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Here we describe the identification of genes and their encoded proteins that are expressed in advanced grade tumors by reconstruction of a sarcoma cancer testis gene 1b/a (catg1b/a) network. CTAG1B/A is an ortholog of the yeast/Drosophila transcription factor Pcc1p, and a member of the KEOPS transcription complex. It has been implicated in telomere maintenance and transcriptional regulation through association with chromatin remodeling factors and is only expressed during adult testis germ cell differentiation. Ctag1b/a is re-activated in synovial sarcomas and myxoid liposarcomas but not in differentiated liposarcomas. We mapped CTAG1B/A protein to sarcoma transcription pathways with gene set expression analysis (GSEA) and using independent samples, we immunohistochemically identified expression of at least two network neighbors, RANBP2, and TLE1, thus validating our approach. This work demonstrates that mapping unknown genes to functional pathways by network re-construction is a powerful tool that can be used to identify candidate oncoproteins.

Melan-A is a cancer testis antigen commonly found in melanoma, and has been shown to stimulate the body's immune response against cancerous cells. We have developed and executed a process utilizing current good manufacturing practices (cGMP) to produce the 6 times-His tagged protein in C41DE3 Escherichia coli for use in Phase I clinical trials. Approximately 11 g of purified Melan-A were produced from a 20 L fed-batch fermentation. Purification was achieved through a three column process utilizing immobilized metal affinity, anion exchange, and cation exchange chromatography with a buffer system optimized for low-solubility, high LPS binding capacity proteins. The host cell proteins, residual DNA, and endotoxin concentration were well below limits for a prescribed dose with a final purity level of 91%., (Copyright © 2013 Elsevier Inc. All rights reserved.)

During cancer progression, malignant cells may evade immunosurveillance. However, evidence for immunological escape in humans is scarce. We report here the clinical course of a melanoma patient whose initial tumor was positive for the antigens NY-ESO-1, MAGE-C1, and Melan-A. Upon immunization with a recombinant vaccinia/fowlpox NY-ESO-1 construct, the patient experienced a mixed clinical response and spreading of the NY-ESO-1 epitopes in the CD4+ T cell compartment. After NY-ESO-1 protein + CpG immunization, the patient's anti-NY-ESO-1 IgG response increased. Over the following years, progressing lesions were resected and found to be NY-ESO-1-negative while being positive for MAGE-C1, Melan-A, and MHC-I. The fatal, inoperable brain metastasis was analyzed after his death and also proved to be NY-ESO-1-negative, while being positive for MAGE-C1 and Melan-A, as well as MHC-I. We propose that cancer control and cancer escape in this patient were governed by NY-ESO-1-specific immunological pressure. Our findings provide evidence for the existence of immunoediting and immunoescape in this cancer patient.

We investigated whether antibodies against intracellular tumor-associated antigens support tumor-specific immunity when administered together with a treatment that destroys the tumor. We propose that released antigens form immune complexes with the antibodies, which are then efficiently taken up by dendritic cells. We cloned the first human monoclonal antibodies against the Cancer/Testis (CT) antigen, NY-ESO-1. We tested whether the monoclonal anti-NY-ESO-1 antibody (12D7) facilitates cross-presentation of a NY-ESO-1-derived epitope by dendritic cells to human CD8+ T cells, and whether this results in the maturation of dendritic cells in vitro. We investigated the efficacy of 12D7 in combination with chemotherapy using BALB/c mice bearing syngeneic CT26 tumors that express intracellular NY-ESO-1. Human dendritic cells that were incubated with NY-ESO-1:12D7 immune complexes efficiently stimulated NY-ESO-1(157-165)/HLA-A2-specific human CD8+ T cells to produce interferon-γ, whereas NY-ESO-1 alone did not. Furthermore, the incubation of dendritic cells with NY-ESO-1:12D7 immune complexes resulted in the maturation of dendritic cells. Treatment of BALB/c mice that bear CT26/NY-ESO-1 tumors with 5-fluorouracil (5-FU) plus 12D7 was significantly more effective than chemotherapy alone. We propose systemic injection of monoclonal antibodies (mAbs) against tumor-associated antigens plus a treatment that promotes the local release of those antigens resulting in immune complex formation as a novel therapeutic modality for cancer.

