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T L Whiteside

Publications and source records attributed to T L Whiteside.

At least 37 records · Page 2Linked to original sources
PubMed2000

Generation of T cells specific for the wild-type sequence p53(264-272) peptide in cancer patients: implications for immunoselection of epitope loss variants.

Alterations in the p53 gene occur frequently and can lead to accumulation of p53 protein in squamous cell carcinomas of the head and neck (SCCHN). Since accumulation of p53 is associated with enhanced presentation of wild-type sequence (wt) p53 peptides to immune cells, the development of pan vaccines against SCCHN has focused on wt p53 epitopes. We used the HLA-A2.1-restricted wt p53(264-272) epitope to generate CTL from circulating precursor T cells of HLA-A2.1(+) healthy donors and patients with SCCHN. Autologous peptide-pulsed dendritic cells were used for in vitro sensitization. CTL specific for the wt p53(264-272) peptide were generated from PBMC obtained from two of seven normal donors and three of seven patients with SCCHN. These CTL were HLA class I restricted and responded to T2 cells pulsed with p53(264-272) peptide as well as HLA-A2-matched SCCHN cell lines naturally presenting the epitope. Paradoxically, none of the tumors in the three patients who generated CTL could adequately present the epitope; two had a wt p53 genotype and no p53 protein accumulation, while the third tumor expressed a point mutation (R to H) in codon 273 that prevents presentation of the p53(264-272) epitope. In contrast, patients who did not generate CTL had tumors that accumulated altered p53 and potentially could present the p53(264-272) epitope. These findings suggest that in vivo, CTL specific for the wt p53(264-272) peptide might play a role in the elimination of tumor cells expressing this epitope and in immunoselection of epitope-loss tumor cells. Immunoselection of tumors that become resistant to anti-p53 immune responses has important implications for future p53-based vaccination strategies.

Autoantibodies↗
PubMed2000

Generation of tumor-specific T-lymphocytes by cross-priming with human dendritic cells ingesting apoptotic tumor cells.

It has been suggested that dendritic cells (DCs) are capable of ingesting apoptotic tumor cells (ATCs) and presenting tumor-associated antigens to immune cells. We evaluated the potential of human DCs, which have ingested ATCs, to serve as a source of antigenic epitopes for presentation to T cells specific for PCI-13, a squamous cell carcinoma of the head and neck cell line. Immature DCs (DCimm) generated in the presence of interleukin 4 and granulocyte machrophage colony-stimulating factor from peripheral blood monocytes of HLA-A2+ healthy donors were incubated in the presence of ATCs. Uptake of ATCs by DCs was monitored by flow cytometry and confocal microscopy after 2-18 h of coincubation. When DCs were matured (DCmat) in the presence of proinflammatory cytokines, their capacity to uptake ATCs was reduced. Responses of PCI-13-specific CD8+ T cells to unmodified PCI-13 cells and to DCimm or DCmat +/- ATCs or +/- tumor lysates were tested in gamma-IFN enzyme-linked immunospot and cytotoxicity assays. Unmodified tumor cells were found to be the best stimulators of antitumor activity of the established T-cell line, and ATCs alone were minimally stimulatory. However, DCs that ingested ATCs were able to present tumor antigens to CTLs, and DCimm and DCmat were almost equally stimulatory. When DCs plus various tumor-derived preparations were used as antigen-presenting cells with autologous HLA-A2+ T cells obtained from normal donors, DCs that had ingested ATCs were more effective in generating CD8+ CTLs than tumor cells alone or DCs pulsed with tumor lysates. The results indicate that human DCs fed with ATCs and then matured effectively generated T cell-mediated antitumor responses in vitro.

Antigens, CD↗
PubMed2000

Analysis of therapeutic and immunologic effects of R(24) anti-GD3 monoclonal antibody in 37 patients with metastatic melanoma.

