W e have come a long way since the identification of the first human tumor antigen recognized by autologous CTL. This report provides a brief appraisal of these antigens and their potential for cancer immunotherapy. Our comments will be restricted to nonviral antigens. The initial work carried out on mouse tumors revealed two possible mechanisms for generating new antigens that might be suflficiendy tumor-specific to be of relevance to immunotherapy. The first mechanism involved a point mutation, and the second involved the transcriptional activation o fa gene not expressed in normal tissues (1-3). Subsequent work on mouse tumors provided two interesting examples of tumor antigens resulting from point mutations (4, 5). Tumor-specific Shared Antigens. Three families of genes that appear to code for highly specific tumor antigens have been identified so far, namely, the MAGE, BAGE, and GAGE genes (6-9). These genes are frequently expressed in a wide range of tumor types such as melanoma, lung carcinoma, sarcoma, and bladder carcinoma, but very rarely in other tumor types such as brain tumors, renal carcinoma, and leukemia (7, 10-12). The only normal tissues where expression of these genes has been observed are testis and placenta (7). Starting from CTL clones obtained by stimulating lymphocytes with an autologous melanoma cell line, six antigens encoded by MAGE-1, MAGE-3, BAGE, and GAGE have been identified (8, 9, 13-15). For these six antigens, both the presenting HLA molecule and the antigenic peptide have been completely defined. Remarkably, all the relevant CTL were derived from the same melanoma patient, a patient with metastatic disease who enjoyed an extraordinarily favorable chnical course. Blood samples from several patients with a tumor expressing some or all of these genes were tested, and no such CTL were obtained by stimulating the lymphocytes with autologous tumor cells. More than 60% of Caucasian melanoma patients bear one of the presently defined antigens encoded by MAGE, BAGE, and GAGE. For other cancers such as head and neck tumors and bladder cancer, the frequencies range from 40% to 28%. For several reasons, it appears increasingly unlikely that immunization of patients against one of these antigens will cause harmful immunological side effects caused by the expression of the relevant gene in the testis. First, this expression appears to occur in germline cells, more precisely spermatocytes and spermatogonia (16). A similar observation has been made with the mouse equivalent of a MAGE gene by in situ hybridization (17). Because these germline cells do not express classical M H C class I molecules, gene expression should not result in antigen expression (18). These conclusions are further strengthened by immunization studies carried out with mouse tumor antigen P815A, which is encoded by a gene that is also expressed only in the testis. After immunization with P815 tumor cells, which carry this antigen, male mice produced a strong CTL response. No inflammation of the testis was observed in the following months, and the fertihty of these mice was normal (Uyttenhove, C., manuscript in preparation). A new mode of origin for antigens that are also tumorspecific shared antigens is described in this issue (19). Here, it seems that a gene that is ubiquitously expressed, namely, N-acetyl-glucosaminyltransferase V, contains an intron that appears to carry near its end a promoter that is activated only in melanoma cells. This atypical activation occurs in >50% of melanomas. This produces a message containing a new open reading frame, which codes for the antigenic peptide in its intronic part. Some CTL directed against breast, ovarian, and pancreatic carcinomas recognize an epitope of mucin, a surface protein composed of multiple tandem repeats of 20 amino acids (20-23). Whereas in normal cells mucin is heavily glycosylated, in these tumors the peptide repeats are unmasked by underglycosylation, resulting in CTL recognition. Remarkably, this recognition, which depends on the presence of multiple repeats, occurs in the absence of HLA restriction. The presence of this epitope was recently reported on myeloma cells, and mucin-specific CTL were isolated from the blood of a myeloma patient (24). These mucin antigens appear to be very specific for tumor cells, and the lack of HLA restriction should facilitate therapeutic vaccination trials. Differentiation Antigens. The observation that autolognus CTL can be generated readily against differentiation antigens present on normal melanocytes as well as melanoma cells was unexpected. Four genes encoding melanoma differentiation antigens have been identified: tyrosinase, Melan-A/Mart-1, gpl00, and gp75 (25-30). Most of the identified antigenic peptides are presented by HLA-A2, but other HLA-peptide combinations have been found (29-38). One tyrosinase peptide is presented by HLA-DR4 to CD4 T cells (34). The pattern of CTL precursors directed against these dif-

