-linked oligosialosides by probing substrate binding to the enzyme, α(2→8)-sialyltransferase.

Vaccine-induced antibody responses in patients with carcinoma

Cancer vaccines based on defined antigens are capable of inducing antibodies that recognize and kill tumor cells. Antibodies are ideally suited to address minimal residual disease, and vaccination in an adjuvant setting may favorably influence the outcome of a disease. The present article gives a short summary of antibody production by B cells, and the mechanism of action of antibodies, as well as a description of the current methods for measuring antibody responses and for assessing their antitumor efficacy in the context of clinical trials. It concludes with an overview of antibody responses induced by vaccines based on structurally defined tumor-associated antigens tested in patients with carcinomas. Correlation between antibody responses, T-cell responses and clinical outcome has been noted in a few studies, signaling the importance of vaccine design and adjuvants to exploit the interactions of the innate and adaptive immune system. However, humoral responses, which may provide a surrogate marker for T-helper responses and simplify monitoring of large Phase III trials, are still not or incompletely explored in many vaccination trials.

Bridging innate and adaptive antitumor immunity targeting glycans

Effective immunotherapy for cancer depends on cellular responses to tumor antigens. The role of major histocompatibility complex (MHC) in T-cell recognition and T-cell receptor repertoire selection has become a central tenet in immunology. Structurally, this does not contradict earlier findings that T-cells can differentiate between small hapten structures like simple glycans. Understanding T-cell recognition of antigens as defined genetically by MHC and combinatorially by T cell receptors led to the “altered self” hypothesis. This notion reflects a more fundamental principle underlying immune surveillance and integrating evolutionarily and mechanistically diverse elements of the immune system. Danger associated molecular patterns, including those generated by glycan remodeling, represent an instance of altered self. A prominent example is the modification of the tumor-associated antigen MUC1. Similar examples emphasize glycan reactivity patterns of antigen receptors as a phenomenon bridging innate and adaptive but also humoral and cellular immunity and providing templates for immunotherapies.

Translational research in melanoma

Current treatment of malignant melanoma exemplifies not only the need for translational research but also many of the challenges of moving from bench to bedside. Melanoma remains unique among solid tumors in that its treatment primarily is surgical. Radiation is of limited benefit, and chemotherapy has been disappointing in both the adjuvant and metastatic settings. This leaves clinicians with few options for reducing the chance of recurrence after surgery and for treating unresectable disease. With this in mind, there has been a fervent attempt to identify novel approaches to melanoma therapy and translate them into clinical use.

Development of an ELISA to detect Sin Nombre virus-specific IgM from deer mice (Peromyscus maniculatus)

Peromyscus maniculatus (deer mouse) is the primary reservoir for Sin Nombre virus (SNV). Although the presence of IgG antibodies is often used as a marker of infection, it provides little information on active infections in a population but usually is an indicator of past infections. The presence of IgM antibodies is a much better marker for determining whether active infections are present in a population. A mu-capture SNV-specific IgM enzyme linked immunosorbent assay (ELISA) was developed. From live-trap and release studies a total of 68 rodent sera were studied for the presence of Sin Nombre virus-specific IgG and IgM antibodies. In these studies, IgM responses were detected in a number of animals. In some cases early SNV infection was determined through the presence of anti-SNV IgM before IgG antibodies could be detected. From the set of animals analyzed, it was concluded that the IgM response against SNV can persist anywhere from 1 to up to over 2 months, with a median of less than 1 month. Most importantly, it was demonstrated that anti-Sin Nombre virus IgM is an important tool for detection of early infections in rodents and should be considered as a key diagnostic tool.

Antibody response to GD3 ganglioside is independent of NKT cells

BACKGROUND

NKT cells recognize glycolipids presented by CD1d on antigen-presenting cells (APC) and have been largely characterized by their ability to be activated by alpha-galactosylceramide, a glycolipid not expressed on mammalian cells. We have shown previously that GD3 can be cross-presented by CD1d to NKT cells and is the first tumor-derived glycolipid recognized by NKT cells. But the ability of NKT cells to modulate B-cell responses to tumor glycolipids that are themselves recognized by NKT cells has not been explored.

