阿霉素增强抗人DR5单克隆抗体mDRA-6诱导HL-60细胞凋亡的作用

目的观察抗死亡受体5（DR5）单克隆抗体（单抗）mDRA-6与阿霉素（Adr）对HL-60细胞的协同杀伤作用。方法用DR5蛋白免疫BALB／c小鼠，融合筛选抗DR5杂交瘤细胞，制备抗人DR5单抗mDRA-6；流式细胞术测定Adr对HL-60细胞表面DR5表达的影响；荧光显微镜下观察mDRA-6与Adr协同作用下HL-60细胞的形态变化；MTT法测定1μg／ml Adr与不同浓度的mDRA-6对HL-60细胞存活的影响；琼脂糖凝胶电泳检测mDRA-6与Adr联合对HL-60细胞DNA片断化的影响。结果Adr诱导HL-60细胞表面DR5表达，mDRA-6作用后HL-60细胞出现染色质浓缩、断裂，细胞出芽，凋亡小体形成，mDRA-6与Adr联用细胞形态变化更明显；mDRA-6与Adr对HL-60细胞具有明显的协同杀伤作用，20ng／ml的mDRA-6作用HL-60细胞10h，细胞死亡率为9．32％，1μg／mlAdr作用HL-60细胞10h，细胞死亡率为17.47％，20ng／ml mDRA-6联合1μg／mlAdr，可使HL-60细胞死亡率增至65．06％；20μg／ml mDRA-6与1μg／mlAdr联合作用于HL-60细胞3h，DNA琼脂糖凝胶电泳显示明显“梯形”条带。结论抗DR5单抗mDRA-6与Adr对HL-60细胞具有强大的协同杀伤作用。     

Signalling by proteolysis: death receptors induce apoptosis

Apoptosis, or programmed cell death, is a genetically regulated mechanism with a central role in both metazoan development and homeostasis. Death receptors (Fas, TNFR-2, DR3, and TRAIL receptors) induce apoptosis upon ligation to cognate ligands or ectopic expression. The assembly of a death-inducing signalling complex occurs in a hierarchical manner upon receptor activation. The death domain of the receptor binds to the corresponding domain of the adapter molecule FADD, which in turn recruits the zymogen form of the death protease FLICE (MACH/caspase-8). Upon approximation, FLICE “zymogens” attain a sufficient concentration to self-activate and to trigger the apoptotic pathway. For the first time, a transmembrane receptor directly engaging a protease at the signalling complex and subsequently triggering a proteolytic signalling cascade is described.     

c-FLIP mediates resistance of Hodgkin/Reed-Sternberg cells to death receptor-induced apoptosis

Resistance to death receptor-mediated apoptosis is supposed to be important for the deregulated growth of B cell lymphoma. Hodgkin/Reed-Sternberg (HRS) cells, the malignant cells of classical Hodgkin's lymphoma (cHL), resist CD95-induced apoptosis. Therefore, we analyzed death receptor signaling, in particular the CD95 pathway, in these cells. High level CD95 expression allowed a rapid formation of the death-inducing signaling complex (DISC) containing Fas-associated death domain-containing protein (FADD), caspase-8, caspase-10, and most importantly, cellular FADD-like interleukin 1beta-converting enzyme-inhibitory protein (c-FLIP). The immunohistochemical analysis of the DISC members revealed a strong expression of CD95 and c-FLIP overexpression in 55 out of 59 cases of cHL. FADD overexpression was detectable in several cases. Triggering of the CD95 pathway in HRS cells is indicated by the presence of CD95L in cells surrounding them as well as confocal microscopy showing c-FLIP predominantly localized at the cell membrane. Elevated c-FLIP expression in HRS cells depends on nuclear factor (NF)-kappaB. Despite expression of other NF-kappaB-dependent antiapoptotic proteins, the selective down-regulation of c-FLIP by small interfering RNA oligoribonucleotides was sufficient to sensitize HRS cells to CD95 and tumor necrosis factor-related apoptosis-inducing ligand-induced apoptosis. Therefore, c-FLIP is a key regulator of death receptor resistance in HRS cells.     

