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Purpose: CD137 molecule is expressed by activated lymphocytes, and in patients with cancer identifies the tumor-reactive T cells. In solid tumors, high levels of circulating CD137+ T cells are associated with the clinical response and the disease-free status. Here, we examined the role of the CD137+ T cells in the improvement of patients' selection for immunotherapy treatment. Experimental Design: Peripheral blood mononuclear cells derived from 109 patients with metastatic cancer (66 patients for the identification cohort and 43 for the validation cohort) were analyzed for the expression of CD3, CD4, CD8, CD137, and PD1 molecules before the beginning of anti-PD1 therapy. Twenty healthy donors were used as control. The soluble form of CD137 (sCD137) was also analyzed. The CD137+ T cell subsets and the sCD137 were correlated with the clinicopathologic characteristics. The distribution of CD137+ T cells was also examined in different tumor settings. Results: The percentage of CD137+ T cells was higher in healthy donors and in those patients with a better clinical status (performance status = 0–1, n°metastasis≤2) and these high levels were ascribed to the CD8+CD137+ T cell population. The high frequency of CD137+ and CD8+CD137+ T cells resulted as a prognostic factor of overall survival (OS) and progression-free survival (PFS), respectively, and were confirmed in the validation cohort. High levels of CD3+CD137+PD1+ lymphocytes were associated with a low number of metastasis and longer survival. Instead, the high concentration of the immunosuppressive sCD137 in the serum is associated with a lower PFS and OS. In tumor bed, patients with a complete response showed a high percentage of CD137+ and CD8+ T cells. Conclusions: We propose the CD137+ T subset as an immune biomarker to define the wellness status of the immune system for successful anticancer immunotherapy.

Background Immune checkpoint inhibitors (ICIs) have particular, immune-related adverse events (irAEs), as a consequence of interfering with self-tolerance mechanisms. The incidence of irAEs varies depending on ICI class, administered dose and treatment schedule. The aim of this study was to define a baseline (T0) immune profile (IP) predictive of irAE development. Methods A prospective, multicenter study evaluating the immune profile (IP) of 79 patients with advanced cancer and treated with anti-programmed cell death protein 1 (anti-PD-1) drugs as a first- or second-line setting was performed. The results were then correlated with irAEs onset. The IP was studied by means of multiplex assay, evaluating circulating concentration of 12 cytokines, 5 chemokines, 13 soluble immune checkpoints and 3 adhesion molecules. Indoleamine 2, 3-dioxygenase (IDO) activity was measured through a modified liquid chromatography–tandem mass spectrometry using the high-performance liquid chromatography-mass spectrometry (HPLC–MS/MS) method. A connectivity heatmap was obtained by calculating Spearman correlation coefficients. Two different networks of connectivity were constructed, based on the toxicity profile. Results Toxicity was predominantly of low/moderate grade. High-grade irAEs were relatively rare, while cumulative toxicity was high (35%). Positive and statistically significant correlations between the cumulative toxicity and IP10 and IL8, sLAG3, sPD-L2, sHVEM, sCD137, sCD27 and sICAM-1 serum concentration were found. Moreover, patients who experienced irAEs had a markedly different connectivity pattern, characterized by disruption of most of the paired connections between cytokines, chemokines and connections of sCD137, sCD27 and sCD28, while sPDL-2 pair-wise connectivity values seemed to be intensified. Network connectivity analysis identified a total of 187 statistically significant interactions in patients without toxicity and a total of 126 statistically significant interactions in patients with toxicity. Ninety-eight interactions were common to both networks, while 29 were specifically observed in patients who experienced toxicity. Conclusions A particular, common pattern of immune dysregulation was defined in patients developing irAEs. This immune serological profile, if confirmed in a larger patient population, could lead to the design of a personalized therapeutic strategy in order to prevent, monitor and treat irAEs at an early stage.

Cabozantinib (XL-184) is a multitarget tyrosine kinase inhibitor (TKI) targeting receptor tyrosine kinases (RTKs) involved in oncogenesis and angiogenesis. It is currently the standard therapy for medullary thyroid cancer (MTC), metastatic renal cell carcinoma (mRCC), and hepatocellular carcinoma (HCC). Combination of Cabozantinib with immunotherapy is now a standard treatment in metastatic renal cancer, and its efficacy is being tested in ongoing clinical trial in prostate cancer patients. Here, we report that Cabozantinib may exert an immunostimulatory role by inducing immunogenic stress of prostate cancer cells and directly modulating dendritic cells (DCs). Cabozantinib treatment arrested the cell cycle and triggered immunogenic cell death (ICD) in prostate cancer cells in vitro. Cabozantinib had a direct effect on DCs by the down-modulation of β-catenin and change in migratory and costimulatory phenotype of the DCs. These results may suggest possible immunomodulatory effects induced by Cabozantinib that could be exploited to optimize patient-tailored immunotherapeutic treatments.

