FasL is more frequently expressed in liver metastases of colorectal cancer than in matched primary carcinomas

The role of CD95 and CD95 ligand in cancer

CD95 (Fas/APO-1) and its ligand, CD95L, have long been viewed as a death receptor/death ligand system that mediates apoptosis induction to maintain immune homeostasis. In addition, these molecules are important in the immune elimination of virus-infected cells and cancer cells. CD95L was, therefore, considered to be useful for cancer therapy. However, major side effects have precluded its systemic use. During the last 10 years, it has been recognized that CD95 and CD95L have multiple cancer-relevant nonapoptotic and tumor-promoting activities. CD95 and CD95L were discovered to be critical survival factors for cancer cells, and were found to protect and promote cancer stem cells. We now discuss five different ways in which inhibiting or eliminating CD95L, rather than augmenting, may be beneficial for cancer therapy alone or in combination with standard chemotherapy or immune therapy.

Apolipoprotein A1 as a potential biomarker in the ascitic fluid for the differentiation of advanced ovarian cancers

CONTEXT

Primary ovarian cancer and ovarian metastasis from non-ovarian cancers in advanced stage are closely mimicking conditions whose therapeutics and prognosis are different.

OBJECTIVE

To identify biomarkers that can differentiate the two variants of advanced ovarian cancers.

METHODS

Gel-based proteomics and antibody-based assays were used to study the differentially expressed proteins in the ascitic fluid of fourteen patients with advanced ovarian cancers.

RESULTS

Programmed Cell Death 1-Ligand 2, apolipoprotein A1, apolipoprotein A4 and anti-human fas antibody are differentially expressed proteins.

CONCLUSIONS

Apolipoprotein A1 with a 61.8 ng/ml cut-off is a potential biomarker with the best differentiating statistical parameters.

Prognostic value of the Fas/Fas ligand system in breast cancer

Fas and its ligand (FasL) are known to play a crucial role in the genetically controlled mechanism of cell death, and their deregulation in cancer cells is involved in the immune escape of the tumor. The aim of this review is to analyze the current knowledge on the prognostic value of Fas/FasL in breast cancer patients. Both the results of other authors and our own experiences indicate that the lack of Fas ligand, and particularly Fas, is related to a significantly worse prognosis. It probably results from the resistance of Fas-deficient breast tumors to the mechanisms of apoptosis. On the other hand, some results suggest that the Fas/FasL-dependent mechanisms of tumor spread may be different for various target tissues. The expression of the Fas/Fas-ligand system has potential prognostic application in view of current knowledge, and consequently should be considered as an additional prognostic factor in breast cancer patients.

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.

Apoptosis: why and how does it occur in biology?

The literature on apoptosis has grown tremendously in recent years, and the mechanisms that are involved in this programmed cell death pathway have been enlightened. It is now known that apoptosis takes place starting from early development to adult stage for the homeostasis of multicellular organisms, during disease development and in response to different stimuli in many different systems. In this review, we attempted to summarize the current knowledge on the circumstances and the mechanisms that lead to induction of apoptosis, while going over the molecular details of the modulator and mediators of apoptosis as well as drawing the lines between programmed and non-programmed cell death pathways. The review will particularly focus on Bcl-2 family proteins, the role of different caspases in the process of apoptosis, and their inhibitors as well as the importance of apoptosis during different disease states. Understanding the molecular mechanisms involved in apoptosis better will make a big impact on human diseases, particularly cancer, and its management in the clinics.

CD95 is a key mediator of invasion and accelerated outgrowth of mouse colorectal liver metastases following radiofrequency ablation

BACKGROUND & AIMS

Recently, we have shown that micro-metastases, in the hypoxic transition zone surrounding lesions generated by radiofrequency ablation (RFA), display strongly accelerated outgrowth. CD95 is best known for its ability to induce apoptosis but can also promote tumorigenesis in apoptosis-resistant tumor cells. Therefore, we tested whether CD95 signaling plays a role in accelerated outgrowth of colorectal liver metastases following RFA.

METHODS

Hypoxia-induced invasion was assessed in three-dimensional EGFP-expressing C26 tumor cell cultures by confocal microscopy. CD95 localization was tested by immunofluorescence. Invasion and outgrowth of liver metastases following RFA were analyzed by post-mortem confocal microscopy and by morphometric assessment of tumor load. Neutralization of CD95L was performed by using antibody MFL4. CD95 was suppressed by lentiviral RNA interference. The role of host CD95L was assessed using gld mice.

RESULTS

Micro-metastases in the hypoxic transition zone following RFA displayed a highly invasive phenotype and increased expression of CD95 and CD95L. Hypoxia-induced tumor cell invasion in vitro increased the expression of CD95 and CD95L and induced translocation of CD95 to the invasive front. In vitro invasion, metastasis invasion, and accelerated tumor growth in the transition zone were strongly suppressed by neutralizing CD95L or by suppressing tumor cell CD95. In contrast, metastasis invasion and outgrowth were unaffected in gld mice.

CONCLUSIONS

Hypoxia causes autocrine activation of CD95 on colorectal tumor cells, thereby promoting local invasion and accelerated metastasis outgrowth in the hypoxic transition zone following RFA. Further pre-clinical work is needed to assess the role of CD95L neutralization, either alone or in combination with chemotherapy, in limiting aggressive recurrence of liver metastases following RFA.

Current hypotheses on how microsatellite instability leads to enhanced survival of Lynch Syndrome patients

High levels of microsatellite instability (MSI-high) are a cardinal feature of colorectal tumors from patients with Lynch Syndrome. Other key characteristics of Lynch Syndrome are that these patients experience fewer metastases and have enhanced survival when compared to patients diagnosed with microsatellite stable (MSS) colorectal cancer. Many of the characteristics associated with Lynch Syndrome including enhanced survival are also observed in patients with sporadic MSI-high colorectal cancer. In this review we will present the current state of knowledge regarding the mechanisms that are utilized by the host to control colorectal cancer in Lynch Syndrome and why these same mechanisms fail in MSS colorectal cancers.

