Research advance in tumor specific antigens

Introduction

Cancer immunotherapy is emerging as a newly developed standard treatment strategy in some types of cancers. Since immune checkpoint inhibitors (ICIs) have achieved improvement of survival outcomes comparing with standard cytotoxic chemotherapy in some settings of various malignancies, it has been recognized as one of the standard therapeutic options. On the other hand, it is further clinical need to identify biomarkers in predicting response to ICIs as well as agents facilitating its efficacy. Tumor specific antigens recognized by T cells are emerging, as they reportedly play a key role in anti-tumor immune response. Many researchers had attempted to identify high immunogenic tumor specific antigens which could be a novel target of T cell therapy and cancer vaccination therapy. Thus, most current efforts in cancer immunotherapy are focusing on induction of tumor-specific T cell response with tumor specific antigens. In the current article, we are comprehensively reviewing overview and future perspective of tumor specific antigens in cancer immunotherapy with key publications.

History of identifying cancer antigens

First attempt of immunotherapy has been documented since 1890s, to facilitate anti-tumor immunity with using bacterial extracts. William B. Coley, a surgeon in New York Hospital reported that he administered heat-killed Streptococcus pyogenes and Serratia marcescens to patients with inoperable soft tissue sarcoma and over 50% of cases achieved complete tumor regression at the time of therapy, exhibiting subsequently more than 5-year survival (1). He also found that the treatment efficacy is positively correlated with height of fever (2). Thus, it is generally recognized that the efficacy of Coley’s toxin attributed to the anti-cancer immune response. Although the response rates that they reported unsurpassed by modern immunotherapy, subsequent researchers did not demonstrate similar efficacy, especially in carcinoma patients who had been treated with Coley’s toxin (3). The reason why Coley’s toxin failed in carcinoma patients may be that the mechanism of its efficacy depends on non-specific immune activation.

There had been long controversy whether tumor cells originated from host own normal cells could be recognized by host immune cells. In 1953, Foley reported that implantation of methylcholanthrene-induced sarcoma lead immunity against same sarcomas, resulting in preventing its growth (4). As “immune tolerance” had been elucidated (5,6), it became to be considered skeptical in general.

After 1970s, several researchers demonstrated that chemical carcinogenesis exhibited various cancer antigens for each mouse which could not induce immunity by transplantation into other mouse even with same genetic background as well as same chemical carcinogenesis method (7,8). Since Ikeda et al. reported that methylcholanthrene-induced sarcomas elicited significantly stronger cytotoxic T cell response and stable compared with non-chemical-induced ones (9). Their findings may suggest difficulty of applying cancer antigen-based immunotherapy in clinical practice. Thereafter, since 1980s, “cancer antigens” recognized by host T cells in mice model was based on individual acquired genetic alterations, which was so-called “neo-antigens” (9,10). In addition, cancer-testis antigens MAGE (human) and P1A (mouse) were identified as “cancer antigens” (11,12). They are expressed in a variety of cancers, but not in normal adult tissues except for the testis. Therefore, cancer-testis antigen became emerging target for immunotherapy (13,14). Then, methodology for identifying cancer antigens have been gradually advanced, especially gene sequencing technique has been rapidly progressed. In 2005, Lennerz et al. identified five neo-antigens derived from somatic mutations in addition to three previously unknown peptides processed from melanosomal proteins tyrosinase and demonstrated a dominant role of neoantigen-specific T cells in controlling melanoma (15). After that, neo-antigens have become the next target for immunotherapy as next-generation sequencing has been commercially applied for research as well as clinical practice (16).

Classes of tumor antigens recognized by T cells

“Tumor antigens” recognized by T cells are not necessarily expressed in a tumor-specific manner. They include antigens expressed in cancer cells as well as some part of normal cells in some extent, those overexpressed in cancer cells, and those exclusively expressed in cancer cells but not in normal cells as shown in Figure 1 (17).

Figure 1 Major classes of tumor antigens recognized by CD8 T cells on tumors.

Tissue differentiation antigens

Differentiation antigens are specifically expressed in tumor cells and normal cells of tissue which is origin of the tumor with the specific feature of tissue differentiation. The first literature regarding this type of antigens by Anichini et al. demonstrated that cytotoxic T cells in melanoma patients can recognize both tumor cells and normal melanocytes through “tumor antigens” (18). In melanoma patients, tissue differentiation antigen expression was shared between tumor cells and melanocytes, gp100, Melan A/MART-1, tyrosinase, and so on (19). They were enzymes which are specifically expressed in melanosomes in normal melanocytes and overexpress in melanoma cells so that the difference of expression levels could be distinguishable (20).

