The decreased expression of CD3 zeta chains in cancer patients is not reversed by IL-2 administration

Effect of CRISPR/Cas9-Mediated PD-1-Disrupted Primary Human Third-Generation CAR-T Cells Targeting EGFRvIII on In Vitro Human Glioblastoma Cell Growth

Glioblastoma (GBM), which is the most common malignant brain tumor, is resistant to standard treatments. Immunotherapy might be a promising alternative for the treatment of this cancer. Chimeric antigen receptor (CAR) is an artificially modified fusion protein that can be engineered to direct the specificity and function of T cells against tumor antigens. However, the antitumor effects of EGFRvIII-targeting CAR-T (EvCAR-T) cells in GBM are limited. The inhibitory effect is induced by the interaction between programmed cell death protein 1 (PD-1) on activated EvCAR-T cells and its ligands on GBM cells. In the present study, PD-1-disrupted EvCAR-T cells were established using the clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9). The sgRNA/Cas9 expression vectors designed precisely disrupted the target region of PD-1 and inhibited the expression of PD-1 in EvCAR-T cells. The PD-1-disrupted EvCAR-T cells had an in vitro growth inhibitory effect on EGFRvIII-expressing GBM cells without altering the T-cell phenotype and the expression of other checkpoint receptors. In the future, the in vivo antitumor effect of this vector should be evaluated in order to determine if it could be applied clinically for improving the efficacy of EvCAR-T cell-based adoptive immunotherapy for GBM.

Expression of Breast Cancer-Related Epitopes Targeting the IGF-1 Receptor in Chimeric Human Parvovirus B19 Virus-Like Particles

Breast cancer is a worldwide health problem, and the complexity of the disease, as well as the lack of treatment specificity, generates an urgent need for developing prophylactic and therapeutic measures. Searching for novel epitope-based approaches able to induce tumour immunity, we designed virus-like particles (VLPs) derived from Human parvovirus B19 assembled of chimeric VP2 proteins displaying two epitopes from the insulin-like growth factor-1 receptor (IGF-1R). Here, we present the generation of two chimeric VP2s that retain the stability, solubility and conditions of purification and assembly of the native VP2. We generated versatile chimeric multiepitope anti-cancer vaccine candidates, which prevented and delayed tumour growth when used in a prophylactic scheme of 4 weekly immunizations prior to 4T1 cell inoculation in female BALB/c mice. The presence of specific antibodies against the displayed epitopes suggests their participation in the protective effect; in contrast, no significant proliferative T-cell responses were recorded following stimulation by specific epitopes. The results comprise an approach whereby fusing desired epitopes from cancer to the N-terminus of B19 VP2 protein can generate a library of chimeric VP2-desired epitopes for further assembly in a designed and personalized epitope delivery system.

The immune system and head and neck squamous cell carcinoma: from carcinogenesis to new therapeutic opportunities

Head and neck squamous cell carcinomas (HNSCCs) exhibit complex interactions with the host immune system that may simultaneously explain resistance to various therapeutic modalities and that may also provide opportunities for therapeutic intervention. Discoveries in immunologic research over the last decade have led to an increased understanding of these interactions as well as the development of a multitude of investigational immunotherapies. Here, we describe the interaction between HNSCC and the immune system, including a discussion of immune cells involved with tumor carcinogenesis and the role of immune-modulating factors derived from tumors. We also describe the current immunotherapeutic approaches being investigated for HNSCC, including a discussion of the successes and limitations. With this review, we hope to present HNSCC as a model to guide future research in cancer immunology.

TCR zeta-chain downregulation: curtailing an excessive inflammatory immune response

The T-cell receptor (TCR) functions in both antigen recognition and signal transduction, which are crucial initial steps of antigen-specific immune responses. TCR integrity is vital for the induction of optimal and efficient immune responses, including the routine elimination of invading pathogens and the elimination of modified cells and molecules. Of the TCR subunits, the zeta-chain has a key role in receptor assembly, expression and signalling. Downregulation of TCR zeta-chain expression and impairment of T-cell function have been shown for T cells isolated from hosts with various chronic pathologies, including cancer, and autoimmune and infectious diseases. This review summarizes studies of the various pathologies that show this phenomenon and provides new insights into the mechanism responsible for downregulation of zeta-chain expression, its relevance and its clinical implications.