METHODS

We tested whether NKT cells are required for antibody (Ab) responses to GD3. We immunized wild-type mice, mice deficient in invariant chain NKT cells (iNKT cells) and mice deficient in total NKT cells against GD3. Ab titer against GD3 was measured by ELISA.

RESULTS

We found the IgM and IgG responses against GD3 were similar among the three strains of mice, including the IgG isotypes induced. Pre-expanded NKT cells to GD3 did not affect the anti-GD3 Ab response.

DISCUSSION

We conclude that Ab responses to GD3 are independent of NKT cells and that strategies to manipulate NKT cells in vivo are not likely to enhance the anti-GD3 Ab response induced by vaccines.

Recombinant human hexamer-dominant IgM monoclonal antibody to ganglioside GM3 for treatment of melanoma

PURPOSE

L612, a human IgM monoclonal antibody produced by an EBV-transformed human B-cell line, binds to ganglioside GM3 and kills GM3-positive human melanoma cells in the presence of complement. It has been shown to be effective in some patients with late-stage melanoma. L612 consists of hexameric IgM (about 20%), pentameric IgM (about 74%), and other minor IgM molecules. Because hexameric IgM activates complement more effectively than pentameric IgM, we developed and evaluated a hexamer-dominant recombinant IgM for clinical applications.

EXPERIMENTAL DESIGN

Chinese hamster ovary (CHO) cells were transfected with heavy- and light-chain genes of L612, with or without the joining-chain gene. Antitumor effects of the recombinant IgM secreted from CHO cells were evaluated in vitro and in vivo.

RESULTS

Recombinant IgM secreted from CHO cells without the joining chain (designated CA19) was approximately 80% hexameric, whereas recombinant IgM from CHO cells transfected with heavy-, light-, and joining-chain genes (designated CJ45) was about 90% pentameric. Both CA19 and CJ45 recombinant IgMs caused complement-dependent cytotoxicity against human and mouse melanoma cell lines, but the amount of CA19 required for 50% specific cytotoxicity was 5 to 10 times smaller. I.v. injection of CA19 compared with CJ45 or native L612 elicited more profound antitumor activity in nude rats bearing a GM3-positive mouse melanoma xenograft.

CONCLUSIONS

A hexamer-dominant human IgM against GM3 may provide a more potent treatment option for patients with GM3-positive melanoma.

Preclinical studies of carbohydrate mimetic peptide vaccines for breast cancer and melanoma

Limited immune responses to tumor-associated carbohydrate antigens (TACA) are due in part to their being self-antigens. Immunization with xenoantigens of TACA provides an approach to break tolerance and augment responses to TACA. Carbohydrate mimetic peptides (CMPs) as xenoantigens can induce serum antibodies that target shared carbohydrate residues on differing carbohydrate structures. In preclinical studies, we observe that CMP immunization in mice induce immune responses that are effective in inhibiting the in vitro and in vivo growth of breast cancer and melanoma tumor cells expressing self-target antigens. CMPs of TACA can be further defined that induce IgM antibodies with broadened responses to both breast and melanoma cells. Consequently, CMPs are effective at generating a multifaceted carbohydrate-reactive immune response that should be clinically evaluated for their ability to amplify carbohydrate immune responses against circulating or disseminated tumor cells.

The immune response to disialoganglioside GD3 vaccination in normal dogs: a melanoma surface antigen vaccine

