The immunopeptidomic landscape of ovarian carcinomas.

Immunotherapies, particularly checkpoint inhibitors, have set off a revolution in cancer therapy by releasing the power of the immune system. However, only little is known about the antigens that are essentially presented on cancer cells, capable of exposing them to immune cells. Large-scale HLA ligandome analysis has enabled us to exhaustively characterize the immunopeptidomic landscape of epithelial ovarian cancers (EOCs). Additional comparative profiling with the immunopeptidome of a variety of benign sources has unveiled a multitude of ovarian cancer antigens (MUC16, MSLN, LGALS1, IDO1, KLK10) to be presented by HLA class I and class II molecules exclusively on ovarian cancer cells. Most strikingly, ligands derived from mucin 16 and mesothelin, a molecular axis of prognostic importance in EOC, are prominent in a majority of patients. Differential gene-expression analysis has allowed us to confirm the relevance of these targets for EOC and further provided important insights into the relationship between gene transcript levels and HLA ligand presentation.

Graft versus self (GvS) against T-cell autoantigens is a mechanism of graft-host interaction.

Graft-versus-host disease (GVHD) represents the major nonrelapse complication of allogeneic hematopoietic cell transplantation. Although rare, the CNS and the eye can be affected. In this study, manifestation in the retina as part of the CNS and T-cell epitopes recognized by the allogeneic T cells were evaluated. In 2 of 6 patients with posttransplantation retina diseases and 6 of 22 patients without ocular symptoms, antigen-specific T-cell responses against retina-specific epitopes were observed. No genetic differences between donor and recipient could be identified indicating T-cell activation against self-antigens (graft versus self). Transplantation of a preexisting immunity and cross-reactivity with ubiquitous epitopes was excluded in family donors and healthy individuals. In summary, an immunological reaction against retina cells represents a mechanism of graft-versus-host interaction following hematopoietic cell transplantation.

First case report of malignant peritoneal mesothelioma and oral verrucous carcinoma in a patient with a germline PTEN mutation: a combination of extremely rare diseases with probable further implications.

BACKGROUND: The PTEN-hamartoma-tumor-syndrome (PHTS) is caused by germline mutations in Phosphatase and Tensin homolog (PTEN) and predisposes to the development of several typical malignancies. Whereas PTEN mutations have been implicated in the occurrence of malignant mesotheliomas, the genetic landscape of verrucous carcinomas (VC) is largely uncharted. Both VC and malignant peritoneal mesotheliomas (MPM) are exceedingly rare and a potential link between these malignancies and PHTS has never been reported. CASE PRESENTATION: We here describe the clinical course of a PHTS patient who, in addition to a typical thyroid carcinoma at the age of 36 years, developed a highly-differentiated oral VC and an epithelioid MPM six years later. The patient with a history of occupational asbestos exposure underwent cytoreductive surgery and hyperthermic intraperitoneal chemotherapy for MPM. The clinical diagnosis of PHTS was consequently corroborated by a germline PTEN deletion. Sequencing of tumor tissue revealed a second hit in PTEN in the thyroid carcinoma and VC, confirmed by a PTEN loss and activation of the PI3K/AKT pathway in immunohistochemistry. Furthermore, additional somatic mutations in the thyroid carcinoma as well as in the VC were detected, whereas the genetics of MPM remained unrevealing. DISCUSSION AND CONCLUSIONS: We here report the very unusual clinical course of a patient with rare tumors that have a germline mutation first hit in PTEN in common. Since this patient was exposed to asbestos and current evidence suggests molecular mechanisms that might render PHTS patients particularly susceptible to mesothelioma, we strongly recommend PHTS patients to avoid even minimal exposure.

Pharmacodynamics of Oxaliplatin-Derived Platinum Compounds During Hyperthermic Intraperitoneal Chemotherapy (HIPEC): An Emerging Aspect Supporting the Rational Design of Treatment Protocols.

