Common Tumor-associated Antigens Research Articles

Convergence, plasticity, and tissue residence of regulatory T cell response via TCR repertoire prism.

Suppressive function of regulatory T cells (Treg) is dependent on signaling of their antigen receptors triggered by cognate self, dietary, or microbial peptides presented on MHC II. However, it remains largely unknown whether distinct or shared repertoires of Treg TCRs are mobilized in response to different challenges in the same tissue or the same challenge in different tissues. Here we use a fixed TCRβ chain FoxP3-GFP mouse model to analyze conventional (eCD4) and regulatory (eTreg) effector TCRα repertoires in response to six distinct antigenic challenges to the lung and skin. This model shows highly 'digital' repertoire behavior with easy-to-track challenge-specific TCRα CDR3 clusters. For both eCD4 and eTreg subsets, we observe challenge-specific clonal expansions yielding homologous TCRα clusters within and across animals and exposure sites, which are also reflected in the draining lymph nodes but not systemically. Some CDR3 clusters are shared across cancer challenges, suggesting a response to common tumor-associated antigens. For most challenges, eCD4 and eTreg clonal response does not overlap. Such overlap is exclusively observed at the sites of certain tumor challenges, and not systematically, suggesting transient and local tumor-induced eCD4=>eTreg plasticity. This transition includes a dominant tumor-responding eCD4 CDR3 motif, as well as characteristic iNKT TCRα CDR3. In addition, we examine the homeostatic tissue residency of clonal eTreg populations by excluding the site of challenge from our analysis. We demonstrate that distinct CDR3 motifs are characteristic of eTreg cells residing in particular lymphatic tissues, regardless of the challenge. This observation reveals the tissue-resident, antigen-specific clonal Treg populations.

Convergence, plasticity, and tissue residence of regulatory T cell response via TCR repertoire prism

Suppressive function of regulatory T cells (Treg) is dependent on signaling of their antigen receptors triggered by cognate self, dietary, or microbial peptides presented on MHC II. However, it remains largely unknown whether distinct or shared repertoires of Treg TCRs are mobilized in response to different challenges in the same tissue or the same challenge in different tissues. Here we use a fixed TCRβ chain FoxP3-GFP mouse model to analyze conventional (eCD4) and regulatory (eTreg) effector TCRα repertoires in response to six distinct antigenic challenges to the lung and skin. This model shows highly ‘digital’ repertoire behavior with easy-to-track challenge-specific TCRα CDR3 clusters. For both eCD4 and eTreg subsets, we observe challenge-specific clonal expansions yielding homologous TCRα clusters within and across animals and exposure sites, which are also reflected in the draining lymph nodes but not systemically. Some CDR3 clusters are shared across cancer challenges, suggesting a response to common tumor-associated antigens. For most challenges, eCD4 and eTreg clonal response does not overlap. Such overlap is exclusively observed at the sites of certain tumor challenges, and not systematically, suggesting transient and local tumor-induced eCD4=>eTreg plasticity. This transition includes a dominant tumor-responding eCD4 CDR3 motif, as well as characteristic iNKT TCRα CDR3. In addition, we examine the homeostatic tissue residency of clonal eTreg populations by excluding the site of challenge from our analysis. We demonstrate that distinct CDR3 motifs are characteristic of eTreg cells residing in particular lymphatic tissues, regardless of the challenge. This observation reveals the tissue-resident, antigen-specific clonal Treg populations.

Abstract 2780: Induced pluripotent stem cell (iPSC) based vaccines potentializes anti-CTLA4 immune response in a murine lung carcinoma model