Mechanisms of tumor evasion from the immune response

The results from in vitro immunological experiments, murine tumor models and patients with cancer clearly demonstrate that tumors have multiple mechanisms to evade the immune response. During the early stages of tumor development malignant cells can be poor stimulators, present poor targets or become resistant to the innate immune response, while at later stages, progressively growing tumors impair the adaptive immune response by blocking the maturation and function of APCs and causing alterations in T-cell signal transduction and function. Preliminary results also suggest a correlation between some of these changes and an increased metastatic potential of the tumor cells, a diminished response to immunotherapy, and poor prognosis. Carefully coordinated basic research studies and clinical immunotherapy trials will be required to fully determine the impact of these mechanisms of tumor evasion on the outcome of the disease and the response to treatment. However, understanding the mechanisms used by tumor cells to evade the immune system could result in new therapeutic approaches for preventing and/or reversing these immune alterations and could have the potential of improving the current results of immunotherapy trials.

Restored T-cell activation mechanisms in human tumour-infiltrating lymphocytes from melanomas and colorectal carcinomas after exposure to interleukin-2

We investigated the effects of interleukin-2 (IL-2) exposure on T-cell signal transduction molecules and apoptosis markers in tumour-infiltrating lymphocytes (TIL) isolated from 20 melanoma and 16 colorectal carcinoma metastases and expanded in vitro for therapeutic reinfusion. Before IL-2 culture, TIL showed undetectable or very low levels of T-cell receptor (TCR) epsilon chain, p56(lck), Fas ligand (FasL) and Bax expression, while Bcl-2 values were elevated. Cancer cells were characterised by low or absent Fas and Bcl-2 and high Bax expression. Notably, they also expressed FasL. After 41-48 days of IL-2 culture, TCR epsilon chain and p56(lck) expression of TIL rose to median values of approximately 80 and 30% positive cells, respectively (P<0.001), FasL expression was detected in 45% cells from melanomas (P<0.001) and in 3% from colorectal carcinomas (P=0.09), and Bax-positive cells increased from 17.5 to 70% (P=0.005). Moreover, TCR zeta chain-positive cells were significantly increased from baseline (P=0.001), Bcl-2-positive cells dropped from 50 to 1% (P=0.007) and perforin content was high, while Fas expression was not significantly modified by IL-2 culture. In conclusion, our data suggest that the degree of immunosuppression in TIL from melanomas and colorectal carcinomas is very high, and the apoptosis markers' repertoire of cancer cells resembles that of immune-privileged tissue. Interleukin-2 culture appears to restore lymphocyte activation mechanisms, resulting in consistent FasL expression and perforin production.

Expression of zeta in T cells prior to interleukin-2 therapy as a predictor of response and survival in patients with ovarian carcinoma

Expression levels of T-cell receptor (TcR)-associated zeta chain were reported to reflect functional competence of T lymphocytes in patients with cancer. This retrospective study was performed to evaluate zeta chain expression in circulating T cells obtained from clinical responders and nonresponders among 19 patients with advanced ovarian carcinoma treated with intraperitoneal interleukin-2 (IL-2) biotherapy. Banked lymphocytes, which were collected from the patients who participated in a phase I clinical trial performed between 1987 and 1990, were used for quantitative flow cytometry to measure zeta-chain expression in T lymphocytes prior to and at the end of therapy. The data were correlated with 7-year survival. The patients (9 responders and 10 nonresponders) were stratified into two groups based on zeta chain expression in CD3+ T cells above or below the mean. Patients with lower zeta expression in circulating T cells had shorter survival compared to patients whose T cells expressed high zeta. Pretherapy zeta expression was significantly lower (p = 0.03) in CD8+T cells of nonresponders than in CD8+T cells of normal controls. In patients with advanced ovarian carcinoma, low expression of the zeta chain in peripheral blood T cells prior to biotherapy might both reflect a large tumor burden and predict a poor of response to IL-2 bio-therapy.

