The role of Fas/FasL in immunosuppression induced by human tumors

Prognostic value of pretreatment lymphocyte percentage in oral cancer: A prospective cohort study

OBJECTIVE

To assess the prognostic role of pretreatment lymphocyte percentage (LY%) for patients with oral squamous cell carcinoma (OSCC).

METHODS

A large-scale prospective cohort study between July 2002 and March 2021 was conducted. Propensity score-matched (PSM) analysis and inverse probability of treatment weighting (IPTW) analysis were performed to adjust for potential confounders. Using random survival forest (RSF), the relative importance of pretreatment LY% in prognosis prediction was also assessed.

RESULTS

A total of 743 patients were enrolled and followed up (median: 2.75 years, interquartile range: 1.25-4.42 years). A high pretreatment LY% was significantly associated with better disease-specific survival of patients with OSCC (Hazard ratio [HR] = 0.60, 95% confidence interval [CI]: 0.42, 0.84). The same tendency was observed in PSM (HR = 0.57, 95% CI: 0.38, 0.85) and IPTW analysis (HR = 0.57, 95% CI: 0.40, 0.82). RSF showed that LY% ranked the fifth among importance ranking of all prognostic factors.

CONCLUSION

Pretreatment LY% showed a moderate predictive ability, suggesting it might be a valuable tool to predict prognosis for patients with OSCC.

Exosomes in Cancer Progression and Therapy Resistance: Molecular Insights and Therapeutic Opportunities

The development of therapy resistance still represents a major hurdle in treating cancers, leading to impaired treatment success and increased patient morbidity. The establishment of minimally invasive liquid biopsies is a promising approach to improving the early diagnosis, as well as therapy monitoring, of solid tumors. Because of their manifold functions in the tumor microenvironment, tumor-associated small extracellular vesicles, referred to as exosomes, have become a subject of intense research. Besides their important roles in cancer progression, metastasis, and the immune response, it has been proposed that exosomes also contribute to the acquisition and transfer of therapy resistance, mainly by delivering functional proteins and RNAs, as well as facilitating the export of active drugs or functioning as extracellular decoys. Extensive research has focused on understanding the molecular mechanisms underlying the occurrence of resistance and translating these into strategies for early detection. With this review, we want to provide an overview of the current knowledge about the (patho-)biology of exosomes, as well as state-of-the-art methods of isolation and analysis. Furthermore, we highlight the role of exosomes in tumorigenesis and cancer treatment, where they can function as therapeutic agents, biomarkers, and/or targets. By focusing on their roles in therapy resistance, we will reveal new paths of exploiting exosomes for cancer diagnosis and treatment.

Evaluation of Immunoregulatory Biomarkers on Plasma Small Extracellular Vesicles for Disease Progression and Early Therapeutic Response in Head and Neck Cancer

Head and Neck Cancers (HNCs) have highly immunosuppressive properties. Small extracellular vesicles (sEVs), including exosomes, nanosized mediators of intercellular communication in the blood, carry immunosuppressive proteins and effectively inhibit anti-tumor immune responses in HNCs. This study evaluates immunosuppressive markers on sEVs from 40 HNC patients at different disease stages and 3- and 6-month follow-up after surgery and/or chemoradiotherapy. As controls, sEVs from normal donors (NDs) are examined. Immunoregulatory surface markers on sEVs were detected as relative fluorescence intensity (RFI) using on-bead flow cytometry, and their expression levels were monitored in the early and late stages of HNC and during follow-up. In parallel, the sEV-mediated apoptosis of CD8⁺ Jurkat cells was assessed. Together with TGF-β1 and PD-L1 abundance, total sEV proteins are elevated with disease progression. In contrast, total sEV protein, including TGF-β1, PD-1 and PD-L1, decrease upon therapy response during follow-up. Overall survival analysis implies that high sEV PD-1/PD-L1 content is an unfavorable prognostic marker in HNC. Consistently, the sEV-mediated induction of apoptosis in CD8⁺ T cells correlates with the disease activity and therapy response. These findings indicate that a combination of immunoregulatory marker profiles should be preferred over a single marker to monitor disease progression and therapy response in HNC.

Immunotherapy using regulatory T cells in cancer suggests more flavors of hypersensitivity type IV

Regulatory T cells (Tregs) profoundly affect tumor microenvironment and exert dominant suppression over antitumor immunity in response to self-antigen expressed by tumor. Immunotherapy targeting Tregs lead to a significant improvement in antitumor immunity. Intradermal injection of tumor antigen results in negative delayed-type hypersensitivity (DTH) type IV. However, anti-Tregs treatment/use of adjuvant along with tumor antigens turns DTH to positive. Considering Tregs as the earliest tumor sensor/responders, tumor can be regarded as Treg-mediated type IV hypersensitivity and negative DTH to tumor antigen is due to anti-inflammatory action of Tregs to tumor antigens at the injection site. Such a view would help us in basic and clinical situations to testify a candidate vaccine via dermal administration and evaluation of Treg proportion at injection site.

GBM Derived Gangliosides Induce T Cell Apoptosis through Activation of the Caspase Cascade Involving Both the Extrinsic and the Intrinsic Pathway

Previously we demonstrated that human glioblastoma cell lines induce apoptosis in peripheral blood T cells through partial involvement of secreted gangliosides. Here we show that GBM-derived gangliosides induce apoptosis through involvement of the TNF receptor and activation of the caspase cascade. Culturing T lymphocytes with GBM cell line derived gangliosides (10-20μg/ml) demonstrated increased ROS production as early as 18 hrs as indicated by increased uptake of the dye H₂DCFDA while western blotting demonstrated mitochondrial damage as evident by cleavage of Bid to t-Bid and by the release of cytochrome-c into the cytosol. Within 48-72 hrs apoptosis was evident by nuclear blebbing, trypan blue positivity and annexinV/7AAD staining. GBM-ganglioside induced activation of the effector caspase-3 along with both initiator caspases (-9 and -8) in T cells while both the caspase-8 and -9 inhibitors were equally effective in blocking apoptosis (60% protection) confirming the role of caspases in the apoptotic process. Ganglioside-induced T cell apoptosis did not involve production of TNF-α since anti-human TNFα antibody was unable to protect T cells from nuclear blebbing and subsequent cell death. However, confocal microscopy demonstrated co-localization of GM2 ganglioside with the TNF receptor and co-immunoprecipitation experiments showed recruitment of death domains FADD and TRADD with the TNF receptor post ganglioside treatment, suggesting direct interaction of gangliosides with the TNF receptor. Further confirmation of the interaction between GM2 and TNFR1 was obtained from confocal microscopy data with wild type and TNFR1 KO (TALEN mediated) Jurkat cells, which clearly demonstrated co-localization of GM2 and TNFR1 in the wild type cells but not in the TNFR1 KO clones. Thus, GBM-ganglioside can mediate T cell apoptosis by interacting with the TNF receptor followed by activation of both the extrinsic and the intrinsic pathway of caspases.