As a result of its metastatic potential, canine malignant melanoma like its human counterpart like its human counter part, has a poor response to conventional treatment protocols. This prompted us to investigate the possibility of enhancing the immune response against the melanoma cell surface antigen, disialoganglioside GD3. Initially a flow cytometric study was designed in which the incidence of GD3 on the cell surface, recognized by the monoclonal antibody Mel-1 (R24), was established in canine melanoma cell lines. Results from the flow cytometry found GD3 to be highly expressed (94.2%) in six out of seven canine melanoma cell lines. Since it was thus potentially a good target, a study in which normal dogs were vaccinated intradermally with a vaccine containing GD3 plus adjuvants was designed. The adjuvant included CpG oligodeoxynucleotide (CpG-ODN) sequences and RIBI-adjuvant, which are known to target toll-like receptors (TLR) of the innate immune system. From a cohort of 10 dogs, 4 were vaccinated 3 times, at 4 weekly intervals with GD3 plus adjuvant, and 4 received only RIBI-adjuvant, and 2 phosphate buffered saline. Caliper measurements were collected to assess skin reaction at the vaccination site and sera assayed for IgM and IgG antibodies against GD3 and cell-mediated cytotoxicity against a melanoma cell line. Results from the study found significant differences (P<0.05) in the vaccine site reactions, IgM/IgG levels and cell-mediated cytotoxicity in the vaccinated versus unvaccinated dogs. The addition of CpG-ODN sequences and increasing GD3 concentration in the vaccine increased the inflammation response at the injection site. GD3 IgG and IgM antibodies in vaccinated dogs showed increasing titers over time and achieved significance at weeks 9 and 12, respectively. Cell-mediated cytotoxicity was only detected in peripheral blood mononuclear cells from vaccinated dogs. In conclusion, by combining the tumor antigen GD3 (a known weak self-antigen) and an adjuvant, tolerance was overcome by an innate and adaptive immune response in this population of normal dogs.

Development of human–human hybridoma from anti-Her-2 peptide–producing B cells in immunized NOG mouse

OBJECTIVE

Numerous monoclonal antibodies have been developed for the purpose of medical treatments, including cancer treatment. For clinical application, the most useful are human-derived antibodies. In this study, we tried to prepare designed antigen-specific antibodies of completely human origin using immunodeficient mouse.

METHODS

Nonobese diabetic/severe combined immunodeficient/IL-2 receptor gamma null mouse (NOG) mouse was used to reconstitute the human immune system with umbilical cord blood hematopoietic stem cells (CB-NOG mouse) and to prepare human-derived Her-2-epitope-specific antibodies. Hybridoma lines were prepared by fusing the human myeloma cell line Karpas707H.

RESULTS

Serum of immunized NOG mouse contained human-derived immunoglobulin M (IgM) antibodies specific for a short peptide sequence of 20 amino acids, including the epitope peptide of apoptotic Her-2 antibody CH401. Hybridoma lines were successfully prepared with spleen B cells obtained from the immunized CB-NOG mouse. One of these cell lines produced human IgM against the epitope peptide that can recognize surface Her-2 molecule.

CONCLUSION

We could produce human-derived IgM antibody against Her-2 epitope peptide in CB-NOG mouse, succeeding in generation of human hybridoma-secreting IgM against a given peptide.

Cellular and humoral immune response to N-Glycolyl-GM3 elicited by prolonged immunotherapy with an anti-idiotypic vaccine in high-risk and metastatic breast cancer patients

In this study, the immunogenicity and toxicity profile of 1E10, an anti-idiotypic vaccine mimicking the N-glycolyl-GM3 ganglioside, was investigated with an extended vaccination protocol. The year-long vaccination scheme consisted of 6 biweekly intradermal injections (induction phase), followed by 10 monthly boosters (maintenance). Nineteen patients with high-risk (stage III) or metastatic breast cancer were vaccinated with different dose levels of 1E10 (0.5, 1, and 2 mg). The humoral and cellular responses to 1E10 and the targeted ganglioside were assessed at baseline and throughout the treatment. Local skin reactions represented the most common adverse event (National Cancer Institute Toxicity Criteria (NCIC) grades I and II), followed by mild flu-like symptoms lasting for 1 to 2 days. Two patients were removed from the study because of vaccine-related hypersensitivity reactions. A third patient was removed from the study after a transient loss of consciousness with uncertain relation to the vaccine. All patients showed a strong antibody response to the targeted ganglioside. In addition, ganglioside-specific T-cell responses were recorded in 5 of 13 evaluable patients. Vaccination with 1E10 was immunogenic and relatively well tolerated. Because similar results were observed with the 3 tested dose levels, the 0.5-mg dose level was selected for future trials.

