Enhancement of germ cell apoptosis induced by ethanol in transgenic mice overexpressing Fas Ligand

It was suggested that chronic ethanol exposure could result in testicular germ cell apoptosis, but the mechanism is still unclear. In the present study, we use a model of transgenic mice ubiquitously overexpressing human FasL to investigate whether Fas ligand plays a role in ethanol-induced testicular germ cell apoptosis. Both wild-type (WT)mice and transgenic (TG) mice were treated with acute ethanol (20% v/v) by introperitoneal injection for five times.After ethanol injection, WT mice displayed up-regulation of Fas ligand in the testes, which was shown by FITCconjugated flow cytometry and western blotting. Moreover, TG mice exhibited significantly more apoptotic germ cells than WT mice did after ethanol injection, which was demonstrated by DNA fragmentation, PI staining flow cytometry and TUNEL staining. In addition, histopathological examination revealed that degenerative changes of epithelial component of the tubules occurred in FasL overexpressing transgenic mice while testicular morphology was normal in wild-type mice after acute ethanol exposure, suggesting FasL expression determines the sensitivity of testes to ethanol in mice. In summary, we provide the direct evidences that Fas ligand mediates the apoptosis of testicular germ cells induced by acute ethanol using FasL transgenic mice.

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 immunohistochemistry 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 (x2 = 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) ofinfiltrating lymphocytes in adenoma, chronic cholecystitis, well-differentiated carcinoma and Nevin Ⅰ-Ⅲ carcinoma wasvery 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.

Utility of adenovirus-mediated Fas ligand and bcl-2 gene transfer to modulate rat liver allograft survival

BACKGROUND: Expression of Fas ligand (FasL) on the graft by gene transduction is expected to introduce apoptosis to lymphocytes to protect rejection, but the FasL-expressing graft cells may also induce apoptosis as the graft usually expresses Fas antigens. In this study, a strong antiapoptotic gene, bcl-2, was cotransfected with the FasL gene in rat liver graft to protect against Fas- mediated cell death and to prolong recipient survival. METHODS: Orthotopic liver transplantation was done in a strain combination of DA to LEW rats. After donor vascular isolation, adenovirus-mediated FasL and bcl-2 genes were cotransfected in the liver graft. RESULTS: Intragraft expression of FasL mRNA was constitutively expressed after adenovirus-mediated transduction, although expression of FasL increased mildly in control grafts. Bcl-2 mRNA was highly expressed at 2 days after reperfusion. In contrast, lower expression of bcl-2 was observed in the control group. The average survival of the gene transferred allografts increased from (9.8+1.3) days to (18.5+8.7) days compared with the control group. CONCLUSION: Our results indicate that rat liver allografts can be protected against host immune responses by adenovirus-mediated FasL and bcl-2 transfection, and that bcl-2 expression prevents the graft from Fas-mediated apoptosis.

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 investigatedby 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 detectedby 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.