Oncogenic K-Ras turns death receptors into metastasis-promoting receptors in human and mouse colorectal cancer cells

BACKGROUND & AIMS

Death receptors expressed on tumor cells can prevent metastasis formation by inducing apoptosis, but they also can promote migration and invasion. The determinants of death receptor signaling output are poorly defined. Here we investigated the role of oncogenic K-Ras in determining death receptor function and metastatic potential.

METHODS

Isogenic human and mouse colorectal cancer cell lines differing only in the presence or absence of the K-Ras oncogene were tested in apoptosis and invasion assays using CD95 ligand and tumor necrois factor-related apoptosis-inducing ligand (TRAIL) as stimuli. Metastatic potential was assessed by intrasplenic injections of green fluorescent protein- or luciferase-expressing tumor cells, followed by intravital fluorescence microscopy or bioluminescence imaging, and confocal microscopy and immunohistochemistry. Ras-effector pathway control of CD95 output was assessed by an RNA-interference and inhibitor-based approach.

RESULTS

CD95 ligand and TRAIL stimulated invasion of colorectal tumor cells and liver metastases in a K-Ras-dependent fashion. Loss of mutant K-Ras switched CD95 and TRAIL receptors back into apoptosis mode and abrogated metastatic potential. Raf1 was essential for the switch in CD95 function, for tumor cell survival in the liver, and for K-Ras-driven formation of liver metastases. K-Ras and Raf1 suppressed Rho kinase (ROCK)/LIM kinase-mediated phosphorylation of the actin-severing protein cofilin. Overexpression of ROCK or LIM kinase allowed CD95L to induce apoptosis in K-Ras-proficient cells and prevented metastasis formation, whereas their suppression protected K-Ras-deficient cells against apoptosis.

CONCLUSIONS

Oncogenic K-Ras and its effector Raf1 convert death receptors into invasion-inducing receptors by suppressing the ROCK/LIM kinase pathway, and this is essential for K-Ras/Raf1-driven metastasis formation.

Fas/CD95 deficiency in ApcMin/+ mice increases intestinal tumor burden

BACKGROUND

Fas, a member of the tumor necrosis family, is responsible for initiating the apoptotic pathway when bound to its ligand, Fas-L. Defects in the Fas-mediated apoptotic pathway have been reported in colorectal cancer.

METHODOLOGY/PRINCIPAL FINDINGS

In the present study, a variant of the Apc(Min/+) mouse, a model for the human condition, Familial Adenomatous Polyposis (FAP), was generated with an additional deficiency of Fas (Apc(Min/+)/Fas(lpr)) by cross-breeding Apc(Min/+) mice with Fas deficient (Fas(lpr)) mice. One of the main limitations of the Apc(Min/+) mouse model is that it only develops benign polyps. However, Apc(Min/+)/Fas(lpr) mice presented with a dramatic increase in tumor burden relative to Apc(Min/+) mice and invasive lesions at advanced ages. Proliferation and apoptosis markers revealed an increase in cellular proliferation, but negligible changes in apoptosis, while p53 increased at early ages. Fas-L was lower in Apc(Min/+)/Fas(lpr) mice relative to Apc(Min/+) cohorts, which resulted in enhanced inflammation.

CONCLUSIONS/SIGNIFICANCE

This study demonstrated that imposition of a Fas deletion in an Apc(Min/+) background results in a more aggressive phenotype of the Apc(Min/+) mouse model, with more rapid development of invasive intestinal tumors and a decrease in Fas-L levels.

Expression of TNF-related apoptosis-inducing ligand (TRAIL) in keratinocytes mediates apoptotic cell death in allogenic T cells

The objective of the present study was to evaluate the aptitude of TRAIL gene expression for inducing apoptosis in co-cultivated T-cells. This should allow preparing a strategy for the development of a durable, allogenic skin substitute based on the induction of an immune-privileged transplant. In order to counteract the significant potential of rejection in transplanted allogenic keratinocytes, we created a murine keratinocyte cell line which expressed TRAIL through stable gene transfer. The exogenic protein was localized on the cellular surface and was not found in soluble condition as sTRAIL. Contact to TRAIL expressing cells in co-culture induced cell death in sensitive Jurkat-cells, which was further intensified by lymphocyte activation. This cytotoxic effect is due to the induction of apoptosis. We therefore assume that the de-novo expression of TRAIL in keratinocytes can trigger apoptosis in activated lymphocytes and thus prevent the rejection of keratinocytes in allogenic, immune-privileged transplants.

The immune system and cancer

Cancer patients mount adaptive immune responses against their tumor. However, while tumor-infiltrating lymphocytes and natural-killer (NK) cells try to detect and eliminate malignant cells, they eventually fail when these malignant cells develop mechanisms to evade effective immunosurveillance. First, malignant cells produce immunosuppressive cytokines and prostaglandins that skew the immune response toward a Th2 response, resulting in a humoral response with significantly less antitumor capacities, generating a low interleukin-2 environment blocking NK cell division, T-helper cell proliferation, and T-cytotoxic cell proliferation and function. Second, immunoresistant malignant cell variants emerge through selection of major histocompatibility class I and II and antigen-processing mutants reducing antigenicity. Finally, malignant cells may actively eliminate T-cells via activation-induced cell death or by mounting a counterattack through Fas ligand expression.