Emerging melanoma vaccines

No satisfactory treatment currently exists for melanoma once it has spread beyond its original site. At present, the only FDA-approved treatment for advanced melanoma is IFN-alpha2b. Vaccines are an experimental therapy intended to stimulate the immune system to react more strongly against patients' own melanoma cells, thereby destroying the tumour or slowing its progression. Unfortunately, the exact tumour antigens that can stimulate an effective tumour-protective response in humans remain unknown. The approach that is increasingly followed to circumvent this problem is to prepare polyvalent vaccines containing a variety of melanoma antigens, as the greater the number of antigens in a vaccine, the greater the chance it will contain the correct antigen(s) to stimulate an antitumour response. Two recent randomised trials suggest that this approach results in vaccines that can be clinically effective. One is a double-blind, placebo-controlled trial of a polyvalent, shed antigen melanoma vaccine developed by Bystryn and licenced to NeoVac; the other is a larger randomised trial of Melacine (Corixa Corp.), a vaccine prepared from the lysate of two melanoma cell lines adjuvanted with Detox, which was developed by Mitchell and commercialized by Corixa. In both cases, tumour progression was delayed in the vaccine-treated patients, although in the latter trial, this was only observed in patients with certain human leukocyte antigen phenotypes. Several other vaccines are currently in Phase III trials, but the results of these trials are still pending. The major issues that need to be addressed are designing more effective melanoma vaccines with a mix of melanoma-associated antigens that can stimulate clinically beneficial antitumour immune responses, and finding an adjuvant that can safely, easily and powerfully boost the frequency and magnitude of these responses.

Active specific immunotherapy of melanoma with a GM3 ganglioside-based vaccine: a report on safety and immunogenicity

A novel cancer vaccine was obtained by combining GM3 ganglioside with Neisseria meningitidis outer membrane protein complex to obtain very-small-size proteoliposomes (GM3/VSSP). The authors report the results of a phase 1 study of intramuscular administration of GM3/VSSP/Montanide ISA 51 to patients with metastatic melanoma. Twenty-six patients were included in three dose-level cohorts of 120, 240, and 360 mug. The first five doses (induction phase) were given at 2-week intervals, and the remaining four doses were given monthly. Patients were evaluated for dose-related toxicities and antitumor effects. In addition, serum and peripheral blood mononuclear cells were obtained at baseline and throughout treatment to evaluate humoral and cellular immune responses. One episode of severe hypotension and fever was observed in a patient included at the highest dose level. Other toxicities consisted of local reactions at the site of injection and mild fever and chills. Five doses of GM3/VSSP induced an anti-GM3 IgM response in 44% of patients. Serum reactivity was also observed against melanoma cell lines and tumor biopsies. GM3/VSSP was shown to induce very strong in vitro IFNgamma secretion in all evaluated melanoma patients. Furthermore, in one patient IFNgamma secretion was shown to be GM3-specific. A 62% reduction of a mediastinal mass was documented in one patient (partial response), while a second patient benefited from initial disease stabilization followed by tumor reduction in nonmeasurable soft tissue lesions accompanied by vitiligo.

Metastatic melanoma secreted IL-10 down-regulates CD1 molecules on dendritic cells in metastatic tumor lesions

CD1 molecules are expressed by antigen-presenting cells such as dendritic cells and mediate primary immune responses to lipids and glycolipids which have been shown to be expressed by various tumors. Glycolipids are expressed by melanoma cells but, despite their immunogenicity, no efficient spontaneous immune responses are elicited. As IL-10 has previously been shown to down-regulate CD1a on dendritic cells and is known to be expressed by various melanoma cell lines, we investigated if melanoma-derived IL-10 could down-regulate CD1 molecule expression on dendritic cells as a possible way to circumvent immune recognition. We found that CD1a, CD1b, CD1c, and CD1d were significantly down-regulated on dendritic cells in metastatic (n = 10) but not in primary melanoma lesions (n = 10). We further detected significantly higher IL-10 protein levels in metastatic than in primary melanomas. Moreover, supernatants from metastatic melanomas were significantly more effective in down-regulating CD1 molecules on dendritic cells than supernatants from primary melanoma cultures. This effect was blocked using a neutralizing IL-10 antibody in a dose dependent manner. Our findings suggest that metastatic but not primary melanomas can down-regulate CD1 molecules on infiltrating dendritic cells by secreting IL-10 which may represent a novel way to escape the immune response directed against the tumor.

