Fas ligand mediates immune privilege and not inflammation in human colon cancer, irrespective of TGF-beta expression

Analysing the relevance of TGF-β and its regulators in cervical cancer to identify therapeutic and diagnostic markers

The role of transforming growth factor-beta (TGF-β) is dual, such that, it inhibits tumor development in initial stage and promotes metastasis in later stage. The present study is aimed to analyse the relevance of different types of TGF-β and their receptors on the overall survival (OS) and TGF-β driven gene expression in individuals with cervical cancer (CC) using ONCODB and GEPIA databases. The in-silico gene expression analysis showed, TGF-β1 and TGFβR2 are upregulated in cells infected with human papilloma virus (HPV)16, whereas, TGF-β2, TGFβR1 and TGFβR3 expression were downregulated. In HPV 18 infected cells, TGF-β1, TGF-β2 and TGFβR1 were downregulated, meanwhile, TGF-β3, TGFβR2 and TGFβR3 were upregulated. OS analysis of CC patients with different TGF-β expression revealed that, TGF-β1, TGF-β2, TGF-β3 and TGFβR2 were associated with reduced survival rate. Further, we identified four microRNAs (miRNAs) (hsa-miR-21-5p, hsa-miR-29b-3p, hsa-miR-101-3p and hsa-miR-130a-3p) interacted favorably with TGF-β in HPV 16 and 18 positive samples using MIENTURNET. This present review further emphasizes that, targeting TGF-β could be a novel and futuristic approach for CC management and therapeutics.

Dendritic cell-based vaccine prolongs survival and time to next therapy independently of the vaccine cell number

In 2009, new EU legislation regulating advanced therapy medicinal products (ATMPs), consisting of gene therapy, tissue engineering and cell-based medicines, was introduced. Although less than 20 ATMPs were authorized since that time, the awarding of the Nobel Prize for Physiology or Medicine in 2018 revived interest in developing new cancer immunotherapies involving significant manipulation of the patient's own immune cells, including lymphocytes and dendritic cells. The lymphocytes are mainly thought to directly affect tumour cells, dendritic cells are involved in indirect mechanisms by antigen presentation to other leukocytes orchestrating the immune response. It is the latter cells that are the focus of this brief review. Based on the recent results of our study treating patients with castration-resistant prostate cancer (CRPC) with an immunohybridoma cell construct (termed aHyC), produced by electrofusion of autologous tumour and dendritic cells, we compare their effectiveness with a matched documented control group of patients. The results revealed that cancer-specific survival and the time to next in-line therapy (TTNT) were both significantly prolonged versus controls. When patients were observed for longer periods since the time of diagnosis of CRPC, 20% of patients had not yet progressed to the next in-line therapy even though the time under observation was ~ 80 months. Interestingly, analysis of survival of patients revealed that the effectiveness of treatment was independent of the number of cells in the vaccine used for treatment. It is concluded that autologous dendritic cell-based immunotherapy is a new possibility to treat not only CRPC but also other solid tumours.

The Kynurenine Pathway Is a Double-Edged Sword in Immune-Privileged Sites and in Cancer: Implications for Immunotherapy

The term “immune privilege” was originally coined to describe the suppression of inflammatory responses within organs protected by anatomic barriers, ie, the eyes, brain, placenta, and testes. However, cellular and metabolic processes, which orchestrate immune responses, also control inflammation within these sites. Our current understanding of tolerogenic mechanisms has extended the definition of immune privilege to include hair follicles, the colon, and cancer. By catabolizing tryptophan, cells expressing the enzyme indoleamine-2,3-dioxygenase produce kynurenine metabolites, which orchestrate local and systemic responses to control inflammation, thus maintaining immune privilege. This review highlights the double-edged role played by the kynurenine pathway (KP), which establishes and maintains immune-privileged sites while contributing to cancer immune escape. The identification of the underlying molecular drivers of the KP in immune-privileged sites and in cancer is essential for the development of novel therapies to treat autoimmunity and cancer and to improve transplantation outcomes.

Adoptive Transfer of Dendritic Cells Expressing Fas Ligand Modulates Intestinal Inflammation in a Model of Inflammatory Bowel Disease

Background

Inflammatory bowel diseases (IBD) are chronic relapsing inflammatory conditions of unknown cause and likely result from the loss of immunological tolerance, which leads to over-activation of the gut immune system. Gut macrophages and dendritic cells (DCs) are essential for maintaining tolerance, but can also contribute to the inflammatory response in conditions such as IBD. Current therapies for IBD are limited by high costs and unwanted toxicities and side effects. The possibility of reducing intestinal inflammation with DCs genetically engineered to over-express the apoptosis-inducing FasL (FasL-DCs) has not yet been explored.

Objective

Investigate the immunomodulatory effect of administering FasL-DCs in the rat trinitrobenzene sulfonic acid (TNBS) model of acute colitis.

Methods

Expression of FasL on DCs isolated from the mesenteric lymph nodes (MLNs) of normal and TNBS-colitis rats was determined by flow cytometry. Primary rat bone marrow DCs were transfected with rat FasL plasmid (FasL-DCs) or empty vector (EV-DCs). The effect of these DCs on T cell IFNγ secretion and apoptosis was determined by ELISPOT and flow cytometry for Annexin V, respectively. Rats received FasL-DCs or EV-DCs intraperitoneally 96 and 48 hours prior to colitis induction with TNBS. Colonic T cell and neutrophil infiltration was determined by immunohistochemistry for CD3 and myeloperoxidase activity assay, respectively. Macrophage number and phenotype was measured by double immunofluorescence for CD68 and inducible Nitric Oxide Synthase.

Results

MLN dendritic cells from normal rats expressed more FasL than those from colitic rats. Compared to EV-DCs, FasL-DCs reduced T cell IFNγ secretion and increased T cell apoptosis in vitro. Adoptive transfer of FasL-DCs decreased macroscopic and microscopic damage scores and reduced colonic T cells, neutrophils, and proinflammatory macrophages when compared to EV-DC adoptive transfer.