Glycosylation, the posttranslational linking of sugar molecules to proteins, is notoriously altered during tumor transformation. More specifically in carcinomas, GalNAc-type O-glycosylation, is characterized by biosynthetically immature truncated glycans present on the cancer cell surface, which profoundly impact anti-tumor immune recognition. The tumor-associated glycan pattern may thus be regarded as a biomarker of immune modulation. In epithelial ovarian cancer (EOC) there is a particular lack of specific biomarkers and molecular targets to aid early diagnosis and develop novel therapeutic interventions. The aim of this study was to investigate the ovarian cancer O-glycoproteome and identify tumor-associated glycoproteins relevant in tumor&ndash, dendritic cell (DC) interactions, mediated by macrophage galactose-like C type lectin (MGL), which recognizes the tumor-associated Tn O-glycan. Lectin weak affinity chromatography (LWAC) was employed to probe the O-glycopeptidome by MGL and Vicia villosa agglutinin (VVA) lectin using glycoengineered ovarian cancer cell lines and ovarian cancer tissues as input material. Biochemical and bioinformatics analysis gave information on the glycan arrangement recognized by MGL in tumor cells. The potential MGL binders identified were located, as expected, at the cell membrane, but also within the intracellular compartment and the matrisome, suggesting that MGL in vivo may play a complex role in sensing microenvironmental cues. The tumor glycoproteins binders for MGL may become relevant to characterize the interaction between the immune system and tumor progression and contribute to the design of glycan targeting-based strategies for EOC immunotherapeutic interventions.

With the introduction of immune checkpoint inhibitors (ICIs) and next-generation vascular endothelial growth factor receptor&ndash, tyrosine kinase inhibitors (VEGFR&ndash, TKIs), the survival of patients with advanced renal cell carcinoma (RCC) has improved remarkably. However, not all patients have benefited from treatments, and to date, there are still no validated biomarkers that can be included in the therapeutic algorithm. Thus, the identification of predictive biomarkers is necessary to increase the number of responsive patients and to understand the underlying immunity. The clinical outcome of RCC patients is, in fact, associated with immune response. In this exploratory pilot study, we assessed the immune effect of TKI therapy in order to evaluate the immune status of metastatic renal cell carcinoma (mRCC) patients so that we could define a combination of immunological biomarkers relevant to improving patient outcomes. We profiled the circulating levels in 20 mRCC patients of exhausted/activated/regulatory T cell subsets through flow cytometry and of 14 immune checkpoint-related proteins and 20 inflammation cytokines/chemokines using multiplex Luminex assay, both at baseline and during TKI therapy. We identified the CD3+CD8+CD137+ and CD3+CD137+PD1+ T cell populations, as well as seven soluble immune molecules (i.e., IFN&gamma, sPDL2, sHVEM, sPD1, sGITR, sPDL1, and sCTLA4) associated with the clinical responses of mRCC patients, either modulated by TKI therapy or not. These results suggest an immunological profile of mRCC patients, which will help to improve clinical decision-making for RCC patients in terms of the best combination of strategies, as well as the optimal timing and therapeutic sequence.

Background: Glioblastoma (GBM) is the most common primary malignant brain cancer in adults, with very limited therapeutic options. It is characterized by a severe immunosuppressive milieu mostly triggered by suppressive CD163+ tumor-associated macrophages (TAMs). The efficacy of immune checkpoint inhibitor interventions aimed at rescuing anti-tumor immunity has not been proved to date. Thus, it is critically important to investigate the immunomodulatory mechanisms acting within the GBM microenvironment for the better design of immunotherapeutic strategies. Methods: The immunohistochemical analysis of a panel of immune biomarkers (CD3, FoxP3, CD163, IDO, PDL-1, PD-1 and TIGIT) was performed in paired samples of the tumor core (TC) and peritumoral area (PTA) of nine GBM patients. Results: CD163+ cells were the most common cell type in both the PTA and TC. IDO and PDL-1 were expressed in most of the TC samples, frequently accompanied by TIGIT expression, on the contrary, they were almost absent in the PTA. CD3+ cells were present in both the TC and PTA, to a lesser extent than CD163+ cells, they often were accompanied by PD-1 expression, especially in the TC. FoxP3 was scarcely present. Conclusion: Distinct inhibitory mechanisms can act simultaneously in both the TC and PTA to contribute to the strong immunosuppression observed within the GBM microenvironment. Nevertheless, the PTA shows strongly reduced immunosuppression when compared to the TC, thus representing a potential target for immunotherapies. Moreover, our results support the working hypothesis that immunosuppression and T-cell exhaustion can be simultaneously targeted to rescue anti-tumor immunity in GBM patients.