Based on their inability to express argininosuccinate synthetase (ASS), some cancer entities feature the characteristic of L-arginine (Arg) auxotrophy. This inability to intrinsically generate Arg makes them applicable for arginine deiminase (ADI) treatment, an Arg-depleting drug. Arg is also used for the synthesis of endothelial nitric oxide (NO), which mainly confers vasodilatation but is also considered to have a major influence on tumor vascularization. The purpose of this study was to define changes in tumor vasculature in an ADI-treated melanoma xenograft mouse model using the blood pool agent AngioSense 750 and fluorescence molecular tomography (FMT). We used an ASS-negative melanoma xenograft mouse model and subjected it to weekly ADI treatment. Changes in tumor size were measured, and alterations in tumor vasculature were depicted by FMT and CD31 immunohistochemistry (IHC). On ADI treatment and effective antitumor therapy, we observed a drop in NO plasma levels and visualized changes in tumor vascularization with FMT and IHC. ADI treatment in melanoma xenografts has a tumor-reducing effect, which can be noninvasively imaged by quantifying tumor vascularization with FMT and IHC.

Cancer/testis (CT) antigens are considered target molecules for cancer immunotherapy. To identify novel CT antigens, immunoscreening of a testicular cDNA library was performed using serum obtained from a colon cancer patient who was immunized with a new dendritic cell vaccine. We isolated 64 positive cDNA clones comprised of 40 different genes, designated KP-CoT-1 through KP-CoT-40. Three of these putative antigens, including KP-CoT-23 (CCDC83), had testis-specific expression profiles in the Unigene database. RT-PCR analysis showed that the expression of 2 KP-Cot-23 variants was restricted to the testis in normal adult tissues. In addition, KP-CoT-23 variants were frequently expressed in a variety of tumors and cancer cell lines, including colon cancer. A serological western blot assay showed IgG antibodies to the KP-CoT-23 protein in 26 of 37 colon cancer patients and in 4 of 21 healthy patients. These data suggest that KP-CoT-23 is a novel CT antigen that may be useful for the diagnosis and immunotherapy of cancer.

SEREX has proven to be a powerful method that takes advantage of the presence of spontaneous humoral immune response in some cancer patients. In this study, immunoscreening of normal testis and two ovarian cancer cell line cDNA expression libraries with sera from ovarian cancer patients led to the isolation of 75 independent antigens, designated KP-OVA-1 through KP-OVA-75. Of these, RT-PCR showed KP-OVA-52 to be expressed strongly in normal testis, in ovarian cancer cell lines (3/9) and in ovarian cancer tissues (1/17). The expression of KP-OVA-52 in cancer cells is also induced by the demethylating agent 5‑aza‑2'‑deoxycytidine (ADC). To test immunogenicity, we used the Serum Antibody Detection Assay (SADA) to analyze anti-IgG antibodies against the 75 antigens that were initially isolated by SEREX. Four of the 75 antigens (KP‑OVA‑25, KP‑OVA‑35, KP‑OVA‑68 and KP‑OVA‑73) reacted exclusively with sera from cancer patients. However, KP‑OVA‑52 reacted with 1 of 20 ovarian cancer sera. These data suggest that the KP-OVA-52 can be considered a novel CT antigen that is regulated by DNA methylation.

Unlabelled: Because of deficiencies in l-arginine biosynthesis, some cancers are susceptible to therapeutic intervention with arginine deiminase (ADI), an enzyme responsible for consuming the dietary supply of l-arginine to deprive the disease of an essential nutrient. ADI is currently being evaluated in several clinical trials, and fully realizing the drug's potential will depend on invoking the appropriate metrics to judge clinical response. Without a clear biologic mandate, PET/CT with (18)F-FDG is currently used to monitor patients treated with ADI. However, it is unclear if it can be expected that (18)F-FDG responses will indicate (or predict) clinical benefit., Methods: (18)F-FDG responses to ADI therapy were studied in preclinical models of melanoma in vitro and in vivo. The molecular mechanism of response to ADI therapy was also studied, with a particular emphasis on biologic pathways known to regulate (18)F-FDG avidity., Results: Although proliferation of SK-MEL 28 was potently inhibited by ADI treatment in vitro and in vivo, no clear declines in (18)F-FDG uptake were observed. Further investigation showed that ADI treatment induces the posttranslational degradation of phosphatase and tensin homolog and the activation of the PI3K signaling pathway, an event known to enhance glycolysis and (18)F-FDG avidity. A more thorough mechanistic study showed that ADI triggered a complex mechanism of cell death, involving apoptosis via poly (ADP-ribose) polymerase cleavage-independent of caspase 3., Conclusion: These findings suggest that some unexpected pharmacologic properties of ADI preclude using (18)F-FDG to evaluate clinical response in melanoma and, more generally, argue for further studies to explore the use of PET tracers that target apoptotic pathway activation or cell death.