Abstract Despite the development of new immunotherapy strategies, lung cancer remains the leading cause of cancer-related deaths. One of the reasons is attributed to the persistence of cancer stem cells (CSCs) within the tumor, contributing to drug resistance, dormancy and metastatic spread. To eradicate CSCs, iPSC-based vaccination represents a novel approach based on the paradigm that CSCs and iPSCs share common tumor associated antigens (TAAs) with the ability to elicit a strong anti-tumor immune response.We previously showed that induced allogeneic pluripotent stem cells (miPSCs), combined with a histone deacetylase inhibitor (HDACi), induced a major reduction of tumor growth and metastatic spread to lungs in an aggressive triple negative breast cancer model (4T1) in syngeneic mice. We report here the use of the same protocol in a lung carcinoma model using LLC1 cell line in combination with an anti-CTLA4 antibody. We compared the effectiveness of allogenic miPSCs treatment alone or with an anti-CTLA4 mouse antibody on mice-bearing LLC1-Luc tumors (mean+se: 17,5+0,6 mm3). Five mice received 5 subcutaneous (SC) injection of 2 × 106 miPSCs, 5 mice received 3 intraperitoneal injections of anti-CTLA4 antibody at 5mg/kg and 5 mice were treated with the combinatory regimen (miPSCs and anti- CTLA4) with the same doses. In addition, all treated mice received a HDACi in the drink water throughout the experience.After 24 days, all tumor volumes from the 3 groups were significantly reduced compared to the control mice receiving only PBS. We obtained a reduction of 72% (p=0.007) and 74% (p=0.009) respectively for the mice treated solely with miPSCs or anti-CTLA4. An important synergic effect was obtained for the mice treated with miPSCs and anti- CTLA4 with a reduction of the tumor size by 92% (p=0.005) compared to the control mice. We also found a significant inhibition of metastatic spread to lungs for the 3 groups that was more pronounced in mice receiving the combination treatment with a significant reduction of 91 % compared to the control group. All these therapeutic effects were correlated with a significant increase of CD4+ and CD8+ cells that was more pronounced in mice receiving the combinatory regimen.We also have performed single-cell RNA sequencing analysis (10x Genomics) of LLC1 tumors treated with miPSCs and anti- CTLA4 compared to mice treated with monotherapy and untreated mice. T-distributed stochastic neighbor embedding plot reveals distinct clusters of stromal and immune cells across tumors with a significant upregulation of CD8+ and CD4+ T cells in mice receiving the combinatory regimen.Overall, these results demonstrate for the first time the clinical relevance of using an off-the-shelf allogeneic iPSC-based vaccine combined with an anti-CTLA4 antibody as a new anti-cancer immunotherapy strategy against aggressive non-small cell lung cancer (NSCLC) with metastatic potential. Citation Format: Frank Griscelli, Diana Chaker, Noufissa Oudrhiri, Christophe Desterke, Ali G. Turhan, Annelise Bennaceur Griscelli. Induced pluripotent stem cell (iPSC) based vaccines potentializes anti-CTLA4 immune response in a murine lung carcinoma model [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 2780.

Abstract 889: The efficacy and safety of PD-L1-specific CAR-T in advanced gastric cancer

Abstract [Purpose] Heterogeneity and the tumor microenvironment are major obstacles to overcoming incurable advanced gastric cancer (AGC). Although Epstein-Barr virus-positive and microsatellite instability subtypes can be detected early and properly treated, they are rare in AGC. In this regard, recent combinational therapy of immune checkpoint inhibitors (ICIs) such as PD-1/PD-L1 inhibitors and other various therapeutics has been tried, but there are clinically limited doses and drug resistance. We hypothesized that CAR-T targeting PD-L1, the common tumor-associated antigen (TAA), which expresses in most advanced cancer cells, would make a significant breakthrough in curing a solid tumor. This study aimed to evaluate the killing effects of anti-PD-L1 CAR-T against gastric cancer cell lines. Removal of PD-L1-expressing cells in the AGC TME will improve the clinical outcomes of current therapies. [Results] We constructed a second-generation PD-L1 CAR lentiviral vector targeting PD-L1, which has an intermediate affinity with PD-L1 in solid tumor TME. As the secondary signaling motif, CD28 was chosen and tested along with the CD3 zeta chain. The effector CAR-T, named Vax-CAR-T, specifically recognized the PD-L1-expressing AGC cell line, SNU638, and exhibited rapid and robust cytotoxic activity in vitro. When compared to untransduced T cells, the level of the CD25 activation marker was higher in Vax-CAR-T cells. Besides, the inhibitory markers of Tim3 and LAG3 were expressed even higher than the untransduced. Despite high Tim3 and LAG3 expression in the final manufacturing process, Vax-CAR-T cells significantly suppressed tumor growth in both bigger (>95mm3) and smaller (≤50mm3) AGC xenograft NSG mouse models. More importantly, Vax-CAR-T-treated mice have well tolerated the CAR-T therapy with no significant adverse events during the CRS monitoring period, 2 weeks after Vax-CAR-T injection and have gradually recovered weight gains 5 days after CAR-T cell injection. [Conclusion] We believe that a new autologous CAR-T targeting PD-L1 could be a promising new tool for removing heterogeneous solid tumors in TME, which would be a significant step forward in improving current conventional and immunotherapeutic strategies. Citation Format: Hye-Seong Park, Eun-Ji Choi, Jae-In Yu, Kyung-Sik Lee, Yeo-Jin Lim, Se-Ryeong Choi, Yoonjoo Choi, Bum Chan Park, Jae Eun Park, Mihwa Kim, Je-Jung Lee, Joon Haeng Rhee. The efficacy and safety of PD-L1-specific CAR-T in advanced gastric cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 889.