BACKGROUND: Hyperthermic intraperitoneal chemotherapy (HIPEC) is used to treat peritoneal surface malignancies with application of cytostatic drugs such as oxaliplatin (OX) after cytoreductive surgery. Despite its increased use, evidence for optimal drug dosage, and notably duration of HIPEC, is scarce. METHODS: In this study, OX distribution was comprehensively assessed in nine patients during HIPEC (300 mg OX/m2 body surface area in Physioneal solution for 30 min). Oxaliplatin and its derivatives were measured in peritoneal perfusates over time by liquid chromatography coupled with mass spectrometry (LC-MS), and the resulting total platinum concentration in tissue was analyzed by atomic absorption spectrometry. Additionally, a novel impedance-based real-time cytotoxicity assay was used to evaluate the bioactivity of perfusates ex vivo. RESULTS: Compared with amounts of OX expected in peritoneal perfusates by calculation, only 10-15% of the parent drug could be detected by LC-MS during HIPEC. Notably, the study additionally detected platinum compounds consistent with OX transformation, accounting for a further fraction of the applied drug. The cytotoxic properties of perfusates remained unchanged during HIPEC, with only a slight but significant attenuation evidenced after 30 min. CONCLUSIONS: The bioactivity of peritoneal perfusates ex vivo is a useful parameter for evaluating the actual cytotoxic potential of OX and its derivatives used in HIPEC over time, overcoming important limitations and disadvantages associated with respective drug monitoring only. Ex vivo cytotoxicity assays may be a promising tool to aid guiding future standardization and harmonization of HIPEC protocols based on drug-mediated effects.

Haploidentical hematopoietic cell transplantation using in vitro T cell depleted grafts as salvage therapy in patients with disease relapse after prior allogeneic transplantation.

Disease relapse after one or more allogeneic hematopoietic cell transplantations (HCT) represents a therapeutic challenge with all options bearing a significant morbidity and mortality. Haploidentical HCT may induce more pronounced anti-leukemic effects and was evaluated at our center in 25 consecutive patients with disease relapse after preceding HCT receiving haploidentical grafts after in vitro T cell depletion. Overall survival at 1 and 2 years was 32 and 14%, respectively. Of note, patients with complete remission (CR) before haploidentical HCT had a very favorable overall survival of 41.7% at 2 years. Cumulative incidence of non-relapse mortality was 36 and 40% at 1 and 2 years, respectively. With a cumulative incidence for relapse of 36 and 45.6% at 1 and 2 years, disease-free survival (DFS) was 28 and 14.4%, respectively. Here also, patients with CR before haploidentical HCT had a favorable DFS of 42% at 2 years. Only very limited acute (11 patients (44%) with a median grade 1) and chronic graft versus host disease (GvHD) (5 patients (11%), limited grade only) was observed. The main complications and causes of death comprised-besides relapse-infections and bleeding complications. Hence, haploidentical HCT can achieve long-term survival comparable to second transplantation with matched or mismatched donors for patients with otherwise deleterious prognosis and should be considered as a treatment option for patients experiencing disease relapse after previous allogeneic HCT.

Choroidal metastases from thymic carcinoma during pregnancy: Case Report.

BACKGROUND: Rare sites of metastases, atypical symptoms and paraneoplastic syndromes are often neglected or misinterpreted, especially when they represent early symptoms of an underlying malignant disease. Hence, an interdisciplinary approach to these patients is essential to avoid tumor progression and metastatic spread in order to provide curative treatment options to the patients. We here report the case of a young woman presenting with visual loss which led to diagnosis of a thymic carcinoma. CASE PRESENTATION: A 28-year old white woman presented with subacute loss of vision in the last trimester of her first pregnancy which was first interpreted as an exacerbation of a pre-existing dermatomyositis and treated with steroids. After failure of steroid therapy choroidal metastases from an undifferentiated thymic carcinoma were diagnosed. This also shed a new light on the dermatomyositis the patient had been suffering from for seven years possibly representing a paraneoplastic syndrome from the tumor. Despite aggressive chemotherapy, the patient died from progressive disease eight years after first onset of dermatomyositis and 14 months after initial diagnosis of the thymic carcinoma. CONCLUSIONS: Choroidal metastases from a thymic carcinoma have never been reported before but should be included into the differential diagnosis of choroidal masses.