BACKGROUND: Antitumor effects of antibodies against ganglioside antigens of melanoma have been reported, but neither optimal doses nor mechanisms have been established. METHODS: This Phase IB trial of the murine immunoglobulin IgG(3) monoclonal antibody R(24) against disialoganglioside GD3 was conducted with 37 patients to define better the dose-response relation and mechanism of action of R(24) in patients with metastatic melanoma. RESULTS: Dose-limiting toxicity consisted of a pulmonary capillary leak syndrome in 3 of 5 patients in the 80 mg/M(2)/day dosage tier. Serial blood and tumor biopsy samples were obtained prior to therapy and on Days 5, 9, and 22 following R(24) infusion. Tumor biopsy-infiltrating lymphocytes were enumerated in peritumoral, endotumoral, and perivascular compartments: endotumoral CD4(+) and CD8(+) T cells and HLA-DR(+) T cells increased over time on R(24) antibody. Endotumoral CD4 lymphoid infiltrate activation (DR expression) and antibody-dependent cytotoxicity were the greatest in the one patient who achieved a complete response. CONCLUSIONS: Clinical response was associated with depression in natural killer (CD56(+) and CD56(+)DR(+)) blood cells (P = 0.03) and was associated with R(24) dosage (P = 0.01). A complete response that lasted 2 years and a partial response that lasted 2 months occurred at a dose of 1 mg/M(2)/day. The limited number of clinical responses observed in this trial hampered the correlation of antitumor and immune parameters but provided a rational foundation for the future evaluation of antiganglioside antibodies.

Adult↗
PubMed2000

Generation of PSA-reactive effector cells after vaccination with a PSA-based vaccine in patients with prostate cancer.

BACKGROUND: JBT 1001 is a vaccine used for therapy of prostate cancer (CA), which consists of recombinant prostate-specific antigen (PSA) with lipid A formulated in liposomes. Patients with prostate CA were vaccinated with JBT 1001 emulsified in mineral oil (n = 5) or with the vaccine in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF) administered locally at the site of vaccination (n = 5). Frequency of PSA-reactive T cells was measured in peripheral blood mononuclear cells (PBMC) before and after immunization, using an interferon-gamma (IFN-gamma) enzyme-linked immunospot (ELISPOT) assay with autologous dendritic cells (DC) as antigen-presenting cells. The hypothesis tested was that PSA-based vaccines induce T cell responses to human PSA. METHODS: In order to expand precursor cells, in vitro sensitization (IVS) was performed. Microcultures of peripheral blood lymphocytes (PBL) (1 x 10(5)/well) in medium supplemented with interleukin-2 (IL-2) (10 IU/ml) and interleukin-7 (IL-7) (10 ng/ml) were stimulated twice (day 0 and day 7) with monocyte-derived autologous DC, generated by culture with interleukin-4 (IL-4) and GM-CSF and pulsed with PSA (10 microg/ml) at an effector to stimulator ratio of 10:1. ELISPOT assays were performed on day 14 of culture. In addition, PBMC were separated on immunobeads into CD4(+) and CD8(+) subsets for ELISPOT assays performed without IVS. RESULTS: Two patients had PSA-reactive responses before vaccination (frequency range, 1/700-1/4,400). After vaccination, 8/10 patients had measurable PSA-reactive T-cell frequencies, ranging from 1/200-1/1900, using IVS. In contrast, without IVS, but after immunoselection to enrich in CD8(+) and CD4(+) T cells, only 2/10 patients had detectable PSA-reactive T cells after vaccination, at a frequency ranging from 1/2,600-1/4,000. CONCLUSIONS: Vaccination with PSA formulated into liposomes induced T-cell responses in 8/10 patients with prostate carcinoma. The frequency of PSA-reactive precursor T cells was relatively low in the blood of these patients, and IVS, leading to amplification of the precursor cells prior to ELISPOT, was necessary for quantification of the PSA-responding T cells. Cellular responses to PSA were predominantly mediated by CD4(+) T lymphocytes.

Aged↗
PubMed2000

B7.1 on human carcinomas: costimulation of T cells and enhanced tumor-induced T-cell death.

Human squamous cell carcinomas of the head and neck (SCCHN) do not express the costimulatory molecules B7.1 or B7.2 in situ or in culture. Transduction of B7.1(-) SCCHN cells with the retroviral B7. 1 and neo(r) genes resulted in the expression of high levels of the transgene in these tumor cells. When B7.1(+) SCCHN cells were used as stimulators of autologous or allogeneic PBL in mixed lymphocyte-tumor cultures (MLTC), T-cell proliferation and generation of antitumor effector T cells as well as levels of their lytic activity were significantly increased. At the same time, a proportion of activated T cells seen to undergo apoptosis was found to be significantly higher upon coincubation with B7.1(+) SCCHN than with B7.1(-) SCCHN. Both B7.1(+) and B7.1(-) SCCHN cells were found to express FasL on the cell surface and in the cytoplasm, as well as mRNA for FasL and mRNA for TRAIL. However, expression of the B7.1 transgene did not lead to increased expression of FasL protein on tumor cells. Yet, up to 50% of activated CD28(+) allogeneic T cells, which were CD95(+), showed evidence of DNA fragmentation in JAM and TUNEL assays upon incubation with an excess of B7.1(+) SCCHN for 24 h. Tumor-induced T-cell death was equally and only in part blocked by anti-Fas antibodies in both B7.1(+) and B7.1(-) MLTC. While surface expression of B7.1 molecules on SCCHN cells enhanced T-cell costimulation via B7.1-CD28 interactions, it did not rescue activated T cells from tumor-induced apoptosis. The outcome of MLTC under these conditions was dependent on the ratio of tumor to T cells. Thus, in the presence of an excess of B7.1(+) tumor cells, activated T cells showed increased sensitivity to apoptosis which did not appear to be Fas/FasL mediated. These data are important for the development of B7.1 gene therapy and efforts directed at the generation of effector cells in MLTC.