TRAF1在霍奇金淋巴瘤细胞中的表达和作用机制的探讨

目的 探讨肿瘤坏死因子受体相关因子(TRAF)1以及CD30-TRAF1信号通路在B细胞件霍奇金淋巴瘤细胞中的作用.方法分别采用荧光定量RT-PCR和Western blot法检测B细胞性霍奇金淋巴瘤细胞株TRAF1 mRNA和蛋白质表达水平,并进一步研究CD30信号活化对TRAF1表达的作用.采用RNA干扰技术研究TRAF1沉默对霍奇金淋巴瘤细胞存活的影响,并通过TransAM方法定量分析核转录因子(NF)-κB的DNA结合活性的变化.通过Western blot法测定NAPK/ERK信号通路中JunB蛋白的表达.结果 B细胞性霍奇金淋巴瘤细胞株LA28和KM-H2细胞中TRAF1在mRNA和蛋白质水平均表达.CD30配体作用后L428细胞中TRAF1 mRNA相对表达水平自3.50±0.20上调至7.26±0.23;蛋白相对表达水平自2.31±0.35上升至4.53±0.55.TRAF1沉默后凋亡细胞百分率由(5.7±1.2)%上升至(27.7±5.8)%,并伴随p50和RelA活力的下降.JunB的表达在TRAF1沉默细胞中未发生明显变化.结论 TRAF1在B细胞系来源的霍奇金淋巴瘤细胞中表达增加,并受到CD30信号通路活化的调控.TRAF1为介导经典性NF-κB活性的关键性调节分子,参与霍奇金淋巴瘤细胞的抗凋亡活性.     

Intracellular triggering of Fas aggregation and recruitment of apoptotic molecules into Fas-enriched rafts in selective tumor cell apoptosis

We have discovered a new and specific cell-killing mechanism mediated by the selective uptake of the antitumor drug 1-O-octadecyl-2-O-methyl-rac-glycero-3-phosphocholine (ET-18-OCH(3), Edelfosine) into lipid rafts of tumor cells, followed by its coaggregation with Fas death receptor (also known as APO-1 or CD95) and recruitment of apoptotic molecules into Fas-enriched rafts. Drug sensitivity was dependent on drug uptake and Fas expression, regardless of the presence of other major death receptors, such as tumor necrosis factor (TNF) receptor 1 or TNF-related apoptosis-inducing ligand R2/DR5 in the target cell. Drug microinjection experiments in Fas-deficient and Fas-transfected cells unable to incorporate exogenous ET-18-OCH(3) demonstrated that Fas was intracellularly activated. Partial deletion of the Fas intracellular domain prevented apoptosis. Unlike normal lymphocytes, leukemic T cells incorporated ET-18-OCH(3) into rafts coaggregating with Fas and underwent apoptosis. Fas-associated death domain protein, procaspase-8, procaspase-10, c-Jun amino-terminal kinase, and Bid were recruited into rafts, linking Fas and mitochondrial signaling routes. Clustering of rafts was necessary but not sufficient for ET-18-OCH(3)-mediated cell death, with Fas being required as the apoptosis trigger. ET-18-OCH(3)-mediated apoptosis did not require sphingomyelinase activation. Normal cells, including human and rat hepatocytes, did not incorporate ET-18-OCH(3) and were spared. This mechanism represents the first selective activation of Fas in tumor cells. Our data set a framework for the development of more targeted therapies leading to intracellular Fas activation and recruitment of downstream signaling molecules into Fas-enriched rafts.     

Natural Killer (NK) Cell–mediated Cytotoxicity: Differential Use of ?TRAIL and Fas Ligand by Immature and Mature Primary Human NK Cells

Mature natural killer (NK) cells use Ca²⁺-dependent granule exocytosis and release of cytotoxic proteins, Fas ligand (FasL), and membrane-bound or secreted cytokines (tumor necrosis factor [TNF]-α) to induce target cell death. Fas belongs to the TNF receptor family of molecules, containing a conserved intracytoplasmic “death domain” that indirectly activates the caspase enzymatic cascade and ultimately apoptotic mechanisms in numerous cell types. Two additional members of this family, DR4 and DR5, transduce apoptotic signals upon binding soluble TNF-related apoptosis-inducing ligand (TRAIL) that, like FasL, belongs to the growing TNF family of molecules. Here, we report that TRAIL produced or expressed by different populations of primary human NK cells is functional, and represents a marker of differentiation or activation of these, and possibly other, cytotoxic leukocytes. During differentiation NK cells, sequentially and differentially, use distinct members of the TNF family or granule exocytosis to mediate target cell death. Phenotypically immature CD161⁺/CD56⁻ NK cells mediate TRAIL-dependent but not FasL- or granule release–dependent cytotoxicity, whereas mature CD56⁺ NK cells mediate the latter two.     