Particle size and activation threshold: a new dimension of danger signaling.

Previous studies have shown that single-stranded RNA (ssRNA) mixed with protamine forms particles and activates immune cells through Toll-like receptors (TLRs). We have found that the size of protamine-RNA particles generated depends on the electrolyte content when mixing the 2 components. Moreover, we have evidenced that (1) nanometric particles induce production of interferon-alpha, whereas (2) micrometric particles mainly induce production of tumor necrosis factor-alpha (TNF-alpha) in human immune cells. We found that the mechanisms underlying these observations are (1) nanoparticles but not microparticles are selectively phagocytosed by plasmacytoid dendritic cells (pDCs), which produce interferon-alpha and (2) monocytes that produce TNF-alpha have a higher activation threshold than that of pDCs. Thus, at the same time as sensing pathogen-associated molecular patterns such as ssRNA, the immune system distinguishes the size of the associated structure in such a way as to trigger the adapted antivirus (nanometric) or antibacterial/antifungal (micrometric) immune response. Our results introduce a new dimension in danger signaling--how size qualitatively affects innate response.

Analysis of Coil Configurations for a Contactless Thermal Tumor Ablation With Implanted Devices.

In the wide field of tumor treatment, thermal ablation procedures are very promising. Alternating magnetic fields are used to transfer the energy from outside the patient to the tumor area located anywhere in the body. This energy is converted to heat by implanted devices located in the tumor area. In this paper, the spatial distribution of the magnetic field of different circular coil configurations is analyzed and optimized with focus on patients' safety and on coil configuration performance. The analysis is based on several performance criteria and is conducted with respect to the worst case scenario of a contactless thermal tumor ablation of deep-seated tumors, in which the energy has to be transferred over a considerably large distance. The magnetic field and the specific absorption rate (SAR) are calculated numerically and the performance criteria are evaluated based on a model of a human body including a tumor area. The most suitable coil configurations for different application scenarios are presented and a thermal analysis is done. Based on this, the minimum required heating power, coil current and number of coil windings, and the corresponding maximum SAR to achieve an adequate rise of tissue temperature are evaluated. For a heating power of 1.45 W, a minimum SAR of 130 mW/kg, a maximum power transfer efficiency of 1.05%, and a maximum coupling coefficient of 0.00695 is achieved. This paper shows the potential to enhance the safety of the patients significantly by choosing the appropriate coil configuration for a specific application scenario.

Analysis of tumor antigen-specific T cells and antibodies in cancer patients treated with radiofrequency ablation.

Radiofrequency (RF) ablation is a minimally invasive technique routinely applied for the treatment of primary and secondary liver tumors. It induces cell death by thermal coagulative necrosis of tumor tissues, whereas cellular metabolism can still take place in a transition zone surrounding the necrotic area. An increase in heat shock protein expression occurs shortly after treatment, suggesting that the induction of activating signals may stimulate the host immune system. In addition, various effects on immune effectors have also been observed, including stimulation of tumor-directed T lymphocytes. Here, we prospectively assessed the activation of tumor antigen-specific antibodies, as well as antigen-specific CD4(+) and CD8(+) T cells in patients suffering from primary or secondary malignancies and treated by RF ablation with or without concomitant chemotherapy. An increase of antibodies (in 4 patients of 49), CD4(+) T cells or CD8(+) T cells (in 2 patients of 49) could be detected several weeks to months following intervention. These findings suggest that in addition to the local control of tumor growth, RF ablation can provide the appropriate conditions for activating tumor-antigen specific immune responses.