The effect of peripheral blood lymphocyte stimulation on zeta chain expression and IL-2 production in Hodgkin's disease

It has been reported that peripheral blood T cells and NK cells express reduced levels of the T-cell receptor signal-transducing zeta chain in Hodgkin's disease (HD). The zeta chain has emerged as a key subunit of the T-cell antigen receptor, which plays a central role in the signal-transducing events leading to T and NK-cell activation. We were interested in determining whether the low zeta chain expression in HD could be corrected by anti-CD3, anti-CD3-rIL-2 ex vivo stimulation. Zeta chain expression was analysed by dual immunofluorescence on permeabilized cells before and after 72 hours of culture. The IL-2 concentration in the culture supernatants was measured by ELISA. Zeta chain was significantly reduced on unstimulated CD4+, CD8+ and CD56+ cells from patients in active disease compared with normal subjects. In patients in complete remission, the values were normal except for CD8+ cells, on which zeta expression remained significantly reduced. Stimulation with anti-CD3 did not change zeta expression. Co-stimulation with rIL-2 increased but did not normalize the proportions of CD4(+)/zeta(+), CD8(+)/zeta(+)and CD56(+)/zeta(+)cells and IL-2 production in active disease. Stimulation of cells from patients in clinical remission with anti-CD3(+)rIL-2 increased the proportion of CD8(+)zeta(+)cells and normalized IL-2 production levels. Considering the pivotal role of CD3-zeta in immune response, our data suggest that successful immunotherapy approaches in active HD should consider inclusion of other potent cytokines, as well as genetically engineered tumour vaccines.

Interferon α prevents spontaneous apoptosis of clonal Th2 cells associated with chronic hypereosinophilia

A recent study identified a clonal expansion of CD3−CD4+cells secreting Th2-type cytokines in 4 patients with chronic hypereosinophilia. Because interferon α (IFN-α) is used in the therapy of the idiopathic hypereosinophilic syndrome, the effects of this cytokine on the survival of clonal Th2 cells isolated from the blood of 2 patients were determined. First, these cells displayed a high rate of spontaneous apoptosis on culture in cytokine-free medium and were also sensitive to Fas-mediated apoptosis induced by soluble Fas ligand. Addition of IFN-α or interleukin-2 (IL-2) to culture medium resulted in significant protection against spontaneous but not Fas-induced apoptosis. Although spontaneous apoptosis of the clonal Th2 cells was clearly associated with down-regulation of both bcl-2 and bcl-xL levels, IFN-α had no significant effect on the expression of these antiapoptotic proteins, whereas addition of IL-2 resulted in higher levels of bcl-2. On the other hand, IFN-α decreased the numbers of cells with disrupted mitochondrial transmembrane potential both during spontaneous apoptosis and after exposure to protoporphyrin IX. Thus, IFN-α might promote the survival of clonal Th2 cells, an effect that could be relevant to the therapeutic approach for patients with chronic hypereosinophilia caused by clonal expansion of Th2-type cells.

Interferon α prevents spontaneous apoptosis of clonal Th2 cells associated with chronic hypereosinophilia

A recent study identified a clonal expansion of CD3−CD4+cells secreting Th2-type cytokines in 4 patients with chronic hypereosinophilia. Because interferon α (IFN-α) is used in the therapy of the idiopathic hypereosinophilic syndrome, the effects of this cytokine on the survival of clonal Th2 cells isolated from the blood of 2 patients were determined. First, these cells displayed a high rate of spontaneous apoptosis on culture in cytokine-free medium and were also sensitive to Fas-mediated apoptosis induced by soluble Fas ligand. Addition of IFN-α or interleukin-2 (IL-2) to culture medium resulted in significant protection against spontaneous but not Fas-induced apoptosis. Although spontaneous apoptosis of the clonal Th2 cells was clearly associated with down-regulation of both bcl-2 and bcl-xL levels, IFN-α had no significant effect on the expression of these antiapoptotic proteins, whereas addition of IL-2 resulted in higher levels of bcl-2. On the other hand, IFN-α decreased the numbers of cells with disrupted mitochondrial transmembrane potential both during spontaneous apoptosis and after exposure to protoporphyrin IX. Thus, IFN-α might promote the survival of clonal Th2 cells, an effect that could be relevant to the therapeutic approach for patients with chronic hypereosinophilia caused by clonal expansion of Th2-type cells.