Conclusion

FasL-DCs are effective at treating colonic inflammation in this model of IBD and represent a possible new treatment for patients with IBD.

Novel N-amidinopiperidine-based proteasome inhibitor preserves dendritic cell functionality and rescues their Th1-polarizing capacity in Ramos-conditioned tumor environment

The tumor microenvironment represents a burden that hampers the proper activation of immune cells, including the dendritic cells (DCs). It is, therefore, desired that the important characteristics of a given anticancer drug candidate be seen as consisting not solely of its antitumor properties, but that it also lacks potential side effects that could additionally constrain the development and function of immune cells associated with tumor immunity. We have previously identified compounds with a N-amidinopiperidine scaffold that selectively induce apoptosis in Burkitt's lymphoma cells through proteasome inhibition. Here, we demonstrate that SPI-15 affected neither the viability of DCs nor their differentiation. In addition, the compound had no significant effect on their cytokine secretion or allostimulatory capacity. Moreover, DC functionality in the context of tumor microenvironment was also unaffected, as demonstrated by experiments performed on DCs differentiated in Ramos-conditioned media in the presence or absence of SPI-15. The cytokine profile and functional assays revealed that SPI-15 rescues DC differentiation from the immunosuppressive environment produced by Ramos cells; this was seen by their reacquired ability to induce IFN-γ-secretion from naïve CD4(+)CD45RA(+) T cells and the consequently induced Th1-effector differentiation. Herein, we present novel characteristics of an N-amidinopiperidine-based protease inhibitor whose anticancer properties are not associated with the immunosuppression of DCs. We propose future studies toward the design of structurally similar compounds with the aim of developing potent anticancer drugs with minimal negative effects on crucial factors involved in tumor immunity.

Dendritic cell cancer vaccines: from the bench to the bedside

The recognition that the development of cancer is associated with acquired immunodeficiency, mostly against cancer cells themselves, and understanding pathways inducing this immunosuppression, has led to a tremendous development of new immunological approaches, both vaccines and drugs, which overcome this inhibition. Both "passive" (e.g. strategies relying on the administration of specific T cells) and "active" vaccines (e.g. peptide-directed or whole-cell vaccines) have become attractive immunological approaches, inducing cell death by targeting tumor-associated antigens. Whereas peptide-targeted vaccines are usually directed against a single antigen, whole-cell vaccines (e.g. dendritic cell vaccines) are aimed to induce robust responsiveness by targeting several tumor-related antigens simultaneously. The combination of vaccines with new immuno-stimulating agents which target "immunosuppressive checkpoints" (anti-CTLA-4, PD-1, etc.) is likely to improve and maintain immune response induced by vaccination.

Cancer immunotherapy: accomplishments to date and future promise

Cancer remains a devastating disease as existing therapies are too often ineffective and toxicities remain unacceptably high. Immunotherapies for cancer offer the promise of the specificity and memory of the immune system against malignant cells to achieve durable cure with minimal toxicity. Beginning with the success of bone marrow transplantation for blood-borne cancers, and the more recent development of monoclonal antibody therapeutics for a variety of tumors, immunotherapies are already among the most successful class of treatments for cancer. Greater understanding of immunoregulatory mechanisms and improved techniques for immune cell manipulation and engineering have led to new immunomodulatory approaches and cell-based therapies for cancer that have generated great excitement within the biomedical community. As these technologies continue to improve, and as new approaches for harnessing the power and specificity of the immune system are developed, immunotherapies will play an increasingly important role in the treatment of cancer. Here, we review the history of immunotherapies for cancer and discuss existing and emerging immunotherapy technologies that hope to translate the promise of immunotherapy into clinical reality.

Expression of apoptosis regulating proteins identifies stage II and III colon cancer patients with high risk of recurrence

BACKGROUND AND OBJECTIVES

Deregulation of apoptosis related genes may be associated with poor outcome in cancer. Aim of the present study was to investigate the prognostic role of expression levels of apoptosis related proteins in stage II and III colon cancer.

METHODS

From tumor samples of 386 stage II and III colon cancer patients, DNA was isolated and tissue microarrays were constructed. Expression of Bcl-2, Bcl-X, BAX, XIAP, Fas, FasL and c-FLIP was evaluated and PCR-based microsatellite instability analysis was performed.

RESULTS

High FasL expressing tumors were associated with high disease recurrence rates in stage II colon cancer patients overall, as was low Bcl-X expression in microsatellite stable stage II patients. In stage II patients, a multivariable model based on FasL and Bcl-XL expression revealed a significant association with disease free survival (DFS). In stage III colon cancer patients, low Bcl-2, low BAX and low Fas expression levels were associated with worse outcome. In these patients a multivariable model based on angioinvasion and Bcl-2, Fas and FasL expression was significantly associated with DFS.

CONCLUSIONS

Stage II patients with low Bcl-X and high FasL protein expression levels and stage III patients with low Fas, high FasL and low Bcl-2 expression could be considered as high risk for disease recurrence.

Superior anti-tumor protection and therapeutic efficacy of vaccination with dendritic cell/tumor cell fusion hybrids for murine Lewis lung carcinoma

BACKGROUND

The development of protocols for the ex vivo generation of dendritic cells (DCs) has led to intensive research into their potential use in immunotherapy in the treatment of cancer. In this study, we examined the efficacy of dendritic cell-tumor cell fusion hybrid vaccines in eliciting an immune response against Lewis lung carcinoma (LLC) cells, as compared to other types of tumor vaccines. In addition, we also tested whether the efficacy of the vaccines was affected by the route of administration. Four different tumor vaccines were compared: (1) HC (hybrid cell), consisting of DC/LLC hybrids; (2) DC+LLC (DCs pulsed with apoptotic LLCs); (3) DC without antigen loading/pulsing; (4) LLC (apoptotic/irradiated tumor cells). We also compared four different routes of administration for each vaccine: (1) Preimmunization; (2) Vaccination therapy; (3) Adoptive immunotherapy; (4) Vaccination therapy combined with adoptive immunotherapy. Anti-tumor immunity was assessed in vivo and the CTL (cytotoxic T lymphocyte) response as well as the expression of key cytokines, IFN-γ and IL-10 were further evaluated using in vitro assays.