Advances in adoptive cellular therapy for colorectal cancer: a narrative review.

In recent years, adoptive cell therapy (ACT) has shown great potential in antitumor treatment. To significantly improve the clinical efficacy of ACT against solid tumors, we may need to carefully study the latest developments in ACT. As one of the most common malignancies, colorectal cancer (CRC) is a major risk to human health and has become a significant burden on global healthcare systems. This article reviews the recent advances in the treatment of CRC with ACT. We searched PubMed for articles related to ACT for CRC published as of August 31, 2022, and retrieved relevant clinical trial information on the National Institutes of Health ClinicalTrials.gov website. Based on search results, comprehensive and systematic review is made. This article provides an overview of the research progress of ACT for CRC, including chimeric antigen receptor (CAR) T-cell therapy, T-cell receptor (TCR)-engineered T-cell therapy, and tumor-infiltrating lymphocyte (TIL) therapy. Common tumor-associated antigens (TAAs) in clinical trials of CAR-T cell therapy for CRC are described. Despite many obstacles, ACT shows great promise in treating CRC. Therefore, more basic experimental studies and clinical trials are warranted to further clarify the effectiveness and safety of ACT.

Dual Targeting of Cancer Cells with DARPin-Based Toxins for Overcoming Tumor Escape.

Simple SummaryTargeted therapy of solid tumors represents a great challenge because of heterogeneity of tumor-associated antigen expression. To overcome this obstacle we propose a dual targeting therapy based on protein preparations capable of recognizing different of tumor-associated antigens on a tumor cell producing a directed cytotoxic effect. The dual specific therapy of breast carcinoma-bearing mice using the designed preparations eliminates both the primary tumor and distant metastases. The mono-targeting therapy aimed at single tumor-associated antigen did not suppress metastases at all. The proposed approach can serve as a potential therapeutic strategy that surpasses mono-specific targeting strategies in the anti-cancer efficacy.We report here a combined anti-cancer therapy directed toward HER2 and EpCAM, common tumor-associated antigens of breast cancer cells. The combined therapeutic effect is achieved owing to two highly toxic proteins—a low immunogenic variant of Pseudomonas aeruginosa exotoxin A and ribonuclease Barnase from Bacillus amyloliquefaciens. The delivery of toxins to cancer cells was carried out by targeting designed ankyrin repeat proteins (DARPins). We have shown that both target agents efficiently accumulate in the tumor. Simultaneous treatment of breast carcinoma-bearing mice with anti-EpCAM fusion toxin based on LoPE and HER2-specific liposomes loaded with Barnase leads to concurrent elimination of primary tumor and metastases. Monotherapy with anti-HER2- or anti-EpCAM-toxins did not produce a comparable effect on metastases. The proposed approach can be considered as a promising strategy for significant improvement of cancer therapy.

High-throughput screening for rare antigen-reactive TCRs using natively-paired TCRαβ expression libraries generated from millions diverse primary T cells

Abstract A major goal of T cell research is to profile the repertoire of antigen-reactive TCRs targeting specific peptide:MHCs (pMHC). Single cell sorting of pMHC-binding T cells using multimers and ex vivo antigen expansion are the current gold standards for identifying antigen-reactive primary T cells. However, functional validation of the TCRs identified by these approaches requires resource intensive cloning of each individual TCRαβ pair. Additionally, primary T cells, especially tumor infiltrating lymphocytes (TILs), are a limited resource, which restricts the number of antigens that can be screened. To address this, we developed a microfluidic approach to capture and functionally express natively-paired TCRαβ libraries from millions of single T cells. Unlike DNA barcoding approaches that mark single cells by adding a sequence tag, we physically link the TCRα-TCRβ chains to generate sequencing and full-length expression libraries which we introduce into Jurkat cells for functional testing. Using these methods, we captured over 2.9 million TCRαβ clonotypes from six healthy PBMC donors and over 0.5 million from expanded melanoma TIL samples. We applied pMHC binding and cellular activation screens to identify and validate 14 TCRs reactive to common viral and tumor associated antigens with starting library frequencies of <0.0001 – 0.3% and functional avidities ranging from 0.3 – 592nM. We found that including the cellular activation screen reduced our false-positive TCR discovery rate from 65% for pMHC binding alone to 18%. We are further developing these cellular activation enrichment approaches and applying them to broadly profile anti-tumor TCR reactivity from TILs.