EXPRESSION OF MATRIX METALLOPROTEINASE-7 AND FAS LIGAND: THEIR APOPTOSIS-INDUCING EFFECT ON GASTRIC CANCER CELLS

Objective: To investigate the expression of matrix metalloproteinase-7 (MMP-7) and Fas ligand (FasL) in gastric cancer and explore their role in progression of gastric cancer. Methods: Formalin-fixed paraffin and embedded tissues of primary gastric cancer and adjacent non-tumor mucosa from 113 cases were evaluated for MMP-7, FasL and Capase-3 expression by streptavidin-peroxidase (S-P) immunohistochemistry. The expression of the first two proteins in cancer cells of primary foci was compared with clinicopathological parameters of tumors. We also observed the correlation of MMP-7 and FasL expression with Caspase-3 expression in cancer cells of primary foci. Results: MMP-7 positive immunostaining was less frequently detected in adjacent epithelial cells than in cancer cells of primary foci of gastric cancer (P<0.05, 29.2% vs 69.0%), and so was FasL (P<0.05, 34.5% vs 54.0%). MMP-7 expression was associated with tumor size, Borrmann抯 classification, invasive depth, metastasis and TNM staging (P<0.05), but not with growth pattern, Lauren抯 classification, or histological classification (P>0.05). FasL expression was correlated with tumor size, invasive depth, metastasis, Lauren抯 classification, histological classification (P<0.05), while not with Borrmann抯 classification, TNM staging or growth pattern (P>0.05). Cancer cells of primary foci expressed less Caspase-3 than their adjacent epithelial cells (P<0.05, 32.7% vs 50.4%). There was an obvious correlation between FasL, MMP-7 and Caspase-3 expression in cancer cells of primary foci (P<0.05). Co-expression of MMP-7 and FasL paralleled with Caspase-3 expression in cancer cells of primary foci (P<0.05). Conclusion: MMP-7 and FasL expression was up-regulated in gastric carcinogenesis and was principally involved in progression of gastric cancer. FasL expression could reflect the differentiation of gastric cancer cells and underlie the molecular mechanisms of different pathways of gastric tumorigenesis. Co-expression of MMP-7 and FasL could have apoptosis-inducing effect on gastric cancer cells.

Association between Up-regulation of Fas Ligand Expression and Apoptosis of Tumor-infiltrating Lymphocytes in Human Breast Cancer

In order to study the significance of FasL expression in immune escape of breast cancer, FasL protein expression and the number of tumor-infiltrating lymphocytes （TILs） in 40 specimens of breast cancer were detected by immunohistochemitry. The expression of FasL mRNA was measured by in situ hybridization in the consecutive tissue slices of 40 breast cancers respectively. By using terminal deoxynucleotidyl transferase-mediaed dUTP nick end labeling （TUNEL）, apoptotic cells were detected in 40 specimens of breast cancer. The expression of FasL was detected in all 40 specimens to varying degrees. In the consecutive tissue slices, the location of expression of FasL protein corresponded with that of FasL mRNA. In those with FasL extensive expression, the number of TILs was less （P〈0.05）, the apoptotic index （AI） of TILs was higher and the AI of tumor cells was lower （P〈0.01） than those with FasL weak expression respectively. The AI of TILs was correlated with that of tumor cells （r=-0.629, P〈0.01）. In conclusion, breast cancer cells can induce the apoptosis of TILs through the expression of FasL, which can counterattack the immune system. This may be a mechanism of immune evasion in breast cancer.

Study on the Expression of Fas Ligand on the Surfaces of Human Cytotrophoblasts in Normal Pregnancy

To further study the mechanism of maternal-fetal immune tolerance, the expression of Fas ligand (FasL) on the surfaces of human cytotrophoblasts in normal pregnancy was detected by using immunohistochemical method. High precise color-image measure system for immuno-histo- chemistry was used to quantitatively analyze the expression of FasL. The results showed that FasL were expressed on the surfaces of placental cytotrophoblasts throughout normal pregnancy. The variance among the first, second and term pregnant stages was also detected. It was suggested that the expression of FasL on the surfaces of placental cytotrophoblasts might play an important role both in the maintenance of pregnancy and in the normal development of fetus. The maternal speific T cell apoptosis induced by Fas/FasL is one of the significant mechanisms of maternal-fetal immune tolerance.

Up-regulation of Fas Ligand Expression by Sirtuin 1 in both Flow-restricted Vessels and Serum-stimulated Vascular Smooth Muscle Cells