Gangliosides as therapeutic targets for cancer

Gangliosides, sialic acid-containing glycosphingolipids, have engendered great interest for more than 20 years in the search for target molecules of relevance for tumour growth and formation of metastases and as potential targets for immunotherapy. These molecules show large quantitative and structural variability, which is related to cell type and developmental stage. Their potential role in the formation of tumour metastases was suggested from data supporting that they are involved in cell growth regulation and in cell-cell and cell-matrix adhesion. Moreover, gangliosides are expressed on the cell surface and thereby are accessible for antibodies or other ganglioside-binding molecules to induce cell death, inhibit cell growth and/or inhibit formation of tumour metastasis. All tumours exhibit aberrant ganglioside expression. This includes overexpression of normal ganglioside constituents, which appears to be common among various tumours, and expression of gangliosides not found in normal adult tissue but often found during fetal development. The ganglioside composition of melanoma cells has been found to correlate with their metastatic potential and also to be selectively expressed in cells of a tumour mass and invading tumour cells. Passive immunotherapy using murine or murine/human chimeric monoclonal antiganglioside antibodies in their native form or combined with various effector molecules has been investigated. However, the vaccination strategy using native or structurally modified tumour-associated gangliosides in combination with adjuvants is currently the dominant method in clinical trials. The outcomes reported so far vary between type of tumour and treatment strategies. However, we believe that targeting gangliosides is as promising as any other immune therapeutic strategy, and basic research as well as clinical trials utilising new aspects is encouraged.

Granulocyte-macrophage colony-stimulating factor gene-modified autologous tumor vaccines in non-small-cell lung cancer

To evaluate the feasibility, safety, and efficacy of vaccination with autologous tumor cells genetically modified with an adenoviral vector (Ad-GM) to secrete human granulocyte-macrophage colony-stimulating factor (GM-CSF), we conducted a phase I/II multicenter trial in patients with early and advanced stage non-small-cell lung cancer (NSCLC). Vaccines were generated from autologous tumor harvests. Intradermal injections were given every 2 weeks for a total of three to six vaccinations. Tumors were harvested from 83 patients, 20 with early-stage NSCLC and 63 with advanced- stage NSCLC; vaccines were successfully manufactured for 67 patients, and 43 patients were vaccinated. The most common toxicity was a local injection-site reaction (93%). Three of 33 advanced-stage patients, two with bronchioloalveolar carcinoma, had durable complete tumor responses (lasting 6, 18, and >or=22 months). Longer survival was observed in patients receiving vaccines secreting GM-CSF at more than 40 ng/24 h per 10(6) cells (median survival = 17 months, 95% confidence interval [CI] = 6 to 23 months) than in patients receiving vaccines secreting less GM-CSF (median survival = 7 months, 95% CI = 4 to 10 months) (P =.028), suggesting a vaccine dose-related survival advantage.

Phase I pilot clinical trial of human IgM monoclonal antibody to ganglioside GM3 in patients with metastatic melanoma

PURPOSE

A human monoclonal antibody (L612 HuMAb) that binds to ganglioside GM3 has been developed in our laboratory. L612 HuMAb is a 100% human IgM protein. L612 HuMAb binds to cell surface of melanoma and can kill the cells in the presence of complement. The primary objective of this study was to test the toxicity and pharmacokinetics associated with administration of L612 HuMAb to melanoma patients whose tumor cells expressed GM3.

EXPERIMENTAL DESIGN

Nine patients with measurable metastatic melanoma (American Joint Committee on Cancer stage IV) were entered in the study. Eight had failed previous treatments that included chemotherapy, radiation therapy, melanoma cell vaccine, and/or biological therapy. All patients received a 48-h continuous infusion of L612 HuMAb at a dose of 960 mg, 1,440 mg, or 1,920 mg. Five of these patients received a second infusion and one patient received a third infusion, all with the previous dose.