As a target for immunotherapy, vaccination therapy with melanocyte differentiation antigens including Melan-A/MART-1, tyrosinase, and gp100 demonstrated objective response rate of 2.5% in patients with metastatic melanoma in integrated analysis of the clinical trials (21). In addition, ocular and systemic autoimmunity-related adverse events in melanocyte differentiation antigens treatment were also reported (22,23). Thus, tissue differentiation antigens have gradually become out of focus as a target of immunotherapy.

Overexpressed antigens

Antitumor immune response should begin recognition of tumor antigens in which a minimal number of HLA-peptide complexes that displayed at the cell surface were required. The threshold should contribute to tumor specificity for T cells recognizing peptides derived from proteins that are overexpressed in tumor cells comparing to normal cells. This type of tumor antigens is called as “overexpressed antigens” highly expressed in cancer cells, which mainly play a relevant role in the growth and survival of cancer cells. For example, WT-1, Her-2/neu, and CEA are overexpressed in various types of cancer. For clinical application, it is considerable issue that the antigenicity and specificity of overexpressed antigens are not sufficient. A large difference in expression levels between normal and tumor tissues is necessary to be specifically recognized by T cells.

The oncogene encoding the growth factor receptor, Her-2/neu, is overexpressed in many epithelial malignancies including ovarian and breast cancer. A number of clinical trials investigating overexpressed antigens have demonstrated limited efficacy and some adverse effects (21,24-26).

Cancer-testis antigens

Cancer-testis antigens exclusively express in normal testis, normal placenta, and cancer tissue, sharing among patients with each type of cancer. Since gonadal tissue does not express HLA class I that means not to be recognized as a target of cytotoxic T cells, it is considered that this type of antigens can lead immune response in tumor-specific manner. The first cancer-testis antigen, MAGEA1 was discovered in the 1990s (12,27). Various cancer-testis antigens including MAGE, NY-ESO-1 and XAGE1 have been identified (28) and they reportedly have high tumor antigenicity that could be applied for promising immunotherapeutic target (29).

Cancer-testis antigens including MAGE and NY-ESO-1 have been investigated in clinical trials, demonstrating limited efficacy as cancer vaccine treatment (21,30,31). It should be noted that some of cancer-testis antigens are expressed normal tissues in the embryonic period, some adult tissues, and in addition highly homologous family molecules are expressed in normal tissue, even though most of them have high antigenicity that may be expected to be good targets for cancer immunotherapy.

Viral antigens

Some viruses are involved in carcinogenesis, and they are said to contribute to the development of cancer in about 20% (32), and gene products derived from viruses may act as tumor antigen peptides. Human T-cell leukemia virus, Epstein-Barr virus associated with head and neck cancer, high-risk human papillomavirus (HPV) is recognized by the immune system as a cancer rejection antigen associated with oncogenesis. Among them, HPV virus antigens E6 and E7 showed high expression in cervical cancer which can be target antigens for cytotoxic T cells. However, there are a limited number of clinical trials investigating the efficacy and feasibility of viral antigen vaccine therapy to date (33,34).

Neo-antigens

In multi-step process of carcinogenesis, important gene mutations related to cell proliferation, growth and survival (i.e., driver gene mutations), abundant of concomitant mutations caused by genomic instability related to cancer-inducing factors including ultraviolet rays and tobacco smoking (i.e., passenger mutations) accumulate in somatic genes. Proteins derived from cancer-specific gene mutations are non-self proteins that do not exist in normal tissues and mostly unique to each patient are called neo-antigens. T cells do not acquire immune tolerance to neo-antigens during the differentiation process in the thymus, and thus can induce a strong immune response to the neo-antigens. On the other hand, since this reaction does not occur in normal cells and is tumor-specific, neo-antigens are considered as ideal therapeutic targets of cancer immunotherapy in various malignancies.