Objective To study the role of sirtuin 1 （SIRT1） in Fas ligand （FasL） expression regulation during vascular lesion formation and to elucidate the potential mechanisms. Methods SIRT1 and FasL protein levels were detected by Western blotting in either mouse arteries extract or the whole rat aortic vascular smooth muscle cell （VSMC） lysate. Smooth muscle cell （SMC）-specific human SIRT1 transgenic （Tg） C57BL/6 mice and their littermate wild-type （WT） controls underwent complete carotid artery ligation （ligation groups） or the ligation-excluded operation （sham groups）. The carotid arteries were collected 1 day after operation. Reverse transcription-polymerase chain reaction was performed to detect the mRNA levels of SIRT1 and FasL. Luciferase reporter assays were performed to detect the effect of WT-SIRT1, a dominant-negative form of SIRT1 （SIRT1H363Y）, and GATA-6 on the promoter activity of FasL. Flow cytometry assay was applied to measure the hypodiploid DNA content of VSMC so as to monitor cellular apoptosis. Results SIRTI was expressed in both rat aortic VSMCs and mouse arteries. Forced SIRT1 expression increased FasL expression both in injured mouse carotid arteries 1 day after ligation （P〈0.001） and VSMCs treated with serum （P〈0.05 at the transcriptional level, P〈0.001 at the protein level）. No notable apoptosis was observed. Furthermore, transcription factor GATA-6 increased the promoter activity of FasL （P〈0.001）. The induction of FasL promoter activity by GATA-6 was enhanced by WT-SIRT1 （P〈0.001）, while SIRT1H363Y significantly relieved the enhancing effect of WT-SIRT1 on GATA-6 （P〈0.001）. Conclusions Overexpression of SIRT1 up-regulates FasL expression in both flow-restricted mouse carotid arteries and serum-stimulated VSMCs. The transcription factor GATA-6 participates in the transcriptional regulation of FasL expression by SIRT 1.

Effects of Ureaplasma Urealyticum on Fas Ligand Expression in Rat Sertoli Cell

To investigate the effect of ureaplasma urealyticum (UU) on the expression of Fas ligand (FasL) on rat Sertoli cell Materials & Method Isolated rat Sertoli cells were infected by living UU, UU super- natants, inactivated UU, then Fluorescence Activated Cell Sorter and observed fluores- cence microscopy were used to assay for the FasL expression on the surface of Sertoli cells. Results UU infection could increase the expression of FasL in Sertoli cell. Conclusion The functional expression of FasL is related to the immune privilege and can give the immune regulation on the testis.

EXPRESSION OF Fas LIGAND IN HUMAN COLON CANCER CELL LINES

Objective: To investigate the expression of Fas ligand in human colon carcinoma cell lines. Methods: A total of six human colon cancer cell lines were examined for the expression of Fas ligand mRNA and cell surface protein by using RT-PCR and flow cytometry respectively. Results: The results showed that Fas ligand mRNA was expressed in all of the six cancer cell lines and Fas ligand cell surface protein was expressed in part of them. Conclusion: These data suggest that Fas ligand was expressed, at least in part, in human colon cancer cell lines and might facilitate to escape from immune surveillance of the host.

Apoptosis of Leukemia Cells Induced by CD34^+ Cells Transferred Exogenous Fas Ligand

To assess the value of CD34 + cells transferred exogenous Fas ligand (FasL) in inducing apoptosis of human leukemic cells, the CD34 + cells transfected with F asL or without, pretreated with mitomycin C, was mixed with leukemic cell line U937 cells in presence or absence of daunorubicin (DNR) or cytosine arabinoside (Ara C). After l8 h, apoptosis of cells was detected by FCM and TUNEL. Induced for l8 h by CD34 + cells transfected with FasL or without, the ratio of apoptos is of U937 cells was (5.0±1.3) %, (10.8±0.6) % ( P < 0.01), respectively. Induced by FasL +CD34 ++DNR, FasL +CD34 ++Ara C, the ratio was (13.4±1.0) % ( P < 0.05), (17.9±1.3)% ( P <0.01), respectively. The result demonstrated that CD34 + cells transfected with exogenous FasL could induce apoptosis of human leukemic cells and showed a cytotoxic synergistic effect when used in combination with chemotherapeutic drugs, suggesting that it was possible to develop a new method in treatment of leukemia.