In renal cancer emerging treatment options are becoming available and there is a strong need to combine therapies to reformulate and adjourn clinical practice. We here highlight and discuss the need to take advantage of the common immune targets to design combined strategies to increase clinical responses.

e14506 Background: RCC is considered a highly immunogenic tumor responding to anti-angiogenetic TKI and immunotherapy. A better understanding of the functions of immune cells in RCC, the immune-modulatory effects of TKIs treatment as well as defining patients most likely to benefit to the different therapies will be crucial to optimize combined or sequential immunotherapeutic approaches in RCC patients. Methods: Monocyte derived Dendritic Cells (DCs) from 10 healthy donors were differentiated in presence of Pazopanib and Sunitinib used at plasmatic equivalent concentration (Sigma-Aldricht). At the end of the culture, DCs were characterized for marker expression, endocytosis, signal transduction and microvesicle release. Similarly, DCs derived from RCC patients were analyzed together with circulating T cells before and during TKI treatments. Results: Pazopanib and Sunitinib differently affect DC differentiation. Pazopanib, but not Sunitinib, strongly improves DC performance as antigen-presenting cells, promoting the upregulation of the maturation markers HLA-DR (+1,5 fold increase compared to Sunitinib-treated DCs), CD40 (+3 fold increase) and CCR7 (+2 fold increase) a decrease in phagocytosis and the inhibition of pERK1/2 signaling. 99% of Sunitinib-DCs expressed PD-L1 vs 80% Pazopanib-DCs , with a higher expression of the receptor as indicated by mean fluoresce intensity (MFI fold increase of +2,1). Similar results were obtained analyzing shedded microvesicles. Results were confirmed in DCs differentiated from RCC patients during Pazopanib treatment (before and at 30 and 60 days) and suggest a reverse of the tumor induced immunosuppression. Moreover, only Pazopanib treatment appears to induce in these patients a defined circulating CD4+ T cell population highly expressing CD137 molecule (%CD4+CD137+: T0:0,3; T30: 4,7; T60:29,4). Conclusions: TKIs can affect immunity in RCC patients. In particular, Pazopanib appears to function as a potent activator of DCs in vitro and in vivo associated with the neo-activation of a CD137+ T cell population. These results can guide for designing novel protocols to combine TKIs with immunoregulatory receptors targeting in RCC.

Background: Cancer stem cells (CSCs) are tumour-initiating cells with self-renewal properties and chemo/radio-resistance. Regulatory T-cells (Tregs) influence CSCs through several mechanisms. In different solid tumours, the presence of both cell populations correlated with poor survival. In vulvar cancer, little is known regarding biological markers able to predict patient prognosis. We investigated the presence and clinical impact of CSCs and infiltrating Treg in primary vulvar cancer. Materials and Methods: Paraffin-embedded tissue specimens derived from 43 patients with vulvar cancer were analyzed by immunohistochemistry for the expression of prominin-1 (CD133), CD24, ATP-binding cassette sub-family G member 2 (ABCG2) (CSC markers) and forkhead box protein P3 (FOXP3) (Treg marker). Results: CD133 expression correlated with younger age at diagnosis (p