Dendritic cell vaccination and immunostimulation in advanced melanoma

The most recent advances in immunology bear witness to the fact that tumors, in particular melanoma, escape recognition by the host's immune system and can locally inactivate its effectors, T-cells and antigen presenting cells. There is, however, preclinical evidence that the immune system, opportunely stimulated, is capable of recognizing and killing tumor cells. It has been verified that the activation of autologous dendritic cells, derived from peripheral blood and pulsed with tumor antigens, results in the specific stimulation of T-cells against the tumor. Preliminary data from dendritic cell vaccination trials, mainly of advanced melanoma, show unequivocal evidence of immunization and of the first clinical responses. Many questions remain to be answered before more effective and widespread use of this type of vaccination is possible, especially in the early stages of the disease.

Aiming to immune elimination of ovarian cancer stem cells

Ovarian cancer accounts for only 3% of all cancers in women, but it causes more deaths than any other gynecologic cancer. Treatment with chemotherapy and cytoreductive surgery shows a good response to the therapy. However, in a large proportion of the patients the tumor grows back within a few years. Cancer stem cells, that are less responsive to these treatments, are blamed for this recurrence of disease. Immune therapy either cellular or humoral is a novel concept to treat cancer. It is based on the notice that immune cells invade the tumor. However, the tumor invest heavily to escape from immune elimination by recruiting several immune suppressive mechanisms. These processes are normally in place to limit excessive immune activation and prevent autoimmune phenomena. Here, we discuss current knowledge about the immune (suppressive) status in ovarian cancer. Moreover, we discuss the immunological targets of ovarian cancer stem cells.

Metabolism of L-arginine by myeloid-derived suppressor cells in cancer: mechanisms of T cell suppression and therapeutic perspectives

Patients with cancer have an impaired T cell response that can decrease the potential therapeutic benefit of cancer vaccines and other forms of immunotherapy. The establishment of a chronic inflammatory environment in patients with cancer plays a critical role in the induction of T cell dysfunction. The accumulation of myeloid-derived suppressor cells (MDSC) in tumor bearing hosts is a hallmark of malignancy-associated inflammation and a major mediator of the induction of T cell suppression in cancer. Recent findings in tumor bearing mice and cancer patients indicate that the increased metabolism of L-Arginine (L-Arg) by MDSC producing Arginase I inhibits T cell lymphocyte responses. Here, we discuss some of the most recent concepts of how MDSC expressing Arginase I may regulate T cell function in cancer and suggest possible therapeutic interventions to overcome this inhibitory effect.

Immunogene therapy

Antigenic differences between normal and malignant cells of the cancer patient form the rationale for clinical immunotherapeutic strategies. Because the antigenic phenotype of neoplastic cells varies widely among different cells within the same malignant cell-population, immunization with a vaccine that stimulates immunity to the broad array of tumor antigens expressed by the cancer cells is likely to be more efficacious than immunization with a vaccine for a single antigen. A vaccine prepared by transfer of DNA from the tumor into a highly immunogenic cell line can encompass the array of tumor antigens that characterize the patient's neoplasm. Poorly immunogenic tumor antigens, characteristic of malignant cells, can become strongly antigenic if they are expressed by highly immunogenic cells. A DNA-based vaccine was prepared by transfer of genomic DNA from a breast cancer that arose spontaneously in a C3H/He mouse into a highly immunogenic mouse fibroblast cell line, where genes specifying tumor-antigens were expressed. The fibroblasts were modified in advance of DNA-transfer to secrete an immune augmenting cytokine and to express allogeneic MHC Class I-determinants. In an animal model of breast cancer metastatic to the brain, introduction of the vaccine directly into the tumor bed stimulated a systemic cellular antitumor immune response measured by two independent in vitro assays and prolonged the lives of the tumor-bearing mice. Furthermore, using antibodies against the various T-cell subsets, it was determined that the systemic cellular antitumor immunity was mediated by CD8+, CD4+ and NK/LAK cells. In addition an enrichment strategy has also been developed to increase the proportion of immunotherapeutic cells in the vaccine which has resulted in the development of enhanced antitumor immunity. Finally regulatory T cells (CD4+CD25+Fox p3+-positive) were found to be relatively deficient in the spleen cells from the tumor-bearing mice injected intracerebrally with the enriched vaccine. The application of DNA-based genomic vaccines for the treatment of a variety of brain tumors is being explored.

Acupuncture May Stimulate Anticancer Immunity via Activation of Natural Killer Cells

This article presents the hypothesis that acupuncture enhances anticancer immune functions by stimulating natural killer (NK) cells. It provides background information on acupuncture, summarizes the current scientific understanding of the mechanisms through which NK cells act to eliminate cancer cells, and reviews evidence that acupuncture is associated with increases in NK cell quantity and function in both animals and humans. The key contribution of this article involves the use of cellular immunology and molecular biological theory to interpret and synthesize evidence from disparate animal and human studies in formulating the 'acupuncture immuno-enhancement hypothesis': clinicians may use acupuncture to promote the induction and secretion of NK-cell activating cytokines that engage specific NK cell receptors that endogenously enhance anticancer immune function.

Tumor immunosuppressive environment: effects on tumor-specific and nontumor antigen immune responses

The interactions between cancer cells and host immune cells in tumoral microenvironments create an immunosuppressive network that promotes tumor growth, protects the tumor from immune attack and attenuates the efficacy of immunotherapeutic approaches. The development of immune tolerance becomes predominant in the immune system of patients with advanced-stage tumors. Several mechanisms have been described by which tumors can suppress the immune system, including secretion of cytokines, alterations in antigen-presenting cell subsets, costimulatory and coinhibitory molecule alterations and altered ratios of Tregs to effector T cells. It is well demonstrated that these mechanisms of immunosuppression can impair tumor specific immune responses. However, it is not well established whether this immunosuppressive environment can affect immune responses to nontumor antigens, specifically in regard to priming and the development of memory. The few existing studies indicate that responses to nontumor antigens seem unaffected, although there is still a deep lack of understanding of this phenomenon. This is an important issue regarding patient endurance and quality of life. Here, we review the existing evidence on immunosuppression promoted by tumors, with particular attention to its impact on specific immune responses. Understanding these interactions can help us subvert tumor-induced tolerance and optimize anti-tumor therapy.

Elevated levels of select gangliosides in T cells from renal cell carcinoma patients is associated with T cell dysfunction

Increased expression of gangliosides by different tumor types including renal cell carcinoma (RCC) is thought to contribute to the immune suppression observed in cancer patients. In this study, we report an increase in apoptotic T cells from RCC patients compared with T cells from normal donors that coincided with the detection of T cells staining positive for GM2 and that the apoptosis was predominantly observed in the GM2(+) but not the GM2(-) T cell population. Ganglioside shedding from tumor rather than endogenous production accounts for GM2(+) T cells since there was no detectable level of mRNA for GM2 synthase in RCC patient T cells and in T cells from normal healthy donors after incubation with either purified GM2 or supernatant from RCC cell lines despite their staining positive for GM2. Moreover, reactive oxygen species as well as activated caspase 3, 8, and 9 were predominantly elevated in GM2(+) but not GM2(-) T cells. Similarly, increased staining for GD2 and GD3 but not GD1a was detected with patient T cells with elevated levels of apoptosis in the GD2(+) and GD3(+) cells. These findings suggest that GM2, GD2, and GD3 play a significant role in immune dysfunction observed in RCC patient T cells.