RESULTS

Our data demonstrate that vaccination with HC hybrids provides more effective anti-tumor protective immunity and significantly greater therapeutic immunity than vaccination with DC+LLC, DC or LLC. Most remarkably, vaccination therapy with HC hybrids was more successful than combination (vaccination + adoptive) therapy for the induction of anti-tumor responses. Splenocytes harvested from mice immunized with HC hybrids demonstrated the greatest cytotoxic T lymphocyte (CTL) activity and their production of IFN-γ was high, while their production of IL-10 was very low.

CONCLUSIONS

Our results suggest that vaccination therapy with DC-tumor cell fusion hybrids provides more effective protection against lung cancer.

[A probable etiological role of Merkel cell polyomavirus in the development of Merkel cell carcinoma]

Approximately 20% of the tumours in humans are associated with contagious viral agents. Merkel cell carcinoma is a rare and highly aggressive tumour which may originate from the epidermal stratum basale, although the origin is still controversial. This tumour is most commonly found in elderly and immunocompromised patients in sun exposed areas, especially in the head and neck regions. Merkel cell carcinoma often causes a diagnostic challenge with a dramatically increasing incidence. In 2008, a DNA tumour virus, a polyomavirus (Merkel cell polyomavirus) was detected in Merkel cell carcinomas, and this finding helped to understand the etiological background of the disease. The infectious - probably viral - etiology resulted in a paradigm shift in pathogenesis and, hopefully, in therapy as well. This review summarizes the current knowledge related to Merkel cell carcinoma and the first oncogenic human polyomavirus, the Merkel cell polyomavirus, to promote the clinical adaptation of the information.

Pre-existing Fas ligand (FasL) in cancer cells elicits tumor-specific protective immunity, but delayed induction of FasL expression after inoculation facilitates tumor formation

Overexpression of Fas ligand (FasL) in cancer cells elicits potential antitumor effects via recruitment of neutrophils. Conversely, FasL-expressing tumors may counterattack tumor-infiltrating lymphocytes by delivering apoptotic death signals via Fas/FasL interactions, which may lead to tumor escape. In order to distinguish the role of FasL in antitumor activity and tumor progression, Lewis lung carcinoma cells (LLC-1) were used to establish the cell line LLC-FasL, in which FasL expression was repressed by doxycycline (Dox) treatment and induced in the absence of Dox. LLC-FasL cells promote tumor regression when expressing FasL, whereas tumor outgrowth is observed by depletion of FasL expression. To investigate whether initial expression of FasL during tumor formation is critical for FasL-mediated tumor regression, Dox-treated LLC-FasL cells were inoculated into Dox-treated mice, but Dox treatment was stopped 5 days after inoculation. When low cell numbers were inoculated, we observed 80% survival and no tumor formation, whereas no mice survived inoculation with high cell numbers, despite the delayed induction of FasL by Dox withdrawal. The inoculation of a high density of cells may establish a favorable tumor microenvironment before the expression of FasL. Our findings demonstrate that FasL may elicit antitumor activity when it is initially present on injected cancer cells and thus can act prior to tumor microenvironment formation. Furthermore, a well-established tumor microenvironment abrogates FasL-mediated antitumor activity.

CD95 signaling in colorectal cancer

CD95 and its ligand (CD95L) are widely expressed in colorectal tumors, but their role in shaping tumor behavior is unclear. CD95 activation on tumor cells can lead to apoptosis, while CD95L attracts neutrophils, suggesting a function in tumor suppression. However, CD95 can also promote tumorigenesis, at least in part by activating non-apoptotic signaling pathways that stimulate tumor cell proliferation, invasion and survival. In addition, CD95 signaling in stromal cells and tumor-infiltrating inflammatory cells has to be taken into account when addressing the function of CD95 and its ligand in colorectal tumor biology. We present a model in which the tumor-suppressing and tumor-promoting activities of CD95/CD95L together determine colorectal tumor behavior. We also discuss how these multiple activities are changing our view of CD95 and CD95L as potential therapeutic targets in the treatment of colorectal cancer. We conclude that locking CD95 in apoptosis-mode may be a more promising anti-cancer strategy than simply inhibiting or stimulating CD95.

Immunobiology of Merkel cell carcinoma: implications for immunotherapy of a polyomavirus-associated cancer

Merkel cell carcinoma (MCC) is an aggressive skin malignancy with a high mortality rate and an increasing incidence. The recent discovery of Merkel cell polyomavirus has revolutionized our understanding of MCC pathogenesis. Viral oncoproteins appear to play a critical role in tumor progression and are expressed in the majority of MCC tumors. Virus-specific humoral and cellular immune responses are detectable in MCC patients and are linked to the natural history of the disease. Despite persistent expression of immunogenic viral proteins, however, MCC tumors are able to evade the immune system. Understanding of the mechanisms of immune evasion employed by MCC tumors is rapidly increasing and offers opportunities for development of rational immune therapies to improve patient outcomes. Here we review recent discoveries in MCC with a special focus on the pathogenic role of Merkel cell polyomavirus and the immunobiology of this virus-associated disease.

Behavior of circulating CD4+CD25+Foxp3+ regulatory T cells in colon cancer patients undergoing surgery

CD4+CD25+Foxp3+ regulatory T cells (Treg) specialize in suppressing immune responses. In this study, 47 consecutive colon cancer patients were subjected to circulating Treg frequency assessment by flow cytometry before and after cancer resection. Thirty-two healthy subjects served as controls. Circulating Treg frequencies were significantly higher in colon cancer patients with respect to healthy controls. When patients were subgrouped according to Dukes stages, a linear relationship was observed between Dukes stages and Treg frequencies. In radically resected patients, Treg frequencies were shown to have significantly dropped down. Patients with advanced colon cancer were more likely to have significantly higher proportions of circulating Treg frequencies than Dukes A and B patients when compared to healthy subjects. Of note, nonradically resected patients were found to display reductions in-but not normalization of-Treg frequencies. These results suggest that cancer itself may be able to drive Treg recruitment as a strategy of immunoevasion.