Longitudinal T Cell Immunoprofiling of Patients with Relapsed and/or Refractory Myeloma Who Receive Daratumumab Monotherapy: A Subanalysis of a Phase 2 Study (the REBUILD Study)

Recent evidence suggests immunomodulatory effects of daratumumab in heavily pre-treated Multiple Myeloma (MM) patients (pts); however, the precise effects remain under-characterized, particularly at the molecular level. REBUILD is an ongoing prospective, multicenter, non-comparative, open-label, phase II study that evaluates the effects of daratumumab monotherapy on bone metabolism of pts with relapsed and/or refractory MM (RRMM) who have had ≥2 prior lines of therapy, including lenalidomide and a proteasome inhibitor. Secondary endpoint of the study included the evaluation of T cell dynamics by comprehensive analysis of the T cell receptor (TR) repertoire employing next generation sequencing (NGS) and multi-color flow cytometry. Herein we report the results of this secondary endpoint for the first 14 pts who completed 3 cycles of daratumumab monotherapy. In total, we analyzed 28 paired samples collected at screening (n=14) and on Day 1 of Cycle 4 (C4D1, n=14) of treatment in order to assess potential changes in relation to treatment and clinical response. Patients were grouped based on best responses into responders (i.e. patients with partial response [PR, n=1] and very good PR [VGPR, n=6]), and non-responders (i.e. patients with minimal response [MR, n=2], stable disease [SD, n=4], or progressive disease [PD, n=1]). Starting material was peripheral blood mononuclear cells. TRBV-TRBD-TRBJ gene rearrangements were RT-PCR amplified and subjected to paired-end NGS. Raw NGS reads (n=6,715,406 | median 221,145/sample) were processed through a previously published, purpose-built bioinformatics pipeline. Only productive TRBV-TRBD-TRBJ rearrangements were taken into consideration (n=3,097,565 | median 101,670/sample) for the computation of clonotypes (i.e. TRB rearrangements with identical TRBV gene usage and amino acid complementarity-determining region 3 sequence). Overall, 151,153 distinct clonotypes (median 5,084 clonotypes/sample) were assessed. Both groups (responders/non-responders) displayed clonal T cell expansions both pre- and post-treatment. Clonality was found to be increased after treatment for both responders and non-responders, with statistical significance in the former (median cumulative frequency of the 10 most expanded T cell clonotypes/sample: 31% pre-treatment versus 40% post-treatment, respectively | p=0.04). In both groups, the clonotype repertoire appeared to be renewed with only a small fraction of pre-treatment clonotypes remaining after treatment (1% for non-responders; 0.6% for responders). Interestingly, in the responders' group we noticed a significant shift in the major clonotype repertoire at screening vs C4D1. In particular, in the responders' group the 10 most expanded clonotypes/sample at C4D1 represented expansions of clonotypes present at very low frequency at screening, whereas the most expanded clonotypes at screening decreased or even diminished post-treatment, suggesting that daratumumab treatment led to the emergence of anti-myeloma T cell clones which contributed to clinical response. On the contrary, the 10 most expanded pre-treatment clonotypes in the non-responders' group tended to dominate also the post-treatment repertoire. Of note, 13 shared clonotypes were identified amongst the post-treatment repertoires of different patients (responders/non-responders); shared clonotypes were not found in other entities in public databases, raising the possibility that they may be "disease-specific" and selected by common tumor-associated antigens. With a single exception, shared clonotypes were detected in cases with relevant HLA restrictions, which is noteworthy given the random HLA background of our cohort. Finally, flow cytometry analysis revealed a significant increase post treatment in the percentage of CD3+ T cells (median frequency at screening 60% versus 83% at C4D1 | p=0.003), driven mostly by the expansion of the CD8+ T cell compartment (median frequency at screening 30.8% versus 48.9% at C4D1 | p=0.03) in both groups. In conclusion, TR clonality increases post-treatment through a renewal mechanism; however, pre-treatment clones significantly expanded post-treatment in responders, alluding to the existence of clonotypes with anti-MM properties that may be activated after treatment with daratumumab, arguably contributing to clinical response. Disclosures Kastritis: Janssen: Honoraria, Research Funding; Takeda: Honoraria; Pfizer: Honoraria; Prothena: Honoraria; Genesis: Honoraria; Amgen: Honoraria, Research Funding. Hatjiharissi:Janssen: Honoraria. Katodritou:Genesis: Honoraria; Janssen: Honoraria; Takeda: Honoraria; Amgen: Honoraria. Gavriatopoulou:Genesis: Honoraria, Other: Travel expenses; Janssen: Honoraria, Other: Travel expenses; Takeda: Honoraria, Other: Travel expenses; Amgen: Honoraria. Delimpasi:Takeda: Honoraria; Amgen: Honoraria; Janssen: Honoraria; Genesis: Honoraria, Other: Travel grant. Symeonidis:Sanofi: Research Funding; MSD: Membership on an entity's Board of Directors or advisory committees, Research Funding; Novartis: Membership on an entity's Board of Directors or advisory committees, Research Funding; Pfizer: Research Funding; Celgene: Honoraria, Membership on an entity's Board of Directors or advisory committees, Research Funding; Roche: Membership on an entity's Board of Directors or advisory committees, Research Funding; Janssen: Membership on an entity's Board of Directors or advisory committees, Research Funding; Gilead: Membership on an entity's Board of Directors or advisory committees, Research Funding; Tekeda: Membership on an entity's Board of Directors or advisory committees, Research Funding. Stamatopoulos:Janssen: Honoraria, Research Funding; Abbvie: Honoraria, Research Funding. Dimopoulos:Sanofi Oncology: Research Funding. Terpos:Janssen: Honoraria, Other: Travel expenses, Research Funding; Medison: Honoraria; Genesis: Honoraria, Other: Travel expenses, Research Funding; Amgen: Honoraria, Research Funding; Celgene: Honoraria; Takeda: Honoraria, Other: Travel expenses, Research Funding. Chatzidimitriou:Janssen: Honoraria.