https://rupress.org/jem/article-pdf/183/3/725/1107908/725.pdf

Human tumor antigens recognized by t lymphocytes

The immune system evolved to distinguish non-self from self to protect the organism. As cancer is derived from our own cells, immune responses to dysregulated cell growth present a unique challenge. This is compounded by mechanisms of immune evasion and immunosuppression that develop in the tumour microenvironment. The modern genetic toolbox enables the adoptive transfer of engineered T cells to create enhanced anticancer immune functions where natural cancer-specific immune responses have failed. Genetically engineered T cells, so-called 'living drugs', represent a new paradigm in anticancer therapy. Recent clinical trials using T cells engineered to express chimeric antigen receptors (CARs) or engineered T cell receptors (TCRs) have produced stunning results in patients with relapsed or refractory haematological malignancies. In this Review we describe some of the most recent and promising advances in engineered T cell therapy with a particular emphasis on what the next generation of T cell therapy is likely to entail.

Engineered T cells: the promise and challenges of cancer immunotherapy

Introduction of tumor markers into routine clinical practice has been poorly controlled, with few criteria or guidelines as to how such markers should be used. We propose a Tumor Marker Utility Grading System (TMUGS) to evaluate the clinical utility of tumor markers and to establish an investigational agenda for evaluation of new tumor markers. A Tumor Marker Utility Grading Worksheet has been designed. The initial portion of this worksheet is used to clarify the precise characteristics of the marker in question. These characteristics include the marker designation, the molecule and/or substance and the relevant alteration from normalcy, the assay format and reagents, the specimen type, and the neoplastic disease for which the marker is being evaluated. To determine the clinical utility of each marker, one of several potential uses must be designated, including risk assessment, screening, differential diagnosis, prognosis, and monitoring clinical course. For each of these uses, associations between marker assay results and expected biologic process and end points must be determined. However, knowledge of tumor marker data should contribute to a decision in practice that results in a more favorable clinical outcome for the patient, including increased overall survival, increased disease-free survival, improvement in quality of life, or reduction in cost of care. Semiquantitative utility scales have been developed for each end point. The only markers recommended for use in routine clinical practice are those that are assigned utility scores of "++" or " " on a 6-point scale (ranging from 0 to ) in the categories relative to more favorable clinical outcomes. Each utility score assignment should be supported by documentation of the level of evidence used to evaluate the marker. TMUGS will establish a standardized analytic technique to evaluate clinical utility of known and future tumor markers. It should result in improved patient outcomes and more cost-efficient investigation and application of tumor markers.

/pdf/tumor-marker-utility-grading-system-a-framework-to-evaluate-resaib0ov3.pdf

Tumor Marker Utility Grading System: a Framework to Evaluate Clinical Utility of Tumor Markers

A method of inhibiting growth of tumor cells which overexpress a growth factor receptor or growth factor by treatment of the cells with antibodies which inhibit the growth factor receptor function, is disclosed. A method of treating tumor cells with antibodies which inhibit growth factor receptor function, and with cytotoxic factor(s) such as tumor necrosis factor, is also disclosed. By inhibiting growth factor receptor functions tumor cells are rendered more susceptible to cytotoxic factors.

Monoclonal antibodies directed to the HER2 receptor

The identification of antigenic peptides presented on the tumor cell surface by HLA class I molecules and recognized by tumor-specific cytotoxic T lymphocytes may lead to a peptide vaccine capable of inducing protective cellular immunity. We demonstrate that both HLA-A2-restricted breast and ovarian tumor-specific cytotoxic T lymphocytes recognize shared antigenic peptides. At least one of these peptides is derived from the oncogene product of HER2/neu, which is overexpressed in 30-40% of all breast and ovarian cancers. T cells sensitized against this nine-amino acid sequence demonstrate significant recognition of HLA-A2+, HER2/neu+ tumors. Since 50% of the tumor-cell population is HLA-A2+ and many different tumors express HER2/neu, this peptide may be widely recognized and have many clinical applications.

https://www.pnas.org/content/pnas/92/2/432.full.pdf

Breast and ovarian cancer-specific cytotoxic T lymphocytes recognize the same HER2/neu-derived peptide.