TRAIL/死亡受体5途径在缺氧再给氧诱导人肝细胞凋亡中的作用及相关机制

目的:研究肿瘤坏死因子相关凋亡诱导配体(TNF-related apoptosis-inducing ligand,TRAIL)/死亡受体5(Death receptor 5,DR5)途径在人肝细胞缺氧/再给氧(Hypoxia/reoxygenation,H/R)损伤中的作用,并探讨其作用机制。方法:在体外建立肝细胞H/R模型,模拟肝脏的缺血再灌注。H/R处理后,培养基中加入不同浓度外源性TRAIL蛋白,噻唑盐比色法(MTT)和流式细胞术检测细胞活力和凋亡率。半定量RT-PCR检测DR5mRNA的表达。结果:以正常人肝细胞为对照,H/R使人肝细胞的DR5 mRNA的表达上调,再给氧2小时达峰值,此后直至再给氧20小时维持在相对高的水平。单纯缺氧6小时不能引起肝细胞的大量凋亡。TRAIL诱导H/R处理后的肝细胞发生凋亡,并呈浓度依赖性。H/R大大增强TRAIL的肝毒性。结论:H/R使DR5在人肝细胞的表达上调,增加TRAIL的肝毒性。TRAIL/DR5途径可能在IRI诱导人肝细胞凋亡过程中发挥重要作用。     

阿霉素增强TRAIL诱导的人骨髓瘤细胞系KM3细胞凋亡的分子机制研究

目的探讨阿霉素增强肿瘤坏死因子相关凋亡诱导配体（TRAIL）诱导人骨髓瘤细胞系KM3细胞凋亡的分子机制。方法采用TUNEL法和流式细胞术比较单独TRAIL及联合应用阿霉素对KM3细胞凋亡率的影响。Westem blot法检测阿霉素诱导前后KM3细胞核内转录因子NF-κB亚单位蛋白P65以及死亡受体DR5表达的变化。结果流式细胞术分析显示，10、20、50、100ng／ml的TRAIL联合应用1μg／ml阿霉素诱导KM3细胞后，细胞凋亡率分别为20．88％、40．03％、57．87％和60．82％，显著高于单独应用阿霉素或TRAIL诱导的细胞凋亡率；与TUNEL法检测结果一致。KM3细胞经不同浓度阿霉素（0．5、1．0、2．0、4．0μg／m1）联合20ng／ml TRAIL处理后，DR5受体的表达量随应用阿霉素浓度的增加而上升，而细胞核内P65蛋白表达量则随阿霉素浓度的增加而下降。结论骨髓瘤细胞膜DR5表达量提高和NF-κB的核转移是阿霉素协同TRAIL诱导凋亡反应的重要分子机制。     

Molecular,structural, and biological characteristics of the tumor necrosis factor ligand superfamily

The tumor necrosis factor receptor superfamily at present consists of ten different transmembrane (type I) glycoproteins with characteristic limited sequence homology for the cysteine-rich repeats in the extracellular domain. In parallel the tumor necrosis factor ligand superfamily has been recognized by discovery of ligands for all members of the receptor superfamily. These molecules are also transmembrane (type II) glycoproteins, with the exception of lymphotoxin-α which is the only entirely secreted protein of the tumor necrosis factor-like proteins. Several members of the ligand superfamily, including tumor necrosis factor and CD95L also exist in a biologically active soluble form. The tumor necrosis factor ligand superfamily contains at present ten different proteins. In addition, NGFR p75 binds to a second family of proteins (neurotrophins). These nerve growth factor-like dimeric soluble molecules are basic neurotrophic factors and the five members (NGF, BDNF, NT-3, NT-4, NT-5) are not related to the tumor necrosis factor superfamily ligands. The members of the tumor necrosis factor ligand superfamily (TNF, LT-α, LT-β, CD27L, CD30L, CD40L, CD95L, 4-1BB, OX40L, TRAIL) share common biological activities, but some properties are shared by only some ligands, while others are unique. The diverse biological activities but some properties are shared by only some ligands, while others are unique. The diverse biological activities triggered through tumor necrosis factor receptors have been linked to the regulation of cellular activation, including immune responses and inflammatory reactions, but also with the pathology of a series of human diseases.     

Mitogen-activated Protein Kinase Kinase Antagonized Fas-associated Death Domain Protein–mediated Apoptosis by Induced FLICE-inhibitory Protein Expression

Fas and Fas-associated death domain (FADD) play a critical role in the homeostasis of different cell types. The regulation of Fas and FADD-mediated cell death is pivotal to many physiological functions. The activation of T lymphocytes by concanavalin A (Con A) inhibited Fas-mediated cell death. We identified that among the several activation signals downstream of Con A stimulation, mitogen-activated protein (MAP) kinase kinase (MKK) was the major kinase pathway that antagonized Fas-triggered cell death. MKK1 suppressed FADD- but not caspase-3– induced apoptosis, indicating that antagonism occurred early along the Fas-initiated apoptotic cascade. We further demonstrated that activation of MKK1 led to expression of FLIP, a specific inhibitor of FADD. MKK1 inhibition of FADD-induced cell death was abrogated if induction of FLIP was prevented, indicating that FLIP mediates MKK1 suppression of FADD-mediated apoptosis. Our results illustrate a general mechanism by which activation of MAP kinase attenuates apoptotic signals initiated by death receptors in normal and transformed cells.     