RESULTS

Toxicity was limited to transient and mild pruritus and skin rash. One patient complained of pain at the site of subcutaneous metastases. Serum antibody levels peaked 24 to 48 h after starting the infusion. Two patients, one receiving a single course of 960 mg (612 mg/m(2)) and the second receiving two courses of 1,440 mg (911 mg/m(2)) followed by surgical therapy, are without evidence of disease >5 years after antibody infusion.

CONCLUSIONS

The human IgM monoclonal antibody, L612 HuMAb, was well tolerated. Infusion of L612 HuMAb appears to produce significant antitumor activity in melanoma patients.

Clinical application of dendritic cells in cancer vaccination therapy

During the last decade use of dendritic cells (DC) has moved from murine and in vitro studies to clinical trials as adjuvant in cancer immunotherapy. Here they function as delivery vehicles for exogenous tumor antigens, promoting an efficient antigen presentation. The development of protocols for large-scale generation of dendritic cells for clinical applications has made possible phase I/II studies designed to analyze the toxicity, feasibility and efficacy of this approach. In clinical trials, DC-based vaccination of patients with advanced cancer has in many cases led to immunity and in selected patients to tumor regression. However, the majority of clinical trials are still in phase I, and interpretations are hampered by pronounced variation in study design related to technical aspects of DC preparation, treatment and schedule, monitoring of immune response, and clinically relevant endpoints, including toxicity and response evaluation. This paper aims to review the technical aspects and clinical impact of vaccination trials, focusing on the generation of DC-based vaccines, evaluation of immunologic parameters and design of clinical trials necessary to meet the need for good laboratory and clinical practice.

Tumor vaccines: a role in preventing recurrence in melanoma?

Patients presenting with thick primary melanomas or those with regional nodal metastases have a high risk of recurrence after surgery alone. Chemotherapy has limited efficacy in the adjuvant setting, and while the use of high-dose interferon in the adjuvant setting has been reported to improve survival, treatment with interferon is not without significant cost and toxicity. Mounting evidence suggests a prominent role for the immune system in the natural history of melanoma, and the clinical success of interferon highlights the potential for immunotherapy to prevent recurrence. Many researchers hope to use melanoma vaccines to reduce recurrence without significant toxicity, and many different vaccine strategies are under investigation. Peptide vaccines attempt to induce immunity to melanoma MHC-restricted peptide antigens by delivering the peptide to the patient along with an immune adjuvant meant to induce inflammation and stimulate immunity. While peptide vaccines have advantages with regard to cost and feasibility, it is still unclear whether highly purified peptides will stimulate an adequate immune response. An alternative approach is the use of cellular vaccines. Autologous cellular vaccines present all biologically relevant antigens to the immune system, but this is limited to individuals with sufficient tumor to prepare a vaccine. Allogeneic cellular vaccines are based on the fact that melanoma-associated antigens are shared among a large number of patients, so a vaccine prepared from a cultured cell line could stimulate an anti-tumor immune response in many patients. Allogeneic vaccines are available for all patients, and can be standardized, preserved and distributed in a manner akin to any other therapeutic agent. Because of this, they are more readily available for evaluation in large trials, and there are two major allogeneic vaccines presently being evaluated as an adjuvant therapy for melanoma. Several additional approaches to vaccine therapies are being investigated including among others ganglioside vaccines, viral oncolysates, cytokine gene-modified tumor cell vaccines, dendritic cell vaccines, anti-idiotype antibodies and DNA vaccines. While there appears to be tremendous potential for vaccines, it must be remembered that there has been significant interest in immunotherapy for melanoma for over 50 years and, to date, no large prospective, randomized trial has shown a survival benefit.