Prostaglandin E2 stimulates Fas ligand expression via the EP1 receptor in colon cancer cells

Fas ligand (FasL/CD95L) is a member of the tumour necrosis factor superfamily that triggers apoptosis following crosslinking of the Fas receptor. Despite studies strongly implicating tumour-expressed FasL as a major inhibitor of the anti-tumour immune response, little is known about the mechanisms that regulate FasL expression in tumours. In this study, we show that the cyclooxygenase (COX) signalling pathway, and in particular prostaglandin E₂ (PGE₂), plays a role in the upregulation of FasL expression in colon cancer. Suppression of either COX-2 or COX-1 by RNA interference in HCA-7 and HT29 colon tumour cells reduced FasL expression at both the mRNA and protein level. Conversely, stimulation with PGE₂ increased FasL expression and these cells showed increased cytotoxicity against Fas-sensitive Jurkat T cells. Prostaglandin E₂-induced FasL expression was mediated by signalling via the EP1 receptor. Moreover, immunohistochemical analysis using serial sections of human colon adenocarcinomas revealed a strong positive correlation between COX-2 and FasL (r=0.722; P<0.0001) expression, and between EP1 receptor and FasL (r=0.740; P<0.0001) expression, in the tumour cells. Thus, these findings indicate that PGE₂ positively regulates FasL expression in colon tumour cells, adding another pro-neoplastic activity to PGE₂.

Progress in studies on the Fas/FasL expression system and colon carcinoma

Cell apoptosis or programmed cell death is the term used to describe active cell death to maintain stability under physiological and pathological conditions. Interaction of the death receptor and death ligand is one of the main ways to induce apoptosis, of which, the Fas/FasL system is considered as the major signal transduction pathway to mediate apoptosis. Colon carcinoma is one of the common malignant tumors that are a threat to human health. The occurrence and development of colon carcinoma is related to the regulation imbalance of cell apoptosis. This article reviews the relationship between the Fas/FasL expression system and the occurrence and development of colon carcinoma.

The role of death receptor ligands in shaping tumor microenvironment

Death receptor ligands (FasL, TRAIL) activate apoptosis in cells expressing the cognate receptors. Evidence suggests that these ligands also deliver pro-inflammatory signals. In the tumor microenvironment, "Fas counterattack" mounted by tumors against immune cells is mediated by tumor-associated FasL. But death ligands crosslinking their receptors also induce inhibition of apoptosis and activation of the transcription factor, NFkappaB, with a subsequent burst of pro-inflammatory cytokine production and tumor growth promotion. NFkappaB, a key link between inflammation and cancer, regulates dual activities of death ligands, depending on molecular signals in the tumor microenvironment. This paper focuses on death ligands as an example of the extensive repertoire of strategies devised by tumors for escape from immune control.

Biology of colorectal liver metastases: A review

Metastatic growth is a selective, non-random process, which in the case of colorectal cancer, frequently occurs in the liver and is the major cause of cancer related death in these patients. This review summarises attempts to find biological and molecular markers of metastasis and their role in establishment of secondary tumours. Recent evidence suggests that liver metastases are phenotypically different to the primary from which they were derived and thus represent a separate disease entity.

Colon cancer and apoptosis

BACKGROUND

The implementation of new therapeutic options for the management of metastatic colon cancer mandates a revisit to apoptosis and its role in colon cancer tumorigenesis with an emphasis on the mechanisms leading to chemotherapeutic resistance and immune system evasion of colon cancer cells.

DATA SOURCES

Literature regarding molecular apoptosis mechanisms and the role of apoptosis in colon cancer progression are reviewed by this article.

CONCLUSION

Programmed cell death has rapidly emerged as a potential target for cancer treatment at various stages of tumor progression. Chemoprevention, immuno-regulation, and metastasis are prospective targets by which apoptotic mechanisms could be utilized in the prevention and management of tumorigenesis. Understanding how defects in the death receptor pathway of apoptosis permit colon cancer cells to escape the immune system would allow for treatment options whereby the body's immune system could again recognize and eliminate unwanted cells.

The role of the tumor necrosis factor (TNF)--Fas L and HCV in the development of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a major public health problem in Egypt due to the high prevalence of hepatitis C viral (HCV) infection. The mechanism by which HCV exerts its carcinogenic effect on the liver is not yet understood. Previous research has suggested that perturbations of the Fas-Fas L tumor necrosis system could result in uncontrolled cancerous cell growth in the liver. This study aims to assess the relationship of Fas ligand (Fas L) to HCC. A total of 28 cases (HCC) and 56 controls (28 cirrhosis and 28 chronic hepatitis) were included in the study. Sera and tissue biopsies were tested for HCV antibody and HCV-RNA. Fas ligand expression in tissue was examined immunohistochemically using a rabbit purified polyclonal antibody. Levels of soluble Fas L were determined in serum by ELISA. The HCC cases were graded as: 17.9% Grade I, 32.1% Grade II, 35.7% Grade III and 14.3% were Grade IV. Among the cases, 81% had evidence of cirrhosis. All the cases and controls were positive for HCV-RNA. Tissue and serum PCR results were identical within the same subjects. Fas ligand cytoplasmic expression was more pronounced in HCC than in cirrhosis, and in cirrhosis more than in chronic hepatitis. This expression was higher with increasing grades of malignancy and in tissues adjacent to the tumor, than in those without nearby tumor. Soluble Fas L levels were higher in cases than in controls, with similar results as that of immunohistochemical expression. These results suggest that HCV and Fas ligand play a key role in hepatocarcinogenesis, consistent with the hypothesis that HCV induces overexpression of Fas ligand in the liver cells, resulting in escape from killing by the immune system cells, with subsequent uncontrolled growth of tissue and the development of malignancy.