Signaling defects in anti-tumor T cells

The immune response to cancer has been long recognized, including both innate and adaptive responses, showing that the immune system can recognize protein products of genetic and epigenetic changes in transformed cells. The accumulation of antigen-specific T cells within the tumor, the draining lymph node, and the circulation, either in newly diagnosed patients or resultant from experimental immunotherapy, proves that tumors produce antigens and that priming occurs. Unfortunately, just as obviously, tumors grow, implying that anti-tumor immune responses are either not sufficiently vigorous to eliminate the cancer or that anti-tumor immunity is suppressed. Both possibilities are supported by current data. In experimental animal models of cancer and also in patients, systemic immunity is usually not dramatically suppressed, because tumor-bearing animals and patients develop T-cell-dependent immune responses to microbes and to either model antigens or experimental cancer vaccines. However, inhibition of specific anti-tumor immunity is common, and several possible explanations of tolerance to tumor antigens or tumor-induced immunesuppression have been proposed. Inhibition of effective anti-tumor immunity results from the tumor or the host response to tumor growth, inhibiting the activation, differentiation, or function of anti-tumor immune cells. As a consequence, anti-tumor T cells cannot respond productively to developmental, targeting, or activation cues. While able to enhance the number and phenotype of anti-tumor T cells, the modest success of immunotherapy has shown the necessity to attempt to reverse tolerance in anti-tumor T cells, and the vanguard of experimental therapy now focuses on vaccination in combination with blockade of immunosuppressive mechanisms. This review discusses several potential mechanisms by which anti-tumor T cells may be inhibited in function.

Arginine regulation by myeloid derived suppressor cells and tolerance in cancer: mechanisms and therapeutic perspectives

Patients with cancer have an impaired T-cell response that can decrease the potential therapeutic benefit of cancer vaccines and other forms of immunotherapy. L-arginine (L-Arg) is a conditionally essential amino acid that is fundamental for the function of T lymphocytes. Recent findings in tumor-bearing mice and cancer patients indicate that increased metabolism of L-Arg by myeloid derived suppressor cells (MDSCs) producing arginase I inhibits T-lymphocyte responses. Here we discuss some of the most recent concepts how MDSC expressing arginase I may regulate T-cell function in cancer and other chronic inflammatory diseases and suggest possible therapeutic interventions to overcome this inhibitory effect.

Human embryo immune escape mechanisms rediscovered by the tumor

Towards the end of the 1990s, the two opposing theories on immunosurveillance and immunostimulation were extensively studied by researchers in an attempt to understand the complex mechanisms that regulate the relation between tumors and the host's immune system. Both theories probably have elements that would help us to comprehend how the host can induce anti-tumor clinical responses through stimulation of the immune system and which could also give us a deeper insight into the mechanisms of tumor immunosuppression. The model that most resembles the behavior of tumor cells in terms of growth, infiltration and suppression of the immune system of the environment in which they live is undoubtedly that of the embryonic cell. The fetus behaves like an allogenic transplant within the mother's body, using every means it has to escape from and defend itself against the mother's immune system. The majority of these mechanisms are the same as those found in tumor cells: antigenic loss, lack of expression of classic HLA-I molecules, production of immunosuppressive cytokines, induction of lack of expression of co-stimulatory molecules in antigen presenting cells, and induction of apoptosis in infiltrating lymphocytes, with activation of a type Th2 regulatory lymphocyte response. A careful and comparative study of key mechanisms capable of triggering tolerance or cytotoxicity in both embryonic and tumor cells could prove immensely valuable in designing new strategies for anti-tumor immunotherapy.

Renal cell carcinoma tumors induce T cell apoptosis through receptor-dependent and receptor-independent pathways

Tumors can promote their own progressive growth by inducing T cell apoptosis. Though previous studies suggested that tumor-mediated T cell killing is receptor dependent, we recently showed that tumor gangliosides also participate, a notion consistent with reports indicating that, in some cell types, gangliosides can activate the intrinsic apoptotic pathway by stimulating reactive oxygen species production, cytochrome c release, and caspase-9 activation. In this study, we used normal peripheral blood T cells, as well as caspase-8-, caspase-9-, and Fas-associated death domain protein-deficient Jurkat cells, to assess whether the death ligands and gangliosides overexpressed by the renal cell carcinoma (RCC) cell line SK-RC-45 can independently stimulate T cell apoptosis as a mechanism of immune escape. Anti-FasL Abs and the glycosylceramide synthase inhibitor 1-phenyl-2-hexadecanoylamino-3-pyrrolidino-1-propanol (PPPP) each partially inhibited the ability of SK-RC-45 to kill cocultured activated T cells; together, as purified molecules, RCC gangliosides and rFasL induced a more extensive mitochondrial permeability transition and greater levels of apoptosis than either agent alone, equivalent to that induced by the FasL- and ganglioside-expressing RCC line itself. rFasL-mediated apoptosis was completely inhibited in caspase-8- and Fas-associated death domain protein-negative Jurkat cells, though apoptosis induced by purified gangliosides remained intact, findings that correlate with the observed partial inhibition of SK-RC-45-induced apoptosis in the Jurkat lines with defective death receptor signaling. Western blot analysis performed on lysates made from wild-type and mutant Jurkat cells cocultured with SK-RC-45 revealed caspase activation patterns and other biochemical correlates which additionally supported the concept that tumor-associated gangliosides and FasL independently activate the caspase cascade in T cells through the intrinsic and extrinsic pathways, respectively.

Phenotype and in vitro function of mature MDDC generated from cryopreserved PBMC of cancer patients are equivalent to those from healthy donors

Background

Monocyte-derived-dendritic-cells (MDDC) are the major DC type used in vaccine-based clinical studies for a variety of cancers. In order to assess whether in vitro differentiated MDDC from cryopreserved PBMC of cancer patients are functionally distinct from those of healthy donors, we compared these cells for their expression of co-stimulatory and functional markers. In addition, the effect of cryopreservation of PBMC precursors on the quality of MDDC was also evaluated using samples from healthy donors.

Methods

Using flow cytometry, we compared normal donors and cancer patients MDDC grown in the presence of GM-CSF+IL-4 (immature MDDC), and GM-CSF+IL-4+TNFα+IL-1β+IL-6+PGE-2 (mature MDDC) for (a) surface phenotype such as CD209, CD83 and CD86, (b) intracellular functional markers such as IL-12 and cyclooxygenase-2 (COX-2), (c) ability to secrete IL-8 and IL-12, and (d) ability to stimulate allogeneic and antigen-specific autologous T cells.