The novel cancer/testis antigen gene, NY-SAR-35, is expressed exclusively in normal testis and in various histological types of tumor. However, the NY-SAR-35 gene expression is observed to be aberrant in several cancer cell lines and tissues. The analysis of methylation status of the NY-SAR-35 gene promoter in various cancer cell lines showed that its expression was related to methylation of the promoter region. Treatment of human cancer cell lines with the demethylating agent 5-aza-2'-deoxycytidine activated the expression of the NY-SAR-35 gene. In addition, transfection experiments on various fragments of the CpG-rich gene promoter indicate that in vitro methylation of the NY-SAR-35 gene promoter results in the loss of promoter activity. The expression of NY-SAR-35 is therefore activated by hypomethylation of the CpG island in the gene promoter.

Carbonic anhydrase IX (CAIX) is a hypoxia-induced, membrane-tethered enzyme that is highly expressed in many cancers. It catalyses the hydration of CO(2) to HCO(3)(-) and H(+), and the reverse dehydration reaction. Recent studies have shown an important role for CAIX in pH regulation and it has been speculated that CAIX may play a role in supporting cancer progression towards more aggressive forms of the disease. Clinical correlative studies in many tumours have shown that high expression is related to poor outcome. In the present study, we have selected antigen-binding antibody fragments (Fab) against human CAIX by phage-display, and tested these for inhibitory potency on CAIX catalytic activity. Inhibition was assessed from the kinetics of the CAIX-catalysed reaction, using assays performed on intact cells over-expressing CAIX, and their CAIX-containing membrane fragments. Inhibition was also assessed in multi-cellular tissue-models (spheroids) from the kinetics of CO(2) venting. We have identified a Fab antibody, labelled MSC8, and its corresponding full-length IgG that inhibited CAIX by up to 57% and 76%, respectively, with half-maximal inhibition at 0.3μg/ml. Incubation of CAIX-expressing cells with MSC8 IgG produced a lasting inhibitory effect. The inhibitory effect was prompt and was also observed in isolated membrane-fragments, suggesting that a direct inhibitory interaction takes place between the antibody and CAIX. The inhibitory effects in spheroids argue for a physiological relevance of the antibody. Biologically-active antibodies against CAIX can be used as selective, high-affinity inhibitors in experimental studies to dissect the role of CAIX and, possibly, therapeutically by targeting a catalytically-active cancer-related protein., (Copyright © 2011. Published by Elsevier B.V.)

Activation of murine glucocorticoid-induced tumor necrosis factor-related receptor (mGITR) by its natural ligand (GITRL) or antiGITR agonist mAb enhances T-cell responses, inhibits regulatory T-cell (Treg)-mediated suppression and induces tumor immunity in a variety of murine tumor models. However, systemic administration of these costimulatory agents can lead to global T-cell activation and autoimmunity. To specifically manipulate the T-cell compartment in the tumor microenvironment we propose to target the tumor infiltrating T cells with a bispecific mGITRL fusion protein. For that purpose, mGITRL is linked to a single-chain antibody targeting fibroblast activation protein (FAP) as FAP expression is restricted to cancer-associated fibroblasts (CAFs) found in the stroma of epithelial cancers. AntiFAP-mGITRL fusion protein forms dimers and binds to murine GITR with 1.2 μM affinity and to murine FAP with 4.5 nM. The construct is able to costimulate CD8+ and CD4+ effector T cells resulting in increased proliferation, IFN-γ and IL-2 production. This costimulatory effect is enhanced when the fusion protein is bound to a FAP-positive cell line mimicking FAP CAFs. In suppression assays, membrane-bound antiFAP-mGITRL is 100-fold more effective in overcoming Treg-mediated suppression than unbound fusion protein. These studies suggest that targeted tumor therapy with antiFAP-mGITRL fusion protein could induce tumor rejection while minimizing autoimmune side effects.