Vaccination with priming and expansion of tumour reacting T cells is an important therapeutic option to be used in combination with novel checkpoint inhibitors to increase the specificity of the T cell infiltrate and the efficacy of the treatment. In this phase I/II study, 14 high-risk disease-free ovarian (OC) and breast cancer (BC) patients after completion of standard therapies were vaccinated with MUC1, ErbB2 and carcinoembryonic antigen (CEA) HLA-A2+-restricted peptides and Montanide. Patients were subjected to 6 doses of vaccine every two weeks and a recall dose after 3 months. ECOG grade 2 toxicity was observed at the injection site. Eight out of 14 patients showed specific CD8+ T cells to at least one antigen. None of 4 patients vaccinated for compassionate use showed a CD8 activation. An OC patient who suffered from a lymph nodal recurrence, showed specific anti-ErbB2 CD8+ T cells in the bulky aortic lymph nodes suggesting homing of the activated T cells. Results confirm that peptide vaccination strategy is feasible, safe and well tolerated. In particular OC patients appear to show a higher response rate compared to BC patients. Vaccination generates a long-lasting immune response, which is strongly enhanced by recall administrations. The clinical outcome of patients enrolled in the trial appears favourable, having registered no deceased patients with a minimum follow-up of 8 years. These promising data, in line with the results of similar studies, the high compliance of patients observed and the favourable toxicity profile, support future trials of peptide vaccination in clinically disease-free patients who have completed standard treatments.

MUC1 is a large surface glycoprotein expressed by epithelial cells, which is overexpressed and aberrantly glycosylated in carcinomas. MUC1 is involved in epithelial cell interactions and appears to function as a signal-transducing molecule. The finding that MUC1 can also be expressed in the haematopoietic lineages prompted us to further investigate the possible function(s) of this molecule in haematopoietic cells. In bone marrow differentiating cells, MUC1 was strongly and selectively expressed during erythropoiesis; it was also weakly expressed during megakaryocytopoiesis and granulomonocytopoiesis; however, no correlation between MUC1 and differentiation marker expression was observed in these lineages. In vitro CD34+ cells, induced towards erythroid differentiation, acquired MUC1 transiently, while expressing increasing levels of the lineage marker glycophorin A. MUC1 was absent in the circulating erythrocytes. During erythropoiesis, MUC1 expression was transcriptionally regulated and the molecule underwent phosphorylation. To investigate the possible role of MUC1 during erythropoiesis, we studied the ability of MUC1 to act as ligand for cell-cell interaction. The sialylated MUC1 glycoforms selectively expressed on erythroid cells were able to bind the macrophage-restricted molecule sialoadhesin. These results suggest that MUC1 can function as a cross-talk molecule between the erythroblasts and the surrounding cells during erythropoiesis.

Regulatory T cells (Tregs) are physiologically designed to prevent autoimmune disease and maintain self-tolerance. In tumour microenvironments, their presence is related to a poor prognosis, and they influence the therapeutic outcome due to their capacity to suppress the immune response by cell-cell contact and to release immunosuppressive cytokines. In this study, we demonstrate that Treg immunosuppressive activity can be modulated by the cross-linking between the CD45RA expressed by Tregs and the C-type lectin MGL. This specific interaction strongly decreases the im-munosuppressive activity of Tregs, restoring the proliferative capacity of co-cultured T lymphocytes. This effect can be attributed to changes in CD45RA and TCR signalling through the inhibition of Lck and inactivation of Zap-70, an increase in the Foxp3 methylation status and, ultimately, the reduced production of suppressive cytokines. These results indicate a role of MGL as an immunomodulator within the tumour microenvironment interfering with Treg functions, suggesting its possible use in the design of anticancer vaccines.

Tumor-associated glycoproteins are a group of antigens with high immunogenic interest: The glycoforms generated by the aberrant glycosylation are tumor-specific and the novel glycoepitopes exposed can be targets of tumor-specific immune responses. The MUC1 antigen is one of the most relevant tumor-associated glycoproteins. In cancer, MUC1 loses polarity and becomes overexpressed and hypoglycosylated. Changes in glycan moieties contribute to MUC1 immunogenicity and can modify the interactions of tumor cells with antigen-presenting cells such as dendritic cells that would affect the overall antitumor immune response. Here, we show that the form of the MUC1 antigen, i.e., soluble or as microvesicle cargo, influences MUC1 processing in dendritic cells. In fact, MUC1 carried by microvesicles translocates from the endolysosomal/HLA-II to the HLA-I compartment and is presented by dendritic cells to MUC1-specific CD8+ T cells stimulating IFN-γ responses, whereas the soluble MUC1 is retained in the endolysosomal/HLA-II compartment independently by the glycan moieties and by the modality of internalization (receptor-mediated or non–receptor mediated). MUC1 translocation to the HLA-I compartment is accompanied by deglycosylation that generates novel MUC1 glycoepitopes. Microvesicle-mediated transfer of tumor-associated glycoproteins to dendritic cells may be a relevant biologic mechanism in vivo contributing to define the type of immunogenicity elicited. Furthermore, these results have important implications for the design of glycoprotein-based immunogens for cancer immunotherapy. Cancer Immunol Res; 2(2); 177–86. ©2013 AACR.