Biomarkers utilizing tumor antigens

While tumor specific antigens could be candidates of therapeutic targets, it could also be utilized for tumor detection and diagnosis. Tumor antigens are frequently detected in peripheral blood as they are often released into tumor blood vessels. Further, tumor antigens which usually present within intracellular matrix or organelles are much greater released when chemotherapy or radiotherapy cause tumor cell death. Thus, they could be useful also in evaluating therapeutic response and risk of relapse after treatment. Recent advances in technologies enable to easily obtain protein-based biomarkers including tumor antigens. For example, prostate specific antigen (PSA), which is classified as tissue differentiation antigens, are widely used as a diagnostic and predictive marker in prostate cancer (35). There are considerable numbers of tumor antigens other than PSA, which can be utilized as diagnostic markers, including survivin in breast cancer (36), MAGE in hepatocellular carcinoma (37), and NY-ESO-1 and TP53 in ovarian cancer (38). However, these markers other than PSA are not routinely used and not commercially available in general practice as the specificity and sensitivity are limited.

Summary of conventional vaccine therapy

Cancer vaccine therapy is a treatment method that induces a tumor-specific immune response in patient body by directly administering cancer antigens into the patient in a variety of forms to suppress the progression of cancer or eliminate the cancer. Conventionally, cancer vaccine had been developed focusing on shared-antigens that are commonly expressed, but few have been shown to be effective (21). Since shared-antigens such as tissue differentiation antigens, overexpressed antigens, and cancer-testis antigens have been used as targets of cancer vaccine, T cell receptor (TCR) of specific T cells have almost low to intermediate affinity after negative selection of high affinity TCRs in the thymus (Table 1). That may be why conventional cancer vaccine therapy did not show sufficient efficacy in clinical trials to date. It was reported that even cancer-testis antigens which are considered to have high antigenicity, to rarely have high affinity TCRs in human (39). Also, it is also possible that the T cells were exposed to cancer antigens even before vaccination, resulting in fatigue and refractory conditions. Cytotoxic T cells against MART-1 antigen derived from self-antigens have been reported to be refractory to antigen stimulation by regulatory T cell-mediated induction of anergy (40). Altogether, clinical trials have suggested that it may be required other approach overcoming the immune-regulatory mechanisms above.

ICIs and tumor antigens

ICIs targeting molecules such as PD-1/PD-L1 in the immune checkpoint mechanism that suppresses immune hyper-response have been shown to have effectiveness in clinical trials (41-43). On those successful results, ICIs have become one of the standard therapeutic options. Since the objective response rate is not so high, on the other hand, identification of biomarkers for predicting the response for ICIs is emerging issue.

Advances in next-generation sequencing and bioinformatics technologies can provide identification of individual gene mutations in whole genome on patient-basis. On this background, neo-antigens derived from individual gene mutations has become reemerging as a target for immunotherapy. It was reported that the number of gene mutations and the number of predicted neoantigens was significantly correlated with the response rate in non-small cell lung cancer and melanoma where the number of gene mutations and the number of predicted neoantigens were relatively high (44). In addition, cancers with mutated mismatch repair genes exhibited to significantly correlate to response to anti-PD-1 antibodies treatment (45). Then, the mechanism is reported to be associated with microsatellite instability and the number of gene mutations (46). Whereas, in a clinical trial of anti-PD-1 antibody in patients with advanced Merkel cell carcinoma, there was no significant difference in response rate between positive and negative cases of Merkel cell polyomavirus (MCPyV) which is associated with carcinogenesis (47). Merkel cell carcinoma cases demonstrated comparable response rate regardless of positive or negative for MCPyV which is positively correlated with burden of somatic gene mutations, indicating that not only neo-antigens but also T cells that recognize viral antigens involved in the efficacy of ICIs (48). Moreover, Anagnostou et al. documented that a total of 41 neoantigens (7–18 per case) disappeared when four cases showed progressive disease after response to ICI treatment among patients with NSCLC (49). It was suggested that tumor regression by ICIs is mediated by an immune response to neo-antigens, and that the disappearance of neo-antigens may be one of the mechanisms of acquired resistance. Also, loss of antigen presentation caused by genetic alterations involved antigen presentations such as B2M (50) and HLA (51) have been reported.

Since recent breakthrough by ICI have changed clinical practice of various types of cancer worldwide. Especially, treatment strategy of NSCLC has drastically changed by ICI (41-43). The change has great impact on public health as NSCLC is the major cause of cancer-related death. On the background, it is clinically and socially significant in this area.