Prognostic impact of FAS/CD95/APO-1 in urothelial cancers: decreased expression of Fas is associated with disease progression

The death receptor Fas (Apo1/CD95) and Fas ligand (FasL) system is recognised as a major pathway for the induction of apoptosis in vivo, and antiapoptosis via its blockade plays a critical role in carcinogenesis and progression in several malignancies. However, the function of Fas–FasL system in urothelial cancer (UC) has not been elucidated. We therefore investigated the expression of Fas, FasL and Decoy receptor 3 for FasL (DcR3) in UC specimens and cell lines, and examined the cytotoxic effect of an anti-Fas-activating monoclonal antibody (mAb) in vitro. Immunohistochemical examinations of Fas-related molecules were performed on 123 UC and 30 normal urothelium surgical specimens. Normal urothelium showed Fas staining in the cell membrane and cytoplasm. In UC, less frequent Fas expression was significantly associated with a higher pathological grade (P<0.0001), a more advanced stage (P=0.023) and poorer prognosis (P=0.010). Fas and the absence thereof were suggested to be crucial factors with which to select patients requiring more aggressive treatment. Moreover, low-dose anti-Fas-activating mAb sensitised resistant cells to adriamycin, and this synergistic effect could be applied in the development of new treatment strategy for UC patients with multidrug-resistant tumours.

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.

Control of colorectal metastasis formation by K-Ras

Mutational activation of the K-Ras proto-oncogene is frequently observed during the very early stages of colorectal cancer (CRC) development. The mutant alleles are preserved during the progression from pre-malignant lesions to invasive carcinomas and distant metastases. Activated K-Ras may therefore not only promote tumor initiation, but also tumor progression and metastasis formation. Metastasis formation is a very complex and inefficient process: Tumor cells have to disseminate from the primary tumor, invade the local stroma to gain access to the vasculature (intravasation), survive in the hostile environment of the circulation and the distant microvascular beds, gain access to the distant parenchyma (extravasation) and survive and grow out in this new environment. In this review, we discuss the potential influence of mutant K-Ras on each of these phases. Furthermore, we have evaluated the clinical evidence that suggests a role for K-Ras in the formation of colorectal metastases.

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.

Bile salt-induced apoptosis in human colon cancer cell lines involves the mitochondrial transmembrane potential but not the CD95 (Fas/Apo-1) receptor

BACKGROUND AND AIMS

Depending on their physico-chemical characteristics, bile acids can be potent inducers of apoptosis in colon cancer cells. This observation contrasts with bile acids being promoters of colorectal cancer carcinogenesis. Our recent observation of caspase activation in deoxycholate (DC)-treated colon cancer cell lines prompted us to analyze the mechanisms of bile acid-induced colon cancer cell death.

METHODS

CD95 expression was correlated to DC-induced cell death in four colon cancer cell lines. Mitochondrial transmembrane potential (MTP) was determined in whole cells as well as in isolated mitochondria.

RESULTS

On 2 of the 4 human colon cancer cell lines investigated, no CD95 was detected. These data were supported by a lack of CD95 mRNA in those cell lines that did not express CD95 on their surface. The apoptotic response to bile acids did not correlate with CD95 receptor expression on the respective cell lines. Therefore, we analyzed the MTP after the addition of toxic bile acids. MTP was destabilized early after the addition of deoxycholate to SW480 cells. These data were confirmed in isolated mitochondria, which showed strong swelling after the addition of DC. Accordingly, release of cytochrome-c from the mitochondrial intermembrane space into the cytosol, indicating dissipation of the MTP, and subsequent caspase-3 cleavage were detectable as early as 3 min after the addition of DC.

CONCLUSION

In contrast to hepatocytes and hepatic carcinoma cell lines, DC induces apoptosis in colon cancer cell lines via a CD95 receptor-independent mechanism. Direct induction of the mitochondrial permeability transition by toxic bile acids is suggested as the apoptosis-inducing mechanism in colon cancer cells.

FAS and FAS-L expression by tumor cells and lymphocytes in breast carcinomas and their lymph node metastases

FAS receptor (FAS, CD95) and FAS ligand (FAS-L, CD95-L) are complementary members of a particular apoptotic pathway that plays a major role in immune regulation. The activation of FAS-L may trigger cytotoxic mechanisms leading to the death of FAS-expressing cells. Tumor cells and tumor-infiltrating lymphocytes (TIL) may express FAS and FAS-L in various proportions, and their interplay may affect tumor behavior. In the present study, we explored the expression of FAS and FAS-L in 28 mammary carcinomas (19 ductal and 9 lobular) and in their lymph node metastases. The expression of these mediators in immunostained sections was graded and evaluated comparatively between normal and neoplastic mammary epithelium, between tumor cells and TILs, and between mammary carcinoma cells and their lymph node metastases. We demonstrated the coexpression of FAS and FAS-L by breast carcinoma cells and TIL, with FAS expressed more strongly by normal epithelial cells and TIL than tumor cells. FAS-L was better stained on tumor cells than on TIL. There was equal or greater expression of FAS and FAS-L in the primary tumors and their TIL than in the metastatic counterparts. Comparing the expression of FAS with that of FAS-L, we recorded FAS equal or stronger than FAS-L in the primary mammary tumors and the reversal of their expression, FAS-L greater than FAS in the lymph node metastases. These results are consistent with reports of studies with other tumors, suggesting that the upregulated FAS-L indicates an increased ability of tumor cells to induce apoptosis in TIL and in the normal tissues invaded. However, it is understood that the FAS/FAS-L system, although essential for apoptosis, is only a contributing factor to the complex process of tumor invasion and antitumor defense.

