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      Aberrant Glycosylation of Anchor-Optimized MUC1 Peptides Can Enhance Antigen Binding Affinity and Reverse Tolerance to Cytotoxic T Lymphocytes

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          Abstract

          Cancer vaccines have often failed to live up to their promise, although recent results with checkpoint inhibitors are reviving hopes that they will soon fulfill their promise. Although mutation-specific vaccines are under development, there is still high interest in an off-the-shelf vaccine to a ubiquitous antigen, such as MUC1, which is aberrantly expressed on most solid and many hematological tumors, including more than 90% of breast carcinomas. Clinical trials for MUC1 have shown variable success, likely because of immunological tolerance to a self-antigen and to poor immunogenicity of tandem repeat peptides. We hypothesized that MUC1 peptides could be optimized, relying on heteroclitic optimizations of potential anchor amino acids with and without tumor-specific glycosylation of the peptides. We have identified novel MUC1 class I peptides that bind to HLA-A*0201 molecules with significantly higher affinity and function than the native MUC1 peptides. These peptides elicited CTLs from normal donors, as well as breast cancer patients, which were highly effective in killing MUC1-expressing MCF-7 breast cancer cells. Each peptide elicited lytic responses in greater than 6/8 of normal individuals and 3/3 breast cancer patients. The CTLs generated against the glycosylated-anchor modified peptides cross reacted with the native MUC1 peptide, STAPPVHNV, suggesting these analog peptides may offer substantial improvement in the design of epitope-based vaccines.

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          Most cited references42

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          Immunotherapy converts nonimmunogenic pancreatic tumors into immunogenic foci of immune regulation.

          Pancreatic ductal adenocarcinoma (PDAC) is considered a "nonimmunogenic" neoplasm. Single-agent immunotherapies have failed to demonstrate significant clinical activity in PDAC and other "nonimmunogenic" tumors, in part due to a complex tumor microenvironment (TME) that provides a formidable barrier to immune infiltration and function. We designed a neoadjuvant and adjuvant clinical trial comparing an irradiated, granulocyte-macrophage colony-stimulating factor (GM-CSF)-secreting, allogeneic PDAC vaccine (GVAX) given as a single agent or in combination with low-dose cyclophosphamide to deplete regulatory T cells (Treg) as a means to study how the TME is altered by immunotherapy. Examination of resected PDACs revealed the formation of vaccine-induced intratumoral tertiary lymphoid aggregates in 33 of 39 patients 2 weeks after vaccine treatment. Immunohistochemical analysis showed these aggregates to be regulatory structures of adaptive immunity. Microarray analysis of microdissected aggregates identified gene-expression signatures in five signaling pathways involved in regulating immune-cell activation and trafficking that were associated with improved postvaccination responses. A suppressed Treg pathway and an enhanced Th17 pathway within these aggregates were associated with improved survival, enhanced postvaccination mesothelin-specific T-cell responses, and increased intratumoral Teff:Treg ratios. This study provides the first example of immune-based therapy converting a "nonimmunogenic" neoplasm into an "immunogenic" neoplasm by inducing infiltration of T cells and development of tertiary lymphoid structures in the TME. Post-GVAX T-cell infiltration and aggregate formation resulted in the upregulation of immunosuppressive regulatory mechanisms, including the PD-1-PD-L1 pathway, suggesting that patients with vaccine-primed PDAC may be better candidates than vaccine-naïve patients for immune checkpoint and other immunomodulatory therapies.
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            Tecemotide (L-BLP25) versus placebo after chemoradiotherapy for stage III non-small-cell lung cancer (START): a randomised, double-blind, phase 3 trial.