Differential Loss of T Cell Signaling Molecules in Metastatic Melanoma Patients’ T Lymphocyte Subsets Expressing Distinct TCR Variable Regions

In this study we tested the hypothesis that loss of T cell signaling molecules in metastatic melanoma patients’ T cells may affect differently T cell subsets characterized by distinct TCR variable regions. By a two-color immunofluorescence technique, expression of ζ-chain, lck, and ZAP-70 was evaluated in CD3+ T cells and in three representative T cell subsets expressing TCRAV2, TCRBV2, or TCRBV18. Partial loss of lck and ZAP-70 was found in CD3+ T cells from PBL of most melanoma patients, but not of healthy donors. The extent of ζ-chain, lck, and ZAP-70 loss depended on the TCRV region expressed by the T cells, and this association was maintained or increased during progression of disease. Coculture of patients’ or donors’ T cell with melanoma cells, or with their supernatants, but not with normal fibroblasts or their supernatants, down-modulated expression of ζ-chain, lck, and ZAP-70 in a TCRV region-dependent way. Immunodepletion of soluble HLA class I molecules present in tumor supernatants, but not of soluble ICAM-1, blocked the suppressive effect on T cell signaling molecule expression. T cell activation with mAbs to a single TCRV region and to CD28 led to significant and TCRV region-specific re-induction of ζ-chain expression. These findings indicate that extent of TCR signaling molecules loss in T lymphocytes from metastatic melanoma patients depends on the TCRV region and suggest that tumor-derived HLA class I molecules may contribute to induce such alterations.

T-Cell Receptor-Independent Activation of Clonal Th2 Cells Associated With Chronic Hypereosinophilia

We recently observed a clonal expansion of CD3−CD4+ T cells secreting Th2-type cytokines in patients presenting chronic hypereosinophilia. As clonal T cells isolated from such patients did not spontaneously secrete cytokines in vitro, we reasoned that costimulatory signals delivered by antigen-presenting cells might be required to induce their full activation. To address this question, we investigated in two such patients the responses of CD3−CD4+ T cells to dendritic cells (DC). DC elicited proliferation and production of interleukin-5 (IL-5) and IL-13 by clonal cells from patient 1 and upregulated their expression of CD25 (IL-2R-). These effects were abolished when blocking monoclonal antibodies (MoAbs) against IL-2R- and IL-2 were added to cocultures, indicating critical involvement of an autocrine IL-2/IL-2R pathway. Cells from patient 2 were stimulated by DC to produce Th2 cytokines only when rIL-2 or rIL-15 was added to cocultures. In both patients, addition of inhibitory MoAbs against B7-1/B7-2 or CD2 to cocultures resulted in dramatic reduction of cytokine production and inhibited CD25 upregulation. Thus, TCR/CD3-independent activation of clonal Th2 cells by DC is an IL-2–dependent process, which requires signaling through CD2 and CD28.

Human decidualized endometrial T lymphocytes do not substantially down-regulate CD3zeta

PROBLEM

The T-cell antigen receptor (TCR) has been reported to be down-regulated on T-cells in the decidualized endometrium in early pregnancy.

METHOD OF STUDY

The expression of CD3zeta, a component of the TCR complex, has been investigated in human first-trimester decidual T-cells using flow cytometric analysis of permeabilized cells.

RESULTS

Levels of CD3zeta expression were significantly lower in decidual than in peripheral T-cells from non-pregnant women, as assessed by mean fluorescence intensity (4.2 vs. 5.5, logarithmic scale, P < 0.05). However, when decidual and peripheral T-cells from the same subjects were analyzed (n = 10), mean levels of CD3zeta were slightly, but not significantly, lower in decidual than in peripheral T-cells (P > 0.1). CD3zeta was not substantially down-regulated systemically as mean cytoplasmic CD3zeta levels did not differ significantly between peripheral blood T-cells from pregnant women and non-pregnant controls (P > 0.2). CD8+ cells outnumber CD4+ cells in decidua, but neither the proportions of these two T-cell subsets positive for cytoplasmic CD3zeta nor the mean levels of CD3zeta were significantly different.

