Molecular mimicry of carcinoembryonic antigen by peptides derived from the structure of an anti-idiotype antibody

Our goal was to use carcinoembryonic antigen (CEA) as a target for immunotherapy in CEA-positive cancer patients who are all immune tolerant to the native antigen. We isolated and characterized an anti-idiotype monoclonal antibody 3H1, which mimics a distinct and specific epitope of the Mr 180,000 CEA and can be used as a surrogate for CEA. In Phase Ib clinical trials in a group of 23 advanced colorectal cancer patients, 3H1 induced both humoral and cellular anti-3H1 responses, as well as anti-CEA immunity. To study the cellular immunity invoked by 3H1 at the molecular level, we have cloned and sequenced the cDNAs encoding the variable heavy and light chains of 3H1 and deduced the amino acid sequences of the encoded proteins. To identify any cross-reactive peptides of 3H1 and CEA, we compared the amino acid sequences of 3H1 with those of CEA and found several regions of homology in 3H1 heavy and light chain variable domains, as well as in the framework regions. To search for potential cross-reactive T-cell epitopes, a number of peptides were synthesized based on 3H1/CEA homology and were used as stimulants in cell proliferation assays, using peripheral blood mononuclear cells from a group of 3H1-immunized CEA-positive cancer patients in the adjuvant setting. Two partially homologous peptides, designated LCD-2 (from 3H1) and CEA-B (from CEA), were identified in 10 of 21 adjuvant patients by strong proliferation responses (stimulation index, 3-50-fold), which were extensively studied in five of these individuals over an extended period of time (12-24 months). We saw no correlation with the MHC class I haplotype of the patients. Analysis of the subtype of the responding T cells demonstrated that primarily CD4+ T cells were stimulated by both 3H1 and 3H1-derived peptides. Interleukin 2, interleukin 4, and IFN-gamma were assayed in the culture medium of peripheral blood mononuclear cells stimulated with 3H1, CEA, and LCD-2 to determine the T-cell helper subset induced by these stimulants. The in vitro responses were mainly associated with secretion of IFN-gamma, which suggested that the induced T cells were most likely CD4+ Th1 type. Future studies will include the design of second-generation LCD-2 and CEA peptides to further enhance antigenicity, to characterize the responding T-cell populations more fully, and to test refined peptides for immunogenicity.

Tumor-infiltrating lymphocytes. Cytologic, phenotypic and morphometric analysis

OBJECTIVE

To characterize the cytologic, phenotypic and morphometric features of tumor-infiltrating lymphocytes (TILs).

STUDY DESIGN

Morphology and cell size parameters of 50 TILs and five normal donor peripheral blood lymphocyte (PBL) specimens were compared using light microscopy, manual ocular measurements and digital image processing.

RESULTS

Cytologically, all TILs demonstrated similar morphologic findings regardless of the initial tumor type. Changes included large; eccentric nuclei, sometimes hyperlobated; clumped chromatin; and prominent nucleoli. The cytoplasm was abundant and basophilic. Mitotic figures were usually evident. In addition, TIL showed significant increases in cell size parameters as compared to PBLs.

CONCLUSION

The activated morphology of TILs resembles the appearance of high grade lymphoma. Several cell size parameters are increased; that may help to explain differences in previously reported trafficking patterns between TILs and peripheral blood lymphocytes.

Loss of HLA haplotype and B locus down-regulation in melanoma cell lines

The expression of HLA class I molecules on tumor cells is vital for CD8+T cell recognition of tumor Ags. Loss of HLA class I Ag expression as a result of defective beta 2-microglobulin genes has been described in melanoma cells. To further evaluate mechanisms of tumor escape, HLA class I Ag expression was compared in 24 metastatic melanoma cell lines and 20 melanocyte strains by FACS analysis with use of allele-specific mAbs. Total loss of HLA class I Ag expression was not noted; instead, two relatively common phenomena were identified: 1) A variable degree of expression of HLA-B Ags by melanoma cell lines and melanocytes; however, HLA-A Ags were consistently expressed in all cell types. Furthermore, HLA-B locus Ag expression was detected in vivo in only one of six frozen section specimens obtained from six patients having metastatic melanoma. 2) Loss of allelic expression was noted in two of 14 HLA-A2 (14%) and one of three HLA-A29 (33%) melanoma cell lines and included a full haplotype, which suggests loss of a genomic fragment. Allele-specific PCR amplification demonstrated deletion of genes in linkage disequilibrium within the MHC class II, III, and I regions. Aberrations of HLA class I expression in tumor lines should be considered when assessing MHC-restricted phenomena in in vitro models.