DR4去甲基化对髓性白血病K562细胞增殖凋亡作用的研究

目的:研究肿瘤坏死因子死亡受体(DR)4去甲基化对髓性白血病K562细胞增殖、凋亡的影响.方法:取对数期K562细胞,采用地西他滨(DCA)0、0.8、1.6、3.2 μmol/L干预,分别设为对照、DCA低剂量、DCA中剂量和DCA高剂量4组.取对照组细胞,采用肿瘤坏死因子相关凋亡诱导配体(TRAIL)0.5 μg/...     

Hepatitis C virus core protein does not inhibit apoptosis in human hepatoma cells

BACKGROUND: Viral persistence is a major problem after infection with the hepatitis C virus. Recently, it has been reported that hepatitis C virus core protein inhibits cis-platin induced apoptosis in human cervical carcinoma cells and apoptosis induced by overexpression of c-myc in Chinese hamster ovary cells. MATERIALS AND METHODS: This study investigated whether different variants of hepatitis C virus core or E2 protein interfere with tumour necrosis factor alpha or Fas (CD95/ APO-1) antibody-induced programmed cell death in transiently transfected human hepatoma (HepG2) cells. RESULTS: While neither full length or C-terminally truncated variants of hepatitis C virus core protein nor hepatitis C virus E2 protein inhibited tumour necrosis factor alpha- or Fas antibody-induced apoptosis, a strong inhibition was observed with the cowpox virus cytokine response modifier A protein. CONCLUSIONS: Thus, it is unlikely that hepatitis C virus core or E2 protein inhibit apoptosis mediated by apoptosis-signalling pathways sensitive to cytokine response modifier A protein. Discrepancies to previous reports probably reflect specific effects of hepatitis C virus core protein on different apoptotic pathways and/ or cell lines.     

Somatic mutation of the CD95 gene in human B cells as a side-effect of the germinal center reaction

Somatic hypermutation specifically modifies rearranged immunoglobulin (Ig) genes in germinal center (GC) B cells. However, the bcl-6 gene can also acquire somatic mutations during the GC reaction, indicating that certain non-Ig genes can be targeted by the somatic hypermutation machinery. The CD95 gene, implicated in negative selection of B lymphocytes in GCs, is specifically expressed by GC B cells and was recently identified as a tumor suppressor gene being frequently mutated in (post) GC B cell lymphomas. In this study, the 5' region (5'R) and/or the last exon coding for the death domain (DD) of the CD95 gene were investigated in naive, GC, and memory B cells from seven healthy donors. About 15% of GC and memory, but not naive, B cells carried mutations within the 5'R (mutation frequency 2.5 x 10(-4) per basepair). Mutations within the DD were very rare but could be efficiently selected by inducing CD95-mediated apoptosis: in 22 apoptosis-resistant cells, 12 DD mutations were found. These results indicate that human B cells can acquire somatic mutations of the CD95 gene during the GC reaction, which potentially confers apoptosis resistance and may counteract negative selection through the CD95 pathway.     

Chronic inflammation as predictor of 1-year hospitalization and mortality in elderly population

Eur J Clin Invest 2012; 42 (10): 1037-1046 ABSTRACT: Background Systemic low-grade inflammation is thought to be associated with an increased risk of adverse clinical outcomes in elderly population. We tested this notion with the goal of identifying useful potential biomarkers of 1-year hospitalization and mortality in the elderly population. Design A total of 120 institutionalized older subjects were enrolled as participants in this study, including 90 women and 30 men (ranging in age from 68 to 105?years), selected from Santa Teresa nursing home (Oviedo, Spain). We studied functional status, morbidity, socio-demographic characteristics and several inflammation and inflammation-related markers. Results The study included 95 non-hospitalized participants and 23 participants with at least one hospitalization during 1?year (19% of subjects). The study also included 100 survivors and 19 participants who died during the 1-year study (16% of subjects). In logistic regression models adjusted by age, sex, anti-inflammatory drug use and morbid conditions, high levels of interleukin 1 receptor antagonist (IL-1ra) and red blood cell distribution width (RDW) were associated with hospitalization and death at 1?year. Elevated levels of tumour necrosis factor α (TNF-α) were also associated with an increased risk of death at 1?year after adjusting for the same potential confounders. Multivariate logistic regression models showed that elevated serum levels of IL-1ra were intimately associated with 1-year subsequent hospitalization and mortality in aged subjects after adjusting for age, sex, anti-inflammatory drug use and morbid conditions. Conclusions Current data suggest that IL-1ra is a predictor of 1-year hospitalization and mortality in the elderly population.     