Ovarian cancer remains one of the most lethal malignancies in developed countries and recently no improvement in disease free survival (DFS) and overall survival (OS) has been numbered for conventional therapies. Immunotherapy could be employed as consolidation treatment after standard therapies in patients in which disease and immune suppression is minimal. Furthermore, epitope spread and new adjutants have been found to significantly increase the efficacy of novel immunotherapic strategies.This Phase I/II study aimed to improve vaccine potency and enhance immune response of two mucins (MUC-1 and CEA) and Erb-B2 tumour associated antigens (TAAs), with the co-administration of a new adjuvant combination: Montanide ISA51 plus GM-CSF. Keyhole Limpet Hemocyanin (KLH) was adopted as immunological tracker.Ten disease-free HLA-A2 aplotype high-risk serous advanced stage ovarian cancer patients underwent a two-groups safety clinical trial vaccination protocol at “Sapienza” University of Rome from 2007 to 2010. CEA, Erb-B2 and MUC1 expression rates on primary tumours were 40%, 30% and 100%, respectively. Group A (8 patients) received 100μg of each peptide per dose accordingly to the immunohistochemically antigen expression, whereas GroupB (2 patients) was vaccinated with all the peptide regardless TAAs expression at the dose of 500μg each. Vaccination schedule included 6 consecutive peptide vaccine administrations and a recall dose at 3 months from the sixth dose. Results revealed the vaccine to be safe and feasible in ovarian cancer patients. Side effects accounts for ECOG scale 1-2 levels signs (itch, erythema and tumescence at injection site) and symptoms (fever, fatigue and malaise), for both the dose-administered. Good compliance was found to vaccine schedule in all patients enrolled. Secondary endpoints results revealed a 5 years 50% (3/6 patients) DFS and a 83% (5/6 patients) OS in FIGO stages IIIc-IV ovarian cancer patients (60%; 6/10 patients). Moreover, immunological and clinical correlation analysis revealed a significant increased IFNγ CD8+ specific T-cells production along with vaccination steps (χ2=6.67; p

During the last decades, several improvements in treating gynecological malignancies have been achieved. In particular, target therapies, mostly monoclonal antibodies, have emerged as an attractive option for the treatment of these malignancies. In fact, various molecular-targeted agents have been developed for a variety of malignancies with the objective to interfere with a precise tumor associated receptor, essential for cancer cell survival or proliferation, blocking its function, of the cancer cells. Alternatively, monoclonal antibodies have been developed to block immune suppression or enhance functions of immune effector cells. So far, several monoclonal antibodies have been tested for clinical efficacy for the treatment of gynecological cancers. Antibodies against Vascular Endothelial Growth Factor (VEGF) and Epidermal Growth Factor Receptor (EGFR) have been used in different neoplasms such as ovarian and cervical cancer. Catumazumab, a bivalent antibody against CD3 and EpCAM, is effective in the treatment of neoplastic ascites. Other antibodies are peculiar for specific cancer-associated antigen such as Oregovomab against CA125 or Farletuzumab against the folate receptor. Here we describe the preclinical and clinical experience gained up to now with monoclonal antibodies in tumors of the female genital tract and trace future therapeutic and research venues.

Trastuzumab's targeted therapy has become a stronghold for human epidermal growth factor receptor 2 positive breast cancer patients. This humanized monoclonal antibody binds to the extracellular juxta-membrane domain of HER2 and inhibits the proliferation and survival of HER2 dependent cancer cells. The ways by which this molecule exerts its action have been partially elucidated but several new mechanisms are being constantly identified. Several new agents are being introduced that interfere with HER2. Several new immunotherapy strategies are being introduced in order to direct the immune system against cells and tissues that aberrantly overexpressed HER2. We review the strategies currently adopted and those suggested against HER2 expressing tumors.

TPS172 Background: Breast and ovarian cancer remain two of the most lethal malignancies in developed countries (Jemal A. CA Cancer J Clin. 2009;59:225). In breast cancer (Paik S. N Engl J Med. 2008...