In particular, recent clinical trials revealed an emerging issue that response rate to ICI ranged only 15–25% in NSCLC patients and most had primary resistance (41-43). It is thus required to overcome the resistance and shed light on approaches to combine several treatment choices with ICI to maximize the therapeutic benefit from ICI. It is required to broaden the application of immunotherapy including ICI to identify novel therapeutic targets and/or to develop new therapeutic agents modulating immune response. Proposed approaches which possibly induce immunogenicity of cancer cells includes immunogenic cell death (52) led by chemotherapy (53), irradiation (54,55), or chemoradiotherapy (56). This mechanism also facilitates lymphocyte migration to tumor sites, thereby sensitizing tumors to ICI therapy.

To overcome the resistance caused by a loss of antigen presentations may require strategies that eliminate cancers independent of HLA, such as adoptive cell therapy with NK cells or chimeric antigen receptor T cells (57). Recent progress of the adoptive cell therapeutic options may bring benefit hematological and solid malignancies including lung cancer in the near future (58).

Immunotherapy targeting neo-antigens

Since it has been clarified that immune response to neo-antigens play a key role in anti-cancer immunity, cancer vaccine therapy and T cell infusion therapy targeting neo-antigens has been emerging. Although gradual improvement of next-generation sequencing may contribute to individualized immunotherapy based on somatic gene mutations of each patient, immune response to candidate neo-antigens should be verify using tumor infiltrating lymphocytes and peripheral blood lymphocytes in actual.

Anti-tumor effect and suppression of metastasis in addition to feasibility are demonstrated in clinical trial of peptide vaccine treatment targeting neo-antigens in melanoma (59) and glioblastoma (60). The successful results may be caused by that targeting multiple antigens against heterogeneous prevent tumor immune escape. In addition, when an ICI was administered to a case where tumor re-growth occurred during the treatment course of cancer vaccine, disease control was again achieved and the reactivity of specific T cells to the antigens used as the vaccine target was enhanced again (60).

Although neo-antigen has several advantages compared to other tumor antigens, there are some issues including immuno-editing which suppress anti-tumor immune response and exhaustion due to long-term exposure of T cells to the antigens. It can be overcome by combining with immunotherapy having different action points and selecting multiple epitopes. Although cost of sequencing has dropped dramatically, the cost of developing an individualized vaccine is enormous for now.

Summary

Immunotherapy has become emerging again as ICI achieved successful results in clinical trials. Clinical significance of neo-antigens was widely recognized due to association with its relation to response to ICI treatment. Neo-antigens can induce high affinity T cells and has a great advantage that it is not expressed in normal cells at all. On the other hand, there are still some issues to be overcome including exhaustion of T-cells and mechanism of immune editing. Neo-antigens have superiority as therapeutic targets and further research on anti-tumor antigens is expected to be the key to the next breakthrough in immunotherapy.

Acknowledgments

The authors thank Dr. Keith Kretzmer, PhD for the editorial review of this manuscript.

Funding: None.

Footnote

Provenance and Peer Review: This article was commissioned by the Guest Editor (Kei Suzuki) for the series “Immune Response in Lung Cancer” published in AME Medical Journal. The article has undergone external peer review.

Conflicts of Interest: All authors have completed the ICMJE uniform disclosure form (available at https://amj.amegroups.com/article/view/10.21037/amj-20-121/coif). The series “Immune Response in Lung Cancer” was commissioned by the editorial office without any funding or sponsorship. The authors have no other conflicts of interest to declare.

Ethical Statement: The authors are accountable for all aspects of the work in ensuring that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

Open Access Statement: This is an Open Access article distributed in accordance with the Creative Commons Attribution-NonCommercial-NoDerivs 4.0 International License (CC BY-NC-ND 4.0), which permits the non-commercial replication and distribution of the article with the strict proviso that no changes or edits are made and the original work is properly cited (including links to both the formal publication through the relevant DOI and the license). See: https://creativecommons.org/licenses/by-nc-nd/4.0/.