Human FasL gene is a target of β-catenin/T-cell factor pathway and complex FasL haplotypes alter promoter functions

FasL expression on human immune cells and cancer cells plays important roles in immune homeostasis and in cancer development. Our previous study suggests that polymorphisms in the FasL promoter can significantly affect the gene expression in human cells. In addition to the functional FasL SNP -844C>T (rs763110), three other SNPs (SNP -756A>G or rs2021837, SNP -478A>T or rs41309790, and SNP -205 C>G or rs74124371) exist in the proximal FasL promoter. In the current study, we established three major FasL hyplotypes in humans. Interestingly, a transcription motif search revealed that the FasL promoter possessed two consensus T-cell factor (TCF/LEF1) binding elements (TBEs), which is either polymorphic (SNP -205C>G) or close to the functional SNP -844C>T. Subsequently, we demonstrate that both FasL TBEs formed complexes with the TCF-4 and β-catenin transcription factors in vitro and in vivo. Co-transfection of LEF-1 and β-catenin transcription factors significantly increased FasL promoter activities, suggesting that FasL is a target gene of the β-catenin/T-cell factor pathway. More importantly, we found that the rare allele (-205G) of the polymorphic FasL TBE (SNP -205C>G) failed to bind the TCF-4 transcription factor and that SNP -205 C>G significantly affected the promoter activity. Furthermore, promoter reporter assays revealed that FasL SNP haplotypes influenced promoter activities in human colon cancer cells and in human T cells. Finally, β-catenin knockdown significantly decreased the FasL expression in human SW480 colon cancer cells. Collectively, our data suggest that β-catenin may be involved in FasL gene regulation and that FasL expression is influenced by FasL SNP haplotypes, which may have significant implications in immune response and tumorigenesis.

Immunologic monitoring of cellular responses by dendritic/tumor cell fusion vaccines

Although dendritic cell (DC)- based cancer vaccines induce effective antitumor activities in murine models, only limited therapeutic results have been obtained in clinical trials. As cancer vaccines induce antitumor activities by eliciting or modifying immune responses in patients with cancer, the Response Evaluation Criteria in Solid Tumors (RECIST) and WHO criteria, designed to detect early effects of cytotoxic chemotherapy in solid tumors, may not provide a complete assessment of cancer vaccines. The problem may, in part, be resolved by carrying out immunologic cellular monitoring, which is one prerequisite for rational development of cancer vaccines. In this review, we will discuss immunologic monitoring of cellular responses for the evaluation of cancer vaccines including fusions of DC and whole tumor cell.

Regulation of tumor immunity by tumor/dendritic cell fusions

The goal of cancer vaccines is to induce antitumor immunity that ultimately will reduce tumor burden in tumor environment. Several strategies involving dendritic cells- (DCs)- based vaccine incorporating different tumor-associated antigens to induce antitumor immune responses against tumors have been tested in clinical trials worldwide. Although DCs-based vaccine such as fusions of whole tumor cells and DCs has been proven to be clinically safe and is efficient to enhance antitumor immune responses for inducing effective immune response and for breaking T-cell tolerance to tumor-associated antigens (TAAs), only a limited success has occurred in clinical trials. This paper reviews tumor immune escape and current strategies employed in the field of tumor/DC fusions vaccine aimed at enhancing activation of TAAs-specific cytotoxic T cells in tumor microenvironment.

Fas ligand expression in lynch syndrome-associated colorectal tumours

Fas Ligand (FasL) expression by cancer cells may contribute to tumour immune escape via the Fas counterattack against tumour-infiltrating lymphocytes (TILs). Whether this plays a role in colorectal carcinogenesis in Lynch syndrome was examined studying FasL expression, tumour cell apoptosis and number of TILs in colorectal neoplasms from Lynch syndrome patients (50 adenomas, 20 carcinomas) compared with sporadic cases (69 adenomas, 52 carcinomas). FasL expression was observed in 94% of Lynch syndrome adenomas and in all carcinomas. FasL expression patterns and apoptotic indices were similar in Lynch syndrome-associated neoplasms and sporadic cases. The number of TILs was higher in Lynch syndrome neoplasms than in sporadic cases. There were no correlations between FasL expression and tumour cell apoptosis or number of TILs in Lynch syndrome-associated neoplasms. So, FasL expression is an early event in Lynch syndrome and sporadic colorectal carcinogenesis, but not related to TIL number. Taken together, our data do not support a role for the Fas counterattack in colorectal carcinogenesis in Lynch syndrome.

Clinical applications of a peptide-based vaccine for glioblastoma

Glioblastoma multiforme is a malignant, relentless brain cancer with no known cure, and standard therapies leave significant room for the development of better, more effective treatments. Immunotherapy is a promising approach to the treatment of solid tumors that directs the patient's own immune system to destroy tumor cells. The most successful immunologically based cancer therapy to date involves the passive administration of monoclonal antibodies, but significant antitumor responses have also been generated with active vaccination strategies and cell-transfer therapies. This article summarizes the important components of the immune system, discusses the specific difficulty of immunologic privilege in the central nervous system, and reviews treatment approaches that are being attempted, with an emphasis on active immunotherapy using peptide vaccines.

