Fas function and tumor progression: Use it and lose it

AbstractRecent studies have provided evidence that Fas and FasL interactions are important in the control of malignant disease and that changes in the level of Fas expression can determine immune escape and therapeutic responses

A balance between NF-Y and p53 governs the pro- and anti-apoptotic transcriptional response

The transcription factor NF-Y is a trimer with histone-like subunits that binds and activates CCAAT-containing promoters. NF-Y controls the expression of several key regulators of the cell cycle. In this study, we examined the functional and molecular effects of NF-YB knockdown. Cell cycle progression is affected with a G2/M-specific depletion. This is due to the inability of activation of G2/M-specific genes, as evidenced by expression profiling, RT-PCR and ChIP data. Surprisingly, apoptosis is also observed, with Caspase 3/7/8 cleavage. A role of p53 and Bcl-2 family members is important. NF-YB inactivation is sufficient to functionally activate p53, in the absence of DNA damage. Failure to maintain a physiologic level of CCAAT-dependent transcription of anti-apoptotic genes contributes to impairment of Bax/Bcl-2 and Bax/Bcl-XL ratios. Our data highlight the importance of fine balancing the NF-Y-p53 duo for cell survival by (i) maintaining transcription of anti-apoptotic genes and (ii) preventing p53 activation that triggers the apoptotic cascade

Circulating soluble Fas levels and risk of ovarian cancer

BACKGROUND: Dysregulation of apoptosis, specifically overexpression of soluble Fas (sFas), has been proposed to play a role in the development of ovarian cancer. The main objective of the present study was to evaluate serum sFas as a potential biomarker of ovarian cancer risk. METHODS: The association between serum sFas levels and the risk of ovarian cancer was examined in a case-control study nested within three prospective cohorts in New York (USA), Umeå (Sweden), and Milan (Italy). Case subjects were 138 women with primary invasive epithelial ovarian cancer diagnosed between 2 months and 13.2 years after the initial blood donation. Control subjects were 263 women who were free of cancer, and matched the case on cohort, menopausal status, age, and enrollment date. Serum sFas levels were determined using a quantitative sandwich enzyme immunoassay. RESULTS: Serum sFas levels were similar in women subsequently diagnosed with ovarian cancer (median, 6.5 ng/mL; range, 4.4 – 10.2) and in controls (median, 6.8 ng/mL; range, 4.5 – 10.1). Statistically significant trends of increasing serum sFas with age were observed among cases (r = 0.39, p < 0.0001) and controls (r = 0.42, p < 0.0001). Compared to women in the lowest third, women in the highest third of serum sFas were not at increased risk of ovarian cancer after adjustment for potential confounders (odd ratio (OR), 0.87; 95% confidence interval (CI), 0.42 – 1.82). CONCLUSION: The results suggest that serum sFas may not be a suitable marker for identification of women at increased risk of ovarian cancer

Granulocytes mediates the Fas-L-associated apoptosis during lung metastasis of melanoma that determines the metastatic behaviour

The survival of tumour cells in a new tissue environment is crucial for tumour metastasis. Factors contributing to the death of tumour cells during metastasis are not completely understood. In murine melanoma model, activation of Fas (CD95, APO-1) signal in tumour cells reduces their lung metastasis potential, which may be associated with an induction of apoptosis in tumours. To elucidate the cellular mechanism, we used a Fas-ligand (Fas-L) specific ribozyme (Fas-Lribozyme) to suppress the expression of Fas-L but not Fas or TNF-α in B16F10 melanoma cells. The Fas-Lribozyme-carrying cells grew slightly faster in vitro with better viability than controls. Suppression of Fas-L in B16F10 melanoma cells by Fas-Lribozyme enhanced lung metastasis of the cells in C57BL/6 mice, and that was correlated with reductions in both apoptotic tumour cells and granulocytic infiltration. Mice depleted of granulocytes, but not CD4+ and CD8+ cells, showed a greatly elevated susceptibility to lung metastasis. Moreover, apoptosis in tumour cells was significantly reduced in granulocyte-depleted mice during the course of tumour formation. Taken together, our findings indicate that Fas-L-associated apoptosis in tumour cells determines the metastasis behaviour of melanoma in the lung and this apoptosis is primarily mediated by the cytotoxicity of recruited granulocytes