Autocrine secretion of Fas ligand shields tumor cells from Fas-mediated killing by cytotoxic lymphocytes

Mechanisms responsible for resistance of tumors to death receptor-mediated damage by cytotoxic lymphocytes are not well understood. Uveal melanoma cells expressed Fas but were insensitive to Fas triggering induced by bystander cytotoxic T lymphocytes or a Fas-specific agonistic antibody; this could not be ascribed to tumor counterattack against T cells or general resistance of the tumors to apoptosis. Treatment with inhibitors of metalloproteases rendered uveal melanomas sensitive to Fas-mediated cytotoxicity. Metalloprotease inhibitors did not affect the expression of Fas but increased the surface expression of Fas ligand (FasL), which correlated with the disappearance of soluble FasL from culture supernatants of tumor cells. FasL eluted from the surface of uveal melanomas specifically inhibited cytotoxic T lymphocyte lysis of tumor cells pretreated with an inhibitor of metalloproteases. In addition to uveal melanomas, a number of other tumor cell lines of various cellular origins were sensitized to Fas-mediated cytotoxicity by metalloprotease inhibitors. Our results show that autocrine secretion of FasL shields tumor cells from Fas-mediated killing by cytotoxic lymphocytes. This defines a novel mechanism of tumor escape from immune surveillance.

Prognostic implications of Fas-ligand expression in nasopharyngeal carcinoma

BACKGROUND

In nasopharyngeal carcinoma (NPC), Fas-ligand (Fas-L)-mediated apoptosis might contribute to the immune privilege of tumors. In some cancers, dysregulation of Fas-L protein in tumors might lead to disease progression. The purpose of this study was to evaluate the correlations between Fas-L expression and the clinical outcomes in patients with NPC.

METHODS

We recruited 78 patients with primary NPC, classified clinical stages according to the 1997 American Joint Committee on Cancer staging system, and assessed Fas-L with immunohistochemical methods.

RESULTS

Forty-one (53%) of 78 patients were Fas-L-positive. The prevalence was 0%, 57%, 58%, and 82% from stages I to IV, respectively (p <.001). Fas-L expression was associated with the N classification (p=.05) but not the T classification. Patients with positive Fas-L expression had a lower rate of disease-free survival and overall survival (p=.01 for all log-rank tests).

CONCLUSION

Patients with NPC with Fas-L-positive tumors had higher clinical stages and lymph node metastasis at diagnosis and poorer disease-free survival and overall survival; therefore, Fas-L expression may be a potential biomarker of prognosis.

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.

Tumour-induced apoptosis in human mesothelial cells: a mechanism of peritoneal invasion by Fas Ligand/Fas interaction

Gastrointestinal carcinomas frequently disseminate within the abdominal cavity to form secondary peritoneal metastases. Invasion of the peritoneal mesothelium is fundamental to this process, yet the underlying invasive mechanisms remain unclear. Preliminary in vitro work suggested that tumour cells can induce mesothelial apoptosis, representing a novel mechanism of peritoneal invasion. We examined the role of tumour cell-induced mesothelial apoptosis and explored the role of the death ligand/receptor system, Fas Ligand/Fas, as mediators of the apoptotic process. Cultured human mesothelial cells were used to establish in vitro co-culture models with the SW480 colonic cancer cell line. Tumour-induced mesothelial apoptosis was confirmed by phase-contrast microscopy and apoptotic detection assays. Human mesothelial cells and SW480 tumour cells constitutively expressed Fas and Fas Ligand mRNA and protein as determined by RT-PCR and confocal fluorescent microscopy. Stimulation of human mesothelial cells with anti-Fas monoclonal antibody or crosslinked soluble Fas Ligand-induced apoptosis, confirming the functional status of the Fas receptor. Pretreatment of SW480 cells with a blocking recombinant anti-Fas Ligand monoclonal antibody significantly reduced mesothelial apoptosis, indicating that tumour-induced mesothelial apoptosis may, in part, be mediated via a Fas-dependent mechanism. This represents a novel mechanism of mesothelial invasion and offers several new targets for therapeutic intervention.

Ki-67 and CEA expression as prognostic markers in Dukes' C colorectal cancer

This study investigated the relationship between clinicopathological or immunohistochemical factors and postoperative prognosis for Dukes' C colorectal cancer. Short-term survivors died from cancer within 2 years of surgery, whereas long-term survivors were disease-free for over 10 years. The groups differed in Ki-67 antigen and CEA expression in colon cancer, and CEA expression in rectal cancer that was limited to the metastatic lymph nodes. The immunohistochemical scores were higher in short-term survivors. Our data suggest that the characteristics of metastatic lymph nodes are important as a predictor of the aggressiveness of tumor behavior and that the expression of Ki-67 antigen or CEA there may be a useful indicators of patients' survival in Dukes' C colorectal cancer.

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

Many cancers express Fas ligand (FasL/CD95L) in vivo, and can kill lymphoid cells by Fas-mediated apoptosis in vitro. However, overexpression of recombinant FasL in murine tumour allografts revealed a potential antitumour effect of FasL, via recruitment of neutrophils. Transforming growth factor-β1 (TGF-β1) could inhibit these neutrophil-stimulatory effects of FasL. In the present study, we sought to determine directly whether FasL contributes to immune privilege or tumour rejection in human colon cancers in vivo, and whether TGF-β1 regulates FasL function. Serial tumour sections were immunostained for FasL and TGF-β1. Neutrophils and tumour infiltrating lymphocytes (TILs) were detected by immunohistochemistry for lactoferrin and CD45, respectively. Apoptotic TIL were identified by dual staining for TUNEL/CD45. FasL expression by nests of tumour cells was associated with a mean four-fold depletion of TILs (range 1.8–33-fold, n=16, P<0.001), together with a two-fold increase in TIL apoptosis (range 1.6–2.5-fold, n=14, P<0.001), relative to FasL-negative nests within the same tumours. The overall level of neutrophils present in all tumours examined was low (mean 0.3%, n=16), with FasL expression by tumour nests associated with a mean two-fold decrease in neutrophils, irrespective of TGF-β1 expression. Together, our results suggest that tumour-expressed FasL is inhibitory rather than stimulatory towards antitumour immune responses.

