Functional analysis of TRAIL receptors using monoclonal antibodies. (1/819)

mAbs were generated against the extracellular domain of the four known TNF-related apoptosis-inducing ligand (TRAIL) receptors and tested on a panel of human melanoma cell lines. The specificity of the mAb permitted a precise evaluation of the TRAIL receptors that induce apoptosis (TRAIL-R1 and -R2) compared with the TRAIL receptors that potentially regulate TRAIL-mediated apoptosis (TRAIL-R3 and -R4). Immobilized anti-TRAIL-R1 or -R2 mAbs were cytotoxic to TRAIL-sensitive tumor cells, whereas tumor cells resistant to recombinant TRAIL were also resistant to these mAbs and only became sensitive when cultured with actinomycin D. The anti-TRAIL-R1 and -R2 mAb-induced death was characterized by the activation of intracellular caspases, which could be blocked by carbobenzyloxy-Val-Ala-Asp (OMe) fluoromethyl ketone (zVAD-fmk) and carbobenzyloxy-Ile-Glu(OMe)-Thr-Asp (OMe) fluoromethyl ketone (zIETD-fmk). When used in solution, one of the anti-TRAIL-R2 mAbs was capable of blocking leucine zipper-human TRAIL binding to TRAIL-R2-expressing cells and prevented TRAIL-induced death of these cells, whereas two of the anti-TRAIL-R1 mAbs could inhibit leucine zipper-human TRAIL binding to TRAIL-R1:Fc. Furthermore, use of the blocking anti-TRAIL-R2 mAb allowed us to demonstrate that the signals transduced through either TRAIL-R1 or TRAIL-R2 were necessary and sufficient to mediate cell death. In contrast, the expression of TRAIL-R3 or TRAIL-R4 did not appear to be a significant factor in determining the resistance or sensitivity of these tumor target cells to the effects of TRAIL.  (+info)

Involvement of TNF-related apoptosis-inducing ligand in human CD4+ T cell-mediated cytotoxicity. (2/819)

TNF-related apoptosis-inducing ligand (TRAIL) has been identified as a member of the TNF family that induces apoptosis in a variety of tumor cells, but its physiological functions are largely unknown. In the present study, we examined the expression and function of TRAIL in human CD4+ T cell clones by utilizing newly established anti-human TRAIL mAbs. Human CD4+ T cell clones, HK12 and 4HM1, exhibited perforin-independent and Fas ligand (FasL)-independent cytotoxicity against certain target cells, including T lymphoma (Jurkat) and keratinocyte (HaCaT) cell lines, which are susceptible to TRAIL-mediated cytotoxicity. In contrast to FasL, the expression of which was inducible upon anti-CD3 stimulation, TRAIL was constitutively expressed on HK12 and 4HM1 cells, and no further increase was observed after anti-CD3 stimulation. Spontaneous cytotoxic activities of resting HK12 and 4HM1 cells against Jurkat and HaCaT cells were blocked by anti-TRAIL mAb but not by anti-FasL mAb, and bystander cytotoxic activities of anti-CD3-stimulated HK12 and 4HM1 cells were abolished by the combination of anti-TRAIL and anti-FasL mAbs. These results indicate a differential regulation of TRAIL and FasL expression on human CD4+ T cell clones and that TRAIL constitutes an additional pathway of T cell-mediated cytotoxicity.  (+info)

Monocyte-mediated tumoricidal activity via the tumor necrosis factor-related cytokine, TRAIL. (3/819)

TRAIL (tumor necrosis factor [TNF]-related apoptosis-inducing ligand) is a molecule that displays potent antitumor activity against selected targets. The results presented here demonstrate that human monocytes rapidly express TRAIL, but not Fas ligand or TNF, after activation with interferon (IFN)-gamma or -alpha and acquire the ability to kill tumor cells. Monocyte-mediated tumor cell apoptosis was TRAIL specific, as it could be inhibited with soluble TRAIL receptor. Moreover, IFN stimulation caused a concomitant loss of TRAIL receptor 2 expression, which coincides with monocyte acquisition of resistance to TRAIL-mediated apoptosis. These results define a novel mechanism of monocyte-induced cell cytotoxicity that requires TRAIL, and suggest that TRAIL is a key effector molecule in antitumor activity in vivo.  (+info)

To die or not to die--the quest of the TRAIL receptors. (4/819)

The last 18 months have witnessed the characterization of several new members of the tumor necrosis factor (TNF) receptor family. Among these are five receptors for the cytotoxic ligand TRAIL (TNF-related apoptosis-inducing ligand). Two of these receptors, TRAIL-R1 and TRAIL-R2, contain classical cytoplasmic death domains and are able to transduce an apoptotic signal. The others lack functional death domains and are not able to promote cell death. Indeed, one of the receptors for TRAIL, osteoprotegerin (OPG) is a soluble protein whose activities so far have been shown to be inhibition of osteoclastogenesis and increased bone density in vivo. The existence of multiple receptors for TRAIL suggests an unexpected complexity to TRAIL-mediated biological functions.  (+info)

Relation of TNF-related apoptosis-inducing ligand (TRAIL) receptor and FLICE-inhibitory protein expression to TRAIL-induced apoptosis of melanoma. (5/819)