Immunotherapy of advanced breast cancer with a heterophilic ganglioside (NeuGcGM3) cancer vaccine

PURPOSE

A heterophilic ganglioside cancer vaccine was developed by combining NeuGcGM3 with the outer membrane protein complex of Neisseria meningitidis to form very small size proteoliposomes (VSSP). A phase I clinical trial was performed to determine safety and immunogenicity of this vaccine.

PATIENTS AND METHODS

Stage III to IV breast cancer patients received up to 15 (200 micro g) doses of the vaccine by intramuscular injection. The first five doses (induction phase) were given at 2-week intervals, with the remaining treatment (maintenance) administered on a monthly basis.

RESULTS

Twenty-one patients, 11 of whom had metastatic disease, were included. Main toxicities included erythema and induration at the injection site, sometimes associated with mild pain, and low-grade fever (World Health Organization grades 1 and 2). All treated patients who completed the induction phase developed anti-NeuGcGM3 antibody titers between 1:1,280 and 1:164,000 immunoglobulin G (IgG), and 1:640 and 1:164,000 IgM. Noteworthy specific IgA antibodies were induced by vaccination in all stage III patients and in three stage IV patients. Serum antibody levels were higher in the stage III patients, with the larger increases observed after week 32. The antiganglioside IgG subclasses were mainly IgG1 and IgG3. Hyperimmune sera increased complement-mediated cytotoxicity versus P3X63 myeloma cells and a marked IgG differential reactivity against human mammary ductal carcinoma samples.

CONCLUSION

NeuGcGM3/VSSP/Montanide ISA 51 is an unusual immunogenic ganglioside vaccine and also seems to be safe in this small trial. Immunologic surrogates of activity indicate that this reagent warrants further investigation.

Humoral immune response to a therapeutic polyvalent cancer vaccine after complete resection of thick primary melanoma and sentinel lymphadenectomy

PURPOSE

A therapeutic polyvalent cancer vaccine (Canvaxin vaccine; CancerVax Corp, Carlsbad, CA) induces antibodies to a glycoprotein tumor-associated antigen (TA90). However, endogenous immune responses to TA90 have also been reported. This study examined anti-TA90 antibody responses with respect to the survival of patients who received adjuvant vaccine immunotherapy after resection of thick (> or = 4 mm) primary cutaneous melanoma.

PATIENTS AND METHODS

Serum specimens were obtained from 54 patients immediately before and then 1, 2, 4, and 6 months after wide local excision of thick primary cutaneous melanoma and sentinel lymphadenectomy. All patients were offered adjuvant therapies with the vaccine, high-dose interferon, or other agents. An enzyme-linked immunosorbent assay was used to determine serial serum titers of immunoglobulin G (IgG) and IgM antibodies against TA90. These titers were correlated with clinical course.

RESULTS

Forty-three patients chose vaccine therapy, and 11 patients chose postoperative observation. Preoperative anti-TA90 IgG and IgM titers were similar for vaccine and observation groups (P =.184). At a median follow-up of 26 months, univariate analysis of Cox regression showed that disease-free survival and overall survival of vaccine patients were significantly correlated with maximal IgM response (P =.0006 and.006, respectively) but not with maximal IgG response (P =.73 and.95, respectively). Neither response predicted survival in the observation group.

CONCLUSION

Postoperative vaccine therapy may enhance IgG and IgM immune responses to TA90 after surgical resection, but only the IgM response is correlated with improved survival. These findings may become useful to guide selection of patients for postoperative adjuvant therapy of high-risk melanoma.

Adjuvant therapy for high-risk primary and resected metastatic melanoma

Patients with thick, primary melanoma and regional lymph-node metastases are at moderate to high risk of recurrence and death, despite apparent complete surgical removal. Immune responses can be demonstrated against melanoma and this has prompted the conduct of a number of randomized trials of immunotherapy. Several trials have been completed and show minimal benefit in prolonging survival or recurrence from melanoma. Similarly, a large number of trials has been conducted to test the efficacy of alpha-2-interferon (IFN-alpha2) in therapy. Clear benefit in recurrence-free survival was shown in several trials, however there is a lack of convincing evidence of an effect on overall survival. Several trials of vaccine and IFN-alpha2 therapy are still in progress and their results are awaited with great interest. The use of high-dose IFN-alpha2 therapy remains a contentious subject, however available evidence suggests the standard of care remains good surgical management.