Results

Cryopreservation of precursors did affect MDDC marker expression, however, only two markers, CD86 and COX-2, were significantly affected. Mature MDDC from healthy donors and cancer patients up-regulated the expression of CD83, CD86, frequencies of IL-12⁺ and COX-2⁺ cells, and secretion of IL-8; and down-regulated CD209 expression relative to their immature counterparts. Compared to healthy donors, mature MDDC generated from cancer patients were equivalent in the expression of nearly all the markers studied and importantly, were equivalent in their ability to stimulate allogeneic and antigen-specific T cells in vitro.

Conclusion

Our data show that cryopreservation of DC precursors does not significantly affect the majority of the MDDC markers, although the trends are towards reduced expression of co-stimulatory makers and cytokines. In addition, monocytes from cryopreserved PBMC of cancer patients can be fully differentiated into mature DC with phenotype and function equivalent to those derived from healthy donors.

Role of nitric oxide in heat shock protein induced apoptosis of gammadeltaT cells

Activation induced cell death (AICD) has been proposed to serve as a mechanism to limit T lymphocyte proliferation induced by antigenic stimulation. Heat shock proteins (hsp60 and hsp70) expressed on oral tumor cells serve as ligands for peripheral blood gammadeltaT lymphocytes. Tumor cell lysis by gammadeltaT lymphocytes is mediated via recognition of hsp expressed on tumor cells. In the present study, we report that upon stimulation with hsp, gammadeltaT lymphocytes isolated from oral cancer patients undergo AICD as confirmed by DNA ploidy, annexin V staining and confocal microscopy. In cocultures of gammadeltaT lymphocytes and tumor cells, addition of antihsp60 and antihsp70 MAb, but not anti-Fas MAb (ZB4), inhibited DNA fragmentation of gammadeltaT lymphocytes. Flow cytometric analysis revealed a down regulation of Fas expression on gammadeltaT lymphocytes upon incubation with hsp60 and hsp70. Increased expression of iNOS was observed in hsp-stimulated gammadeltaT lymphocytes. Addition of monomethyl L-arginine monoacetate, competitive inhibitor of NOS, inhibited nitric oxide (NO) production and apoptosis of gammadeltaT lymphocytes induced by hsp60 and hsp70. The NO-induced apoptosis of gammadeltaT lymphocytes involves activation of caspase-9 and loss of mitochondrial membrane potential. The present study explains a novel strategy adopted by tumor cells to evade immune recognition by gammadeltaT lymphocytes.

GM2 expression in renal cell carcinoma: potential role in tumor-induced T-cell dysfunction

Multiple mechanisms have been proposed to account for immune escape by tumors. Although gangliosides have long been known to suppress T-cell immunity, few studies have examined the effect of human tumor-derived gangliosides on immune responses. Here, we show that gangliosides isolated from renal cell carcinoma (RCC) cell lines and clear cell tumor tissue can induce apoptosis in peripheral blood T cells. The RCC tissue-derived gangliosides also suppressed IFN-gamma and, in many cases, interleukin-4 production by CD4+ T cells at concentrations (1 ng/mL-100 pg/mL) well below those that induce any detectable T-cell death (4-20 microg/mL). Additional findings show that GM2 expressed by RCC plays a significant role in promoting T-cell dysfunction. This is supported by the demonstration that all RCC cell lines examined (n = 5) expressed GM2 as did the majority of tumors (15 of 18) derived from patients with clear cell RCC. Furthermore, an antibody specific for GM2 (DMF10.167.4) partially blocked (50-60%) T-cell apoptosis induced by coculturing lymphocytes with RCC cell lines or with RCC tissue-derived gangliosides. DMF10.167.4 also partially blocked the suppression of IFN-gamma production induced by RCC tissue-derived gangliosides, suggesting that GM2 plays a role in down-regulating cytokine production by CD4+ T cells.

The tumour microenvironment and implications for cancer immunotherapy

Tumour cells exist in a complex milieu of cellular and non-cellular components comprising fibroblasts, endothelial cells, immune cells and metabolites of cellular respiration. An elaborate interplay between these components and tumour cells exists with implications for immunological recognition of tumour cells. Tumours have been shown to alter their antigen and cytokine profiles, desensitise and impair immune defences, signal fibroblasts to facilitate metastasis, and take advantage of acidic and hypoxic conditions that impede normal cells. This paper aims to review the roles of the stroma, extracellular matrix and chemistry of the microenvironment on tumour growth, with particular emphasis on interactions with the immune system, and to highlight some of the novel therapeutic strategies that target the tumour microenvironment.

The role of immune cells in the tumor microenvironment

Interactions between tumor infiltrating leukocytes and tumor cells have been of great interest because of the possibility that immune cells either interfere with tumor progression or actively promote tumor growth. The tumor microenvironment is shaped by cells entering it, and their functions reflect the local conditions. Successive changes occurring at the tumor site during tumor progression resemble chronic inflammation. This chronic inflammatory reaction seems to be largely orchestrated by the tumor, and it seems to promote tumor survival. Molecular and cellular mechanisms linking the inflammatory reaction and cancer are emerging, and this review summarizes the current understanding of interactions between inflammatory and cancer cells in the tumor microenvironment.

Immune responses to p53 in patients with cancer: enrichment in tetramer+ p53 peptide-specific T cells and regulatory T cells at tumor sites

OBJECTIVE

A majority of human cancers, including head and neck cancer (HNC), "overexpress" p53. Although T cells specific for wild-type (wt) sequence p53 peptides are detectable in the peripheral blood of patients with HNC, it is unknown whether such T cells accumulate in tumor-involved tissues. Also, the localization of "regulatory" T cells (Treg) to tumor sites in HNC has not been investigated to date.

METHODS

Tumor infiltrating lymphocytes (TIL), tumor-involved or non-involved lymph node lymphocytes (LNL) and peripheral blood mononuclear cells (PBMC) were obtained from 24 HLA-A2.1+ patients with HNC. Using tetramers and four-color flow cytometry, the frequency of Treg and CD3+CD8+ T cells specific for wt p53 epitopes as well as their functional attributes were determined.

RESULTS

The CD3+CD8+ tetramer+ cell frequency was significantly higher (P<0.001) in TIL than autologous PBMC as was the percentage of CD4+CD25+ T cells (P<0.003). TIL were enriched in FOXp3+, GITR+ and CTLA-4+ Treg. CD8+ TIL had low Zeta expression and produced little IFN-gamma after ex vivo stimulation relative to autologous PBMC or PBMC from NC.

CONCLUSIONS

Anti-wt p53 epitope-specific T cells and Treg preferentially localize to tumor sites in patients with HNC. However, despite enrichment in tumor peptide-specific T cells, the effector cell population (CD3+CD8+) in TIL or PBMC was unresponsive to activation in the tumor microenvironment enriched in Treg.