Design, expression and evaluation of novel chimeric protein constructed from colorectal tumor‐associated antigen

There were 134,000 new diagnosis and 49,000 deaths in 2016 due to colorectal cancer. Similar to most cancers, early diagnosis increases the chance of successful treatment. Detection of tumor-associated antigens or the immune response against such markers is one of the most common methods of diagnosis. In that regard, we aimed to design and express a chimeric protein from the most common tumor-associated antigens in colorectal cancer and assess its ability to detect the immune response in comparison with the parental tumor-associated antigens in patient's sera. Through bioinformatics approaches a chimeric protein from carcinoembryonic antigen (CEA) and carbohydrate antigen 19.9 (CA19-9) was designed and expressed in E. coli (BL21DE3). Proper folding, expression levels and immune reactivity were assessed by western blot, ELISA and immunohistochemistry. Recombinant proteins functionality and immune reactivity were confirmed by ELISA and Western blot. Results showed that recombinant CEA, recombinant CA19.9 and chimeric protein of CEA- CA19.9 have strong reactivity with antibodies in the sera of colorectal cancer patients, whereas no reactivity was seen with the sera of healthy volunteers. Significantly stronger immune reactivity was seen with the chimeric protein than each of the CEA or CA19.9 alone. Overall, it was concluded that the designed recombinant proteins in this study could be used to detect autoantibodies produced against the colorectal tumor-associated antigens. The chimeric CEA-CA19.9 protein shows a stronger reactivity with the sera antibodies of colorectal cancer patients that CEA or CA19.9 alone.

Influence of ipilimumab on expanded tumour derived T cells from patients with metastatic melanoma.

IntroductionTumour infiltrating lymphocyte (TIL) based adoptive cell therapy (ACT) is a promising treatment for patients with advanced melanoma. Retrospective studies suggested an association between previous treatment with anti-CTLA-4 antibodies and long term survival after subsequent ACT. Thus, we hypothesized that treatment with anti-CTLA-4 antibodies can induce favourable changes to be detected in TILs.ResultsExpanded T cells from Ipilimumab treated patients had a higher proportion of cells expressing CD27, intracellular CTLA-4, TIM-3 and LAG-3. In addition, broader and more frequent T cell responses against common tumour antigens were detected in patients treated with Ipilimumab as compared to anti-CTLA-4 naïve patients.Materials and methodsExpanded TILs were obtained from patients with advanced melanoma who had received Ipilimumab in the previous six months, or had not received any type of anti-CTLA-4 antibody. T cell specificity and expression of phenotypic and exhaustion markers were scrutinized as well as functional properties.ConclusionsIpilimumab may induce tumor-infiltration of T cells of a more naïve phenotype expressing markers related to activation or exhaustion. Additionally, Ipilimumab may increase the frequency of T cells recognizing common tumour associated antigens.

Survey of autoantibody responses against tumor-associated antigens in thyroid cancer.