Apoptosis↗
PubMed2000

Tumor-induced apoptosis of T lymphocytes: elucidation of intracellular apoptotic events.

Our recent studies suggest that human squamous cell carcinoma of the head and neck (SCCHN) is capable of activating an intrinsic mechanism of programmed-cell death in interacting lymphocytes in situ and in vitro. The current study used Jurkat T-cell line as a model to investigate intracellular apoptotic events in T cells interacting with SCCHN. Apoptosis induced in T lymphocytes by tumor cells was in part Fas-mediated, since it was partially, but significantly, inhibited in the presence of anti-Fas ligand Ab or in Fas-resistant Jurkat cells. The synthetic caspase inhibitors, N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (Z-VAD-FMK) and N-benzyloxycarbonyl-Asp-glu-Val-Asp-fluoromethyl ketone (Z-DEVD-FMK), effectively blocked apoptosis of Jurkat cells co-incubated with SCCHN cell lines, suggesting the involvement of caspases in tumor-induced apoptosis of lymphocytes. Overexpression of CrmA, an inhibitor of caspase-1 and caspase-8, partially inhibited tumor-induced T-cell death. Caspase-8 and caspase-3 were identified as effector molecules in the execution of tumor-induced T-cell death, since the proform enzymes were processed into active subunits during co-incubation of T cells with tumor cells. Furthermore, co-incubation with tumor cells resulted in cleavage of poly(ADP-ribose) polymerase (PARP), a common caspase-3 substrate, and in cleavage of TcR-zeta chain, shown by us to be a T-cell specific caspase-3 substrate. Overexpression of Bcl-2 did not provide protection of T cells from SCCHN-induced DNA degradation. Instead, the Bcl-2 protein was cleaved in the target T cells during their co-incubation with tumor cells. These findings demonstrate that tumor cells can trigger in T lymphocytes caspase-dependent apoptotic cascades, which are not effectively protected by Bcl-2. (Blood. 2000;95:2015-2023)

Apoptosis↗
PubMed2000

Identification of a novel tumor necrosis factor-alpha-inducible gene, SCC-S2, containing the consensus sequence of a death effector domain of fas-associated death domain-like interleukin- 1beta-converting enzyme-inhibitory protein.

We report here the isolation and characterization of a novel tumor necrosis factor-alpha (TNF-alpha)-inducible gene, SCC-S2. Based on the nucleotide sequence, the SCC-S2 open reading frame contains a sequence in the amino terminus that shows a significant homology to death effector domain II of cell death regulatory protein, Fas-associated death domain-like interleukin-1beta-converting enzyme-inhibitory protein (FLIP). Unlike FLIP, the SCC-S2 open reading frame contains only one death effector domain and lacks the carboxyl-terminal caspase-like homology domain, raising the possibility that SCC-S2 may be a novel member of the FLIP family. SCC-S2 mRNA expression is found in most normal tissues and malignant cells. The steady state level of SCC-S2 mRNA is significantly induced by TNF-alpha in different tumor cells (TNF-alpha at 20 ng/ml for 3 h: A549, approximately 2-9-fold; SKOV-3, approximately 3-fold; PCI-04A, approximately 3-6-fold). TNF-alpha treatment (100 ng/ml, 4 h) of HeLa cells transiently transfected with FLAG epitope-tagged SCC-S2 cDNA or expression vector alone led to an increase in the number of apoptotic cells as compared with the untreated counterpart. Interestingly, however, SCC-S2 transfectants revealed a significant decrease in the number of apoptotic cells as compared with the vector transfectants (p < 0.001). These data implicate a role of SCC-S2 as a negative mediator of apoptosis in certain cell types.