More than just tumor destruction: immunomodulation by thermal ablation of cancer.

Over the past decades, thermoablative techniques for the therapy of localized tumors have gained importance in the treatment of patients not eligible for surgical resection. Anecdotal reports have described spontaneous distant tumor regression after thermal ablation, indicating a possible involvement of the immune system, hence an induction of antitumor immunity after thermoinduced therapy. In recent years, a growing body of evidence for modulation of both adaptive and innate immunity, as well as for the induction of danger signals through thermoablation, has emerged. Induced immune responses, however, are mostly weak and not sufficient for the complete eradication of established tumors or durable prevention of disease progression, and combination therapies with immunomodulating drugs are being evaluated with promising results. This article aims to summarize published findings on immune modulation through radiofrequency ablation, cryoablation, microwave ablation therapy, high-intensity focused ultrasound, and laser-induced thermotherapy.

Designing a SARS-CoV-2 T-Cell-Inducing Vaccine for High-Risk Patient Groups.

We describe the results of two vaccinations of a self-experimenting healthy volunteer with SARS-CoV-2-derived peptides performed in March and April 2020, respectively. The first set of peptides contained eight peptides predicted to bind to the individual's HLA molecules. The second set consisted of ten peptides predicted to bind promiscuously to several HLA-DR allotypes. The vaccine formulation contained the new TLR 1/2 agonist XS15 and was administered as an emulsion in Montanide as a single subcutaneous injection. Peripheral blood mononuclear cells isolated from blood drawn before and after vaccinations were assessed using Interferon-γ ELISpot assays and intracellular cytokine staining. We detected vaccine-induced CD4 T cell responses against six out of 11 peptides predicted to bind to HLA-DR after 19 days, following vaccination, for one peptide already at day 12. We used these results to support the design of a T-cell-inducing vaccine for application in high-risk patients, with weakened lymphocyte performance. Meanwhile, an according vaccine, incorporating T cell epitopes predominant in convalescents, is undergoing clinical trial testing.

Towards new horizons: characterization, classification and implications of the tumour antigenic repertoire.

Immune-checkpoint inhibition provides an unmatched level of durable clinical efficacy in various malignancies. Such therapies promote the activation of antigen-specific T cells, although the precise targets of these T cells remain unknown. Exploiting these targets holds great potential to amplify responses to treatment, such as by combining immune-checkpoint inhibition with therapeutic vaccination or other antigen-directed treatments. In this scenario, the pivotal hurdle remains the definition of valid HLA-restricted tumour antigens, which requires several levels of evidence before targets can be established with sufficient confidence. Suitable antigens might include tumour-specific antigens with alternative or wild-type sequences, tumour-associated antigens and cryptic antigens that exceed exome boundaries. Comprehensive antigen classification is required to enable future clinical development and the definition of innovative treatment strategies. Furthermore, clinical development remains challenging with regard to drug manufacturing and regulation, as well as treatment feasibility. Despite these challenges, treatments based on diligently curated antigens combined with a suitable therapeutic platform have the potential to enable optimal antitumour efficacy in patients, either as monotherapies or in combination with other established immunotherapies. In this Review, we summarize the current state-of-the-art approaches for the identification of candidate tumour antigens and provide a structured terminology based on their underlying characteristics.

A Non-interventional Clinical Trial Assessing Immune Responses After Radiofrequency Ablation of Liver Metastases From Colorectal Cancer.