Fas ligand expressed in colon cancer is not associated with increased apoptosis of tumor cells in vivo

Expression of Fas ligand (FasL/CD95L) may help to maintain colon cancers in a state of immune privilege by inducing apoptosis of antitumor immune effector cells. Colon tumor-derived cell lines appear to be relatively insensitive to apoptosis mediated by their own or exogenous FasL in vitro, despite expression of cell surface Fas. In our present study, we sought to investigate if FasL upregulated in human colon cancers leads to any increase in apoptosis of the tumor cells in vivo. FasL and Fas receptor (APO-1/CD95) expression by tumor cells were detected immunohistochemically. Apoptotic tumor cell death was detected by immunohistochemistry for caspase-cleaved cytokeratin-18. FasL expression did not correlate with the extent of apoptosis of tumor cells. There was no significant local difference in the frequency of apoptosis of tumor cells between tumor nests that expressed FasL (mean = 2.4%) relative to those that did not (mean = 2.6%) (p = 0.625, n = 10; Wilcoxon signed rank). FasL expressed by the tumor cells appeared to be functional, since FasL expression in tumor nests correlated with diminished infiltration of tumor-infiltrating lymphocytes (TILs). TILs were detected using immunohistochemistry for CD45. Expression of FasL by tumor nests was associated with a mean 4-fold fewer TILs relative to FasL-negative nests (range 2.4-33-fold, n = 10, p < 0.003). Together, our results indicate that colon tumors are insensitive to FasL-mediated apoptosis in vivo.

Co-expression of Fas (APO-1, CD95)/Fas ligand by BeWo and NJG choriocarcinoma cell lines

OBJECTIVE

Fas (CD95) is a transmembrane protein of the tumor necrosis factor receptor superfamily that induces apoptosis in susceptible cells on crosslinking by its ligand (FasL). The Fas loss of function and concurrent expression of its ligand (FasL) have been associated with malignant phenotype. In this study, we sought to investigate the hitherto undescribed expression of Fas and FasL on the immortalized human choriocarcinoma cell lines BeWo and NJG.

METHODS

Receptor and ligand expression was demonstrated using specific antibodies and multiple techniques including immunocytochemistry, confocal immunofluorescence microscopy, flow cytometry, immunoblots, and reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

Data from this study indicate that human choriocarcinoma cell subtypes co-express both Fas and FasL. A specific cytoplasmic and membranous pattern of immunoreactivity was noted that was further confirmed at mRNA transcripts by RT-PCR. In addition, we provide evidence using flow cytometry that the Fas receptors are downregulated. The mean fluorescence intensities for NJG and BeWo were 1.47 +/- 0.5 and 1.59 +/- 0.4, while that for Fas-positive Jurkat cells was 25.6 +/- 3.1.

CONCLUSIONS

To our knowledge, this is the first report on the identification and constitutive co-expression of Fas and FasL in BeWo and NJG choriocarcinoma cells. Choriocarcinoma cells evade immune attack by downregulating the Fas receptor and by killing lymphocytes through expression of FasL. Taken together, our investigations suggest that the Fas/FasL system may represent a mechanism by which malignant trophoblasts become resistant to apoptosis, escape immune surveillance, and metastasize.

Fas ligand and tumour counter-attack in colorectal cancer stratified according to microsatellite instability status

Expression of membrane-bound Fas ligand (FasL) by colorectal cancer cells may allow the development of an immune-privileged site by eliminating incoming tumour-infiltrating lymphocytes (TILs) in a Fas-mediated counter-attack. Sporadic colorectal cancer can be subdivided into three groups based on the level of DNA microsatellite instability (MSI). High-level MSI (MSI-High) is characterized by the presence of TILs and a favourable prognosis, while microsatellite-stable (MSS) cancers are TIL-deficient and low-level MSI (MSI-Low) is associated with an intermediate TIL density. The purpose of this study was to establish the relationship between MSI status and FasL expression in primary colorectal adenocarcinoma. Using immunohistochemistry and a selected series of 101 cancers previously classified as 31 MSI-High, 30 MSI-Low, and 40 MSS, the present study sought to confirm the hypothesis that increased TIL density in MSI-High cancers is associated with low or absent membrane-bound FasL expression, while increased FasL in MSS cancers allows the killing of host TILs. TUNEL/CD3 double staining was also used to determine whether MSS cancers contain higher numbers of apoptotic TILs in vivo than MSI-High or MSI-Low cancers. Contrary to the initial hypothesis, it was found that MSI-High cancers were associated with higher FasL expression (p = 0.04) and a stronger intensity of FasL staining (p = 0.007). In addition, mucinous carcinomas were independently characterized by increased FasL expression (p = 0.03) and staining intensity (p = 0.0005). Higher FasL expression and staining intensity did not correlate with reduced TIL density or increased numbers of apoptotic TILs. However, consistent with the hypothesis that curtailment of the host anti-tumour immune response contributes to the poor prognosis in MSS cancers, it was found that apoptotic TILs were most abundant in MSS carcinomas and metastatic Dukes' stage C or D tumours (p = 0.004; p = 0.046 respectively). This study therefore suggests that MSS colorectal cancers are killing incoming TILs in an effective tumour counter-attack, but apparently not via membrane-bound FasL.