Medullary breast carcinoma (MBC) is a relatively rare malignancy with heavy lymphocytic infiltration that despite cytologically anaplastic features and high mitotic index has more favorable prognosis than other types of breast cancer. Lymphocytic infiltration of tumors reflects ongoing immune response against tumor antigens which could represent a great interest as potential targets for cancer immunotherapy. The search for MBC antigens by SEREX methodology has not been successful due to a very high titer of false positive clones, representing immunoglobulin genes. Here, we describe a novel approach for generating cDNA expression libraries from MBC tumor samples which are depleted of IgG cDNA clones and, therefore, are suitable for the identification of novel tumor-associated antigens (TAA) by SEREX approach. Modified methodology allowed us to isolate a panel of known and novel TAA which are currently under further investigation.

Unlike chemotherapy, which acts directly on the tumor, cancer immunotherapies exert their effects on the immune system and demonstrate new kinetics that involve building a cellular immune response, followed by changes in tumor burden or patient survival. Thus, adequate design and evaluation of some immunotherapy clinical trials require a new development paradigm that includes reconsideration of established endpoints. Between 2004 and 2009, several initiatives facilitated by the Cancer Immunotherapy Consortium of the Cancer Research Institute and partner organizations systematically evaluated an immunotherapy-focused clinical development paradigm and created the principles for redefining trial endpoints. On this basis, a body of clinical and laboratory data was generated that supports three novel endpoint recommendations. First, cellular immune response assays generate highly variable results. Assay harmonization in multicenter trials may minimize variability and help to establish cellular immune response as a reproducible biomarker, thus allowing investigation of its relationship with clinical outcomes. Second, immunotherapy may induce novel patterns of antitumor response not captured by Response Evaluation Criteria in Solid Tumors or World Health Organization criteria. New immune-related response criteria were defined to more comprehensively capture all response patterns. Third, delayed separation of Kaplan-Meier curves in randomized immunotherapy trials can affect results. Altered statistical models describing hazard ratios as a function of time and recognizing differences before and after separation of curves may allow improved planning of phase III trials. These recommendations may improve our tools for cancer immunotherapy trials and may offer a more realistic and useful model for clinical investigation.

Purpose: The Cancer Vaccine Consortium of the Cancer Research Institute (CVC-CRI) conducted a multicenter HLA-peptide multimer proficiency panel (MPP) with a group of 27 laboratories to assess the performance of the assay., Experimental Design: Participants used commercially available HLA-peptide multimers and a well characterized common source of peripheral blood mononuclear cells (PBMC). The frequency of CD8+ T cells specific for two HLA-A2-restricted model antigens was measured by flow cytometry. The panel design allowed for participants to use their preferred staining reagents and locally established protocols for both cell labeling, data acquisition and analysis., Results: We observed significant differences in both the performance characteristics of the assay and the reported frequencies of specific T cells across laboratories. These results emphasize the need to identify the critical variables important for the observed variability to allow for harmonization of the technique across institutions., Conclusions: Three key recommendations emerged that would likely reduce assay variability and thus move toward harmonizing of this assay. (1) Use of more than two colors for the staining (2) collect at least 100,000 CD8 T cells, and (3) use of a background control sample to appropriately set the analytical gates. We also provide more insight into the limitations of the assay and identified additional protocol steps that potentially impact the quality of data generated and therefore should serve as primary targets for systematic analysis in future panels. Finally, we propose initial guidelines for harmonizing assay performance which include the introduction of standard operating protocols to allow for adequate training of technical staff and auditing of test analysis procedures.

In a recent vaccination trial assessing the immunogenicity of an NY-ESO-1 (ESO) recombinant protein administered with Montanide and CpG, we have obtained evidence that this vaccine induces specific cytolytic T lymphocytes (CTL) in half of the patients. Most vaccine-induced CTLs were directed against epitopes located in the central part of the protein, between amino acids 81 and 110. This immunodominant region, however, is distinct from another ESO CTL region, 157-165, that is a frequent target of spontaneous CTL responses in A2+ patients bearing ESO tumors. In this study, we have investigated the CTL responses to ESO 157-165 in A2+ patients vaccinated with the recombinant protein. Our data indicate that after vaccination with the protein, CTL responses to ESO 157-165 are induced in some, but not all, A2+ patients. ESO 157-165-specific CTLs induced by vaccination with the ESO protein were functionally heterogeneous in terms of tumor recognition and often displayed decreased tumor reactivity as compared with ESO 157-165-specific CTLs isolated from patients with spontaneous immune responses to ESO. Remarkably, protein-induced CTLs used T-cell receptors similar to those previously isolated from patients vaccinated with synthetic ESO peptides (Vbeta4.1) and distinct from those used by highly tumor-reactive CTLs isolated from patients with spontaneous immune responses (Vbeta1.1, Vbeta8.1, and Vbeta13.1). Together, these results demonstrate that vaccination with the ESO protein elicits a repertoire of ESO 157-165-specific CTLs bearing T-cell receptors that are structurally distinct from those of CTLs found in spontaneous immune responses to the antigen and that are heterogeneous in terms of tumor reactivity, being often poorly tumor reactive.