Mechanisms of tumor evasion

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 antigen presenting cells 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 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 have the potential of improving the current results of immunotherapy trials.

Immunobiology of head and neck cancer

The development of head and neck cancer (HNC) is strongly influenced by the host immune system. Recent evidence for the presence of functional defects and for apoptosis of tumor-infiltrating as well as circulating T cells in patients with HNC emphasizes the fact that their antitumor responses are compromised. It appears that H&N tumors not only effectively escape from the host immune system but also actively corrupt the host antitumor response via several distinct mechanisms. Strategies for restoring immune competence of patients with HNC and for preventing tumor escape are necessary for more effective control of tumor progression. New immunotherapeutic approaches include cytokine-based and DC-based vaccines which are aimed at the restoration of tumor-specific responses and at the protection of immune cells from tumor-induced apoptosis.

Treatment of transplanted CT26 tumour with dendritic cell vaccine in combination with blockade of vascular endothelial growth factor receptor 2 and CTLA-4

We investigated the anti CT26 tumour effect of dendritic cell based vaccination with the MuLV gp70 envelope protein-derived peptides AH1 and p320-333. Vaccination lead to generation of AH1 specific cytotoxic lymphocytes (CTL) and some decrease in tumour growth of simultaneously inoculated CT26 cells. After combination with an antibody against VEGF receptor 2 (DC101), a significant increase in survival of the tumour cell recipients was observed. Also, monotherapy with an antibody against CTLA-4 (9H10), led to approximately 100% survival of tumour cell recipients. However, effective treatment of mice with already established tumours was only obtained after combination of vaccination, DC101 and 9H10 treatment in which setting 80% of the mice rejected their tumours.

Immunosuppressive mechanisms in the microenvironment of malignant pleural effusions

Malignant effusions in serous cavities constitute a unique milieu for direct contact of tumor cells with host lymphoid cells in a fluid phase. The aim of this study was to depict agents responsible for suppression of lymphoid cells with putative anti-tumor potential. Pleural effusions drawn from 44 (18 non-malignant and 26 malignant) patients were tested for selected cytokines--interleukin-10 (IL-10), transforming growth factor beta (TGF-beta1) and soluble Fas ligand (sFasL) and nuclear membrane proteins (NMPs) content by ELISA. TCR-zeta expression of T cells and TUNEL reaction for apoptosis were evaluated by three color flow cytometry. Both cytokine concentrations were found to be significantly elevated in malignant pleural effusions (MPE) as compared to non-malignant ones. It was also true for sFasL content. Moreover, NMPs corresponding to decoy cell fragments, were also heightened in MPE. Concentrations of NMPs correlated with the percent of apoptotic (TUNEL+) T CD3+ lymphocytes and inversely correlated with the percent of T cells. The low expression of TCR-zeta chain on T cells corresponded to high concentration of sFasL in MPE. In conclusion, the above data suggest that out of three suppression agents tested, only sFasL appears to show correlation with the downregulation of T cells in MPE.

Phenotypic and functional characterization of clinical grade dendritic cells generated from patients with advanced breast cancer for therapeutic vaccination

Dendritic cells (DC) are promising candidates for cancer immunotherapy. However, it is not known whether in vitro-generated monocyte-derived DC from cancer patients are altered compared with DC from healthy donors. In a clinical phase I/II study, monocyte-derived DC were generated in vitro utilizing granulocyte macrophage colony-stimulating factor and rh-interleukin-4 (IL-4) and used for cancer immunotherapy. In this study, we tested the effect of various maturation cocktails and performed a comparative evaluation of the DC phenotype and functional characteristics. Polyriboinosinic polyribocytidylic acid (Poly I:C) + tumour necrosis factor-alpha (TNF-alpha) induced significant IL-12 p70 secretion, which was increased after addition of a decoy IL-10 receptor. The lymph node homing chemokine receptor CCR-7 expression was induced by TNF-alpha + IL-1beta + IL-6 + prostaglandin E2 but was not induced by Poly I:C + TNF-alpha. In general, DC from patients had an intermediate maturity phenotype with a significantly higher expression of CD40 and CD54 compared with healthy donors. In vitro analyses showed an unimpaired capacity of the patient-derived DC for antigen-specific (cytomegalovirus, tetanus and keyhole limpet haemocyanin) T-cell stimulation, whereas the allostimulatory capacity of patient-derived DC was significantly decreased. These data suggest that patient-derived DC are more differentiated but are less sensitive to maturation-inducing agents than DC obtained from healthy individuals.

Plattenepithelkarzinome des Kopf-Hals-Bereichs

Biologic therapies able to induce or up-regulate anti-tumor immune responses could represent a complementary approach to improve the conventional treatment of squamous cell carcinomas of the head and neck (SCCHN). Patients with SCCHN are frequently immunocompromised due to the elimination and dysfunction of critical immune effector cells. Therefore, it might be necessary to restore these immune functions to allow for the generation of effective anti-tumor host responses. Simultaneously, to prevent tumor escape from immunological recognition and destruction, it might also be necessary to alter antigenic and immunogenic attributes of the malignant cells. The present overview summarizes general aspects, historical data, and recent advances in the field of immunotherapy of SCCHN, including non-specific immune stimulation, transfer of immunocompetent cells, gene therapy, use of monoclonal antibodies, and anti-cancer vaccines.

Targeting the immune system: novel therapeutic approaches in squamous cell carcinoma of the head and neck

Despite advances in surgery, radiotherapy, and chemotherapy, the overall survival rates for patients with squamous cell carcinoma of the head and neck (SCCHN) have not changed over the last decades. Clearly, novel therapeutic strategies are needed for this cancer, which is highly immunosuppressive. Therefore, biologic therapies able to induce and/or up-regulate antitumor immune responses could represent a complementary approach to conventional treatments. Because patients with SCCHN are frequently immunocompromised due to the elimination or dysfunction of critical effector cells of the immune system, it might be necessary to restore these immune functions to allow for the generation of more effective antitumor host responses. Simultaneously, to prevent tumor escape, it might be necessary to alter attributes of the malignant cells. The present review summarizes recent advances in the field of immunotherapy of SCCHN, including techniques of nonspecific immune stimulation, the use of monoclonal antibodies, advances in adoptive immunotherapy and genetic engineering, as well as anticancer vaccines. These biologic therapies, alone or in combination with conventional treatment, are likely to develop into useful future treatment options for patients with SCCHN.