The HER-2/neu protooncogene is amplified and overexpressed in 20-40% of invasive breast cancers HER-2/neu protein overexpression is associated with aggressive disease and is an independent predictor of poor prognosis in several subsets of patients The protein may also be related to cancer formation, with overexpression being detectable in 50-60% of ductal carcinomas in situ It has been suggested that it might be possible to develop specific T-cell therapy directed against proteins involved in malignant transformation One question is whether normal proteins that are overexpressed are appropriate targets for therapeutic immune attack This report demonstrates that some patients with HER-2/neu-positive breast cancers have both existent CD4+ helper/inducer T-cell immunity and antibody-mediated immunity to HER-2/neu protein Initial studies performed on 20 premenopausal breast cancer patients identified antibodies to HER-2/neu in 11 individuals Similar antibody responses have been found in some normal individuals The patient with the greatest antibody response was studied in detail In addition to a humoral immune response this patient had evidence of a significant proliferative T-cell response to the HER-2/neu protein and peptides Similar T-cell responses have been detected in additional patients It has been assumed that patients would be immunologically tolerant to HER-2/neu as a self-protein and that immunity might be difficult to generate If immunity could be generated, the result might be destructive autoimmunity The current data support the notion that HER-2/neu-specific immunity might be used in therapy without destroying normal tissue but also raises questions as to the role of existent immunity in immune surveillance and cancer progression

/pdf/existent-t-cell-and-antibody-immunity-to-her-2-neu-protein-2x69yfnp65.pdf

Existent T-cell and antibody immunity to HER-2/neu protein in patients with breast cancer.

The development of T-cell therapy for the treatment of human malignancy has been hindered, in large part, by a lack of identifiable tumor antigens. Studies to identify potential T-cell targets in humans have been difficult because of practical problems limiting the use of in vivo immunization and a lack of reproducible in vitro priming methods. Oncogenic proteins are involved in malignant transformation and maintenance of the transformed phenotype and theoretically are potential targets to T-cell therapy. HER-2/neu protein is a protooncogene product overexpressed in a variety of human malignancies and is associated with malignant transformation and aggressive disease in human breast cancer. Previous studies have shown that some patients with breast cancer have existent helper/ inducer T-cell immunity to p185HER2/neu protein and peptides. The current study represents initial attempts to identify candidate cytotoxic T-lymphocyte (CTL) epitopes. Synthetic peptides were constructed identical to HER-2/neu protein segments with amino acid motifs similar to the published motif for HLA-A2.1-binding peptides. Four peptides were synthesized and two were shown to be avid binders to HLA-A2.1. Two of the four peptides could be shown to elicit peptide-specific CTL by primary in vitro immunization in a culture system using peripheral blood lymphocytes from a normal individual homozygous for HLA-A2. p185HER-2/neu protooncogene protein contains immunogenic epitopes capable of generating human CD8+ CTL. The identification of candidate CTL epitopes will allow studies to determine whether some cancer patients have existent CTL immunity to HER-2/neu protein. The demonstrated ability to generate human peptide-specific CTL in vitro allows screening of other oncogenic proteins to identify candidate T-cell epitopes potentially useful for future immunotherapy studies.

https://cancerres.aacrjournals.org/content/canres/54/4/1071.full.pdf

Ann E. Murphy

Papers

Existent T-cell and antibody immunity to HER-2/neu protein in patients with breast cancer.

In Vitro Generation of Human Cytolytic T-Cells Specific for Peptides Derived from the HER-2/neu Protooncogene Protein