Numerous techniques are available for investigating protein-ligand interactions. The phage display technique is one such method routinely used to identify antibody-antigen interactions and has the benefit of being easily adaptable to high-throughput screening platforms. Once identified, antigen-binding domains on fragment antibodies or single-chain fragment antibodies (scFv) can be expressed and purified for further studies. In this chapter, we describe a method for high-level expression of a phage display-derived scFv in Pichia pastoris. The phage display-derived antibody A33scFv recognizes a cell surface glycoprotein (designated A33) expressed in colon cancer that serves as a target antigen for radioimmunoimaging and/or immunotherapy of human colon cancer. The expression and purification of A33scFv was optimized for the methylotrophic yeast P. pastoris. P. pastoris with a Mut(S) phenotype was selected to express A33scFv under regulation of the methanol-inducible AOX1 promoter. Here we describe a large-scale fed-batch fermentation process with an efficient online closed-loop methanol control for the production of the recombinant protein. Purification of A33scFv from clarified culture medium was done using a two-step chromatographic procedure using anion exchange and hydrophobic interaction chromatography, resulting in a final product with more than 90% purity. This chapter provides protocols that can be used as a base for process development of recombinant protein expression in P. pastoris and purification of these proteins for use in further functionality studies and in diagnostic and therapeutic applications.

Background: We have been studying the native autoimmune response to cancer through the isolation of human monoclonal antibodies that are cancer specific from cancer patients. To facilitate this work we previously developed a fusion partner cell line for human lymphocytes, MFP-2, that fuses efficiently with both human lymph node lymphocytes and peripheral blood lymphocytes. Using this unique trioma fusion partner cell line we isolated a panel of autologous human monoclonal antibodies, from both peripheral blood and lymph node lymphocytes, which are representative of the native repertoire of anti-cancer specific antibodies from breast cancer patients., Methods: The current study employs immunocytochemistry, immunohistochemistry, Western blot analysis as well as Northern blots, Scatchard binding studies and finally SEREX analysis for target antigen identification., Results: By application of an expression cloning technique known as SEREX, we determined that the target antigen for two monoclonal antibodies, 27.B1 and 27.F7, derived from lymph node B-cells of a breast cancer patient, is the PDZ domain-containing protein known as GIPC1. This protein is highly expressed not only in cultured human breast cancer cells, but also in primary and metastatic tumor tissues and its overexpression appears to be cancer cell specific. Confocal microscopy revealed cell membrane and cytoplasmic localization of the target protein, which is consistent with previous studies of this protein., Conclusion: We have determined that GIPC1 is a novel breast cancer-associated immunogenic antigen that is overexpressed in breast cancer. Its role, however, in the initiation and/or progression of breast cancer remains unclear and needs further clarification.

Homeostasis of inorganic phosphate in the human body is maintained by regulated absorption, metabolism, and excretion. Sodium-dependent phosphate transporters (NaPi) mediate the transport of inorganic phosphate (P(i)) in cells in response to dietary phosphate consumption, hormones, and growth factors. NaPi2b is a member of the sodium-dependent phosphate transporter family, with a distinct pattern of expression and regulation. Signaling pathways activated by mitogens, glucocorticoids, and metabolic factors have been implicated in regulating P(i) transport via NaPi2b. Inactivation of NaPi2b function by mutations has been linked to human pathologies, such as pulmonary alveolar microlithiasis. In this study, we describe the generation and characterization of monoclonal antibodies against human NaPi2b. The monoclonal antibodies were shown to recognize specifically transiently overexpressed and endogenous NaPi2b in commonly used immunoassays, including Western blotting, immunoprecipitation, and immunohistochemistry. These properties make them particularly valuable reagents for elucidating NaPi2b function in health and disease.