Lymphocyte recruitment into the tumor site is altered in patients with MSI-H colon cancer

The ability of the host to mount an appropriate immune response to aberrant cells is one factor that determines prognosis in cancer patients. Naturally occurring regulatory T cells (T regs; CD4+ CD25+ cells) are key regulators of peripheral tolerance. It has been suggested that high levels of T regs are detrimental to the patient in some forms of cancer, but the role of these antigen-specific cells in individuals with colorectal cancers with high levels of microsatellite instability is unknown. Herein, we examined the ability of individuals with MSI-H or microsatellite stable colon cancer to recruit lymphocytes to the tumor site. Immunohistochemical staining was performed on archived paraffin-embedded specimens from a total of 38 individuals with MSI-H (n = 25) or MSS (n = 13) colon cancers to determine the proportion of CD3+, CD8+ and CD25+ cells infiltrating the tumor site. Patients with MSI-H colon cancers had increased percentages of CD8+ TILs (cytotoxic T cells) as compared to individuals with MSS colon cancer (47.3 vs. 24.04% of the infiltrate CD8+, respectively). No differences in the levels of CD25+ T cells were observed between individuals with MSI-H colon cancers and MSS colon cancers (0.53 vs. 0.54% CD25+, respectively). Together, these data suggest that the survival advantage enjoyed by patients with MSI-H colorectal cancer may, in part, be attributed to the increased cytolytic response, but not to an antigen-specific immunosuppressive response in MSS patients.

Requirement of inositol 1,4,5-trisphosphate receptors for tumor-mediated lymphocyte apoptosis

Tumor cells strategically down-regulate Fas receptor expression to evade immune attack and up-regulate expression of Fas ligand to promote apoptosis of infiltrating T lymphocytes. Many pathways leading to apoptotic cell death require calcium release from inositol 1,4,5-trisphosphate receptors (IP3Rs). Here, we show that Fas-dependent killing of Jurkat T lymphoma cells by SW620 colon cancer cells requires calcium release from IP3R. General suppression of IP3R signaling significantly reduced SW620-mediated Jurkat cell apoptosis. Significantly, a specific inhibitor of apoptotic calcium release from IP3R strongly blocked lymphocyte apoptosis. Thus, selective pharmacological targeting of apoptotic calcium release from IP3R may enhance tumor cell immunogenicity.

Effects of specific antisense oligonucleotide inhibition of Fas expression on T cell apoptosis induced by Fas ligand

To investigate the effect of specific antisense oligodeoxynucleotide (ASODN) inhibition of Fas expression on T cell apoptosis induced by hepatocarcinoma cells. Fas receptor (Fas) and Fas ligand (FasL) expressed by the hepatocarcinoma cell line HepG2.2.15 and Jurkat T cells were detected by flow cytometry (FCM) and the ability of FasL-inducing T cell apoptosis was tested by co-culture assay in vitro with HepG2.2.15 cells and Jurkat T cells. The Jurkat cells were transfected with Fas-ASODN using lipofectin, and the effects of Fas-ASODN on Fas mRNA level, Fas expression on T cells surface, and apoptosis were investigated by RT-PCR, FCM and co-culture assay, respectively. It was found that HepG2.2.15 cells expressing functional FasL could induce the apoptosis of Jurkat cells as demonstrated by co-culture assays. After the Jurkat cells were transfected with Fas ASODN, the level of Fas mRNA, the expression rate of Fas and the apoptotic rate induced by hepatocarcinoma cells were all decreased. As a conclusion, it is evident that hepatocarcinoma cells expressing FasL can induce apoptosis in Fas-expressing T cells, indicating that transfection of Fas ASODN can partially convert the immune inhibitory condition induced by hepatocarcinoma cells.

Mechanisms involved in Korean mistletoe lectin-induced apoptosis of cancer cells

AIM: To investigate the anti-cancer mechanisms of Korean mistletoe lectin (Viscum album coloratum agglutinin, VCA) using a human colon cancer cell line (COLO).

METHODS: Cytotoxic effects of VCA on COLO cells were determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay in vitro and tumor-killing effects in vivo. To study the mechanisms involved, the expression of various pro-caspases, anti-apoptotic proteins, and death receptors was determined by western blot. To determine which death receptor is involved in VCA-induced apoptosis of COLO cells, cytotoxicity was examined by MTT assay after treatment with agonists or antagonists of death receptors.

RESULTS: VCA killed COLO cells in a time- and dose-dependent manner and induced complete regression of tumors in nude mice transplanted with COLO cells. Treatment of COLO cells with VCA activated caspase-2, -3, -8, and -9 and decreased expression of anti-apoptotic molecules including receptor interacting protein, nuclear factor-κB, X-linked inhibitor of apoptosis protein, and Akt/protein kinase B. We then examined the involvement of death receptors in VCA-induced apoptosis. Only tumor necrosis factor receptor 1, among the death receptors examined, was involved in apoptosis of COLO cells, evidenced by inhibition of VCA-induced apoptosis and decreased activation of caspases, particularly caspase-8, by tumor necrosis factor receptor 1 antagonizing antibody.

CONCLUSION: VCA-induced apoptotic COLO cell death is due to the activation of caspases and inhibition of anti-apoptotic proteins, in part through the tumor necrosis factor receptor 1 signaling pathway.

Review article: immune suppression and colorectal cancer

BACKGROUND

Advances in immunology and molecular biology have shown that colorectal cancer is potentially immunogenic and that host immune responses influence survival. However, immune surveillance and activation is frequently ineffective in preventing and/or controlling tumour growth.

AIM

To discuss potential ways in which colorectal cancer induces immune suppression, its effect upon prognosis and avenues for therapeutic development.

METHOD

A literature review was undertaken for evidence of colorectal cancer-induced immune suppression using PubMed and Medline searches. Further studies were identified from the reference lists of identified papers.

RESULTS

Immune suppression occurs at a molecular and cellular level and can result in a shift from cellular to humoral immunity. Several mechanisms for immune suppression have been described affecting innate and adaptive immunity with suppression linked to poorer clinical outcome.

CONCLUSIONS

Colorectal cancer causes direct inhibition of the host's immune response with a detrimental effect upon prognosis. Immunotherapy offers a therapeutic strategy to counteract these effects with promising results seen particularly in precancerous conditions and early tumours. This review strongly suggests that immunotherapy should be incorporated into adjuvant therapeutic trials for stage 2 tumours and be considered as adjuvant treatment in conjunction with standard chemotherapy regimes for advanced disease.

Influence of antitumor drugs on the expression of Fas system in SW480 colon cancer cells

AIMS

To observe the influence of popular antitumor drugs [5-fluorouracil (5-FU), mitomycin (MMC), cisplatin (CP) and all-trans retinoic acid (ATRA)] on the expression of Fas system in SW480 colon cancer cells.