EXPRESSION OF PERFORIN AND FAS LIGAND IN INFILTRATING CELLS OF MURINE MYOCARDIUM INFECTED WITH COXSACKIEVIRUS B3

Purpose. To clarify the role of perforin-and Fas ligand (L)-mediated cytotoxicity pathogenesis of viral myocarditis. Materials and methods. Forty balb/c mice were randomly divided into experimental group (n = 20) and control group (n = 20), and inoculated intraperitoneally with coxsackievirus B3(CVB3) and Eagle’s solu- tion without CVB3, respectively. The mice were sacrificed and their hearts were removed at day 7 post-in- oculation. Expression of perform and FasL were detected with immunohistochemistry, reverse transcription-polymerase chain reaction (RT-PCR) and in situ hybridization. Results. (1)Perform-and FasL-positiye cells were demonstrated in experimental murine hearts by im- munohistochemistry, however, no cells were discovered in control murine hearts; (2) The examination of RT-PCR showed the positive ratios of perform and FasL mRNA in myocardium were significantly higher in experimental group (100% and 100 % ) than that in control group (20% and 30 %, P<0.05); (3)Positive signals of perform and FasL mRNA were found in myocardium of all the experimental mice by in situ hybridization, but nothing was detected in control group. Conclusion. Perform and FasL can be expressed in infiltrating cells in murine myocardium with acute myocarditis caused by CVB3, suggesting perform and FasL might play an important role in pathogenesis of viral myocarditis.

The Serum Levels of Soluble Fas Ligand and Soluble Fas Receptor in Patients with chronic congestive heart failure

Objectives To investi gate the association of soluble Fas ligand( sFasL) and soluble Fas receptor( sFas) with human chronic con gestive heart failure( CHF) . Methods The serum level of sFasL and sFas in 33 patients with CHF (13 in cardiac function class Ⅱ, 17 in class Ⅲ, 3 in class Ⅳ, NYHA) was assessed with enzyme - linked immunosorbent assay, and was compared with that of 18 age - , blood pressure - matched patients with car diac function class Ⅰ (NYHA). Results There was no difference in the level of sFasL between the two groups [CHF group: 231. 50 + / - 84. 50 (cardiac function class Ⅱ216. 50 + / - 96. 00 , class Ⅲ 226. 80 + / - 85. 70, class Ⅳ 244. 00 + / - 73. 00) vs. cardiac function class I group: 217. 50 + /-89. 00 pg/mL, P>0. 05]. However, the level of sFas was significantly higher in the patients with CHF than those of cardiac function class I group [CHF group: 1353. 30 +/-507. 71 (cardiac function class Ⅱ 1154. 85 + /-371. 20 , class Ⅲ1412.88 + /-493. 62, classⅣ1875. 67 + / - 806. 10) vs. cardiac function class I group: 983. 11+/ -461. 26 pg/mL, P<0. 05 ] . Conclusions sFasL was not associated with human CHF. However, the elevation of serum level of sFas was proportion to the severity of human CHF. sFas may play an important role in the patho- genesis of human CHF.

Clinical significance of Fas and FasL protein expression in gastric carcinoma and local lymph node tissues

AIM:To investigate the relation of Fas and Fas ligand (FasL) protein expression with carcinogenesis and metastasis of gastric carcinoma.METHODS: Immunohistochemistry was used to detect Fas and FasL protein expression in 64 gastric carcinoma tissue samples and 20 normal gastric tissue samples. Relation between FasL and Fas expression, age and gender of gastric cancer patients, and pathological subtype and lymph node metastasis of gastric cancer was analyzed.RESULTS: The Fas expression level was significantly higher in normal gastric tissue samples than in gastric carcinoma tissue samples (85.0% vs 25.0%, P<0.001), while the FasL expression level was signif icantly lower in normal gastric tissue samples than in gastric carcinoma tissue samples (30.0% vs 81.3%, P<0.001). The Fas expression level was significantly higher in invasive lymph nodes than in non-invasive lymph nodes (82.9% vs 56.5%, P<0.003) and in well-differentiated gastric carcinoma tissue samples than in poorly-differentiated gastric carcinoma tissue samples (50.0% vs 18.0%, P=0.015). The FasL expression level was significantly lower in well-differentiated gastric carcinoma tissue samples than in poorly-differentiated gastric carcinoma tissue samples (42.9% vs 84.0%, P=0.021). The Fas and FasL expression levels (25.0% and 81.3%) were signif icantly different in gastric carcinoma tissue samples (P<0.001), but had a non-linear correlation (P=0.575).CONCLUSION: Abnormal Fas and FasL expressions in gastric carcinoma and lymph node tissues are involved in carcinogenesis and metastasis of gastric cancer.