Autoantibodies against tumor-associated antigens (TAAs) have been shown to serve as highly specific serological biomarkers for the diagnosis of various solid cancers. Although the autoimmunity against thyroid tissue specific antigens has been studied extensively, so far, the autoantibody responses against common TAAs such as cancer-testis antigens (CTAs), mutated or differentiation antigens have not been comprehensively analyzed in patients with thyroid cancer. The current study aims to characterize the frequency of autoantibody responses against common TAAs in patients with thyroid cancer and benign thyroid nodules. A phage-displayed antigen microarray comprising 65 TAAs was produced and tested with sera from 53 patients with thyroid cancer, 90 patients with benign thyroid nodules and 96 cancer-free individuals, 100 melanoma, 54 breast cancer and 14 lung cancer patients as controls. A panel of 6 TAAs was identified that preferentially reacted with sera from patients with thyroid cancer. The top ranked antigen in this panel was GAGE1 eliciting autoantibody response in 6% of patients with thyroid cancer but not with benign nodules, whereas no reactivity to other CTAs was detected in the sera from patients with thyroid cancer. Although six TAAs, including one CTA, showed thyroid cancer-associated reactivity, overall, spontaneous humoral immune responses against TAAs are rare in thyroid cancer and their utility for the development of non-invasive assay for the differential diagnosis of thyroid nodules is limited.

A new method combining sequential immunoaffinity depletion and differential in gel electrophoresis to identify autoantibodies as cancer biomarkers

Easily measurable biomarkers are urgently required to detect early stages of cancer progression. Autoantibodies (aAbs), as a component of the humoral immune response against tumor cells, have such potential of diagnostic markers since they are circulating and stable proteins, produced rapidly and easily amenable to in vitro dosage. The identification of aAbs is based on the characterization of tumor-associated antigens (TAA) against which they are directed.Here, we propose a new method for an unbiased identification of TAA and thereby of aAbs as cancer biomarkers. This method that we called sequential immunoaffinity depletion-differential in gel electrophoresis (SID-DIGE) is based on the immunodepletion of tumor cell lysates with IgG from control and tumor-bearing mice and direct matching of the flow throughs of these immunoaffinity separations on the same 2D format. This strategy reduces the complexity of the samples to be analyzed and maximizes the interest of assessing hundreds of proteins simultaneously. SID-DIGE has also the potential, contrary to existing serological proteome analysis (SERPA) techniques, to detect immunogenic proteins with conformational epitopes, including those resulting from post-translational modifications. Using a model of human colorectal tumors in mice for the proof of principle, we showed that SID-DIGE outperforms the conventional SERPA technique, with the identification of 7 common TAA (validating our approach) and 18 additional aAbs proving the potential of this new method. In particular, the identification of aAbs directed against key enzymes supporting glycolysis gives credential to the role of hypoxia as a major determinant of the tumor proteome and thus as a source of immunogenicity. Overall, the developed methodology allowed efficient screening of sera for the identification of aAbs as potential biomarkers.

Cancer Antigens (CEA and CA 19-9) as Markers of Advanced Stage of Colorectal Carcinoma.

ABSTRACTIntroduction:CEA and CA 19-9 are the most common tumor associated antigens used in the staging of patients with rectal cancer and other parts of the colon.Goal:of this study was to evaluate the value of CEA and CA 19-9 in serum of patients with colon cancer and prove its place in the diagnostic staging.Material and Methods:The study was retrospective-prospective performed at the Gastroenterohepatology Clinic, Clinical Center of Sarajevo University. The study included 91 hospitalized patients who had histologically confirmed diagnosis of colon adenocarcinoma in 98% of cases. All patients underwent colonoscopy, targeted biopsy and measurement of CEA and CA 19-9 levels in serum. All of them underwent abdominal CT and MRI of the pelvis in case of rectal cancer.Results:The study analyzed 58 men and 33 women, mean age 66.6 years, with the youngest patient at age of 35 and the oldest at age of 89 years. The largest number of patients was aged 56-75 years. According to localization 77 patients had carcinoma located in the area of the rectum and sigma 37.4 and 37.4 in the rectostigmoid area and sigma. Metastases were observed in 37 patients, with predominance in the liver (22 cases) and both liver and lungs (5 cases). CEA and CA 19-9 were determined in all cases but patients with metastases had high values, especially in the two cases of cecoascendent colon cancer where detected values were extremely high (1789ng/ml and 10780U/ml). Values of CA19 -9 were significantly higher (p<0.05). CEA mean values were highest in patients aged over 75 years. In case of CA 19-9 high mean values have been recorded in patients aged over 75 years with statistically significant differences between the age groups (p<0.05).Conclusion:CEA and CA19-9 are cancer antigens that are late markers of carcinogenesis, with significantly elevated serum concentrations in case of colon cancer with already developed metastases. Older age group of patient has significantly elevated levels of both antigens. Cancer was twice more common in men than in women.