Adaptor Proteins, Signal Transducing↗
PubMed2000

Interleukin-2 expression in human carcinoma cell lines and its role in cell cycle progression.

Human carcinomas were shown to express mRNA and protein for IL-2R alpha, beta and gamma chains. Recently, human carcinomas were also shown to constitutively express protein and mRNA for IL-2 in vivo and in vitro. Here we report that the expression levels of cytoplasmic IL-2 as well as IL-2Rbeta- and gamma-chain in human carcinoma cells change during the cell cycle progression. Carcinoma cells synchronized in the G2/M phase of the cell cycle expressed significantly more intracytoplasmic IL-2 as well as IL-2Rbeta and gamma proteins than tumor cells in the G0/G1 phase. The level of mRNA for IL-2 was 5-10-fold higher in the M phase than in the G0/G1-phase, as shown by quantitative competitive RT-PCR. Expression of the cyclin-dependent kinase (CDK) inhibitor p27kip1 in these carcinoma cells was found to be high in the G0/G1 phase, nearly absent in the S phase, and it increased again in the G2/M phase of the cell cycle. In synchronized cells, the decrease in p27 expression coincided with high levels of expression of IL-2. Using the IL-2 specific antisense oligonucleotide to block synthesis of endogenous IL-2 in tumor cells, we observed increased levels of p27 as well as p21. The antisense oligonucleotides specific for p27 or p21 blocked expression of these proteins but not of IL-2. Thus, endogenous IL-2 is important in regulating expression of p27 as well as p21 and, therefore, in controlling cell cycle progression of tumor cells, while its own expression remains independent of the CDK inhibitors.

Blotting, Western↗
PubMed2000

Inhibition of apoptosis in human tumour cells by the tumour-associated serpin, SCC antigen-1.

The squamous cell carcinoma antigen (SCC Ag) is a tumour-associated protein and a member of the serine protease inhibitor (serpin) family. The SCC Ag has been used as a serologic tumour marker for SCC progression, and its elevated serum levels are a risk factor for disease relapse. However, the biologic significance of this intracytoplasmic protein in cancer cells remains unknown. In this report, we demonstrated that apoptosis induced by 7-ethyl-10-hydroxycamptothecin, tumour necrosis factor-alpha (TNF-alpha) or interleukin (IL)-2-activated natural killer (NK) cells was significantly inhibited in tumour cells transduced with the SCC Ag-1 cDNA, as compared to control cells in vitro. Also, inhibition of the SCC Ag-1 expression in tumour cells by transfection of antisense SCC Ag-1 cDNA was accompanied by significantly increased sensitivity of these cells to apoptosis induced by etoposide or TNF-alpha. The mechanism of protection of tumour cells from apoptosis involved inhibition of caspase-3 activity and/or upstream proteases. In vivo, tumour cells overexpressing the SCC Ag-1 formed significantly larger tumours in nude mice than the SCC Ag-1-negative controls. Thus, overexpression of the SCC Ag-1, a member of the serpin family, in human cancer cells contributed to their survival by mediating protection from drug-, cytokine- or effector cell-induced apoptosis.

Antigens, Neoplasm↗
PubMed2000

Evaluation of the modified ELISPOT assay for gamma interferon production in cancer patients receiving antitumor vaccines.

Frequencies of vaccine-responsive T-lymphocyte precursors in peripheral blood mononuclear cells (PBMC) prior to and after administration of peptide-based vaccines in patients with cancer can be measured by limiting-dilution assays (LDA) or by ELISPOT assays. We have used a modified version of the ELISPOT assay to monitor changes in the frequency of gamma interferon (IFN-gamma)-producing T cells in a population of lymphocytes responding to a relevant peptide or a nonspecific stimulator, such as phorbol myristate acetate-ionomycin. Prior to its use for monitoring of patient samples, the assay was validated and found to be comparable to the LDA performed in parallel, using tumor-reactive cytolytic T-lymphocyte (CTL) lines. The sensitivity of the ELISPOT assay was found to be 1/100,000 cells, with an interassay coefficient of variation of 15%, indicating that it could be reliably used for monitoring of changes in the frequency of IFN-gamma-secreting responder cells in noncultured or cultured lymphocyte populations. To establish that the assay is able to detect the T-cell precursor cells responsive to the vaccine, we used CD8(+) T-cell populations positively selected from PBMC of HLA-A2(+) patients with metastatic melanoma, who were treated with dendritic cell-based vaccines containing gp100, MELAN-A/MART-1, tyrosinase, and influenza virus matrix peptides. The frequency of peptide-specific responder T cells ranged from 0 to 1/2,600 before vaccination and increased by at least 1 log unit after vaccination in two patients, one of whom had a clinical response to the vaccine. However, no increases in the frequency of peptide-responsive T cells were observed in noncultured PBMC or PBMC cultured in the presence of the relevant peptides after the melanoma patients enrolled in another trial were treated with the intramuscular peptide vaccine plus MF59 adjuvant. Thus, while the ELISPOT assay was found to be readily applicable to assessments of frequencies of CTL precursors of established CTL lines and ex vivo-amplified PBMC, its usefulness for monitoring of fresh PBMC in patients with cancer was limited. In many of these patients antitumor effector T cells are present at frequencies of lower than 1/100,000 in the peripheral circulation. Serial monitoring of such patients may require prior ex vivo amplification of specific precursor cells.