FasL Expression in Colorectal Carcinoma and Its Significance in Immune Escape of Cancer

To study the significance of FasL expression in immune escape of colorectal carcinoma, FasL protein expression and the number of tumor infiltrating lymphocytes （TILs） in 80 specimens of colorectal carcinoma were detected by immunohistochemitry. The mRNA of FasL was measured by in situ hybridization in the consecutive tissue slices of 80 colorectal carcinomas respectively. Using terminal deoxynucleotidyl transferase-mediaed dUTP nick end labeling （TUNEL）, apoptotic cells were detected in 80 specimens of colorectal carcinoma. The expression of FasL was detected in all 80 specimens, but it was not even in the same or among different tissues. In the consecutive tissue slices, the location of expression of FasL protein corresponded with that of FasL mRNA. In those with FasL extensive expression, the number of TILs was less than that of FasL weak expression （P〈0. 05）, and the apoptotic index （AI） of TILs was higher and that of tumor cells was lower than that of FasL with weak expression respectively （P〈0. 01）. The AI of TILs was correlated with that of tumor cells （r=-0. 631, P〈0. 01）. It was suggested that colorectal carcinoma cells can induce the apoptosis of TILs through the expression of FasL, which can counterattack the immune system. This may be one of the mechanisms of immune evasion in colorectal carcinoma.

Apoptosis and Fas System Are Significantly Involved in the Process of Liver Cirrhosis Converting into Hepatocellular Carcinoma

To investigate the roles of apoptosis and the Fas system in the process of liver cirrhosis converting into hepatocellular carcinoma , expression of Fas and Fas ligand in 49 LC and 36 HCC samples was detected by immunohistochemical method. Apoptosis was detected by terminal deoxynucleotidyl transferase mediated dUTP nick end labeling method. Serum soluble Fas levels in 28 cases of LC and 27 cases of HCC were measured by enzyme linked immunosorbent assay method. Compared with LC, apoptotic indices in HCC tissues were significantly reduced , expression of Fas was decreased , and that of FasL was increased . Serum sFas levels in HCC patients were significantly higher than those in normal controls. Down regulation of Fas expression, up regulation of FasL expression in hepatocytes and elevation of sFas level in serum might contribute to tumor escape from immune surveillance of the body. Apoptosis and the Fas system are significantly involved in the process of liver cirrhosis converting into hepatocellular carcinoma.

Distinct patterns of mucosal apoptosis in H pylori-associated gastric ulcer are associated with altered FasL and perforin cytotoxic pathways