Background: Radiofrequency ablation (RFA) is an established treatment option for malignancies located in the liver. RFA-induced irreversible coagulation necrosis leads to the release of danger signals and cellular content. Hence, RFA may constitute an endogenous in situ tumor vaccination, stimulating innate and adaptive immune responses, including tumor-antigen specific T cells. This may explain a phenomenon termed abscopal effect, namely tumor regression in untreated lesions evidenced after distant thermal ablation or irradiation. In this study, we therefore assessed systemic and local immune responses in individual patients treated with RFA. Methods: For this prospective clinical trial, patients with liver metastasis from colorectal carcinoma (mCRC) receiving RFA and undergoing metachronous liver surgery for another lesion were recruited (n = 9) during a 5-year period. Tumor and non-malignant liver tissue samples from six patients were investigated by whole transcriptome sequencing and tandem-mass spectrometry, characterizing naturally presented HLA ligands. Tumor antigen-derived HLA-restricted peptides were selected by different predefined approaches. Further, candidate HLA ligands were manually curated. Peripheral blood mononuclear cells were stimulated in vitro with epitope candidate peptides, and functional T cell responses were assessed by intracellular cytokine staining. Immunohistochemical markers were additionally investigated in surgically resected mCRC from patients treated with (n = 9) or without RFA (n = 7). Results: In all six investigated patients, either induced immune responses and/or pre-existing T cell immunity against the selected targets were observed. Multi-cytokine responses were inter alia directed against known tumor antigens such as cyclin D1 but also against a (predicted) mutation contained in ERBB3. Immunohistochemistry did not show a relevant influx of immune cells into distant malignant lesions after RFA treatment (n = 9) as compared to the surgery only mCRC group (n = 7). Conclusions: Using an individualized approach for target selection, RFA induced and/or boosted T cell responses specific for individual tumor antigens were more frequently detectable as compared to previously published observations with well-characterized tumor antigens. However, the witnessed modest RFA-induced immunological effects alone may not be sufficient for the rejection of established tumors. Therefore, these findings warrant further clinical investigation including the assessment of RFA combination therapies e.g., with immune stimulatory agents, cancer vaccination, and/or immune checkpoint inhibitors.

Multi-omics discovery of exome-derived neoantigens in hepatocellular carcinoma.

BACKGROUND: Although mutated HLA ligands are considered ideal cancer-specific immunotherapy targets, evidence for their presentation is lacking in hepatocellular carcinomas (HCCs). Employing a unique multi-omics approach comprising a neoepitope identification pipeline, we assessed exome-derived mutations naturally presented as HLA class I ligands in HCCs. METHODS: In-depth multi-omics analyses included whole exome and transcriptome sequencing to define individual patient-specific search spaces of neoepitope candidates. Evidence for the natural presentation of mutated HLA ligands was investigated through an in silico pipeline integrating proteome and HLA ligandome profiling data. RESULTS: The approach was successfully validated in a state-of-the-art dataset from malignant melanoma, and despite multi-omics evidence for somatic mutations, mutated naturally presented HLA ligands remained elusive in HCCs. An analysis of extensive cancer datasets confirmed fundamental differences of tumor mutational burden in HCC and malignant melanoma, challenging the notion that exome-derived mutations contribute relevantly to the expectable neoepitope pool in malignancies with only few mutations. CONCLUSIONS: This study suggests that exome-derived mutated HLA ligands appear to be rarely presented in HCCs, inter alia resulting from a low mutational burden as compared to other malignancies such as malignant melanoma. Our results therefore demand widening the target scope for personalized immunotherapy beyond this limited range of mutated neoepitopes, particularly for malignancies with similar or lower mutational burden.

A new synthetic toll-like receptor 1/2 ligand is an efficient adjuvant for peptide vaccination in a human volunteer.