Radiofrequency tumor ablation (RFA) is a therapeutic modality for liver cancer patients inducing localized tumor necrosis with maximal preservation of normal liver parenchyma. We investigated the immunomodulatory effects exerted by RFA treatment in liver cancer patients with metastatic liver lesions (13 patients) or hepatocellular carcinoma (HCC) (4 patients). Analysis of lymphocyte subsets by flow cytometry revealed that after RFA, CD3+ T cells, in particular CD4+, were decreased in metastatic cancer patients, while no change was observed in HCC patients. Moreover, RFA induced trafficking of naïve and memory CD62L+ T cells from circulation to tissues. When characterizing the function of T cells, proliferative response to PHA was strongly increased after 48 h from RFA in metastatic cancer patients. Furthermore, T cells produced IFN-gamma in response to the tumor associated MUC1 antigen. In contrast, humoral immune responses against tumor antigens such as MUC1 and HCV proteins were unaffected by RFA treatment, although increase of circulating B cells was observed only in metastatic cancer patients. These results indicate that RFA application can exert an activating effect on the immune system in metastatic cancer patients, favouring trafficking of lymphocyte subsets and enhancing tumor antigen specific cellular immune responses.

The type of interaction between tumor-associated antigens and specialized antigen-presenting cells such as dendritic cells (DCs) is critical for the type of immunity that will be generated. MUC1, a highly O-glycosylated mucin, is overexpressed and aberrantly glycosylated in several tumor histotypes. This results in the expression of tumor-associated glycoforms and in MUC1 carrying the tumor-specific glycan Tn (GalNAcα1-O-Ser/Thr). Glycopeptides corresponding to three tandem repeats of MUC1, enzymatically glycosylated with 9 or 15 mol of GalNAc, were shown to specifically bind and to be internalized by immature monocyte-derived DCs (iDCs). Binding required calcium and the GalNAc residue and was competed out by GalNAc polymer and Tn-MUC1 or Tn-MUC2 glycopeptides. The macrophage galactose-type C-type lectin (MGL) receptor expressed on iDCs was shown to be responsible for the binding. Confocal analysis and ELISA done on subcellular fractions of iDCs showed that the Tn-MUC1 glycopeptides colocalized with HLA class I and II compartments after internalization. Importantly, although Tn-MUC1 recombinant protein was bound and internalized by MGL, the glycoprotein entered the HLA class II compartment, but not the HLA class I pathway. These data indicate that MGL expressed on iDCs is an optimal receptor for the internalization of short GalNAcs carrying immunogens to be delivered into HLA class I and II compartments. Such glycopeptides therefore represent a new way of targeting the HLA class I and II pathways of DCs. These results have possible implications in designing cancer vaccines. [Cancer Res 2007;67(17):8358–67]

Cancer testis tumour associated antigens (C/T-TAAs) were investigated in several gynaecologic and non-gynaecologic neoplasms as possible prognostic markers and targets for immunotherapy. The objective of the present study was to evaluate C/T-TAA expression patterns and prognostic significance in patients affected by vulvar cancer. Melanoma antigen E (MAGE)-A1, MAGE-A4 and NY-ESO-1 expression was determined by immunohistochemistry in paraffin-embedded tissue specimens from 45 primary and 14 recurrent vulvar carcinomas treated with surgery. MAGE-A1, MAGE-A4 and NY-ESO-1 were expressed in 25 (42%), 38 (64%) and 40 (68%) of the 59 samples, respectively. MAGE-A4 was significantly more frequently expressed in tumours with lymph node metastases (p0.002) and in recurrent tumours (p0.02). NY-ESO-1 was more highly expressed by moderately or poorly differentiated tumours (p0.01). This study demonstrates that vulvar cancer frequently expresses C/T-TAAs. Antigen expression correlates with the presence of lymph node metastases and poor tumour differentiation.

The humoral immune response against a tumour-associated antigen, polymorphic epithelial mucin (PEM, MUC1) in cancer patients was studied by isolating specific B cells primed for the antigen. Human B lymphocytes from tumour-draining lymph nodes, obtained from 12 patients with epithelial cancers, were immunoselected with magnetic beads coated with a 60mer synthetic peptide corresponding to three tandem repeats of the protein core of the MUC1 antigen. Short-term cultures of B cells were established utilizing interleukin-10 (IL-10), IL-4 and monoclonal antibody anti-CD40, and were maintained for a maximum of 3␣weeks. B cell culture supernatants contained human anti-MUC1 antibodies, as detected by enzyme-linked immunosorbent assay, in 6/12 of the patients tested. Five of these patients, all with early-stage cancer, also had high levels of circulating anti-MUC1 IgM antibodies in the serum. A significant correlation was found (two-tailed P = 0.041) between the presence of circulating anti-MUC1 antibodies and the ability to isolate PEM-specific B cells from tumour-draining lymph nodes. The technique proposed provides a useful method for the analysis of natural immunity against defined tumour antigens.