METHODS

The expressions of Fas/FasL protein and mRNA in colon cancer line SW480 cells before and after the treatment of the antitumor drugs (5-FU, MMC, CP and ATRA) were detected by immunocytochemistry, flow cytometry and reverse-transcriptase polymerase chain reaction. Coculture assays of colon cancer cells and Jurkat cells (Fas-sensitive cells) were performed to observe the counterattack of colon cancer cells to lymphocytes. Apoptosis of Jurkat cells were detected by flow cytometry and fluorescence microscopy.

RESULTS

SW480 expressed high FasL and low Fas without drug treatments. When treated with 5-FU, Fas expression rates in SW480 increased, but FasL remained unchanged. Both Fas and FasL increased significantly when treated with MMC and CP. Most importantly, ATRA could induce SW480 cells to differentiate, increase the expression of Fas and decrease the expression of FasL. The coculture of SW480 cells and Jurkat cells confirmed the function of FasL in the SW480 cells.

CONCLUSION

Certain antitumor drugs can change the expression of the Fas system in SW480 cells in different ways. In vitro, MMC and CP can increase the sensitivity of colon cancer cells to apoptosis signals, but they possibly facilitate immune escape of tumor cells. 5-FU results in immune escape of colon cancer cells. ATRA can down-regulate the possibility of counterattack of colon cancer cells.

Addressing the "Fas counterattack" controversy: blocking fas ligand expression suppresses tumor immune evasion of colon cancer in vivo

Fas ligand (FasL/CD95L) is a transmembrane protein belonging to the tumor necrosis factor superfamily that can trigger apoptotic cell death following ligation to its receptor, Fas (CD95/APO-1). Expression of FasL may help to maintain tumor cells in a state of immune privilege by inducing apoptosis of antitumor immune effector cells-the "Fas counterattack." However, the ability of FasL to mediate tumor immune privilege is controversial due to studies that indicate FasL has both pro- and anti-inflammatory activities. To resolve this controversy and functionally define the role of FasL in tumor immune evasion, we investigated if suppression of endogenously expressed FasL in colon tumor cells resulted in reduced tumor development and improved antitumor immune challenge in vivo. Specifically, FasL expression in CMT93 colon carcinoma cells was down-regulated following stable transfection with a plasmid encoding antisense FasL cDNA. Down-regulation of FasL expression had no effect on tumor growth in vitro but significantly reduced tumor development in syngeneic immunocompetent mice in vivo. Tumor size was also significantly decreased. Reduced FasL expression by tumor cells led to increased lymphocyte infiltration. The overall level of neutrophils present in all of the tumors examined was low, with no difference between the tumors, irrespective of FasL expression. Thus, down-regulation of FasL expression by colon tumor cells results in an improved antitumor immune challenge in vivo, providing functional evidence in favor of the "Fas counterattack" as a mechanism of tumor immune evasion.

Mechanism of counterattack of colorectal cancer cell by Fas/Fas ligand system

AIM: To determine the role of Fas/Fas ligand (FasL) in the immune escape of colon cancer cells.

METHODS: Immunohistochemistry was used to observe the expression of Fas and FasL in the tissues of colon cancer patients.In situ hybridization was used to detect the localization of FasL mRNA expression in cancer tissues. Terminal deoxynucleotide transferase-mediated dUTP nick end labeling (TUNEL) assay and CD45 staining were performed to detect the apoptosis of tumor-infiltrating lymphocytes (TILs). Co-culture assays of colon cancer cells (SW480) and Jurkat cells (Fas-sensitive cells) were performed to observe the counterattack of colon cancer cells to lymphocytes.

RESULTS: Of 53 cases of colon carcinomas, 23 cases (43.4%) expressed Fas which was significantly lower as compared to the normal colonic mucosa (73.3%, P<0.01), and 45 cases (84.9%) of colon carcinomas expressed FasL, whereas only two cases (3.75%) in normal mucosa expressed FasL. FasL expression in the colon cancer cells was found to be associated with increased cell death of TILs. The apoptotic rate of TIL in the FasL-positive staining regions of tumor cells was significantly higher than that in the FasL-negative staining region (54.84 ± 2.79% vs 25.73 ± 1.98%, P<0.01). The co-culture of SW480 cells and Jurkat cells confirmed the function of FasL on the SW480 cells. The apoptotic rates of Jurkat cells were found to be related with the amount of SW480 cells.

CONCLUSION: Colon cancer cells can escape the immune surveillance and killing via decreasing Fas expression, and can counterattack the immune system via increasing FasL expression. Fas/FasL can serve as potential targets for effective antitumor therapy.

Targeting the Fas/Fas ligand pathway in cancer

Fas is a transmembrane receptor that can induce apoptosis after cross-linking with either agonistic antibodies or with Fas ligand (FasL). Although originally described as an important regulator of peripheral immune homeostasis, accumulating evidence suggests that the Fas/FasL system plays an important role in tumour development. In addition to its proapoptotic functions, accumulating evidence demonstrates that Fas can activate numerous nonapoptotic signalling pathways, and that activation of these pathways can result in increased tumourigenicity and metastasis. This review summarises the current understanding of the Fas/FasL system in tumorigenesis and discusses attempts to utilise the Fas/FasL system in the treatment of cancer.

Effects of alpha fetoprotein on escape of Bel 7402 cells from attack of lymphocytes

BACKGROUND

Involvement of AFP against apoptosis of tumor cell has been implicated in its evasion of immune surveillance. However, the molecular events of immune escape mechanisms are still unknown. The major observations reported here relate to a possible mechanism by which heptoloma Bel 7402 cells escape immune surveillance in vitro.

METHODS

Western blotting and a well-characterized cofocal scanning image were performed to analyze the expression of Fas/FasL and caspase-3 in co-cultured Bel 7402 and Jurkat cells.