References

1. Coley WB. The diagnosis and treatment of bone sarcoma. Glasgow Med J 1936;126:128-64. [PubMed]
2. Orange M, Reuter U, Hobohm U. Coley's lessons remembered: augmenting mistletoe therapy. Integr Cancer Ther 2016;15:502-511. [Crossref] [PubMed]
3. Nauts HC, Fowler GA, Bogatko FH. A review of the influence of bacterial infection and of bacterial products (Coley's toxins) on malignant tumors in man; a critical analysis of 30 inoperable cases treated by Coley's mixed toxins, in which diagnosis was confirmed by microscopic examination selected for special study. Acta Med Scand Suppl 1953;276:1-103. [PubMed]
4. Foley EJ. Antigenic properties of methylcholanthrene-induced tumors in mice of the strain of origin. Cancer Res 1953;13:835-7. [PubMed]
5. Medawar PB, Woodruff MF. The induction of tolerance by skin homografts on newborn rats. Immunology 1958;1:27-35. [PubMed]
6. Medawar PB. Immunological tolerance. Nature 1961;189:14-7. [Crossref] [PubMed]
7. De Plaen E, Lurquin C, Van Pel A, et al. Immunogenic (tum-) variants of mouse tumor P815: cloning of the gene of tum- antigen P91A and identification of the tum- mutation. Proc Natl Acad Sci U S A 1988;85:2274-8. [Crossref] [PubMed]
8. Palmer WN, Swanson TL, Moore GE. Immunogenicity of tumors alkylated with cyclohexyl-, benzyl-. or 2,4-dinitrophenylmethacrylate. Ann N Y Acad Sci 1976;277:412-27. [Crossref] [PubMed]
9. Ikeda H, Ohta N, Furukawa K, et al. Mutated mitogen-activated protein kinase: a tumor rejection antigen of mouse sarcoma. Proc Natl Acad Sci U S A 1997;94:6375-9. [Crossref] [PubMed]
10. Matsushita H, Vesely MD, Koboldt DC, et al. Cancer exome analysis reveals a T-cell-dependent mechanism of cancer immunoediting. Nature 2012;482:400-4. [Crossref] [PubMed]
11. Ramarathinam L, Sarma S, Maric M, et al. Multiple lineages of tumors express a common tumor antigen, P1A, but they are not cross-protected. J Immunol 1995;155:5323-9. [PubMed]
12. Traversari C, van der Bruggen P, Luescher IF, et al. A nonapeptide encoded by human gene MAGE-1 is recognized on HLA-A1 by cytolytic T lymphocytes directed against tumor antigen MZ2-E. J Exp Med 1992;176:1453-7. [Crossref] [PubMed]
13. Stone B, Schummer M, Paley PJ, et al. MAGE-F1, a novel ubiquitously expressed member of the MAGE superfamily. Gene 2001;267:173-82. [Crossref] [PubMed]
14. Stockert E, Jäger E, Chen YT, et al. A survey of the humoral immune response of cancer patients to a panel of human tumor antigens. J Exp Med 1998;187:1349-54. [Crossref] [PubMed]
15. Lennerz V, Fatho M, Gentilini C, et al. The response of autologous T cells to a human melanoma is dominated by mutated neoantigens. Proc Natl Acad Sci U S A 2005;102:16013-8. [Crossref] [PubMed]
16. Kakimi K, Karasaki T, Matsushita H, et al. Advances in personalized cancer immunotherapy. Breast Cancer 2017;24:16-24. [Crossref] [PubMed]
17. Butterfield LH, Kaufman HL. Cancer immunotherapy principles and practice. New York: Demos Medical Pulishing, 2017:30-43.
18. Anichini A, Maccalli C, Mortarini R, et al. Melanoma cells and normal melanocytes share antigens recognized by HLA-A2-restricted cytotoxic T cell clones from melanoma patients. J Exp Med 1993;177:989-98. [Crossref] [PubMed]
19. Vigneron N, Stroobant V, Van den Eynde BJ, et al. Database of T cell-defined human tumor antigens: the 2013 update. Cancer Immun 2013;13:15. [PubMed]
20. Germeau C, Ma W, Schiavetti F, et al. High frequency of antitumor T cells in the blood of melanoma patients before and after vaccination with tumor antigens. J Exp Med 2005;201:241-8. [Crossref] [PubMed]
21. Rosenberg SA, Yang JC, Restifo NP. Cancer immunotherapy: moving beyond current vaccines. Nat Med 2004;10:909-15. [Crossref] [PubMed]