The humoral immune response to the polymorphic epithelial mucin (PEM) was studied by characterising the reactivity of human antibodies generated by EBV-immortalised B-cells from tumourdraining lymph nodes of ovarian cancer patients. All the human antibodies, selected in ELIS A for their reactivity to the protein core tandem repeat sequence, reacted with PEM-expressing tumour cells. Aberrant glycosylation of the peptide core of the PEM molecule in cancer cells leads to the exposure of peptide epitopes that can be considered tumour specific. The epitope mapping of six human antibodies revealed that only one of them contained the PDTR sequence, shown to be the immunodominant epitope in the mouse. Four of the six human antibodies recognised a novel common immunogenic sequence (APPAH) in the tandem repeats. The binding of these human antibodies did not appear to be modulated by the length of the carbohydrate side chains, as shown by O-glycosylation inhibition studies. These results indicate that distinct sequences within the tandem repeat of PEM are target for a humoral immune response in humans. The presence of antibodies directed against different epitopes within the same antigenic region may modulate the antigen presentation process and the ongoing immune response. These data may help in clarifying the mechanisms of the immune response to PEM in cancer patients for the development of PEM-based immunotherapy.

Several tumor associated antigens have been shown to be able to induce an immune response. The identification of such antigens and the effector mechanisms involved is a first step for the development of useful cancer vaccines. PEM is a glycoprotein localized on the luminal surface ofmost simple epithelia. In cancer cells it is overexpressed and undergoes a process of aberrant glycosylation. Cryptic epitopes within the core protein of the extracellular domain are therefore exposed and could be a target for an immune response. An MHC unrestricted T cell response mediated by CD8 cells was described and explained by the particular structure of the molecule made up of tandem repeats (TR). Lymphocytes from tumor draining lymph nodes from patients with gynecological malignancies were utilized to study both the humoral and cellular immune responses of these patients. The human antibodies produced by these patients were directed against different epitopes within the TR sequence of PEM and were able to recognize the tumor associated glycoforms of the molecule. T cell clones were isolated that were able to proliferate in the presence of specific peptides corresponding to the TR of PEM presented by autologous B cells. The functional analysis of these clones revealed a Th phenotype. The possible contribution of T helper cells in generating and maintaining anti-tumor immunity opens new possibilities for effective immunological approaches in cancer therapy. Supported by AIRC and CNR “ACRO”. A.R. is supported by AIRC.

Dendritic cells (DCs) are able to orchestrate innate and acquired immunity and can activate and sustain a long-lasting anti-tumor immune response in vivo when used as anti-tumor cell therapy. The selection of the antigen and the choice of its formulation are key points in designing anti-cancer DC-based vaccines. Cell released vesicles/exosomes have been shown to transfer antigens, HLAI/peptide complexes and co-stimulatory molecules to recipient cells. In this study we describe the generation of an allogenic microvesicle cell factory in which the expression of a specific tumor antigen was combined to the expression of co-stimulatory and allogeneic molecules. The DG75 lymphoblastoid cell line was selected as microvesicle producer and transfected with ErbB2, as tumor antigen prototype. The shed microvesicles transferred antigenic components to recipient DCs, increasing their immunogenicity. DC pulsing resulted in cross-presentation of ErbB2 both in HLAI and HLAII compartments, and ErbB2-specific CD8+ T cells from cancer patients were activated by DCs pulsed with vesicle-bound ErbB2. The microvesicle cell factory proposed may represent a source of cell free immunogen to be used for DC-based cancer therapy.