RESULTS

After co-culture with Jurkat cells, up-regulated Fas and reduced FasL expression could be observed. Treatment with AFP could remarkably inhibit the elevated Fas and, whereas, induce the FasL expression in co-cultured Bel 7402 cells. Cells co-culture could induce the expression of caspase-3 in both cells line. The elevated caspase-3 in Bel 7402 cells was abolished following the treatment of AFP. The expression of caspase-3 was elevated in co-cultured Jurkat cells treated with AFP. No detectable change on the expression of survivin was examined in both cells line. Monoclonal antibody against AFP treatment alone did not obviously influence the growth of cells, as well as the expression of Fas/FasL and caspase-3. However, the effect of AFP could be blocked by antibody.

CONCLUSIONS

our results provide evidence that AFP could promote the escape of liver cancer cells from immune surveillance through blocking the caspase signal pathway of tumor cells and triggering the Fas/FasL interaction between tumor cells and lymphocytes.

Effects of alpha fetoprotein on escape of Bel 7402 cells from attack of lymphocytes

BACKGROUND

Involvement of AFP against apoptosis of tumor cell has been implicated in its evasion of immune surveillance. However, the molecular events of immune escape mechanisms are still unknown. The major observations reported here relate to a possible mechanism by which heptoloma Bel 7402 cells escape immune surveillance in vitro.

METHODS

Western blotting and a well-characterized cofocal scanning image were performed to analyze the expression of Fas/FasL and caspase-3 in co-cultured Bel 7402 and Jurkat cells.

RESULTS

After co-culture with Jurkat cells, up-regulated Fas and reduced FasL expression could be observed. Treatment with AFP could remarkably inhibit the elevated Fas and, whereas, induce the FasL expression in co-cultured Bel 7402 cells. Cells co-culture could induce the expression of caspase-3 in both cells line. The elevated caspase-3 in Bel 7402 cells was abolished following the treatment of AFP. The expression of caspase-3 was elevated in co-cultured Jurkat cells treated with AFP. No detectable change on the expression of survivin was examined in both cells line. Monoclonal antibody against AFP treatment alone did not obviously influence the growth of cells, as well as the expression of Fas/FasL and caspase-3. However, the effect of AFP could be blocked by antibody.

CONCLUSIONS

our results provide evidence that AFP could promote the escape of liver cancer cells from immune surveillance through blocking the caspase signal pathway of tumor cells and triggering the Fas/FasL interaction between tumor cells and lymphocytes.

Role of cytokines in promoting immune escape of FasL-expressing human colon cancer cells

AIM: To investigate the potential role of cytokines in promoting Fas ligand (FasL)-expressing colon cancer cells.

METHODS: Immunohistochemical SABC method was used to observe the expression of Fas receptor and ligand in SW620 colon cancer cell line and Jurkat T cells in order to provide the morphological evidence for the functions of Fas receptor and ligand. To examine the cytotoxicity of effector cells, CytoTox96 non-radioactive cytotoxicity assay was adopted to measure the lactate dehydrogenase-releasing value after SW620 cells were co-cultured with Jurkat T lymphocytes.

RESULTS: The FasL of colon cancer SW620 cells was positive. The positive substances were distributed in the cell membrane and cytoplasm. The Fas receptor of colon cancer SW620 cells was negative. The Fas receptor and ligand of Jurkat T lymphocytes turned out to be positive. The positive substances were distributed in the cell membrane. After phytohemagglutinin (PHA)-stimulated Jurkat T lymp-hocytes were co-cultured with phorbol 12-myristate 13-acetate (PMA)-plus-ionomycin-stimulated (for 48 h) SW620 cells or tumor necrosis factor-alpha (TNF-α)-stimulated (for 48 h) SW620 cells or unstimulated SW620 cells for 4 h, the cytotoxicity of SW620 cells to PHA-stimulated Jurkat cells at effector-to-target ratios of 10:1, 5:1, 2.5:1, and 1.25:1 was 74.6%, 40.8%, 32.4%, and 10.9% (F = 8.19, P < 0.05); or 54.9%, 35.3%, 22.0%, and 10.3% (F = 11.12, P < 0.05); or 14.9%, 10.5%, 6.9%, and 5.8% (F = 3.45, P < 0.05). After PHA-stimulated Jurkat T lymphocytes were co-cultured with unstimulated SW620 cells for 8 h, the cytotoxicity of SW620 cells to PHA-stimulated Jurkat cells at effector-to-target ratios of 5:1, 2.5:1, and 1.25:1 from the experiment was 83.9%, 74.1%, and 28.5% (F = 137.04, P < 0.05) respectively. Non-radioactive cytotoxicity assay showed that the apoptotic rate of Jurkat cells remarkably increased with the increase of planting concentration of SW620 cells and co-culture time after the SW620 cells were co-cultured with the Jurkat T lymphocytes. The cytotoxicity was significantly enhanced by PMA+ionomycin or TNF-α.

CONCLUSION: The FasL expressed in human colon cancer cells may be regulated by endogenous factors in the microenvironment of the host and facilitate the escape of tumor cells from the host immune system.

Action and mechanism of Fas and Fas ligand in immune escape of gallbladder carcinoma

AIM: To study the role of Fas and Fas ligand (FasL) in biological behaviors of gallbladder carcinoma, and their correlated action and mechanism in tumor escape.

METHODS: Streptavidin-biotin-peroxidase immunohisto-chemistry technique was used to study the expression of Fas and FasL protein in 26 gallbladder carcinoma tissues, 18 gallbladder adenoma tissues, 3 gallbladder dysplasia tissues and 20 chronic cholecystitis tissues. Apoptosis of the infiltrating lymphocytes in these tissues was studied by terminal deoxynucleotidyl transferase (TdT)-mediated dUTP nick-end labeling (TUNEL) method. Expression of both proteins and apoptosis of the tumor infiltrating lymphocytes in cancer tissues of primary foci was compared with clinicopathological features of gallbladder carcinoma.