22. Dudley ME, Wunderlich JR, Yang JC, et al. Adoptive cell transfer therapy following non-myeloablative but lymphodepleting chemotherapy for the treatment of patients with refractory metastatic melanoma. J Clin Oncol 2005;23:2346-57. [Crossref] [PubMed]
23. Yeh S, Karne NK, Kerkar SP, et al. Ocular and systemic autoimmunity after successful tumor-infiltrating lymphocyte immunotherapy for recurrent, metastatic melanoma. Ophthalmology 2009;116:981-9.e1. [Crossref] [PubMed]
24. Parkhurst MR, Yang JC, Langan RC, et al. T cells targeting carcinoembryonic antigen can mediate regression of metastatic colorectal cancer but induce severe transient colitis. Mol Ther 2011;19:620-6. [Crossref] [PubMed]
25. Marshall JL, Hoyer RJ, Toomey MA, et al. Phase I study in advanced cancer patients of a diversified prime-and-boost vaccination protocol using recombinant vaccinia virus and recombinant nonreplicating avipox virus to elicit anti-carcinoembryonic antigen immune responses. J Clin Oncol 2000;18:3964-73. [Crossref] [PubMed]
26. Zaks TZ, Rosenberg SA. Immunization with a peptide epitope (p369-377) from HER-2/neu leads to peptide-specific cytotoxic T lymphocytes that fail to recognize HER-2/neu+ tumors. Cancer Res 1998;58:4902-8. [PubMed]
27. van der Bruggen P, Traversari C, Chomez P, et al. A gene encoding an antigen recognized by cytolytic T lymphocytes on a human melanoma. Science 1991;254:1643-7. [Crossref] [PubMed]
28. Almeida LG, Sakabe NJ, deOliveira AR, et al. CTdatabase: a knowledge-base of high-throughput and curated data on cancer-testis antigens. Nucleic Acids Res 2009;37:D816-9. [Crossref] [PubMed]
29. Caballero OL, Chen YT. Cancer/testis (CT) antigens: potential targets for immunotherapy. Cancer Sci 2009;100:2014-21. [Crossref] [PubMed]
30. Jäger E, Gnjatic S, Nagata Y, et al. Induction of primary NY-ESO-1 immunity: CD8+ T lymphocyte and antibody responses in peptide-vaccinated patients with NY-ESO-1+ cancers. Proc Natl Acad Sci U S A 2000;97:12198-203. [Crossref] [PubMed]
31. Thurner B, Haendle I, Röder C, et al. Vaccination with mage-3A1 peptide-pulsed mature, monocyte-derived dendritic cells expands specific cytotoxic T cells and induces regression of some metastases in advanced stage IV melanoma. J Exp Med 1999;190:1669-78. [Crossref] [PubMed]
32. Zur Hausen H. The search for infectious causes of human cancers: where and why. Virology 2009;392:1-10. [Crossref] [PubMed]
33. Kenter GG, Welters MJ, Valentijn AR, et al. Phase I immunotherapeutic trial with long peptides spanning the E6 and E7 sequences of high-risk human papillomavirus 16 in end-stage cervical cancer patients shows low toxicity and robust immunogenicity. Clin Cancer Res 2008;14:169-77. [Crossref] [PubMed]
34. van Driel WJ, Ressing ME, Kenter GG, et al. Vaccination with HPV16 peptides of patients with advanced cervical carcinoma: clinical evaluation of a phase I-II trial. Eur J Cancer 1999;35:946-52. [Crossref] [PubMed]
35. Jemal A, Fedewa SA, Ma J, et al. Prostate cancer incidence and PSA testing patterns in relation to USPSTF screening recommendations. JAMA 2015;314:2054-61. [Crossref] [PubMed]
36. Khan S, Bennit HF, Turay D, et al. Early diagnostic value of survivin and its alternative splice variants in breast cancer. BMC Cancer 2014;14:176. [Crossref] [PubMed]
37. Li R, Gong J, Xiao C, et al. A comprehensive analysis of the MAGE family as prognostic and diagnostic markers for hepatocellular carcinoma. Genomics 2020; [Epub ahead of print]. [Crossref] [PubMed]
38. Hurley LC, Levin NK, Chatterjee M, et al. Evaluation of paraneoplastic antigens reveals TRIM21 autoantibodies as biomarker for early detection of ovarian cancer in combination with autoantibodies to NY-ESO-1 and TP53. Cancer Biomark 2020;27:407-21. [Crossref] [PubMed]
39. Sommermeyer D, Conrad H, Krönig H, et al. NY-ESO-1 antigen-reactive T cell receptors exhibit diverse therapeutic capability. Int J Cancer 2013;132:1360-7. [Crossref] [PubMed]