Loss of HLA haplotype and B locus down-regulation in melanoma cell lines

The expression of HLA class I molecules on tumor cells is vital for CD8+T cell recognition of tumor Ags. Loss of HLA class I Ag expression as a result of defective beta 2-microglobulin genes has been described in melanoma cells. To further evaluate mechanisms of tumor escape, HLA class I Ag expression was compared in 24 metastatic melanoma cell lines and 20 melanocyte strains by FACS analysis with use of allele-specific mAbs. Total loss of HLA class I Ag expression was not noted; instead, two relatively common phenomena were identified: 1) A variable degree of expression of HLA-B Ags by melanoma cell lines and melanocytes; however, HLA-A Ags were consistently expressed in all cell types. Furthermore, HLA-B locus Ag expression was detected in vivo in only one of six frozen section specimens obtained from six patients having metastatic melanoma. 2) Loss of allelic expression was noted in two of 14 HLA-A2 (14%) and one of three HLA-A29 (33%) melanoma cell lines and included a full haplotype, which suggests loss of a genomic fragment. Allele-specific PCR amplification demonstrated deletion of genes in linkage disequilibrium within the MHC class II, III, and I regions. Aberrations of HLA class I expression in tumor lines should be considered when assessing MHC-restricted phenomena in in vitro models.

Locus-specific analysis of human leukocyte antigen class I expression in melanoma cell lines

Surface expression of human leukocyte antigen (HLA) class I antigens on melanoma lines was evaluated by locus-specific monoclonal antibodies (mAbs) with three different techniques: Fluorescence-activated cell sorting (FACS), immunohistochemistry with cytospin preparation (ICP), and complement-mediated cytotoxicity (CMC). Eleven HLA class I-expressing cell lines developed from metastases were used. Specific expression of HLA loci was examined under routine culture conditions and after 48-h incubation in interferon-gamma (IFN-gamma; 500 U/ml). Loss of allelic expression was seen in one line (586-MEL): Products of genes coding for HLA-A29 and -B44, in strong linkage disequilibrium, were not detectable. HLA-A antigens were consistently detected by all methodologies and minimally affected by pretreatment with IFN-gamma. HLA-B antigens were detectable in 8 of 11 lines by ICP and 3 of 11 lines by CMC. By FACS the supratypic specificity HLA-Bw6 was expressed at low levels in most lines (mean fluorescence 47.2 +/- 13.4 and rose to 259.8 +/- 45.9 after incubation with IFN-gamma; p < 0.001). HLA-Cw antigen detection by CMC correlated with HLA-B (p < 0.01), suggesting that down-regulation and sensitivity to IFN-gamma are shared by the two loci. This low expression of the HLA-B antigens may play a role in the evasion of the host immune response and its up-regulation may be useful in allowing tumor antigen recognition.

Hemodynamic effects of the administration of tumor-infiltrating lymphocytes to cancer patients

Tumor-infiltrating lymphocytes (TILs) can mediate tumor regression in selected patients with advanced cancer. To study some of the physiological changes associated with TIL administration, hemodynamic effects were measured while 2 x 10(10) to 20 x 10(10) TILs (mean 10 +/- 1 x 10(10)) were infused into 22 patients. In 10 patients, the first bag of TILs was administered without any interleukin-2 (IL-2) in the infusion bag; subsequent bags in the same patients and all bags in the next 12 patients contained IL-2 in low concentrations (300,000 IU). Two hours following infusion (as compared with baseline), patients developed tachycardia (110 +/- 3.3 vs. 76 +/- 3.5 beats/min; p < 0.001), increased cardiac index (4.9 +/- 0.2 vs. 3.2 +/- 0.13 L/min/m2; p < 0.001), decreased systemic vascular resistance (677 +/- 37 vs. 1185 +/- 63 dyn/s/cm5; p < 0.001), and increased pulmonary artery diastolic pressure (15.9 +/- 1.4 vs. 10.6 +/- 1.1 mm Hg; p = 0.002). No significant changes in systemic blood pressure were noted. Analysis of data obtained in the 10 patients after infusion of the first bag of TILs (4.5 +/- 0.4 x 10(10)) without IL-2 present in the infusate revealed similar, though less severe, changes. No significant correlation was noted between in vitro production of tumor necrosis factor-alpha, interferon-gamma, and granulocyte-macrophage colony-stimulating factor by TILs and hemodynamic effects when administered to patients. These results indicate that TIL infusion can cause hemodynamic changes similar to those previously reported in patients undergoing IL-2 therapy.