Synergistic induction of cell death in liver tumor cells by TRAIL and chemotherapeutic drugs via the BH3-only proteins Bim and Bid

Although death receptors and chemotherapeutic drugs activate distinct apoptosis signaling cascades, crosstalk between the extrinsic and intrinsic apoptosis pathway has been recognized as an important amplification mechanism. Best known in this regard is the amplification of the Fas (CD95) signal in hepatocytes via caspase 8-mediated cleavage of Bid and activation of the mitochondrial apoptosis pathway. Recent evidence, however, indicates that activation of other BH3-only proteins may also be critical for the crosstalk between death receptors and mitochondrial triggers. In this study, we show that TNF-related apoptosis-inducing ligand (TRAIL) and chemotherapeutic drugs synergistically induce apoptosis in various transformed and untransformed liver-derived cell lines, as well as in primary human hepatocytes. Both, preincubation with TRAIL as well as chemotherapeutic drugs could sensitize cells for apoptosis induction by the other respective trigger. TRAIL induced a strong and long lasting activation of Jun kinase, and activation of the BH3-only protein Bim. Consequently, synergistic induction of apoptosis by TRAIL and chemotherapeutic drugs was dependent on Jun kinase activity, and expression of Bim and Bid. These findings confirm a previously defined role of TRAIL and Bim in the regulation of hepatocyte apoptosis, and demonstrate that the TRAIL–Jun kinase–Bim axis is a major and important apoptosis amplification pathway in primary hepatocytes and liver tumor cells

The autocrine role of tumor necrosis factor in the proliferation and functional differentiation of human lymphokine-activated T killer cells (T-LAK) in vitro

The autocrine role of tumor necrosis factor alpha (TNF) in the proliferation and functional differentiation of human lymphokine-activated T-killer cells (T-LAK) in vitro was investigated. Human peripheral blood lymphocytes initially stimulated with IL-2 and phytohemagglutinin-P (PHA) for 48 h will proliferate for long periods in vitro in the presence of IL-2. These T-LAK cells have been shown to be 95% CD3 positive. Employing ELISA techniques, greater than 500 pg/ml of TNF was found to be released in the supernatants of these cells during the first 5 days of culture. However, the levels dropped to 100-200 pg/ml by days 7-10. T-LAK cells grown from days 7 to 10 in the presence of IL-2 and rabbit anti-TNF were significantly growth inhibited (up to 23%). The cytolytic activity of T-LAK cells grown from days 0 to 7 in the presence of anti-TNF was also decreased (up to 75%). Phenotypic analysis of these anti-TNF treated T-LAK cells revealed a decrease in CD8 expression (up to 12%) and increase in CD4 expression (up to 27%) when compared with control cells. The data suggest that TNF has a regulatory role in the growth and functional differentiation of these human T-LAK cells

Immunoregulatory Mechanisms Underlying Prevention of Colitis-Associated Colorectal Cancer by Probiotic Bacteria

Background: Inflammatory bowel disease (IBD) increases the risk of colorectal cancer. Probiotic bacteria produce immunoregulatory metabolites in vitro such as conjugated linoleic acid (CLA), a polyunsaturated fatty acid with potent anticarcinogenic effects. This study aimed to investigate the cellular and molecular mechanisms underlying the efficacy of probiotic bacteria in mouse models of cancer. Methodology/Principal Findings: The immune modulatory mechanisms of VSL#3 probiotic bacteria and CLA were investigated in mouse models of inflammation-driven colorectal cancer. Colonic specimens were collected for histopathology, gene expression and flow cytometry analyses. Immune cell subsets in the mesenteric lymph nodes (MLN), spleen and colonic lamina propria lymphocytes (LPL) were phenotypically and functionally characterized. Mice treated with CLA or VSL#3 recovered faster from the acute inflammatory phase of disease and had lower disease severity in the chronic, tumor-bearing phase of disease. Adenoma and adenocarcinoma formation was also diminished by both treatments. VSL#3 increased the mRNA expression of TNF-a, angiostatin and PPAR c whereas CLA decreased COX-2 levels. Moreover, VSL#3-treated mice had increased IL-17 expression in MLN CD4+ T cells and accumulation of Treg LPL and memory CD4+ T cells. Conclusions/Significance: Both CLA and VSL#3 suppressed colon carcinogenesis, although VSL#3 showed greater anticarcinogeni