40. Maeda Y, Nishikawa H, Sugiyama D, et al. Detection of self-reactive CD8⁺ T cells with an anergic phenotype in healthy individuals. Science 2014;346:1536-40. [Crossref] [PubMed]
41. Gandhi L, Rodríguez-Abreu D, Gadgeel S, et al. Pembrolizumab plus chemotherapy in metastatic non-small-cell lung cancer. N Engl J Med 2018;378:2078-92. [Crossref] [PubMed]
42. Reck M, Rodríguez-Abreu D, Robinson AG, et al. Pembrolizumab versus chemotherapy for PD-L1-positive non-small-cell lung cancer. N Engl J Med 2016;375:1823-33. [Crossref] [PubMed]
43. Motzer RJ, Escudier B, McDermott DF, et al. Nivolumab versus everolimus in advanced renal-cell carcinoma. N Engl J Med 2015;373:1803-13. [Crossref] [PubMed]
44. Snyder A, Makarov V, Merghoub T, et al. Genetic basis for clinical response to CTLA-4 blockade in melanoma. N Engl J Med 2014;371:2189-99. [Crossref] [PubMed]
45. Le DT, Durham JN, Smith KN, et al. Mismatch repair deficiency predicts response of solid tumors to PD-1 blockade. Science 2017;357:409-13. [Crossref] [PubMed]
46. Mandal R, Samstein RM, Lee KW, et al. Genetic diversity of tumors with mismatch repair deficiency influences anti-PD-1 immunotherapy response. Science 2019;364:485-91. [Crossref] [PubMed]
47. Nghiem PT, Bhatia S, Lipson EJ, et al. PD-1 blockade with pembrolizumab in advanced Merkle-cell carcinoma. N Engl J Med 2016;374:2542-52. [Crossref] [PubMed]
48. Lawrence MS, Stojanov P, Polak P, et al. Mutational heterogeneity in cancer and the search for new cancer-associated genes. Nature 2013;499:214-8. [Crossref] [PubMed]
49. Anagnostou V, Smith KN, Forde PM, et al. Evolution of neoantigen landscape during immune checkpoint blockade in non-small cell lung cancer. Cancer Discov 2017;7:264-76. [Crossref] [PubMed]
50. Gettinger S, Choi J, Hastings K, et al. Impaired HLA class i antigen processing and presentation as a mechanism of acquired resistance to immune checkpoint inhibitors in lung cancer. Cancer Discov 2017;7:1420-35. [Crossref] [PubMed]
51. Tran E, Robbins PF, Lu YC, et al. T-cell transfer therapy targeting mutant KRAS in cancer. N Engl J Med 2016;375:2255-62. [Crossref] [PubMed]
52. Kepp O, Senovilla L, Vitale I, et al. Consensus guidelines for the detection of immunogenic cell death. Oncoimmunology 2014;3:e955691. [Crossref] [PubMed]
53. Beyranvand Nejad E, van der Sluis TC, van Duikeren S, et al. Tumor eradication by cisplatin is sustained by CD80/86-mediated Costimulation of CD8+ T cells. Cancer Res 2016;76:6017-29. [Crossref] [PubMed]
54. Gameiro SR, Jammeh ML, Wattenberg MM, et al. Radiation-induced immunogenic modulation of tumor enhances antigen processing and calreticulin exposure, resulting in enhanced T-cell killing. Oncotarget 2014;5:403-16. [Crossref] [PubMed]
55. Galluzzi L, Kepp O, Kroemer G. Immunogenic cell death in radiation therapy. Oncoimmunology 2013;2:e26536. [Crossref] [PubMed]
56. Suzuki Y, Mimura K, Yoshimoto Y, et al. Immunogenic tumor cell death induced by chemoradiotherapy in patients with esophageal squamous cell carcinoma. Cancer Res 2012;72:3967-76. [Crossref] [PubMed]
57. Grosser R, Cherkassky L, Chintala N, et al. Combination immunotherapy with CAR T cells and checkpoint blockade for the treatment of solid tumors. Cancer Cell 2019;36:471-82. [Crossref] [PubMed]
58. Fesnak AD, June CH, Levine BL. Engineered T cells: the promise and challenges of cancer immunotherapy. Nat Rev Cancer 2016;16:566-81. [Crossref] [PubMed]
59. Ott PA, Hu Z, Keskin DB, et al. An immunogenic personal neoantigen vaccine for patients with melanoma. Nature 2017;547:217-21. [Crossref] [PubMed]
60. Keskin DB, Anandappa AJ, Sun J, et al. Neoantigen vaccine generates intratumoral T cell responses in phase Ib glioblastoma trial. Nature 2019;565:234-9. [Crossref] [PubMed]