RESULTS: The positive rates of Fas were not significantly different among carcinoma, adenoma, dysplasia and chronic cholecystitis. The positive rate of FasL in carcinoma was significantly higher than that in chronic cholecystitis (χ² = 4.89, P<0.05). The apoptotic index (AI) in carcinoma was significantly higher than that in adenoma (t’ = 4.19, P<0.01) and chronic cholecystitis (t’ = 8.06, P<0.01). The AI was significantly lower in well-differentiated carcinoma and Nevin I-III carcinoma than that in poorly-differentiated carcinoma (t’ = 2.63, P<0.05) and Nevin IV-V carcinoma (t’ = 3.33, P<0.01). The confidence interval (CI) of infiltrating lymphocytes in adenoma, chronic cholecystitis, well-differentiated carcinoma and Nevin I-III carcinoma was very significantly lower than that in carcinoma (t’ = 6.99, P<0.01), adenoma (t’ = 3.66, P<0.01), poorly-differentiated carcinoma (t’ = 5.31, P<0.01) and Nevin IV-V carcinoma (t’ = 3.76, P<0.01), respectively. The CI of apoptosis of infiltrating lymphocytes in well-differentiated carcinoma was significantly lower than that in poorly-differentiated carcinoma (t = 2.52, P<0.05), and was not significantly lower in Nevin I-III carcinoma than in Nevin IV-V carcinoma (t = 1.42, P>0.05). Apoptosis of infiltrating lymphocytes was not discovered in adenoma and chronic cholecystitis.

CONCLUSION: FasL expressed in gallbladder carcinoma cells permits tumor cells to escape from immune surveillance of organism by inducing apoptosis in infiltrating lymphocytes of carcinoma tissues. Up-regulation of FasL expression plays an important role in invasive depth, histological classification and metastasis of gallbladder carcinoma.

Fas ligand expression in colon cancer: A possible mechanism of tumor immune privilege

AIM: To detect the expression of Fas ligand (FasL) in colon cancer tissues and cell lines and analyze the function of FasL-expressing colon cancer cells in inducing Fas-sensitive T lymphocyte apoptosis.

METHODS: Ninety surgically resected colon cancer tissues and 15 hepatic metastasis specimens were investigated by immunohistochemical method with normal colon mucosa and colon adenoma as control. The relationship between FasL expression and pathologic features was also analyzed. FasL expression of 4 colon cancer cell lines, SW620, Lovo, LS-174T and SW1116, were detected by Western blotting assay. The function of FasL expressed on colon cancer cells was determined by coculture assay with Jurkat T lymphocytes, the apoptotic rate of which was detected by flow cytometry assay.

RESULTS: Fifty-six (62.22%) cases of all the 90 colon cancer tissues and all (100%) the liver metastasis specimens expressed FasL, significantly higher than normal colon mucosa and colonic adenoma. Higher expression of FasL was found in more advanced stage of colon cancer and in cancer tissues with lymphatic or hepatic metastasis. All the colon cancer cell lines were found to express FasL. After coculture with the SW1116 cells for 24 h with an effector: target ratio 10:1, the rate of apoptosis of Jurkat cells rose from 1.9% to 21.0%.

CONCLUSION: The expression of FasL is upregulated in colon cancer and the functionally expressed FasL can induce apoptosis of Fas-expressing T lymphocytes.

Fas Ligand as a Tool for Immunosuppression and Generation of Immune Tolerance

The role of Fas ligand (FasL) in physiologically limiting immune responses and maintaining immune-privileged sites has led to a body of research aiming to confer protection to allogeneic grafts by expressing FasL on the allogeneic tissue or by administrating FasL-transduced donor dendritic cells. In addition, several studies have used FasL to abrogate autoimmune responses. This review presents the results of these studies and discusses the problems associated with FasL usage.

The Fas signalling pathway and its role in the pathogenesis of cancer

Tumor cells frequently exhibit de novo expression of Fas ligand (FasL/CD95L). Coupled with resistance to Fas-mediated apoptosis, FasL expression enables many cancers to deliver a pre-emptive strike or 'counterattack' against the immune system. New studies also indicate that FasL expression on tumor cells could confer a double advantage to these cells by stimulating their own proliferation. However, pro-inflammatory effects of FasL have also been observed. New findings are beginning to reconcile the paradoxical effects of FasL, with the clinical significance of the Fas counterattack only beginning to emerge.

Relationship between expression of functional Fas ligand in human colon cancer cells and tumor's immune escape

AIM: The evidence has pointed to an abnormal increase in apoptosis among activated Fas-positive lymphocytes, mainly in the periphery of the Fas ligand (FasL)-expressing tumors. On the other hand, to a great extent, the occurrence of tumor is due to the fact that the converted cells cannot undergo a normal process of apoptosis. This study was designed to detect the expression of FasL in human colon carcinoma cells and to determine whether colon cancer cells SW620 could induce apoptosis of lymphocytes by Fas system in vitro.

METHODS: By using immunohistochemical SABC method, the expression of Fas receptor and Fas ligand in SW620 colon carcinoma cell line and Jurkat T cells was observed so as to supply morphological evidence for the functions of Fas receptor and Fas ligand. In an effort to examine the cytotoxicity of effector cells, CytoTox 96â non-radioactive cytotoxicity assay was adopted to measure LDH releasing value after the SW620 cells were co-cultured with the Jurkat T lymphocytes.

RESULTS: It was shown that the Fas ligand of colon carcinoma SW620 cells was positive and the positive substances were distributed in the cell membrane and cytoplasm, and the Fas receptor of colon carcinoma SW620 cells was negative. The Fas receptor and the Fas ligand of Jurkat T lymphocytes turned out to be positive. The positive substances were distributed in the cell membrane. The non-radioactive cytotoxicity assay showed that the apoptotic rate of Jurkat cells remarkably increased with the increase of planting concentration of SW620 and co-cultured time with the Jurkat T lymphocytes. The cytotoxicity was significantly enhanced by PMA and ionomycin.

CONCLUSION: The functional expression of FasL in the colon carcinoma SW620 cells can inversely induce apoptosis of Fas-expressing Jurkat T lymphocytes for immune escape.