Extending T-cell transfer therapy to melanoma and oral squamous carcinoma.

e13071 Background: T-cell based immune therapy in melanoma has shown markedly objective clinical responses in a single-center study at the NIH. In order to extend the treatment to other centers and investigate application to other histologies, we compare the characteristics of tumor infiltrating lymphocytes (TIL) expanded from two groups of cancer patients: malignant melanoma (MM) and squamous cell carcinoma (SCC) of the oral cavity. Methods: Expanded TIL cultures were examined for T-cell phenotype subsets using FACS and clonality by TCRBV gene segment semi quantification with PCR. Tumor reactivity was assessed by INFγ Elispot, CD107a expression by FACS and Cr51 release assay. To identify possible Tumor Associated Antigen (TAA) specific populations TIL were screened for a panel of epitopes from the known TAA Survivin, Telomerase, Bcl-x, Bcl-2, Ny-ESO 1, MART-1, and IDO. Results: Preclinical part: In both patient cohorts TIL were expanded within 5 weeks in 80% of the patients. Cultures comprised an oligoclonal repertoire of T effector memory cells (TEM). Tumor activity against HLA-A matched cell lines showed varying responses regarding frequency and magnitude; activity directed against autologous tumor cells were characterized by a strikingly high frequency of INFg producing cells and/or distinct CD107a+ populations with tumorlytic capacity. Peptide screening revealed that specific TIL cultures were not correlated with tumor activity although the TAA mRNA were identified in the tumor cell lines. Clinical part: TIL were expanded in 5 of 5 (100%) MM patients included. Kinetics, phenotypes, and preliminary activity data resemble preclinical results. Three patients have completed treatment and two have been evaluated by CT scan (1 SD and 1 PR). Immune monitoring is pending. Conclusions: Results on ex vivo expanding TEM from both MM and SCC show comparable outcome and demonstrates shared activity against several common TAA. A clinical pilot trial is ongoing in MM patients with metastatic disease and a pilot trial in patients with primary SCC stage T3/T4 will start in 2010. No significant financial relationships to disclose.

A newly generated functional antibody identifies Tn antigen as a novel determinant in the cancer cell-lymphatic endothelium interaction

Malignant transformation of epithelial cells is frequently associated with the alteration of glycosylation pathways. Tn is a common tumor-associated carbohydrate antigen present in 90% of human carcinomas and its expression correlates with metastatic potential and poor prognosis. Despite its relevance, the functional role of Tn in tumor biology has not been firmly established probably for the lack of appropriate experimental tools. Our aims were to produce highly reactive monoclonal antibodies against Tn making use of synthetically produced Tn and to test their usefulness for in vivo imaging as well as to define their potential functional activity in tumor cell spread. We immunized mice with Tn clustered on cationized BSA and screened the positive hybridomas with Tn-biotinylated alginate. Enzyme-linked immuno sorbent assay and immunofluorescence assays revealed that the most reactive anti-Tn IgM mAb (2154F12A4) selectively recognized Tn on the MCF7 breast cancer cell line since its binding to the cell membrane was completely abolished by preincubation with purified Tn. Importantly, QDot 800-conjugated mAb injected in MCF7-tumor bearing mice specifically bound to primary tumor lesions as well as to metastases in lymph nodes. In addition, this mAb was able to inhibit cancer cell adhesion to lymphatic endothelium suggesting a novel involvement of Tn in the lymphatic dissemination of cancer cells and hypothesizing future applications in inhibiting lymphatic metastases.

EpCAM, a human tumor-associated antigen promotes Th2 development and tumor immune evasion

AbstractExperimental tumor vaccination and adoptive T-cell therapies show that interferon-γ (IFN-γ)–producing CD4+ T helper cells (Th1) can be highly effective in tumor prevention and therapy. Unexpectedly, first vaccine trials in humans revealed that tumor immune therapy may not only be protective, but, on the contrary, even promote tumor progression. Here, we analyzed T-cell immune responses to the epithelial cell adhesion molecule (EpCAM), one of the most common tumor-associated antigens (TAA) serving as immune target in colon cancer patients. Th-cell priming against EpCAM inevitably resulted in interleukin-4 (IL-4)–dominated Th2 responses, even under most stringent Th1-inducing conditions. These EpCAM-reactive Th2 cells rather promoted growth of EpCAM-expressing tumors. To analyze the role of IL-4 in tumor immune evasion, we generated EpCAM-reactive Th1 cells from IL-4.ko mice. These Th1 cells provided tumor-specific protection and established highly protective Th1 memory responses, even in naive BALB/c mice. Inhibition of tumor growth by Th1 cells resulted in intra-tumoral expression of cytokines of the IL-12 family and of IFN-γ. Preventing activation-associated death of Th1 cells further increased intratumoral IFN-γ expression and improved therapeutic efficacy. Thus, human TAA may promote tumor immune evasion by strongly favoring Th2 development.