CONCLUSIONS

These results indicate that human decidual T-cells do not greatly down-regulate CD3zeta, but it is unclear if a small decrease in mean levels may be sufficient to compromise their capacity for activation.

Expression of signal transducing T-cell receptor zeta molecules after adoptive immunotherapy in patients with gastric and colon cancer

We and others have shown decreased expression of T-cell receptor-CD3-associated signal transducing zeta molecules (TCRzeta) in tumor infiltrating and peripheral T cells of patients with advanced cancer. In the present study, we performed adoptive immunotherapy (AIT) with tumor-associated lymphocytes (TAL) in patients with gastric (n = 11) and colon (n = 3) cancer with stage IV and investigated whether the alteration of signal transducing molecules was observed with AIT, compared to an untreated control group (n = 13). Autologous TALs isolated from malignant ascites or pleural effusion were cultured with stimulation of autologous tumor in the presence of interleukin-2 (IL-2) and were transferred to the patients. TCR zeta expression in peripheral T cells was measured by flow cytometric analysis of permeabilized cells with anti-zeta monoclonal antibody (MAb) (TIA-2) before and after AIT. We confirmed the down-regulation of TCR zeta expression in peripheral blood lymphocytes (PBL) of patients with gastric and colon cancer with stage IV compared to healthy donors (n = 15). AIT induced up-regulation of TCR zeta expression in 2 of 14 treated patients, caused no significant change of TCR zeta expression in 7 patients and induced further down-regulation in 5 patients. The patients who achieved clinical responses (n = 3) with AIT showed no significant change of TCR zeta expression. On the other hand, in the control group without adoptive transfer, further down-regulation of TCR zeta expression was observed during the corresponding periods, paralleling disease progression. Taken together, TCR zeta expression in the patients was further down-regulated, corresponding to disease progression in individual cancer patients. In some patients, AIT could induce increased or stable TCR zeta expression. The quantitative analysis of TCR zeta expression might provide vital information that can be used to optimize therapy by preserving immune functions within cancer patients.

Variable expression of CD3-zeta and associated protein tyrosine kinases in lymphocytes from patients with myeloid malignancies

In myeloid malignancies, T-cell and NK function has been shown to deteriorate with transformation from pre-leukaemia to advanced disease. Immune dysfunction in solid tumours has been attributed to abnormal signal transduction, possibly through altered expression of intracellular components of the TCR/CD3 complex (e.g. CD3-zeta), receptors on NK cells and their associated protein tyrosine kinases (PTKs; p56lck, p59fyn and ZAP-70). Using a flow cytometric method to detect dual-expression of surface proteins and intracellular components of the TCR/CD3 complex, we have studied 46 patients with myeloid malignancies. CD3-zeta expression was abnormal in 64% of patients, and was more prominent in those with advanced disease. Three patients with reduced CD3-zeta were analysed both pre- and post-treatment, and recovery of CD3-zeta expression was associated with successful remission induction (expression of PTKs was variable and reduced levels were seen all disease stages). The results of this study suggest that loss of signalling proteins is not a result of direct contact of leukaemic cells with lymphocytes per se or the extent of the leukaemia burden, but to a specific property of some myeloid malignancies, which is more frequently acquired with greater malignant transformation.

Antigen presentation by B7-nonprofessional APC does not prevent responses to solid tumor cells

The growth of tumors in vivo often is associated with immune suppression. In this report we tested whether the expression of a known antigen by tumor cells would inhibit the development of antitumor responses when the antigen was subsequently expressed in an immunogenic form. For this, we expressed a well-characterized surrogate tumor antigen, the nucleoprotein (NP) of the PR8 virus, in solid tumor cells. Although the NP+ tumor cells were not rejected in vivo and stimulated nondetectable CTL response in vitro, T cells from these mice differentiated into CTL following i.p. inoculation of PR8 virus and their tumors regressed. The results suggested that prior presentation of tumor antigens by tumor cells does not necessary preclude a response if the peptide is subsequently presented appropriately.