BACKGROUND: We previously showed that the bacterial lipopeptide Pam3Cys-Ser-Ser, meanwhile established as a toll-like receptor (TLR) 1/2 ligand, acts as a strong adjuvant for the induction of virus specific CD8+ T cells in mice, when covalently coupled to a synthetic peptide. CASE PRESENTATION: We now designed a new water-soluble synthetic Pam3Cys-derivative, named XS15 and characterized it in vitro by a TLR2 NF-κB luciferase reporter assay. Further, the capacity of XS15 to activate immune cells and stimulate peptide-specific CD8+ T and NK cells by 6-sulfo LacNAc+ monocytes was assessed by flow cytometry as well as cytokine induction using immunoassays. The induction of a functional immune response after vaccination of a volunteer with viral peptides was assessed by ELISpot assay and flow cytometry in peripheral blood cells and infiltrating cells at the vaccination site, as well as by immunohistochemistry and imaging. XS15 induced strong ex vivo CD8+ and TH1 CD4+ responses in a human volunteer upon a single injection of XS15 mixed to uncoupled peptides in a water-in-oil emulsion (Montanide™ ISA51 VG). A granuloma formed locally at the injection site containing highly activated functional CD4+ and CD8+ effector memory T cells. The total number of vaccine peptide-specific functional T cells was experimentally assessed and estimated to be 3.0 × 105 in the granuloma and 20.5 × 106 in peripheral blood. CONCLUSION: Thus, in one volunteer we show a granuloma forming by peptides combined with an efficient adjuvant in a water-in-oil-emulsion, inducing antigen specific T cells detectable in circulation and at the vaccination site, after one single vaccination only. The ex vivo T cell responses in peripheral blood were detectable for more than one year and could be strongly boosted by a second vaccination. Hence, XS15 is a promising adjuvant candidate for peptide vaccination, in particular for tumor peptide vaccines in a personalized setting.

Fundus autofluorescence in multifocal choroiditis and panuveitis.

PURPOSE: To investigate the autofluorescence findings associated with multifocal choroiditis and panuveits (MCP), a condition that has marked potential to affect the retinal pigment epithelium (RPE). DESIGN: Observational case series. METHODS: This is a retrospective review of consecutive patients with MCP examined in a retinal referral practice. Each patient was given a comprehensive examination including fundus photographs, angiographic studies, and autofluorescence photography with an excitation filter with the bandpass wavelengths of 535 to 585 nm and a barrier filter with a bandpass of 615 to 715 nm. Integrative analysis was performed of the ocular imaging to ascertain abnormalities caused by the disease. RESULTS: Thirty-six eyes of 18 consecutive patients were evaluated. The mean duration of symptoms was 86.2 months and the mean visual acuity was 20/50. Of the 36 eyes, 23 had choroidal neovascularization (CNV). Chorioretinal hypoautofluorescent spots >or= 125 microns usually, but not always, had the clinically evident correlate of a punched-out scar visible by color fundus photography. Chorioretinal hypoautofluorescent spots less than 125 microns, which could number in the hundreds, typically were not visible by color fundus photography. All chorioretinal scars visible by color fundus photography were visible by autofluorescence photography. During follow-up many patients developed new clinically evident chorioretinal scars, which were presaged in earlier autofluorescence photographs. CNV had a hyperautofluorescent boundary, making it readily visible. CONCLUSIONS: Patients with MCP have much more widespread involvement of the RPE than would be suspected by other means of imaging. Autofluorescence photography supplies information about inflammatory damage and secondary CNV in a noninvasive manner.

Systematic Review of Variations in Hyperthermic Intraperitoneal Chemotherapy (HIPEC) for Peritoneal Metastasis from Colorectal Cancer.