Functional and molecular characterization of tumor-infiltrating lymphocytes transduced with tumor necrosis factor-alpha cDNA for the gene therapy of cancer in humans

TNF is effective in causing the regression of selected murine tumors when administered at high concentrations. Therapeutic levels in humans cannot be obtained systemically, however, because of dose-limiting toxicity. The development of immunotherapy with IL-2 and tumor-infiltrating lymphocytes (TIL), which can accumulate at tumor sites in some patients, and of efficient retroviral techniques for gene transfer into eukaryotic cells has allowed new therapeutic approaches using TNF. We have retrovirally transduced human TIL with the gene for TNF in an attempt to deliver high concentrations of TNF to the tumor site without dose-limiting systemic toxicity. Successful gene insertion was confirmed by Southern hybridization in 16 of 16 transduced and selected TIL cultures from 15 different patients, with an estimated 28 to 93% transduced cells within each culture. Transduced selected TIL cultures produced greater amounts of TNF, compared with nontransduced controls, in 11 of 16 cultures evaluated. However, overall production of TNF was > 30-fold lower, compared with a transduced and highly selected tumor cell line control (MEL-TNF). In addition, steady state levels of vector-derived transcript in nine of 10 transduced selected TIL cultures were < 14% of the amount seen in the MEL-TNF control line. In an attempt to increase TNF production, TIL were transduced with a mutated form of TNF containing the IFN-gamma signal peptide in place of the transmembranous region, to enhance secretion into the endoplasmic reticulum. By using this vector, TNF production increased by an average of fivefold. These studies demonstrate that TIL can be genetically modified to express and secrete a protein for use in targeted cancer therapy but that partial expression blockades exist that prevent maximal cytokine production by introduced genes in TIL.

Functional and molecular characterization of tumor-infiltrating lymphocytes transduced with tumor necrosis factor-alpha cDNA for the gene therapy of cancer in humans

TNF is effective in causing the regression of selected murine tumors when administered at high concentrations. Therapeutic levels in humans cannot be obtained systemically, however, because of dose-limiting toxicity. The development of immunotherapy with IL-2 and tumor-infiltrating lymphocytes (TIL), which can accumulate at tumor sites in some patients, and of efficient retroviral techniques for gene transfer into eukaryotic cells has allowed new therapeutic approaches using TNF. We have retrovirally transduced human TIL with the gene for TNF in an attempt to deliver high concentrations of TNF to the tumor site without dose-limiting systemic toxicity. Successful gene insertion was confirmed by Southern hybridization in 16 of 16 transduced and selected TIL cultures from 15 different patients, with an estimated 28 to 93% transduced cells within each culture. Transduced selected TIL cultures produced greater amounts of TNF, compared with nontransduced controls, in 11 of 16 cultures evaluated. However, overall production of TNF was &gt; 30-fold lower, compared with a transduced and highly selected tumor cell line control (MEL-TNF). In addition, steady state levels of vector-derived transcript in nine of 10 transduced selected TIL cultures were &lt; 14% of the amount seen in the MEL-TNF control line. In an attempt to increase TNF production, TIL were transduced with a mutated form of TNF containing the IFN-gamma signal peptide in place of the transmembranous region, to enhance secretion into the endoplasmic reticulum. By using this vector, TNF production increased by an average of fivefold. These studies demonstrate that TIL can be genetically modified to express and secrete a protein for use in targeted cancer therapy but that partial expression blockades exist that prevent maximal cytokine production by introduced genes in TIL.

Patterns of cytokines released by peripheral blood leukocytes of normal donors and cancer patients during interleukin-2 activation in vitro

We have examined the responsiveness to in vitro stimulation with high-dose recombinant interleukin-2 (IL-2) of peripheral blood leukocytes (PBLs), collected from normal donors, or from successive daily cytaphereses of cancer patients with a range of advanced malignancies, following 5 days of continuous infusion with IL-2 in vivo. Normal donor PBLs showed a transient release of tumor necrosis factor (TNF) (up to 400 pg/ml) during the first day, while factors including interferon-gamma (IFN-gamma), soluble IL-2 receptor, and soluble CD-8 showed a gradual increase to modest levels (at best) during the 4 day incubation with IL-2. In contrast, the cancer patients' PBLs, after 5 days of IL-2 activation in vivo, responded with one of two patterns of production of cytokines. In pattern I, exposure to the IL-2 resulted in a transient release of TNF during the first 48 h. The level of TNF released showed a progressive increase from PBLs harvested from the first cytapheresis (up to 50 pg of TNF/ml) through the fourth cytapheresis (up to 2,000 pg of TNF/ml). Additionally, pattern I PBLs showed significant levels of production of IFN-gamma, soluble IL-2 receptor, and soluble CD8. In pattern II, the patients' PBLs from each cytapheresis released only low levels of TNF (less than 300 pg/ml) and minimal levels of IFN-gamma, IL-2 receptor, and CD8. A pattern I response is considered to be consistent with an immunostimulatory role for IL-2, which induces a cooperative interaction of lymphocytes and macrophages that is mediated by other cytokines, while pattern II may reflect an immunosuppression in these patients.(ABSTRACT TRUNCATED AT 250 WORDS)