Identification of an enriched CD4+ CD8alpha++ CD8beta+ T-cell subset among tumor-infiltrating lymphocytes in human renal cell carcinoma

Three-color immunofluorescence flow-cytometric analysis of freshly isolated tumor-infiltrating lymphocytes (TIL) from patients with primary renal cell carcinoma (RCC) revealed a unique, not previously described TIL subset with a CD3+ CD4+ CD8alpha++ CD8beta+ phenotype. This subset represented at least 5% of CD3+ TIL in 15 of 21 patients with clear cell RCC, whereas it was not or only marginally represented in patients with papillary RCC or sarcomatoid RCC. In one-third of the patients with clear cell RCC, more than 20% of CD3+ TIL and in one patient more than half of the CD3+ TIL displayed this phenotype. The occurrence of this subset was not associated with pathological stage, tumor diameter, nuclear grade, cytogenetic abnormalities or vascular invasion in this patient cohort. When present, the CD3+ CD4+ CD8alpha++ CD8beta+ subset was detected in similar proportions in tumor tissue and tumor capsula, and it was also detected in adjacent non-tumoral renal tissue, albeit in much lower proportions. Despite strong cell surface expression of various activation markers (CD69, CD54 and HLA-DR), CD3+ CD4+ CD8alpha++ CD8beta+ cells displayed no ex vivo cytolytic activity in an anti-CD3-redirected cytotoxicity assay. In contrast with CD3+ CD4+ CD8- cells from the same tumor sample, they were markedly deficient in IL-2R alpha up-regulation following anti-CD3 triggering. The possibility that these cells represent either anergic cells or a highly specialized effector population with a discrete, as yet undescribed function is discussed.

CD3 delta deficiency arrests development of the alpha beta but not the gamma delta T cell lineage

The CD3 complex found associated with the T cell receptor (TCR) is essential for signal transduction following TCR engagement. During T cell development, TCR-mediated signalling promotes the transition from one developmental stage to the next and controls whether a thymocyte undergoes positive or negative selection. The roles of particular CD3 components in these events remain unclear. Indeed, it is unknown whether they have specialized or overlapping roles. However, the multiplicity of CD3 components and their evolutionary conservation suggest that they serve distinct functions. Here the developmental requirement for the CD3 delta chain is analyzed by generating a mouse line specifically lacking this component (delta-/- mice). Strikingly, CD3 delta is shown to be differentially required during development. In particular, CD3 delta is not needed for steps in development mediated by pre-TCR or gamma delta TCR, but is required for further development of thymocytes expressing alpha beta TCR. Absence of CD3 delta specifically blocks the thymic selection processes that mediate the transition from the double-positive to single-positive stages of development.

The in vitro effect of Pidotimod on some immune functions in cancer patients

There are several reports concerning an impairment of cellular immune response in patients affected by malignant disease. The aim of this study was to evaluate the in vitro effect of Pidotimod, a synthetic biological response modifier, on some immune functions in 14 cancer patients. In particular, we showed that these subjects had a significantly reduced peripheral blood mononuclear cell (PBMC) proliferation both in response to PHA and to Con A in comparison with a group of healthy subjects. Besides, they showed a significantly reduced PBMC IL2 production, which was evaluated both through an ELISA method and a biological assay. The in vitro addition of increasing concentrations of Pidotimod (10, 25 and 50 ug/ml) was able to enhance PBMC proliferation and IL2 production significantly. However, in spite of the addition of Pidotimod, both immune functions in our neoplastic patients did not reach normal values.

Expression of cytokine genes or proteins and signaling molecules in lymphocytes associated with human ovarian carcinoma