CC531s colon carcinoma cells induce apoptosis in rat hepatic endothelial cells by the Fas/FasL-mediated pathway

The mechanisms involved in colorectal carcinoma with liver metastasis are not well known. Metastasizing colon carcinoma cells express more FasL than primary colon carcinoma cells and cancer cells induce apoptosis in hepatocytes by the Fas/FasL pathway. Therefore, this study focused on Fas/FasL expression and functionality in rat liver sinusoidal endothelial cells (LSECs) and CC531s colon carcinoma cells in vitro and in vivo. RT-PCR and immunochemistry revealed Fas and FasL in LSECs and CC531s, respectively. Functionality of Fas was assessed in vitro by incubation with human recombinant FasL (1-100 ng/ml) with or without enhancer. At concentrations of 10 and 100 ng/ml with enhancer, respectively 21% and 44% of endothelial cells showed signs of apoptosis using Hoechst 33342/propidium iodide staining and electron microscopy. In co-cultures, apoptosis could be detected in endothelial cells neighboring the CC531s and could be inhibited by an antagonistic FasL antibody. Moreover, 18 h after mesenteric injection of CC531s, the sinusoidal endothelium revealed disruption. In conclusion, (i). CC531s cells induce apoptosis in LSECs in vitro by using Fas/FasL; (ii). CC531s cells damage the sinusoidal endothelial lining in vivo; and (iii). this might provide FasL-positive tumor cells a gateway towards the hepatocytes.

Fas ligand expression is correlated with metastasis in colorectal carcinoma

The Fas/Fas ligand (FasL) system is one apoptotic pathway through which malignant tumors can evade immune surveillance. While FasL is expressed in malignant tumors, Fas is conversely downregulated to escape host immune attack, resulting in tumor invasion. The aim of the current study was to find out further clinicopathological significance of FasL expression in carcinoma of the colon and rectum. FasL expression was investigated using immunohistochemical staining in 143 consecutive patients with primary colorectal carcinomas. Seventy-nine carcinomas (55.2%) expressed FasL. The incidence of lymph node and distant metastases in carcinomas expressing FasL was significantly higher than in carcinomas that did not express FasL (p = 0.031 and p = 0.0003, respectively). Although univariate analysis showed that survival in patients with carcinomas expressing FasL was significantly poorer than that in patients with carcinomas without FasL expression (p = 0.001), only Dukes' stage was an independent prognosticator by multivariate analysis. FasL expression was found to be correlated with lymph node involvement and distant metastases in colorectal carcinoma.

Fas ligand expression in cervical adenocarcinoma: relevance to lymph node metastasis and tumor progression

OBJECTIVE

Adenocarcinoma of the cervix carries a worse prognosis than its squamous counterpart. In particular, tumors with lymph node metastasis have a miserably poor prognosis. Fas ligand (FasL) could allow the tumor cells to evade host immune surveillance and would thus promote tumor survival and possibly metastasis formation. We decided to compare FasL expression in cervical adenocarcinoma with lymph node status to determine whether FasL plays a role in lymph node metastases.

METHODS

Using immunohistochemistry, we investigated FasL expression in sections of formalin-fixed, paraffin-embedded tissue from 24 cervical adenocarcinomas. We also studied sections of seven cases with lymph node metastases. The percentage of FasL-positive cells in each tumor was recorded. FasL expression in cervical adenocarcinoma was compared with lymph node status. Statistical analysis was performed by using the Fisher exact test and the Kaplan-Meier method.

RESULTS

FasL expression was detected in 62.5% (15 of 24) of primary lesions. Significantly higher incidence of positive FasL reactivity was demonstrated in 10 of 11 tumors with lymph-vascular space (P = 0.0188), in 10 of 10 with deep stromal invasion (P = 0.0015), and in 8 of 9 cancers with lymph node metastasis (P = 0.0481). All 9 metastatic cervical adenocarcinoma in the lymph nodes showed FasL immunoreactivity in 60.7 +/- 17.7% of the metastatic cancer cells, and 7 (78%) of these had FasL immunoreactivity in greater than 50% of the cells. The survival times of patients with FasL-expressing cervical adenocarcinomas were significantly reduced compared to patients with low FasL-expressing tumors (P = 0.0018).

CONCLUSIONS

These findings indicate that FasL plays an important role in immune evasion, and progression and metastasis of cervical adenocarcinoma.

CD95 (Fas/APO-1)/CD95L in the gastrointestinal tract: fictions and facts

CD95 is a member of the tumor necrosis factor receptor family. It is constitutively expressed on the basolateral membrane of intestinal epithelial cells (IEC) and induces apoptosis when cross-linked by its natural ligand, CD95L. The significance of providing such a death-inducing mechanism in IEC is not yet clear. In recent years a multitude of studies have been published addressing the question of where and under which conditions CD95L is produced in the gut in the normal and neoplastic situation. Although some of these studies have considerably influenced our view on the role of the CD95/CD95L system, it appears necessary to critically review published data which are in part confusing and contradictory. To date compelling evidence of CD95L expression in untransformed IEC is lacking, and involvement of the CD95/CD95L system in the physiological epithelial cell turnover appears unlikely. Whereas CD95L is overexpressed in T-cells under inflammatory conditions, its significance for mucosal damage in inflammatory bowel diseases is obscured by possible redundancies in cell death mechanisms. Finally, recent data indicate that the intriguing CD95L counterattack concept in gastrointestinal tract cancer needs to be revised.

Functional expression of tumor necrosis factor-related apoptosis-inducing ligand in human colonic adenocarcinoma cells

TNF-related apoptosis-inducing ligand (TRAIL) can induce apoptosis in various transformed cell lines. Therefore, we investigated TRAIL sensitivity, TRAIL-induced nuclear factor-kappaB (NF-kappaB) activation, and expression of TRAIL in human colonic adenocarcinoma cell lines (HT-29, LS180, SK-CO-1). All four TRAIL receptors (TRAIL-R1 through TRAIL-R4) are expressed in these cell lines. TRAIL sensitivity was assessed by assay of cell viability. Cancer cell viabilities were 83 +/- 3.1% (HT-29), 90 +/- 4.3% (LS180), and 88 +/- 6.3% (SK-CO-1) at 24 hours after the addition of 100 ng/ml TRAIL, indicating that these cell lines were relatively resistant to TRAIL. Activation of NF-kappaB was variably influenced by TRAIL administration, with no consistent tendency among the cell lines, indicating that TRAIL-induced NF-kappaB activation might be cell-type dependent. In contrast, TRAIL was expressed in the human colonic adenocarcinoma cell lines by Western blotting and RT-PCR. Increased expression of TRAIL on tumor cells was observed by flow cytometry after cytokine stimulation (IFN-gamma, TNF-alpha) or the addition of chemotherapeutic agents (camptothecin, doxolubicin hydrochloride). TRAIL on HT-29 cells was functional and able to induce apoptosis in Jurkat cells. Jurkat cell viability was increased by the addition of TRAILR1-R4-Fc. In the presence of various cytokines or chemotherapeutic agents, functional TRAIL is expressed on the surface of tumor cells, and this expressed TRAIL might contribute to tumor immune privilege by inducing apoptosis of activated human lymphocytes.