Vaccines for melanoma

Melanoma vaccines are now an accepted but still experimental treatment for patients who have been rendered clinically free of disease by surgical resection but are at high risk of recurrence and in selected patients with advanced but still limited disease. In general, there seems to be a correlation between the ability of melanoma vaccines to stimulate antimelanoma cellular or antibody immune responses and improved clinical outcome. Accordingly, a number of strategies are now being pursued to improve the clinical effectiveness of this first generation of vaccines by improving their ability to stimulate antimelanoma immunity. To establish the true effectiveness of vaccines in the treatment of malignant melanoma, several large, prospectively randomized phase III studies are currently being conducted.

Active immunotherapy by reinduction with a polyvalent allogeneic cell vaccine correlates with improved survival in recurrent metastatic melanoma

BACKGROUND

We have observed prolonged survival in patients undergoing vaccine reinduction after resection of recurrent metastatic melanoma and adjuvant polyvalent allogenic cell vaccine (PACV) immunotherapy. We hypothesized that reinduction with a more intensive vaccine regimen would re-stimulate specific immune responses that were correlated with survival after recurrence.

METHODS

From 1996 to 1998, 194 patients developed recurrence during adjuvant PACV (CancerVax vaccine) treatment after resection of metastatic melanoma. Recurrent disease was treated with or without vaccine reinduction. Reinduction regimen entailed an increased vaccine frequency and coadministration of two doses of bacille Calmette-Guérin (BCG). PACV Delayed-type hypersensitivity (DTH) responses were prospectively recorded. Survival was defined as the interval from recurrence to death.

RESULTS

Ninety-four patients underwent reinduction immunotherapy. DTH responses to PACV before recurrence increased significantly after reinduction therapy (P =.0001). The median survival time was 37 months for reinduced patients and 17 months for other patients. On multivariate analysis, reinduction status remained a significant prognostic variable (P =.0277). In the reinduction group, there was a significant correlation between PACV DTH responses and survival (P =.0178).

CONCLUSIONS

Reinduction vaccine regimen can enhance immune responses in previously immunized patients and is associated with prolonged survival after recurrence in patients receiving the same active specific immunotherapy.

Immunologic monitoring of cancer vaccine therapy: results of a workshop sponsored by the Society for Biological Therapy

The Society for Biological Therapy held a Workshop last fall devoted to immune monitoring for cancer immunotherapy trials. Participants included members of the academic and pharmaceutical communities as well as the National Cancer Institute and the Food and Drug Administration. Discussion focused on the relative merits and appropriate use of various immune monitoring tools. Six breakout groups dealt with assays of T-cell function, serologic and proliferation assays to assess B cell and T helper cell activity, and enzyme-linked immunospot assay, tetramer, cytokine flow cytometry, and reverse transcription polymerase chain reaction assays of T-cell immunity. General conclusions included: (1) future vaccine studies should be designed to determine whether T-cell dysfunction (tumor-specific and nonspecific) correlated with clinical outcome; (2) tetramer-based assays yield quantitative but not functional data (3) enzyme-linked immunospot assays have the lowest limit of detection (4) cytokine flow cytometry have a higher limit of detection than enzyme-linked immunospot assay, but offer the advantages of speed and the ability to identify subsets of reactive cells; (5) antibody tests are simple and accurate and should be incorporated to a greater extent in monitoring plans; (6) proliferation assays are imprecise and should not be emphasized in future studies; (7) the reverse transcription polymerase chain reaction assay is a promising research approach that is not ready for widespread application; and (8)there is a critical need to validate these assays as surrogates for vaccine potency and clinical effect. Current data and opinion support the use of a functional assay like the enzyme-linked immunospot assay or cytokine flow cytometry in combination with a quantitative assay like tetramers for immune monitoring. At present, assays appear to be most useful as measures of vaccine potency. Careful immune monitoring in association with larger scale clinical trials ultimately may enable the correlation of monitoring results with clinical benefit.