Immunosuppression in Renal Cancer: Differential Expression of Signal Transduction Molecules in Tumor-Infiltrating, Near-Tumor Tissue, and Peripheral Blood Lymphocytes

Alterations in the expression of signal activation molecules, such as the T-cell receptor (TCR) zeta and epsilon chains and p56lck tyrosine kinase, are described in tumor-infiltrating lymphocytes (TIL). The aim of this study was to ascertain if such molecules were present in near-tumor-tissue lymphocytes (NTTL) and peripheral blood lymphocytes (PBL), as well as TIL, of renal cell carcinoma patients, to verify whether this tumor induces immunosuppression only locally or affects distant lymphocytes as well. Tissue from the tumor and from healthy nearby sites, as well as blood samples, were obtained from 27 consecutive patients who had undergone radical nephrectomy for renal cell carcinoma. Phenotype analysis and immunohistochemical staining of the TCR zeta and epsilon chains and p56lck were performed with standard techniques on TIL, NTTL, and PBL, and values were compared for each patient. Low expression of the TCR zeta chain and an almost complete absence of TCR epsilon chain and p56lck expression was observed in TIL (median values: 10% for zeta chain and 0% for epsilon and p56lck). In NTTL, these signal transduction molecules were expressed by a higher percentage of cells (60%, 50%, and 60%, respectively; p=0.000 vs. TIL), whereas PBL showed an almost normal expression of zeta and epsilon chains (80% and 90%, respectively; p=0.000 vs. TIL). Conversely, p56lck was detected in a greater proportion of NTTL than PBL (50% vs. 10%; p=0.001). The absence or the very low expression of signaling activation molecules in TIL compared with NTTL and PBL in renal cancer patients suggest that tumor-induced immunosuppression generally occurs or starts locally.

Down-regulation of zeta-chain expression in T cells: a biomarker of prognosis in cancer?

The zeta chain is a 16-kDa molecule associated with the T-cell receptor (TCR)-CD3 complex in T lymphocytes and FcgammaRIII in CD3(-)CD56(+)CD16(+) natural killer (NK cells). The zeta chain functions as a transmembrane signaling molecule in lymphocytes. Expression of zeta was found to be decreased in CD4(+) and CD8(+) T lymphocytes isolated from the tumor site or from the peripheral circulation of patients with cancer. A quantitative flow cytometry-based assay for zeta-chain expression allows for reproducible serial evaluations of disease- or therapy-associated changes in expression of this signaling molecule in phenotypically defined subsets of immune cells. Semiquantitative evaluation of zeta expression in paraffin-embedded tissue specimens can link it to the conventional markers of prognosis or survival. Several distinct mechanisms may be responsible for decreased/absent zeta in T cells of patients with cancer. Monitoring for zeta expression is useful for assessing immune competence in these patients and for following changes in immune competence during anticancer therapies. Correlations made between clinical findings, pathologic results, and zeta expression in immune cells suggest that low/absent zeta is predictive of poor prognosis and survival in patients with cancer. Thus, zeta is emerging as a clinically relevant signaling molecule, which also seems to predict a favorable response to biologic therapies and could be helpful in a selection of patients for immunotherapy trials. Validation studies have yet to be performed for this putative immunologic biomarker. Its consistent use for monitoring under standardized conditions of cancer patients treated with biotherapies may help in confirming a role for zeta as a correlate of prognosis or survival.

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.

Adjuvant, adoptive immunotherapy with tumor infiltrating lymphocytes plus interleukin-2 after radical hepatic resection for colorectal liver metastases: 5-year analysis

BACKGROUND AND OBJECTIVES

Conventional chemotherapy has not proven effective in improving long-term results of surgery for liver metastases from colorectal cancer. We assessed the usefulness of immunotherapy with tumor infiltrating lymphocytes (TIL) plus Interleukin-2 (IL-2) as adjuvant treatment.

METHODS

Between 1995 and 1998, 47 patients were enrolled onto a prospective protocol; 25 entered the treatment group (A) and 22 entered the control group (B). All patients had undergone radical liver resection. TIL obtained from surgical specimens from group A patients were cultured and activated in vitro with IL-2, then reinfused into the patients with IL-2. We investigated pre- and post-IL-2 stimulation expression of T cell receptor (TCR) zeta- and epsilon-chains, p56(lck), Fas, and Fas-L by TIL immunostaining.

RESULTS

Fourteen patients from group A (56%) received immunotherapy; 14 from group B (60%) underwent conventional chemotherapy, and the remaining 19 patients did not receive any treatment. No significant differences between the two groups were found in the actuarial and disease-free survival (DSF) rates after 1, 3, and 5 years. After IL-2 exposure, TCR zeta-chain expression significantly increased (P = 0.001); An increase in TCR epsilon-chain expression (P = 0.04), and p56(lck) (P = 0.03) was detected; TCR epsilon-chain expression was significantly increased in disease-free patients compared to those who relapsed (P = 0.04). Fas-L expression was correlated with the TCR epsilon-chain and p56(lck) levels (P = 0.05).

CONCLUSIONS

Our data suggest that we are still a long way from being able to propose TIL + IL-2 treatment as an effective adjuvant therapy. However, the results confirm that the biological indicators examined could play an important role in modulating immunitary response against tumor cells.

Dendritic cell biology and cancer therapy

Dendritic cells (DCs) are nature's best antigen-presenting cells. They possess attributes that allow them to effectively fulfill the requirements for priming/activating T cells and mediating tumor-specific immune responses. In this review, emphasis is placed on those aspects of DC biology that best illustrate their usefulness in immunotherapy of cancer. Culture, maturation, and polarization conditions for human DC are discussed, as are strategies for antigen-loading of DCs and for their delivery to patients with cancer. A concise recommendation for monitoring of DC-based vaccination trails is provided.

Insights Into Novel Biological Mediators of Clinical Manifestations in Cancer

A myriad of novel mediators in neoplastic development and progression are currently being explored. Of significance are those that directly explain clinical manifestations of cancer, because understanding these may lead to new diagnostic, preventive, and therapeutic strategies. This review focuses on novel mediators that address how cancer, before it is treated, can induce cachexia, pain, hematological, and immune alterations. It highlights two concepts: first, that a synergy between tumor and stromal cells may be partly responsible for these manifestations, and second, that soluble factors, and in particular cytokines are being identified as major players in tumor-induced local and systemic effects.