Antibodies, Monoclonal↗
PubMed2000

Immunologic monitoring of clinical trials in patients with cancer: technology versus common sense.

Monitoring of CTL or helper T -cell responses to tumor antigens in the course of clinical trials is an essential and necessary component of specific immunotherapy of cancer. While a variety of new immunologic or molecular technologies are now available for measuring these responses at a single-cell level, none has been standardized or validated to meet this need. The clinical investigator is thus faced with a selection of a method that is most likely to meet the desirable objective of establishing a correlation between clinical and immunologic responses to biotherapy. Selection of a relevant assay for this purpose is not a trivial task. Furthermore, few immunologic techniques can be easily adapted to reliable serial monitoring of patients on clinical protocols. The ELISPOT assay performs well in this setting, allowing for tracking of antigen specific T cells in the peripheral blood of cancer patients who receive tumor vaccines. In our hands, this assay is sensitive, accurate and cost effective. Its reliable performance in the context of clinical vaccination trials is highly likely to provide information necessary for optimizing vaccine administration to cancer patients, including timing, route of delivery, antigen concentration and use of DC or other adjuvants.

Cancer Vaccines↗
PubMed2000

Interleukin-2: developing additional cytokine gene therapies using fibroblasts or dendritic cells to enhance tumor immunity.

PURPOSE: Recombinant interleukin (IL)-2 administration can mediate regression of solid tumors in patients with melanoma and renal cell carcinoma. A better understanding of the mechanisms of IL-2-mediated antitumor effects has led to the investigation of novel immunotherapeutic approaches. The rationale for these immunotherapeutic approaches and the results of preliminary clinical studies are presented. PATIENTS AND METHODS: The therapeutic potential of dendritic cells and the role of FLT3 ligand, a potent hematopoietic growth factor, was investigated in a variety of preclinical models. In addition, a clinical study with autologous dendritic cells pulsed with synthetic melanoma peptides derived from the MART1/ Melan A, gp100, and tyrosinase proteins was conducted. Twenty-eight human leukocyte antigen (HLA)-A2+ melanoma patients received an average of 106 dendritic cells a week for 4 weeks. RESULTS: In a murine liver metastases model, FLT3 ligand administration alone or in combination with IL-12 or IL-2 had significant antitumor effects and resulted in significant infiltration of the tumor border by lymphocytes and dendritic cells, which was associated with an increased number of apoptotic figures. Administration of melanoma peptide-pulsed dendritic cells to 28 patients with advanced metastatic melanoma produced a complete response in two patients and a partial response in one. Significant infiltration of T cells and dendritic cells into melanoma lesions was observed. CONCLUSION: These studies confirm the feasibility of immunotherapeutic approaches using dendritic cells and FLT3 ligand and demonstrate their potential antitumor activity. These approaches may be effective for patients with metastatic melanoma and other solid tumors and will likely be used to improve the efficacy of IL-2-based immunotherapy.

Cancer Vaccines↗
PubMed2000

A wild-type sequence p53 peptide presented by HLA-A24 induces cytotoxic T lymphocytes that recognize squamous cell carcinomas of the head and neck.