            Effective maintenance therapies after chemoradiotherapy for lung cancer are lacking. Our aim was to investigate whether the MUC1 antigen-specific cancer immunotherapy tecemotide improves survival in patients with stage III unresectable non-small-cell lung cancer when given as maintenance therapy after chemoradiation. The phase 3 START trial was an international, randomised, double-blind trial that recruited patients with unresectable stage III non-small-cell lung cancer who had completed chemoradiotherapy within the 4-12 week window before randomisation and received confirmation of stable disease or objective response. Patients were stratified by stage (IIIA vs IIIB), response to chemoradiotherapy (stable disease vs objective response), delivery of chemoradiotherapy (concurrent vs sequential), and region using block randomisation, and were randomly assigned (2:1, double-blind) by a central interactive voice randomisation system to either tecemotide or placebo. Injections of tecemotide (806 μg lipopeptide) or placebo were given every week for 8 weeks, and then every 6 weeks until disease progression or withdrawal. Cyclophosphamide 300 mg/m(2) (before tecemotide) or saline (before placebo) was given once before the first study drug administration. The primary endpoint was overall survival in a modified intention-to-treat population. This study is registered with ClinicalTrials.gov, number NCT00409188. From Feb 22, 2007, to Nov 15, 2011, 1513 patients were randomly assigned (1006 to tecemotide and 507 to placebo). 274 patients were excluded from the primary analysis population as a result of a clinical hold, resulting in analysis of 829 patients in the tecemotide group and 410 in the placebo group in the modified intention-to-treat population. Median overall survival was 25.6 months (95% CI 22.5-29.2) with tecemotide versus 22.3 months (19.6-25.5) with placebo (adjusted HR 0.88, 0.75-1.03; p=0.123). In the patients who received previous concurrent chemoradiotherapy, median overall survival for the 538 (65%) of 829 patients assigned to tecemotide was 30.8 months (95% CI 25.6-36.8) compared with 20.6 months (17.4-23.9) for the 268 (65%) of 410 patients assigned to placebo (adjusted HR 0.78, 0.64-0.95; p=0.016). In patients who received previous sequential chemoradiotherapy, overall survival did not differ between the 291 (35%) patients in the tecemotide group and the 142 (35%) patients in the placebo group (19.4 months [95% CI 17.6-23.1] vs 24.6 months [18.8-33.0], respectively; adjusted HR 1.12, 0.87-1.44; p=0.38). Grade 3-4 adverse events seen with a greater than 2% frequency with tecemotide were dyspnoea (49 [5%] of 1024 patients in the tecemotide group vs 21 [4%] of 477 patients in the placebo group), metastases to central nervous system (29 [3%] vs 6 [1%]), and pneumonia (23 [2%] vs 12 [3%]). Serious adverse events with a greater than 2% frequency with tecemotide were pneumonia (30 [3%] in the tecemotide group vs 14 [3%] in the placebo group), dyspnoea (29 [3%] vs 13 [3%]), and metastases to central nervous system (32 [3%] vs 9 [2%]). Serious immune-related adverse events did not differ between groups. We found no significant difference in overall survival with the administration of tecemotide after chemoradiotherapy compared with placebo for all patients with unresectable stage III non-small-cell lung cancer. However, tecemotide might have a role for patients who initially receive concurrent chemoradiotherapy, and further study in this population is warranted. Merck KGaA (Darmstadt, Germany). Copyright © 2014 Elsevier Ltd. All rights reserved.
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              The relationship between class I binding affinity and immunogenicity of potential cytotoxic T cell epitopes.

              The relationship between binding affinity for HLA class I molecules and immunogenicity of discrete peptide epitopes has been analyzed in two different experimental approaches. In the first approach, the immunogenicity of potential epitopes ranging in MHC binding affinity over a 10,000-fold range was analyzed in HLA-A*0201 transgenic mice. In the second approach, the antigenicity of approximately 100 different hepatitis B virus (HBV)-derived potential epitopes, all carrying A*0201 binding motifs, was assessed by using PBL of acute hepatitis patients. In both cases, it was found that an affinity threshold of approximately 500 nM (preferably 50 nM or less) apparently determines the capacity of a peptide epitope to elicit a CTL response. These data correlate well with class I binding affinity measurements of either naturally processed peptides or previously described T cell epitopes. Taken together, these data have important implications for the selection of epitopes for peptide-based vaccines, and also formally demonstrate the crucial role of determinant selection in the shaping of T cell responses. Because in most (but not all) cases, high affinity peptides seem to be immunogenic, our data also suggest that holes in the functional T cell repertoire, if they exist, may be relatively rare.
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                Author and article information

                Contributors
                Role: Academic Editor
                Journal
                Biomolecules
                Biomolecules
                biomolecules
                Biomolecules
                MDPI
                2218-273X
                29 June 2016
                September 2016
                : 6
                : 3
                : 31
                Affiliations
                [1 ]Department of Biochemistry and Molecular Biology, College of Medicine, Mayo Clinic in Arizona, 13400 E. Shea Boulevard, Scottsdale, AZ 85259, USA; pathangey.latha@ 123456mayo.edu (L.B.P.); lakshminarayanan.vani@ 123456gmail.com (V.L.)
                [2 ]Department of Immunology, College of Medicine, Mayo Clinic in Arizona, 13400 E. Shea Boulevard, Scottsdale, AZ 85259, USA; pmukherj@ 123456uncc.edu
                [3 ]Cancer Center Statistics, Mayo Clinic, 200 First Street SW, Rochester, MN 55905, USA; suman.vera@ 123456mayo.edu
                [4 ]Department of Surgery, Mayo Clinic in Arizona, Mayo Clinic Hospital, 5777 E. Mayo Boulevard, Phoenix, AZ 85054, USA; pockaj.barbara@ 123456mayo.edu
                Author notes
                [* ]Correspondence: gendler.sandra@ 123456mayo.edu ; Tel.: +1-480-301-7062; Fax: +1-480-301-9162
                [†]

                Present address: Department of Biology, University of North Carolina, Charlotte, NC 28223, USA.

                Article
                biomolecules-06-00031
                10.3390/biom6030031
                5039417
                27367740
                ce6fda8e-de9b-4d98-a1de-063f50cc7ca8
                © 2016 by the authors; licensee MDPI, Basel, Switzerland.

                This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC-BY) license ( http://creativecommons.org/licenses/by/4.0/).

                History
                : 30 April 2016
                : 07 June 2016
                Categories
                Article

                tn antigen,vaccine,immunotherapy,ctl,breast cancer,mucin1,heteroclitic antigen

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