T cell-mediated immunity to microbes and to cancer can be enhanced by the activation of dendritic cells (DCs) via TLRs. In this study, we evaluated the safety and feasibility of topical imiquimod, a TLR7 agonist, in a series of vaccinations against the cancer/testis Ag NY-ESO-1 in patients with malignant melanoma. Recombinant, full-length NY-ESO-1 protein was administered intradermally into imiquimod preconditioned sites followed by additional topical applications of imiquimod. The regimen was very well tolerated with only mild and transient local reactions and constitutional symptoms. Secondarily, we examined the systemic immune response induced by the imiquimod/NY-ESO-1 combination, and show that it elicited both humoral and cellular responses in a significant fraction of patients. Skin biopsies were assessed for imiquimod's in situ immunomodulatory effects. Compared with untreated skin, topical imiquimod induced dermal mononuclear cell infiltrates in all patients composed primarily of T cells, monocytes, macrophages, myeloid DCs, NK cells, and, to a lesser extent, plasmacytoid DCs. DC activation was evident. This study demonstrates the feasibility and excellent safety profile of a topically applied TLR7 agonist used as a vaccine adjuvant in cancer patients. Imiquimod's adjuvant effects require further evaluation and likely need optimization of parameters such as formulation, dose, and timing relative to Ag exposure for maximal immunogenicity.

Background: Assessing cancer margins, lymph nodes, and small cancer deposits intraoperatively can be challenging. A new device has become available that allows the detection of positron emission tomography (PET) radiotracers through both high-energy gamma and short-range beta emissions. These PET probes are handheld, allowing for real-time evaluation of cancer using a tool that provides surgeons with better intraoperative assessment of tumor sites., Methods: Within the context of two institutional review board (IRB)-approved protocols investigating new applications of antibody-labeled PET scanning, (124)I-labeled humanized monoclonal antibodies specific for colorectal cancer (huA33) and renal tumors (cG250) were constructed. Patients underwent preoperative PET scans, approximately seven days post-tracer infusion, when tumor-to-nontumor ratios were high. Suspected tumor deposits were evaluated intraoperatively with handheld beta and gamma PET probes., Results: Handheld PET probes detected emissions from all tumors. Count rates from the gamma probe on tumor ranged from 48 to 306 cps, and for the beta probe ranged from 18 to 190 cps. Gamma and beta emissions exhibited a strong positive correlation. The ratio of gamma and beta counts was at least twice that of the background counts for all tumors evaluated., Conclusions: This study is the first to demonstrate the utility of beta probes for the intraoperative detection of radiolabeled antibodies targeting cancer. Importantly, the recorded beta count rates from the beta probe correlate with the count rates from the high-energy gamma probe. Furthermore, the beta probe may offer superior specificity for real-time localization of small tumor deposits, compared to gamma probes. The intraoperative portable PET probe may prove a valuable bridge to combining tumor biology and PET technology to guide surgical therapy.

Introduction: Lewis Y (Le(y)) is a blood group antigen with robust expression on the surface of epithelial tumors, including small cell lung cancer (SCLC), making it a potential target for antibody-based immunotherapy. 3S193, an immunoglobulin G3 monoclonal antibody, has demonstrated superior specificity, affinity, and cytotoxicity over other anti-Le(y) antibodies. A phase I trial of humanized 3S193 (hu3S193) with dosing up to 40 mg/m2 demonstrated tumor targeting without serious toxicities or the development of human anti-human antibodies., Methods: We tested the targeting and pharmacokinetics of hu3S193 in patients with SCLC. Eligibility required progressive SCLC treated with up to three previous chemotherapy regimens, measurable disease not previously irradiated, and tumor samples positive for 3S193 by immunohistochemistry. Patients received four weekly injections of hu3S193, five patients at 10 mg/m2 and five patients at 20 mg/m2. The first and fourth injections were radiolabeled with indium-111 for gamma camera imaging., Results: Of 40 patients screened, 25 of 34 (74%) assessable SCLC tumor samples were 3S193 positive by immunohistochemistry. Ten patients were treated with hu3S193; nine completed all four injections. All fluorodeoxyglucose (FDG)-avid lesions >2 cm were visualized on antibody single-photon emission computed tomography. Some lesions overlying vascular structures could not be visualized. No difference was noted in imaging or pharmacokinetics between the first and fourth injections. Toxicities included grade 2 urticaria (n = 1), grade 1 vomiting (n = 2), and grade 2 hypertension (n = 1) transiently after infusion at the higher dose., Conclusions: Given the strong tumor targeting, particularly at the higher dose, the favorable toxicity profile, and the potential for immunomodulatory effects, hu3S193 warrants further investigation in SCLC.