Biological therapy of colorectal cancer

In this review, the immunogenicity of colorectal cancer (CRC) and the results of clinical and recent preclinical studies are discussed. Evidence for immune reactivity has been found in several preclinical models and the prognostic value of some of these immune responses have been reported. The possible mechanisms are discussed. Treatment with monoclonal antibodies is still experimental; as previously described benefit of treatment with monoclonal antibodies could not be confirmed. Labelled monoclonal antibody therapy has produced mixed results and also need further investigation. Several antigens are used in active specific immunotherapy (ASI). Its targets and modifications are discussed, as are their use in clinical studies. Although some of the results are promising, the results still have to be confirmed in larger studies. Since there is sufficient evidence for immune reactivity in CRC, further research on immunotherapeutic strategies is justified and will be focused on the development of humanised antibodies, the search for other relevant T-cell epitopes and ways to induce a more effective T cell response.

Humoral immunodeficiency in chronic lymphocytic leukemia: role of CD95/CD95L in tumoral damage and escape

B cell chronic lymphocytic leukemia (B-CLL) is the most frequent hematological neoplasm in the human adult life. This tumor is often associated with hypogammaglobulinemia and infections. This review focuses on recently reported mechanisms underlying the humoral immunodeficiency occurring in B-CLL. Tumoral cells provoke several alterations to normal regulatory T cells, which, in turn, can impair the correct maturation of B cells. In addition, the direct inhibitory effect of B-CLL cells on immunoglobulin (Ig)-secreting plasma cells (PC) may account for the humoral immunodeficiency. This phenomenon is mediated by the interaction of CD95L molecules expressed by B-CLL cells with the death receptor CD95 that is up-regulated on patients' PC, leading to PC apoptosis and subsequently to hypogammaglobulinemia. Furthermore, the presence of CD95L on B-CLL cells could play an additional role in tumoral immune-escape, as reported in other neoplasms.

Fas ligand is up-regulated during the colorectal adenoma-carcinoma sequence

AIMS

Fas ligand (FasL) expression by cancer cells may mediate tumour immune privilege. The purpose of the present study was to investigate the timing and significance of FasL expression during the colorectal adenoma-carcinoma sequence.

METHODS

FasL expression was studied by immunohistochemistry in 170 formalin-fixed tissue sections representing the entire colorectal adenoma-carcinoma sequence. Reverse transcriptase polymerase chain reaction (RT-PCR) was used to search for FasL mRNA. Analysis of survival was performed in patients with carcinomas.

RESULTS

A significant positive linear correlation was found between FasL expression and tumour progression throughout the colorectal adenoma-carcinoma sequence (r(s)=0.677 P<0.001). A pattern of high FasL expression was detected in 19% of high grade adenomas, 40% of stage I-II, 67% of stage III and 70% of stage IV carcinomas. No significant differences were observed between FasL expression in the primary tumours and that in the corresponding liver metastases. The specificity of FasL expression was confirmed at RT-PCR. For stage I-II carcinomas, the 5 year survival was 90% in patients without, or with moderate, tumoural FasL expression compared with 60% in those with high tumoural FasL expression (P<0.05).

CONCLUSIONS

Our findings suggest that FasL expression may be involved in the development of colorectal cancer and its progression.

Differential expression of cell cycle and apoptosis related proteins in colorectal mucosa, primary colon tumours, and liver metastases

AIMS

Tumour cell growth results from a disturbance in the balance between the rate of proliferation and cell death. In this study, proteins involved in the regulation of cell cycle arrest and apoptosis were studied as possible factors responsible for uncontrolled cell growth in colorectal cancer.

METHODS

The expression of proteins involved in these processes was investigated in 48 metastases from patients with colorectal cancer and compared with eight normal colon mucosa samples and 14 primary tumours. Both primary tumours and metastases were obtained from eight patients. The expression of thymidylate synthase (TS), p53, retinoblastoma protein (Rb), Fas receptor, Fas ligand, bcl-2, mcl-1, bax, and bcl-x was measured using immunohistochemistry. Proliferation was determined by Ki67 staining, whereas apoptosis was assessed by M30 immunostaining, which recognises cleaved cytokeratin 18.

RESULTS

In the limited number of cases in which paired comparisons were possible, the expression of TS and Ki67 was significantly higher in metastases than in the matched primary tumour samples (p = 0.014 and 0.016, respectively), whereas Rb expression was lower in metastases than in primary tumours (p = 0.024). Fas receptor expression was high in normal mucosa but absent in primary tumours and metastases, whereas the opposite was seen for p53. The expression of bax, mcl-1, and bcl-x in normal mucosa was more apical than that seen in malignant cells, where a more diffuse expression pattern was seen (p < 0.04). Apoptosis was more abundant in primary tumours than in metastases.

CONCLUSIONS

These results demonstrate that proliferation and apoptosis are disturbed during colorectal cancer progression, and this is accompanied by loss of Rb and Fas expression, the accumulation of p53 and TS, and changes in the expression patterns of bax, mcl-1, and bcl-xl.