BACKGROUND: Cytoreductive surgery (CRS), followed by hyperthermic intraperitoneal chemotherapy (HIPEC), combines radical surgery with abdominal heated chemotherapy, constituting a multimodal treatment approach. Since clear standards for HIPEC conduct in colorectal carcinoma (CRC) are lacking, we aimed to provide a comprehensive structured survey. Data sources and study eligibility criteria: A systematic literature search was performed in PubMed, with keywords "HIPEC" and "colorectal cancer", according to established guidelines. Articles were systematically screened, selecting 87 publications complemented by 48 publications identified through extended search for subsequent synthesis and evaluation, extracting inter alia details on used drugs, dosage, temperature, exposure times, and carrier solutions. RESULTS: Compiled publications contained 171 reports on HIPEC conduct foremost with mitomycin C and oxaliplatin, but also other drugs and drug combinations, comprising at least 60 different procedures. We hence provide an overview of interconnections between HIPEC protocols, used drugs and carrier solutions as well as their volumes. In addition, HIPEC temperatures and dosing benchmarks, as well as an estimate of in vivo resulting drug concentrations are demonstrated. CONCLUSIONS AND IMPLICATIONS: Owing to recent developments, HIPEC conduct and practices need to be reassessed. Unfortunately, imprecise and lacking reporting is frequent, which is why minimal information requirements should be established for HIPEC and the introduction of final drug concentrations for comparability reasons seems sensible.

Platelet-mediated shedding of NKG2D ligands impairs NK cell immune-surveillance of tumor cells.

Platelets promote metastasis, among others by coating cancer cells traveling through the blood, which results in protection from NK cell immune-surveillance. The underlying mechanisms, however, remain to be fully elucidated. Here we report that platelet-coating reduces surface expression of NKG2D ligands, in particular MICA and MICB, on tumor cells, which was mirrored by enhanced release of their soluble ectodomains. Similar results were obtained upon exposure of tumor cells to platelet-releasate and can be attributed to the sheddases ADAM10 and ADAM17 that are detectable on the platelet surface and in releasate following activation and at higher levels on platelets of patients with metastasized lung cancer compared with healthy controls. Platelet-mediated NKG2DL-shedding in turn resulted in impaired "induced self" recognition by NK cells as revealed by diminished NKG2D-dependent lysis of tumor cells. Our results indicate that platelet-mediated NKG2DL-shedding may be involved in immune-evasion of (metastasizing) tumor cells from NK cell reactivity.

Mapping the HLA Ligandome of Colorectal Cancer Reveals an Imprint of Malignant Cell Transformation.

Immune cell infiltrates have proven highly relevant for colorectal carcinoma prognosis, making colorectal cancer a promising candidate for immunotherapy. Because tumors interact with the immune system via HLA-presented peptide ligands, exact knowledge of the peptidome constitution is fundamental for understanding this relationship. Here, we comprehensively describe the naturally presented HLA ligandome of colorectal carcinoma and corresponding nonmalignant colon (NMC) tissue. Mass spectrometry identified 35,367 and 28,132 HLA class I ligands on colorectal carcinoma and NMC, attributable to 7,684 and 6,312 distinct source proteins, respectively. Cancer-exclusive peptides were assessed on source protein level using the Kyoto Encyclopedia of Genes and Genomes (KEGG) and protein analysis through evolutionary relationships (PANTHER), revealing pathognomonic colorectal carcinoma-associated pathways, including Wnt, TGFß, PI3K, p53, and RTK-RAS. Relative quantitation of peptide presentation on paired colorectal carcinoma and NMC tissue further identified source proteins from cancer- and infection-associated pathways to be overrepresented merely within the colorectal carcinoma ligandome. From the pool of tumor-exclusive peptides, a selected HLA-ligand subset was assessed for immunogenicity, with the majority exhibiting an existing T-cell repertoire. Overall, these data show that the HLA ligandome reflects cancer-associated pathways implicated in colorectal carcinoma oncogenesis, suggesting that alterations in tumor cell metabolism could result in cancer-specific, albeit not mutation-derived, tumor antigens. Hence, a defined pool of unique tumor peptides, attributable to complex cellular alterations that are exclusive to malignant cells, might comprise promising candidates for immunotherapeutic applications.Significance: Cancer-associated pathways are reflected in the antigenic landscape of colorectal cancer, suggesting that tumor-specific antigens do not necessarily have to be mutation-derived but may also originate from other alterations in cancer cells. Cancer Res; 78(16); 4627-41. ©2018 AACR.