Evidence has accumulated indicating that HLA-A2-restricted CTLs specific for human wild-type sequence p53 epitopes lyse tumor cells expressing mutant p53. To explore the possibility that wild-type sequence p53 peptides could also be used in vaccines for patients expressing HLA-A24 antigen, another frequent HLA class I allele, we investigated the induction of HLA-A24-restricted p53-specific CTLs from the peripheral blood lymphocytes of normal donors. Of six p53-derived peptides possessing an HLA-A24 binding motif, the p53 peptide 125-134 (p53(125-134)) was found to have a high binding capacity and induced peptide-specific CTLs from peripheral blood mononuclear cells, using peptide-pulsed autologous dendritic cells and subsequent cultivation with cytokines interleukin 2 and interleukin 7. Bulk CTL populations lysed peptide-pulsed HLA-A24+ targets as well as HLA-A24+ squamous cell carcinoma of the head and neck (SCCHN) cell lines. However, IFN-gamma pretreatment of HLA-A24+ SCCHN cell lines was necessary for lysis, suggesting that a ligand density higher than that normally expressed by tumor cells is required for these CTLs to mediate lysis. Moreover, a cloned CTL, designated TH#99, isolated from the bulk population by limiting dilution, lysed HLA-A24+ SCCHN targets more efficiently than the bulk CTL population. Lysis was inhibited by anti-HLA class I monoclonal antibody but not by anti-HLA-DR monoclonal antibody. These results indicate that HLA-A24-restricted CTLs recognizing the wild-type sequence p53(125-134) can be generated using autologous dendritic cells from precursors present in peripheral blood lymphocytes obtained from normal HLA-A24+ donors. This finding suggests that vaccine strategies targeting wild-type sequence p53 epitopes can be extended to a wider range of cancer patients.

Amino Acid Sequence↗
PubMed2000

Spontaneous apoptosis of CD8+ T lymphocytes in peripheral blood of patients with advanced melanoma.

Peripheral blood mononuclear cells (PBMCs) obtained from patients with advanced melanoma but not from healthy individuals were found to undergo spontaneous ex vivo apoptosis upon incubation in medium. PBMCs were evaluated for evidence of apoptosis using Annexin V binding, caspase-3 activation, and DNA fragmentation (terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling). PBMCs of patients with melanoma contained a significantly higher proportion (P = 0.0027) of spontaneously apoptotic cells than PBMCs of controls after 24-h incubation in medium alone. The relative proportion of activated Fas+ and tumor necrosis factor receptor 1-positive (TNFR1+) PBMCs was significantly higher in patients with melanoma than that observed in controls. To demonstrate that the TNF family of receptors and ligands was involved in this type of apoptosis, PBMCs were incubated in the presence of agonistic anti-Fas antibody (CH-11) or TNF-alpha. The proportion of terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling-positive PBMCs undergoing spontaneous apoptosis was found to be comparable with that induced by CH-11 antibody or TNF-alpha. Three-color flow cytometry revealed that CD3+ Fas+ T cells were especially sensitive to apoptosis and were preprogrammed in vivo to die. Apoptosis occurred in all subsets of PBMCs but was significantly higher (P = 0.01) in the CD3+ CD8+ T-cell subset in patients relative to controls. In two patients with melanoma, who responded clinically to dendritic cell-based peptide vaccines, the proportion of apoptotic T cells was decreased by half after therapy. In patients who were treated previously with vaccination-based therapies, levels of T-cell apoptosis were lower than in the other melanoma patients. The observed accelerated death of T cells, which are activated and susceptible to apoptosis in patients with melanoma, may contribute to a rapid turnover of immune cells, resulting in a decreased immunocompetence.

Adult↗
PubMed1999

Constitutive expression and role of the TNF family ligands in apoptotic killing of tumor cells by human NK cells.

Natural killer cells mediate spontaneously secretory/necrotic killing against rare leukemia cell lines and a nonsecretory/apoptotic killing against a large variety of tumor cell lines. The molecules involved in nonsecretory/apoptotic killing are largely undefined. In the present study, freshly isolated, nonactivated, human NK cells were shown to express TNF, lymphotoxin (LT)-alpha, LT-beta, Fas ligand (L), CD27L, CD30L, OX40L, 4-1BBL, and TNF-related apoptosis-inducing ligand (TRAIL), but not CD40L or nerve growth factor. Complementary receptors were demonstrated to be expressed on the cell surface of solid tumor cell lines susceptible to apoptotic killing mediated by NK cells. Individually applied, antagonists of TNF, LT-alpha1beta2, or FasL fully inhibited NK cell-mediated apoptotic killing of tumor cells. On the other hand, recombinant TNF, LT-alpha1beta2, or FasL applied individually or as pairs were not cytotoxic. In contrast, a mixture of the three ligands mediated significant apoptosis in tumor cells. These findings demonstrate that human NK cells constitutively express several of the TNF family ligands and induce apoptosis in tumor cells by simultaneous engagement of at least three of these cytotoxic molecules.

Antigens, CD↗