Thirty-four ovarian and breast cancer patients received autologous peripheral blood progenitor cell transplantation after high-dose myeloablative chemotherapy and either granulocyte-colony-stimulating factor (G-CSF) or granulocyte/macrophage-colony-stimulating fictor (GM-CSF) in the immediate post-transplant period. The recovery of T cell functionality was monitored by a three-color flow-cytometric approach using carboxyfluorescein diacetate succinimidyl ester, a probe the fluorescence intensity of which halves at each round of cell replication, in conjunction with CD3 and CD25 monoclonal antibodies. There was no significant difference between the two treatments on days 12, 20, and 40, T cell proliferation always being considerably lower than that of control cultures from healthy donors. At day 80, a significantly higher proportion of mitogen-stimulated T cells from GM-CSF-treated patients expressed interleukin-2 receptor, and a higher proportion of these T cells were actively proliferating. This phenomenon did not reflect any difference in the relative proportion of various lymphocyte subsets (T cells, CD4 and CD8+ T cells, CD45RA+ and CD45RO- T cells, and natural killer cells). At the end of follow-up (1-1.5 years) T cell proliferation had returned to values typically observed in healthy individuals in both groups of patients. Soon after transplantation (day 12), neutrophils from G-CSF-treated patients had a more elevated Fcgamma receptor I density and monocytes from GM-CSF-treated patients had a more elevated Fcgamma receptor II and MHC class II molecules density. The up-modulation of Fcgamma receptor II was maintained until day 40. Thus, administering G-CSF and GM-CSF in the post-transplant period affects T lymphocyte proliferation and phagocyte membrane molecules differently.

e13528 Background: Dendritic cells (DCs) are the most potent antigen presenting cells and are employed in cancer vaccination. Several receptors are being studied in order to identif strategies to i...

Epithelial mucins have obtained increasing clinical relevance since they were found in the serum of cancer patients and were shown to be elevated in metastatic disease. We report here the characterization of the monoclonal antibody (MAb) 436 which recognises the protein core of the polymorphic epithelial mucin (PEM) of the human breast. MAb 436 was generated by immunizing Balb/c mice with membrane-enriched fractions prepared from metastatic lesions in the axillary lymph nodes. The antigenic determinant recognized by the MAb 436 is expressed on the surface of breast cancer cells and was measured by ELISA on all of 50 cytosol preparations of primary breast tumors. Immunohistochemistry showed 98% of primary and 100% of metastatic breast cancer lesions to be positive with the 436 antigenic determinant expressed both in the cytoplasm and at the plasma membrane level of the tumor cells. Moreover, the antigen was expressed in a homogeneous fashion (80-100% of the total number of tumor cells) in more than 60% of the tumors. Reactivity with normal tissues was rare and scattered and restricted to glandular structures particularly at the luminal border level except for the distal and collecting tubules of adult and fetal kidney, where a cytoplasmic 436 antigen distribution was observed. Other cancers proved positive but the reactivity was always variable and heterogeneous. The antigen recognized by MAb 436 appears in Western Blotting as a Mr of more than 200,000 daltons protein resolved in two bands. Epitope mapping experiments using overlapping octapeptides in the repeat unit of the PEM identified in the RPAP (Arg-Pro-Ala-Pro) sequence the binding site of the 436 antigen.With the selective reactivity shown and the homogeneous expression of the corresponding epitope in breast cancer cells of primary and metastic lesions, the MAb 436 represents a good reagent with potential application in the diagnosis and therapy of breast cancer.

The induction of an efficacious anti-tumor immune response (IR) requires the cross-processing and presentation of tumor antigen by Dendritic Cells (DCs). Block of endocytated tumor associated antigen (TAA) in the early compartments of the intracellular processing machinery shifts the IR towards a Th2 balance. MUC1 is one of the most relevant tumor associated glycoprotein expressed by epithelial cells and its immunogenicity is altered by the glycosylation profile. Moreover soluble MUC1 antigen has shown to be stucked in endolysosomal compartment of DCs thus inducing mostly a Th2 response. Objective of this study was to investigate whether glycosylation pattern and MUC1 bound to microvesicles could influence the antigen processing by DCs. MUC1 as soluble molecule, independently by the glycosylation profile, appears to be blocked in the pre-endosomal compartment. Receptor-mediated endocytosis pushes further the processing in the HLAII compartment. Cross-processing of MUC1 in HLAI compartment is observed only when MUC1 is carried by microvesicles (MUC1-MVs). Moreover only DCs stimulated with MUC1-MVs are able to induce IFN-γ production by MUC1 specific CD8+T cells. The distinct processing of the MUC1 membrane bound is accompanied by deglycosylation processes thus generating Tn-MUC1 immunogenic glycoforms. These results show that MUC1 undergoes to alternative processing pathways depending by its form of release (MVs vs soluble) thus modifying MUC1 immunogenicity. Moreover these experimental evidence can be important to design efficacious glycoantigen formulations for DC-based cancer vaccines.