Rapid turnover of the CD8(+)CD28(-) T-cell subset of effector cells in the circulation of patients with head and neck cancer

CD8(+) T cells in the circulation of patients with head and neck cancer (HNC) were previously shown to be significantly more sensitive to, and preferentially targeted for, apoptosis than CD4(+) T cells (Hoffmann et al., Clin Cancer Res, 8:2553-2562, 2002). To distinguish global from CD8(+) subset-specific apoptosis, we studied Annexin-binding to naïve, memory, and effector subsets of CD8(+) cells by multicolor flow cytometry. Age-related changes in naïve and effector CD8(+) cell subsets were observed in patients and normal controls (NC). The frequencies of naïve (CD28(+)CD45RO(-)) CD8(+) T cells were lower and those of memory (CD28(+)CD45RO(+)) and effector (CD28(-)) CD8(+) T cells significantly higher in the circulation of HNC patients relative to age-matched NC. Among CD8(+) T cells, the CD28(-) effector cell subset contained the highest proportion of Annexin-binding cells, while the naïve CD28(+)CD45RO(-) subset contained the lowest. This suggested a high turnover rate of the CD8(+)CD28(-) effector cell subset in patients with HNC, which was being compensated by a rapid transition of naïve CD8(+) T cells to the effector cell pool. Following tumor resection, the frequency of CD8(+)CD28(-) T cells normalized in the patients, an indication that the presence of tumor had an influence on the size of CD8(+)CD28(-) T-cell pool. Ex vivo, in mixed lymphocyte-tumor cultures (MLTC) with semiallogeneic T cells as responders, CD8(+)CD28(-) T cells could be generated from CD8(+)CD28(+) cells by repeated stimulations with tumor cells. These CD8(+)CD28(-) effector cells lysed the tumor, produced IFN-gamma in response to the tumor, and strongly expressed granzyme B. Thus, the high rate of their apoptosis in the circulation of patients with HNC might be expected to contribute to tumor progression. However, the ex vivo generation of this cell subset was suppressed by strong CD28/B7 ligation or by overexpresson of MHC molecules on tumor cells, suggesting that adequate costimulation is necessary for protection from apoptosis. It appears that interactions of immune and tumor cells might determine the fate of this terminally differentiated effector cell subset.

Immune monitoring of human gene therapy trials: potential application to leukemia and lymphoma

Therapeutic genetically modified vaccines administered to patients with cancer are expected to induce and sustain tumor-specific immune responses. To measure these responses, monitoring strategies including a range of antibody-based and cellular assays have been developed. Single-cell cellular assays capable of detecting fewer than 1/10,000 of antigen-specific T lymphocytes in the tested population are currently in demand. ELISPOT assay, cytokine flow cytometry, and tetramer binding were recently compared by us in the context of monitoring of a dendritic cell-based multi-peptide vaccination trial in patients with metastatic melanoma. These single-cell assays were not found to be concordant in measurements of the frequency of peptide-specific T cells or in detecting pre- to post-vaccine changes in the frequency of these T cells. Implications of the results for monitoring of genetically modified vaccines are discussed, and the plan for a rational approach to monitoring and for selection of monitoring assays is proposed. Monitoring of human gene therapy or vaccination trials in patients with advanced cancers, who are often immunocompromised and thus poorly responsive, is a challenge. This challenge is best met by utilizing experienced reference laboratories for immune monitoring of clinical trials.

Soluble Fas (sFas) and soluble Fas ligand (sFas-L) balance in laryngeal carcinoma before and after surgical treatment

BACKGROUND AND OBJECTIVES

Fas and its specific ligand (Fas-L), both of which are involved in apoptosis, exist in membrane-bound and soluble forms. The soluble forms (sFas and sFas-L) have been observed in various tumours, but their clinical significance has not yet been clarified. The aim of this study was to assess serum sFas and sFas-L levels in patients with laryngeal squamous cell carcinoma (LSCC) and their possible correlations with surgical treatment.

METHODS

Serum sFas and sFas-L levels were determined by ELISA in samples taken from 26 LSCC patients on the day before surgery (T0), and 2 weeks (T1) and 6 months after surgery (T2), and in samples taken from 35 healthy volunteers.

RESULTS

The mean serum sFas levels in the 35 healthy volunteers and the 26 LSCC patients at T0 were respectively 5941 +/- 411 pg/ml and 6290 +/- 652 pg/ml (P = 0.63), and the mean serum sFas-L levels were 0.1 +/- 0.05 ng/ml and 2.95 +/- 0.8 ng/ml (P < 0.0001). After surgery, there was a statistically significant decrease in sFas at both T1 (P < 0.05) and T2 (P < 0.01), and in sFas-L at T2 (P < 0.01).

CONCLUSIONS

The decrease in sFas and sFas-L levels after surgery suggest that they may be produced by or closely linked to tumour cells. Larger prospective clinical studies of patients with LSCC will be needed to establish the clinical significance of sFas and sFas-L, as reported for other neoplasms.

Human acute lymphoblastic leukemia (ALL) blasts as accessory cells during T-cell activation: differences between patients in costimulatory capacity affect proliferative responsiveness and cytokine release by activated T cells

The ability of acute lymphoblastic leukemia (ALL) blasts to mediate costimulatory signals during T-lymphocyte activation was investigated in an experimental model in which monoclonal T-cell populations were stimulated with standardized activation signals (anti-CD3 and anti-CD28 monoclonal antibodies; phytohemagglutinin, PHA). Leukemia cells from 12 consecutive ALL patients with high peripheral blood blast counts were studied. Proliferative T-cell responses were detected for a majority of these patients when irradiated leukemia blasts were used as accessory cells during activation. T-cell cytokine release was also observed for most patients when using nonirradiated ALL accessory cells. Low or undetectable cytokine levels were usually observed for CD8+ clones, whereas the CD4+ clones often showed a broad cytokine response with release of interleukin-2 (IL-2), IL-4, IL-10, IL-13 and interferon gamma(IFN-gamma) in the presence of the ALL accessory cells. ALL blasts were also able to function as allostimulatory cells for normal peripheral blood mononuclear responder cells. However, both T-cell proliferation and cytokine release showed a wide variation between ALL patients. The accessory cell function of ALL blasts showed no correlation with the release of immunomodulatory mediators (IL-2, IL-10, IL-15) or the expression of any single adhesion/costimulatory membrane molecule (CD54, CD58, CD80, CD86) by the blasts. We conclude that for a majority of patients, native ALL blasts can mediate costimulatory signals needed for accessory cell-dependent T-cell activation, but differences in costimulatory capacity between ALL patients affects both the proliferative responsiveness and cytokine release by activated T cells.

Soluble Fas in malignant pleural effusion and its expression in lung cancer cells

Soluble Fas (sFas) has the ability to block Fas-mediated apoptosis, suggesting that sFas at tumor sites might inhibit tumor cell-killing by immune effector cells. We examined the sFas level in pleural effusion associated with lung cancer. The level of sFas in malignant pleural effusion was significantly higher than those in transudate and tuberculous pleural effusion. There was no significant difference in the sFas concentration among various histological types of lung cancer. The cytotoxicity mediated by anti-Fas agonistic antibody against Jurkat cells was inhibited by the addition of malignant pleural effusion, being inversely correlated with the sFas concentration. When Fas expression was examined using flow cytometry, eight of ten (80%) lung cancer cell lines expressed cell surface Fas. On the other hand, sFas protein and mRNA were detected in six of ten (60%) lung cancer cell lines, but there was no correlation between Fas and sFas expression. Furthermore, although the expressions of Fas and sFas were clearly detected in tumor cells derived from malignant effusion, the sFas expression was down-regulated in an in vitro culture. These results suggest that sFas in malignant pleural effusion is at least in part produced by lung cancer cells, and might play a role in local immunosuppression by tumor cells.