AIM: To analyze the level of apoptosis in different mucosal compartments and the differential expression of Fas/Fas-ligand and perforin in H pylori-associated gastric ulcer. METHODS: Antral specimens from patients with H pylori-related active gastric ulcer (GU), H pylori-related gastritis, and non-infected controls were analysed for densities and distribution of apoptotic cells determined by the TdT-mediated dUDP-biotin nick-end-labelling method. GU patients were submitted to eradication therapy with follow-up biopsy after 60 d. Fas, FasL, and perforin-expressing cells were assessed by immunoper- oxidase, and with anti-CD3, anti-CD20 and anti-CD68 by double immunofluorescence and confocal microscopy. Quantitative analysis was performed using a computer- assisted image analyser. RESULTS: H pylori-infected antrum showed greater surface epithelial apoptosis which decreased after eradi- cation therapy. In the lamina propria, higher rates of mononuclear cell apoptosis were observed in H pylori- gastritis. Co-expression of Fas with T-cell and macro- phage markers was reduced in GU. FasL- and perforin-expressing cells were increased in H pylori-infection and correlated with epithelial apoptosis. Perforin-expressing cells were also increased in GU compared with H pylori- gastritis. CONCLUSION: Epithelial apoptosis is increased in H pylori-infection and correlates to FasL- and perforin- expression by T cells. Expression of perforin is correlated with the tissue damage, and may represent the enhance- ment of a distinct cytotoxic pathway in GU. Increased expression of FasL not paralleled by Fas on T-cells and macrophages may indicate a reduced susceptibility to the Fas/FasL-mediated apoptosis of lymphoid cells in H pylori-infection.

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 lymphocytes 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.

The Effect of the Fas/FasL Pathway during Chemotherapeutic Drug-induced Apoptosis of Leukameic Cells

The mechanism of chemotherapeutic drug-induced apoptosis in leukaemic cells was studied to further investigate whether Fas/FasL system was involved in apoptosis induced by chemotherapeutic drugs and assess their effects when used in combination with soluble FasL (sFasL). The expression of Fas on human leukaemic cell lines K562, HL-60 and U937 treated with daunorubicin (DNR) or cytosine arabinoside (Ara-C) was detected by using flow cytometry. The activities of sFasL, DNR and Ara-C inducing apoptosis of leukaemic cells, in the absence or presence of neutralizing anti-Fas IgG antibody, were detected by using flow cytometry and TUNEL. The results showed that flow cytometric profiles of K562, HL-60 and U937 cells treated with DNR or Ara-C failed to show any significant increase in Fas expression over 18 h (P>0.05). Anti-Fas monoclonal antibody (IgG) could not block the apoptosis in leukaemic cells induced by DNR or Ara-C, but could block the apoptosis induced by sFasL. A role of sFasL in a cytotoxic synergistic effect when used in combination with chemotherapeutic drugs was revealed. It was concluded that chemotherapeutic drug-induced apoptosis in human leukaemic cells (UG37, HL-60) is independent of the Fas/FasL system, but combination of sFasL and drug treatment produces a synergistic cytotoxic effect on human luekaemic cells.

The expression of Fas, FasL and their biological behavior in human cervical carcinoma

Objective： To investigate the relationship between the expression of Fas and Fas ligand （FasL） and its biological behavior in human cervix carcinoma. Methods： Immunohistochemisty technique was used to detect the expression of Fas and FasL in 47 cases of cervical carcinoma, 16 cases of cervical interaepithelial neoplasia, 10 cases of chronic cervicitis and 10 cases of normal cervix. TUNEL technique was used to observe the apoptic cells in 47 cases of cervical carcinoma. Retrospective study was carried out to find the relationship between the expression of Fas and FasL and cell apoptosis, clinical stage, pathological classification, lymph node metastasis, prognosis and age. Results： The expression of Fas and FasL was significantly different in different cervix （P 〈 0.01）, and also related to the degree of differentiation, lymph node metastasis and prognosis （P 〈 0.05）. But had no relation with clinical stage or age （P 〉 0.05） ; Cervix carcinoma cells apoptosis in different pathological classification appeared negative relation （Rs=-0.35, P 〈 0.05 ）. Cervix carcinoma cell apoptosis was significantly higher in Fas-positive and FasL- positive than that in Fas-negative and FasL-negative （P 〈 0.05）. By retrospective investigation, Fas-negative and FasL-positive were related to poor prognoses of the patients with cervical carcinoma （P 〈 0.05 ）. Conclusion： The development of apoptosis in cervix carcinoma has a promoting regulation function in Fas and FasL expression. Gene treatment can alter apoptosis abnormality, thus induce apoptosis in cancerous cell expressing Fas and FasL. Fas or FasL may be taken as a marker in the prognostic character- ization.