Past studies have shown that apoptosis mediated by TNF-related apoptosis-inducing ligand (TRAIL) is regulated by the expression of two death receptors [TRAIL receptor 1 (TRAIL-R1) and TRAIL-R2] and two decoy receptors (TRAIL-R3 and TRAIL-R4) that inhibit apoptosis. In previous studies, we have shown that TRAIL but not other members of the tumor necrosis factor family induce apoptosis in approximately two-thirds of melanoma cell lines. Here, we examined whether the expression of TRAIL-R at the mRNA and protein level in a panel of 28 melanoma cell lines and melanocytes correlated with their sensitivity to TRAIL-induced apoptosis. We report that at least three factors appear to underlie the variability in TRAIL-induced apoptosis. (a) Four of nine cell lines that were insensitive to TRAIL-induced apoptosis failed to express death receptors, and in two instances, lines were devoid of all TRAIL-Rs. Southern analysis suggested this was due to loss of the genes for the death receptors. (b) Despite the presence of mRNA for the TRAIL-R, some of the lines failed to express TRAIL-R protein on their surface. This was evident for TRAIL-R1 and more so for the TRAIL decoy receptors TRAIL-R3 and -R4. Studies on permeabilized cells revealed that the receptors were located within the cytoplasm and redistribution from the cytoplasm may represent a posttranslational control mechanism. (c) Surface expression of TRAIL-R1 and -R2 (but not TRAIL-R3 and -R4) showed an overall correlation with TRAIL-induced apoptosis. However, certain melanoma cell lines and clones were relatively resistant to TRAIL-induced apoptosis despite the absence of decoy receptors and moderate levels of TRAIL-R1 and -R2 expression. This may indicate the presence of inhibitors within the cells, but resistance to apoptosis could not be correlated with expression of the caspase inhibitor FLICE-inhibitory protein. mRNA for another TRAIL receptor, osteoprotegerin, was expressed in 22 of the melanoma lines but not on melanocytes. Its role in induction of apoptosis remains to be studied. These results appear to have important implications for future clinical studies on TRAIL.  (+info)

Molecular cloning and functional analysis of the mouse homologue of the KILLER/DR5 tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) death receptor. (6/819)

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and its receptors are members of the tumor necrosis factor superfamily. TRAIL selectively kills cancer cells but not normal cells. We report here the cloning of the mouse homologue of the TRAIL receptor KILLER/DR5 (MK). The cDNA of MK is 1146 bp in length and encodes a protein of 381 amino acids. MK contains an extracellular cysteine-rich domain, a transmembrane domain, and a cytoplasmic death-domain characteristic of Fas, tumor necrosis factor, and human TRAIL receptors. MK is highly homologous and binds TRAIL with similar affinity as human DR4 and KILLER/DR5. MK induces apoptosis in mouse and human cells and inhibits colony growth of NIH3T3 cells. Expression of MK is p53-dependent and up-regulated by tumor suppressor p53 and by DNA damaging agents in mouse cells undergoing apoptosis. This is the first report describing a mouse TRAIL receptor gene and also demonstrating that the p53-dependent regulation of KILLER/DR5-mediated apoptosis is conserved between human and mouse.  (+info)

Implication of p53 in growth arrest and apoptosis induced by the synthetic retinoid CD437 in human lung cancer cells. (7/819)

CD437 is a novel retinoid that can induce apoptosis in a variety of tumor cell types by an unknown mechanism. We found that CD437 up-regulated the expression of p21(WAF1/CIP1), Bax, and Killer/DR5 and induced G1 arrest and rapid apoptosis in three human non-small cell lung carcinoma cell lines with wild-type p53 but not in five cell lines with mutant p53, suggesting a role for p53 in the effects of CD437. Using H460 cells in which wild-type p53 protein was degraded by transfection of the human papillomavirus 16 E6 (HPV-16 E6) gene and H460 cells transfected with a control plasmid only, we found that CD437 increased p53, p21(WAF1/CIP1), Bax, and Killer/DR5 in the control transfectants. In contrast, the constitutive p53 protein level was suppressed, and the ability of CD437 to increase p53 and its downstream genes was compromised in E6 transfectants. In addition, CD437 induced G1 arrest and apoptosis in the control transfectants but not in the E6-transfected cells. These results indicate that p53 plays a role in CD437-induced growth inhibition and apoptosis in human non-small cell lung carcinoma cells.  (+info)

TRAIL death pathway expression and induction in thyroid follicular cells. (8/819)

To determine whether programmed cell death in thyroid follicular cells can be related to activation of the tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) pathway, we examined the expression and function of this pathway in primary thyroid follicular cells and a papillary thyroid carcinoma cell line in vitro. Despite the expression of TRAIL receptors death receptor 4 and death receptor 5, purified TRAIL could not induce programmed cell death (PCD) in any of the thyroid follicular cells examined. However, pre-incubation with cycloheximide before TRAIL facilitated the induction of rapid and massive PCD. This suggested that despite the presence of a labile inhibitor of the TRAIL pathway, TRAIL could mediate PCD under appropriate conditions. To determine whether there were sources of TRAIL in the thyroid that could interact with thyroid follicular cell TRAIL receptors, RNase protection assays were used to determine TRAIL mRNA expression. TRAIL message was expressed in intrathyroidal lymphocytes isolated from a patient with thyroiditis, and unexpectedly, thyroid follicular cells themselves could be induced to express abundant TRAIL message in the presence of the inflammatory cytokines interferon gamma, tumor necrosis factor alpha, and interleukin 1beta. Furthermore, the papillary thyroid carcinoma cell line could be induced to kill the TRAIL-sensitive lymphoma cell line BJAB through a TRAIL-dependent mechanism.  (+info)