Adjuvant immunotherapy with tumor infiltrating lymphocytes and interleukin-2 in patients with resected stage III and IV melanoma

Adoptive immunotherapy with tumor infiltrating lymphocytes (TIL) and interleukin (IL)-2 is reasonably effective in the treatment of patients with advanced melanoma. However, theoretically it should be of greater benefit as adjuvant therapy, especially in high-risk stages (resected stages III and IV). In a preliminary study, 25 patients (aged 23-72 years) with stage III-IV melanoma who underwent resection of metachronous metastases were reinfused with TIL cultivated and expanded in vitro with IL-2 from surgically removed metastases. IL-2 (starting dose 12 x 10 IU/m ) was co-administered as a continuous infusion according to West's scheme. A total of 8/22 (36.3%) evaluable patients were disease-free (DF) at a median follow-up of 5 years. DF survival (DFS) and overall survival (OS) rates were 44% and 37%, respectively, at 2 years, and 52% and 45% at 3 years. The CNS was the only site of disease recurrence in 57% of patients who relapsed. DF patients received a higher median dose of IL-2 than those who progressed (total dose 110 x 10 versus 86 x 10 IU/m, respectively). The progressive reduction in IL-2 dosage allowed all patients to complete treatment without permanent grade 4 toxicity. Analysis of tumor immunosuppression factors in lymphocytes inside the tumor (TCR zeta and epsilon chains, p56, FAS, and FAS-ligand) confirmed that the immunologic potential of TIL, depressed at the time of metastasectomy, was significantly restored after in vitro culture with IL-2. Adoptive immunotherapy with TIL and IL-2 could improve DFS and OS, although further work is required to determine its role in the treatment of patients with high-risk melanoma.

22. Immune responses to malignancies

Immune responses to tumor-associated antigens exist in tumor-bearing hosts but are usually not successful in eliminating malignant cells or preventing the development of metastases. Patients with cancer generate robust immune responses to infectious agents (bacteria and viruses) perceived as a "danger signal" but only ineffective, weak responses to tumor-associated antigens, which are considered as "self." This fundamental difference in responses to self versus non-self is further magnified by the ability of tumors to subvert the host immune system. Tumors induce dysfunction, as well as apoptosis in CD8(+) antitumor effector cells. The escape of tumors from immune cells is mediated by several distinct molecular mechanisms. Insights into these mechanisms and more effective control of tumor-orchestrated immune dysfunction are needed. Novel strategies for immunotherapy of cancer must address protection and survival of antitumor effector cells in the tumor microenvironment.

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.

Cells behaving badly: a theoretical model for the Fas/FasL system in tumour immunology

One proposed mechanism of tumour escape from immune surveillance is tumour up-regulation of the cell surface ligand FasL, which can lead to apoptosis of Fas receptor (Fas) positive lymphocytes. Based upon this 'counterattack', we have developed a mathematical model involving tumour cell-lymphocyte interaction, cell surface expression of Fas/FasL, and their secreted soluble forms. The model predicts that (a) the production of soluble forms of Fas and FasL will lead to the down-regulation of the immune response; (b) matrix metalloproteinase (MMP) inactivation should lead to increased membrane FasL and result in a higher rate of Fas-mediated apoptosis for lymphocytes than for tumour cells. Recent studies on cancer patients lend support for these predictions. The clinical implications are two-fold. Firstly, the use of broad spectrum MMP inhibitors as anti-angiogenic agents may be compromised by their adverse effect on tumour FasL up-regulation. Also, Fas/FasL interactions may have an impact on the outcome of numerous ongoing immunotherapeutic trials since the final common pathway of all these approaches is the transduction of death signals within the tumour cell.

Immunologic monitoring of cancer vaccine therapy: results of a workshop sponsored by the Society for Biological Therapy

The Society for Biological Therapy held a Workshop last fall devoted to immune monitoring for cancer immunotherapy trials. Participants included members of the academic and pharmaceutical communities as well as the National Cancer Institute and the Food and Drug Administration. Discussion focused on the relative merits and appropriate use of various immune monitoring tools. Six breakout groups dealt with assays of T-cell function, serologic and proliferation assays to assess B cell and T helper cell activity, and enzyme-linked immunospot assay, tetramer, cytokine flow cytometry, and reverse transcription polymerase chain reaction assays of T-cell immunity. General conclusions included: (1) future vaccine studies should be designed to determine whether T-cell dysfunction (tumor-specific and nonspecific) correlated with clinical outcome; (2) tetramer-based assays yield quantitative but not functional data (3) enzyme-linked immunospot assays have the lowest limit of detection (4) cytokine flow cytometry have a higher limit of detection than enzyme-linked immunospot assay, but offer the advantages of speed and the ability to identify subsets of reactive cells; (5) antibody tests are simple and accurate and should be incorporated to a greater extent in monitoring plans; (6) proliferation assays are imprecise and should not be emphasized in future studies; (7) the reverse transcription polymerase chain reaction assay is a promising research approach that is not ready for widespread application; and (8)there is a critical need to validate these assays as surrogates for vaccine potency and clinical effect. Current data and opinion support the use of a functional assay like the enzyme-linked immunospot assay or cytokine flow cytometry in combination with a quantitative assay like tetramers for immune monitoring. At present, assays appear to be most useful as measures of vaccine potency. Careful immune monitoring in association with larger scale clinical trials ultimately may enable the correlation of monitoring results with clinical benefit.

Tumor-induced death of immune cells: its mechanisms and consequences

FasL is a death-inducing as well as pro-inflammatory molecule. The seemingly opposing consequences of Fas/FasL interactions appear to be dependent on the context of the tumor or tissue microenvironment. The term 'contextual' has been coined to describe cellular and molecular events that may be opposing, yet are mediated by the engagement of the same receptor-ligand pair. Because Fas is one of the death-inducing receptors, its ligand is dangerous. Hence, the availability of FasL for cross-linking of the receptor has to be extremely carefully regulated. Different levels of control appear to exist, some involving cell membrane-associated MMPs and others depending on cytokines released from neighboring cells. In tumors, which shape their microenvironment to make it unwelcome to immune effector cells, FasL is used to kill infiltrating cells without damage to the tumor, which develops multiple means of hiding/inhibiting the death pathway. On the other hand, in situations provoking inflammatory responses such as allograft rejection, infection, and tissue necrosis, FasL assumes the role of attractant for inflammatory cells. In these situations, FasL acts in conjunction with other cytokines, and its effects might be modified in the context of unfolding events. When put in the context of biologic interactions that take place at the tumor site, the Fas/FasL pathway emerges as a molecular mechanism, which contributes to immune privilege and tumor escape, but which can also enhance anti-tumor inflammatory responses. FasL, like many cytokines, is pleiotropic. It is also worth bearing in mind that other molecular players, including the other known members of the TNF family, almost certainly participate in establishing immune privilege status of tumors. While a broad body of new information has contributed to clarifying the dual role of FasL in the tumor biology, much remains to be learned about molecular mechanisms that control its effects in the tumor and in normal tissues.