Keith R. Jerome

Bio: Keith R. Jerome is an academic researcher from Duke University. The author has contributed to research in topics: Antigen & Epitope. The author has an hindex of 3, co-authored 3 publications receiving 613 citations.

Cytotoxic T-lymphocytes derived from patients with breast adenocarcinoma recognize an epitope present on the protein core of a mucin molecule preferentially expressed by malignant cells.

Abstract: A population of tumor-reactive cytotoxic T-cells can be propagated from tumor-draining lymph nodes of patients with breast adenocarcinoma. These T-cells specifically recognize breast and pancreatic tumor cells in a major histocompatibility complex (MHC)-unrestricted fashion but not other tumors of epithelial origin or the natural killer target K562. The tumor-specific but MHC-unrestricted lytic activity of these cytotoxic T-lymphocytes (CTLs) is mediated through the alpha/beta T-cell receptor. The molecule recognized by these CTLs is ductal epithelial mucin produced by breast and pancreatic adenocarcinomas. The protein core of the mucin consists of multiple tandem repeats of a 20-amino acid sequence. Antibody SM3, directed against a determinant on the mucin protein core preferentially expressed on malignant cells is able to significantly inhibit lysis of tumor cells by the CTL, while other antibodies binding to different core epitopes are not. Normal breast epithelial lines, which also express mucin but not the SM3 epitope, are not lysed by these tumor-reactive CTLs or act as cold target inhibitors of lysis of tumor lines. The data suggest that the highly repetitive nature of the mucin allows cross-linking of the T-cell receptor on mucin-specific T-cells and therefore accounts for the lack of MHC restriction seen in this system. They further suggest that the mucin core epitope recognized on tumor cells is not expressed on normal epithelial cells in a manner that can be recognized by tumor-reactive CTLs. These findings support the role of mucins as important tumor-associated antigens mediating the cellular response to certain human cancers and suggest that epithelial mucin core sequences might form the basis for an effective vaccine to augment the antitumor immune response.

Tumor-specific cytotoxic T cell clones from patients with breast and pancreatic adenocarcinoma recognize EBV-immortalized B cells transfected with polymorphic epithelial mucin complementary DNA.

Abstract: Human breast and pancreatic adenocarcinomas are tumors of ductal epithelial cell origin and as such produce and express on their surface polymorphic epithelial cell mucin encoded by the MUC 1 gene. We have previously reported that tumor-specific cytotoxic T cells derived from patients bearing such tumors recognize specific epitopes on the mucin polypeptide core. This recognition was not MHC-restricted because of the highly repetitive sequence of the polypeptide core, which allows simultaneous recognition of many identical epitopes, and cross-linking and aggregation of TCR on mucin-specific T cells. Those studies were performed with limited numbers of tumor cells or allogeneic tumor cell lines. A renewable source of autologous cells presenting this Ag was necessary to further explore mucin-specific immunity. We report here successful establishment and functional analysis of mucin-specific CTL lines and clones derived from breast and pancreatic cancer patients, using either autologous or allogeneic mucin-transfected B cells as Ag. Our results demonstrate that transfection of autologous or allogeneic B cells with mucin confers upon them tumor Ag-presenting ability as well as susceptibility to lysis by mucin-specific CTL. Transfection of APC with this or any other human tumor Ag that may be molecularly defined in the future provides a unique and powerful tool with which to examine the ability of a tumor-associated Ag to stimulate T cell responses.

Expression of tumor-associated epitopes on Epstein-Barr virus-immortalized B-cells and Burkitt's lymphomas transfected with epithelial mucin complementary DNA.

Abstract: Mucins are among the best described human tumor-associated antigens. At least 73 tumor-reactive anti-mucin antibodies have been described; in addition, we have previously demonstrated the existence of tumor-specific cytotoxic T-lymphocyte epitopes on the mucin produced by breast and pancreatic tumors. To determine whether the appearance of tumor-associated mucin epitopes can be explained by altered post-translational modification of mucin in tumors, or whether the generation of these epitopes requires changes in the mucin gene itself, we studied four Burkitt's lymphomas and six Epstein-Barr virus-immortalized B-cell lines transfected with an expression construct containing the mucin complementary DNA. Transfected cell lines showed stable maintenance of the mucin gene, which comprises 20 or more tandem repeats of a 60-nucleotide sequence. Transfected cells expressed many tumor-associated mucin epitopes, suggesting that the changes in mucin synthesis seen in breast and pancreatic tumors are present in other malignant cell types as well. Furthermore, even though each cell line was transfected with the identical mucin construct, each expressed a different subset of tumor-associated mucin epitopes. This suggests that the specificity of these epitopes for tumors is not due to genetic alterations of the mucin gene in tumors. Incubating transfected cells with phenyl-N-acetyl-alpha-galactosaminide, an inhibitor of O-linked glycosylation, altered cell surface carbohydrate structures and resulted in increased expression of all tumor-associated epitopes, implicating incomplete glycosylation of mucin in the generation of these epitopes. These findings suggest that alterations in the posttranslational modification of normal gene products can result in the expression of novel epitopes. Furthermore, the ability to transfect cancer patients' Epstein-Barr virus-immortalized B-cell lines with mucin will provide an unlimited supply of autologous, mucin-bearing cells with which to study these patients' T-cell response to mucin.

Progress in human tumour immunology and immunotherapy

Abstract: Studies of the administration of interleukin-2 to patients with metastatic melanoma or kidney cancer have shown that immunological manipulations can mediate the durable regression of metastatic cancer. The molecular identification of cancer antigens has opened new possibilities for the development of effective immunotherapies for patients with cancer. Clinical studies using immunization with peptides derived from cancer antigens have shown that high levels of lymphocytes with anti-tumour activity can be raised in cancer-bearing patients. Highly avid anti-tumour lymphocytes can be isolated from immunized patients and grown in vitro for use in cell-transfer therapies. Current studies are aimed at understanding the mechanisms that enable the cancer to escape from immune attack.

Human tumor antigens recognized by t lymphocytes

Abstract: 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-

MUC1, the renaissance molecule.

Abstract: MUC1 is a large, heavily glycosylated mucin expressed on the apical surfaces of most simple, secretory epithelia including the mammary gland, gastrointestinal, respiratory, urinary and reproductive tracts. Although MUC1 was thought to be an epithelial-specific protein, it is now known to be expressed on a variety of hematopoietic cells as well. Mucins function in protection and lubrication of epithelial surfaces. Transmembrane mucins, which contain cytoplasmic tail domains, appear to have additional functions through their abilities to interact with many proteins involved in signal transduction and cell adhesion. The goal of this review is to highlight recent discoveries that suggest that MUC1 may be a multifunctional protein, located on the surfaces of cells as a sensor of the environment, poised to signal to the interior when things go awry.