Human Tumor Antigens Tn and Sialyl Tn Arise from Mutations inCosmc

Neoplastic lesions typically express specific carbohydrate antigens on glycolipids, mucins, and other glycoproteins. Such antigens are often under epigenetic control and are subject to reversion and loss upon therapeutic selective pressure. We report here that two of the most common tumor-associated carbohydrate antigens, Tn and sialyl Tn (STn), result from somatic mutations in the gene Cosmc that encodes a molecular chaperone required for formation of the active T-synthase. Diverse neoplastic lesions, including colon cancer and melanoma-derived cells lines, expressed both Tn and STn antigen due to loss-of-function mutations in Cosmc. In addition, two human cervical cancer specimens that showed expression of the Tn/STn antigens were also found to have mutations in Cosmc and loss of heterozygosity for the cross-linked Cosmc locus. This is the first example of somatic mutations in multiple types of cancers that cause global alterations in cell surface carbohydrate antigen expression.

Elimination of regulatory T cells is essential for an effective vaccination with tumor lysate‐pulsed dendritic cells in a murine glioma model

Both melanoma and glioma cells are of neuroectodermal origin and share common tumor associated antigens. In this article, we report that the melanocyte differentiation antigen TRP2 (tyrosinase-related protein 2) is not predominantly involved in the tumor rejection of a syngeneic murine glioma. Although GL261 glioma cells endogenously expressed TRP2 and were lysed by TRP2 specific cytotoxic T cells (CTLs) in vitro, vaccinations with TRP2 peptide-pulsed dendritic cells (DCs) could only induce minor antiglioma responses in a prophylactic setting and failed to work in a stringent setting where vaccine and tumor were administered on the same day. Further analysis revealed that TRP2 is not recognized by bulk CTLs after depletion of regulatory T cells which results in tumor rejections in vivo. In contrast to TRP2 peptide-pulsed DC, tumor lysate-pulsed DCs were more potent as a vaccine and completely protected mice from tumor outgrowth in a prophylactic setting. However, the vaccine efficacy of tumor lysate-pulsed DC was not sufficient to prevent the tumor outgrowth when tumors were inoculated the same day. In this case, Treg depletion before vaccination was essential to boost antiglioma immune responses leading to the rejection of 80% of the mice and long-term immunity. Therefore, we conclude that counteracting the immunosuppressive glioma tumor environment via depletion of regulatory T cells is a prerequisite for successful eradication of gliomas after targeting multiple tumor antigens by using tumor lysate-pulsed DCs as a vaccine in a more stringent setting.

266. Gene Modification of T Antigen Presenting Cells for the Induction of Antitumor Immunity

Introduction: Activated T cells proliferate rapidly, upregulate molecules important for antigen-presentation including CD80 and CD86 and can readily be modified to express neo-antigens by retrovirus transduction suggesting that T cells might be useful in immunotherapy protocols including cancer vaccines and adoptive T cell transfer. Here, we assess whether T antigen presenting cells (T- APC) are capable of inducing antitumor immune responses against two common tumor associated antigens, MAGE-3 and MART-1.

Human tumor cell lysates as a protein source for the detection of cancer antigen-specific humoral immunity

Measurement of humoral tumor-specific immunity can predict what proteins are specific tumor antigens, be used to evaluate patient diagnosis or prognosis, and function as a method by which one can measure the effects of an immune intervention, such as a vaccine. Antibody assays can easily be adapted to high throughput formats; however, specific reagents needed for assay development often are not available. Developing methods to produce large quantities of purified recombinant tumor antigen proteins for indirect ELISA is both laborious and expensive. In addition, using proteins derived from E. coli might preclude the detection of certain antibody epitopes. We questioned whether a human tumor cell-based ELISA could be developed to assess antibody immunity to common tumor-associated antigens and whether such an ELISA could be optimized to the clinical standards needed for evaluation of large scale trials. Assays were based on the detection of HER-2/neu and p53 antibodies by capture ELISA, using human tumor cell lysate as a protein source. After optimization, the HER-2/neu and p53 ELISA intra-assay coefficients of variation (CV) of positive control sera were consistently 9% and 12%, respectively, at a 1:100 dilution. The HER-2/neu and p53 inter-assay CV of positive control sera over a 5-month time period were 20% and 15%, respectively. The sensitivity and specificity of the ELISAs were evaluated based on comparison to immunoblot. Analysis demonstrated the HER-2/neu ELISA had a specificity of 77% and sensitivity of 89%, and the p53 ELISA had a specificity of 100% and sensitivity of 93%. Cell-based ELISA can be developed to be Clinical Laboratory Improvement Act (CLIA)-compliant and the flexibility of the approach will allow adaptation of the assay to multiple tumor antigen systems.