NY-ESO-1 is a highly immunogenic tumor antigen and a promising vaccine candidate in cancer immunotherapy. Access to purified protein both for vaccine formulations and for monitoring antigen-specific immune responses is vital to vaccine development. Currently available recombinant Escherichia coli-derived NY-ESO-1 is isolated from inclusion bodies as a complex protein mixture and efforts to improve the purity of this antigen are required, especially for later-stage clinical trials. Using yeast cell surface display and fluorescence activated cell sorting techniques, we have engineered an NY-ESO-1 variant (NY-ESO-L5; C(75)A C(76)A C(78)A L(153)H) with a 100x improved display level on yeast compared to the wild-type protein. This mutant can be effectively produced as an Aga2p-fusion and purified in soluble form directly from the yeast cell wall. In the process, we have identified the epitope recognized by anti-NY-ESO-1 mAb E978 (79-87, GARGPESRL). The availability of an alternative expression host for this important antigen will help avoid artifactual false positive tests of patient immune response due to reaction against expression-host-specific contaminants.

Modification in the function of dendritic cells (DC), such as that achieved by microbial stimuli or T cell help, plays a critical role in determining the quality and size of adaptive responses to Ag. NKT cells bearing an invariant TCR (iNKT cells) restricted by nonpolymorphic CD1d molecules may constitute a readily available source of help for DC. We therefore examined T cell responses to i.v. injection of soluble Ag in the presence or the absence of iNKT cell stimulation with the CD1d-binding glycolipid alpha-galactosylceramide (alpha-GalCer). Considerably enhanced CD4(+) and CD8(+) T cell responses were observed when alpha-GalCer was administered at the same time as or close to OVA injection. This enhancement was dependent on the involvement of iNKT cells and CD1d molecules and required CD40 signaling. Studies in IFN-gammaR(-/-) mice indicated that IFN-gamma was not required for the adjuvant effect of alpha-GalCer. Consistent with this result, enhanced T cell responses were observed using OCH, an analog of alpha-GalCer with a truncated sphingosine chain and a reduced capacity to induce IFN-gamma. Splenic DC from alpha-GalCer-treated animals expressed high levels of costimulatory molecules, suggesting maturation in response to iNKT cell activation. Furthermore, studies with cultured DC indicated that potentiation of T cell responses required presentation of specific peptide and alpha-GalCer by the same DC, implying conditioning of DC by iNKT cells. The iNKT-enhanced T cell responses resisted challenge with OVA-expressing tumors, whereas responses induced in the absence of iNKT stimulation did not. Thus, iNKT cells exert a significant influence on the efficacy of immune responses to soluble Ag by modulating DC function.

The serological analysis of antigens by recombinant expression cloning (SEREX) has identified a multitude of new tumor antigens in many different tumor entities. These antigens can be grouped into different classes according to their specificities, with cancer/testis antigens appearing to be the most attractive candidates for vaccine development. The observation that CD8 and CD4 T-cell responses against cancer/testis antigens such as NY-ESO-1 correlate with the presence of specific antibodies demonstrates the importance of serological monitoring patients participating in vaccine trials. However, all serological assays available (Western blot, phage display and ELISA) are hampered by the fact that the protein cannot be analyzed in its natural conformation. We have thus developed a yeast display system where the antigen is expressed on the yeast surface (RAYS), allowing for a more natural folding of the protein. To validate this approach we displayed the A33 colorectal cancer antigen on the yeast cell surface and demonstrated specific binding by an A33 monoclonal antibody recognizing a conformation-dependent epitope on the A33 antigen. We then compared RAYS with the more commonly used ELISA and Western blot serological monitoring methods by analyzing 50 sera from cancer patients with known NY-ESO-1 antibody status and 10 sera from patients with unknown SSX2 antibody status in a blind fashion. RAYS appears at least equivalent to both ELISA and Western blotting for the monitoring of antibodies against NY-ESO-1 as regards specificity and sensitivity, while antibodies against SSX2 were detected more frequently by RAYS than by ELISA or phage display.