We have reported that tumor-associated T or natural killer (NK) lymphocytes purified from ascites of women with ovarian carcinoma show defective expression and function of signaling proteins, including reduced expression of TcR-zeta chains and p56(lck). In this study, the cytokine profiles of both tumor cells and tumor-associated lymphocytes (TAL) recovered from the tumor milieu were examined. Expression of cytokine genes was studied by semi-quantitative RT-PCR and Southern hybridization, and the presence of intracellular cytokine proteins was confirmed by immunostaining. Levels of mRNA encoding the cytokine genes typically transcribed in activated T lymphocytes, including IFN-gamma, IL-2 and IL-4, were markedly reduced, as was expression of the corresponding proteins, in TAL-T or TAL-NK cells relative to normal PBL-T or PBL-NK cells, respectively. Levels of TGF-beta and IL-6 were unaltered, while those of IL-10 were up-regulated. Although both tumor cells and TALs contributed to the enhanced level of IL-10 expression, a higher proportion of TAL-T lymphocytes than normal PBL-T cells expressed IL-10 protein. The altered profile of cytokine genes and proteins in TALs, TAL-T or TAL-NK cells was associated with impaired expression and/or function of signaling molecules, zeta chain and p56(lck). Our data suggest that abnormalities in signal transduction commonly seen in lymphocytes obtained from the tumor micro-environment are related to the concomitantly observed altered patterns of expression of cytokine transcripts and proteins.

Altered CD3 chain and cytokine gene expression in tumor infiltrating T lymphocytes during the development of mesothelioma

The mechanisms whereby tumors escape immunosurveillance remain poorly understood. De-activation or deviation of T lymphocyte responses may occur following exposure to tumor-associated or -derived signals. In the present study it is demonstrated that during development of syngeneic malignant mesothelioma in mice, the relative CD3 delta, CD3 gamma and CD3 zeta mRNA levels expressed by tumor infiltrating lymphocytes (TIL) decrease, while CD3 epsilon mRNA levels remain relatively constant. Expression of IFN gamma mRNA by TIL decreased during tumor development, while IL-2 mRNA levels showed slight increases. IL-3 mRNA was not detected at any time during tumor development and IL-4 transcripts were detected in the later stages of tumor development. In the spleens of tumor-bearing mice, IL-2 transcripts were detected throughout the time course from days 1 to 22(24), while IFN gamma mRNA was only detected at early times from days 0-13. Previous work demonstrated a role for tumor cell-derived TGF beta in the immunobiology of mesothelioma. Here it is shown that the suppression of CD3-subunit expression by TIL was ameliorated in tumors where TGF beta -expression was reduced by inducible TGF beta-specific antisense-RNA, thus, suggesting that lymphocytes may become de-activated upon infiltration of the tumor micro-environment.

IL-2 gene therapy of solid tumors: an approach for the prevention of signal transduction defects in T cells

The identification of tumor-associated antigens has focused attention on the mechanisms that underlie the failure of T cells to destroy tumor cells. A deeper understanding of the process of signal transduction following the binding of ligand by the T cell receptor can help to identify underlying defects that may be involved. Gene therapy using tumor cells genetically modified to express cytokines or surface determinants is a promising technique for stimulating antitumor responses. A potential pitfall in its application to cancer, however, is that some patients' T cells are immune suppressed and may resist stimulation by such genetically engineered vaccines. Recent studies have demonstrated that T cells from tumor-bearing patients exhibit abnormalities in signal transduction events, possibly rendering them unable to respond to activation signals. Gene therapy with interleukin 2 secreting tumor cells in an animal model has been shown effective in preventing the onset of signaling defects. A more precise definition of the molecular mechanisms that enable cytokine-secreting tumor cells to stimulate specific antitumor responses may make it feasible to optimize immunotherapeutic approaches resulting in better clinical results.

The impact of gene therapy on T cell function in cancer

Studies of signal transduction by T cells are slowly identifying the intracellular messengers that must be generated for full T cell activation to take place. The recent, convincing identification of several tumor-associated antigens (TAA) has transformed our task into trying to define the mechanisms that underlie the failure of T cells to destroy antigenic tumor cells. Although there are a variety of hypotheses that explain why tumors grow progressively, even if they are antigenic, recent evidence suggests that T cells from tumor-bearing patients exhibit abnormalities in signal transduction that render them unable to respond to appropriate activation signals, even following proper stimulation. Gene therapy with interleukin-2 (IL-2)-secreting tumor cells in an animal model has been effective in preventing the onset of these signaling defects. Discovery of the molecular mechanisms by which such cytokine-secreting tumor cells induce immune responses and how they may best be applied clinically may provide clearer indications of the directions to pursue to alter the balance between the T cell and the tumor cell in the patient's favor.