Enhanced apoptosis following treatment with TRA-8 anti-human DR5 monoclonal antibody and overexpression of exogenous Bax in human glioma cells

Specific activation of apoptosis in tumor cells offers a promising approach for cancer therapy. Induction of apoptosis leads to activation of specific proteases. Two major pathways for caspase activation in mammalian cells have been described. One apoptotic pathway involves members of the tumor necrosis factor family of cytokine receptors (eg death receptor 5 (DR5)). The other pathway is controlled by the Bcl-2 family of proteins. The purpose of this study was to investigate whether increased apoptosis occurs in human glioma cells following infection with a recombinant adenoviral vector encoding the human Bax gene under the control of human vascular endothelial growth factor (VEGF) promoter element (AdVEGFBax) in combination with an anti-human DR5 monoclonal antibody (TRA-8). Specific overexpression of exogenous Bax protein induced apoptosis and cell death in glioma cell lines, through activation of both caspase-8 and -9, leading to activation of downstream caspase-3. The relative sensitivity to AdVEGFBax for the glioma cell lines was U251MG>U373MG>U87MG>D54MG. The recently characterized TRA-8 monoclonal antibody induces apoptosis of most TRAIL-sensitive tumor cells by specific binding to DR5 receptors on the cellular membrane. TRA-8 induced rapid apoptosis and cell death in glioma cells, but did not demonstrate detectable cytotoxicity of primary normal human astrocytes. The efficiency of TRA-8-induced apoptosis was variable in different glioma cell lines. The relative sensitivity to TRA-8 was U373MG>U87MG>U251MG>D54MG. The combination of TRA-8 treatment and overexpression of Bax overcame TRA-8 resistance of glioma cells in vitro. Cell viability of U251MG cells was 71.1% for TRA-8 (100 ng/ml) alone, 75.9% for AdVEGFBax (5 MOI) alone and 41.1% for their combination as measured by MTS assay. Similar enhanced apoptosis results were obtained for the other glioma cell lines. In vivo studies demonstrated that the combined treatment significantly (P<0.05) suppressed the growth of U251MG xenografts and produced 60% complete tumor regressions without recurrence. These data suggest that the combination of TRA-8 treatment with specific overexpression of Bax using AdVEGFBax may be an effective approach for the treatment of human malignant gliomas.     

Roles of the Tumor Suppressor p53 and the Cyclin-dependent Kinase Inhibitor p21WAF1/CIP1 in Receptor-mediated Apoptosis of WEHI 231 B Lymphoma Cells

Treatment of WEHI 231 immature B lymphoma cells with an antibody against their surface immunoglobulin M (anti-IgM) induces apoptosis and has been studied extensively as a model of self-induced B cell tolerance. Since the tumor suppressor protein p53 has been implicated in apoptosis in a large number of cell types and has been found to be mutated in a variety of B cell tumors, here we sought to determine whether p53 and the p53 target gene cyclin-dependent kinase inhibitor p21^WAF1/CIP1 were involved in anti-IgM–induced cell death. Anti-IgM treatment of WEHI 231 cells increased expression of p53 and p21 protein levels. Ectopic expression of wild-type p53 in WEHI 231 cells induced both p21 expression and apoptosis. Ectopic expression of p21 similarly induced apoptosis. Rescue of WEHI 231 cells from apoptosis by costimulation with CD40 ligand ablated the increase in p21 expression. Lastly, a significant decrease in anti-IgM–mediated apoptosis was seen upon downregulation of endogenous p53 activity by expression of a dominant-negative p53 protein or upon microinjection of an antisense p21 expression vector or antibody. Taken together, the above data demonstrate important roles for p53 and p21 proteins in receptor-mediated apoptosis of WEHI 231 B cells.     

Dual Signaling of the Fas Receptor: Initiation of Both Apoptotic and Necrotic Cell Death Pathways

Murine L929 fibrosarcoma cells were transfected with the human Fas (APO-1/CD95) receptor, and the role of various caspases in Fas-mediated cell death was assessed. Proteolytic activation of procaspase-3 and -7 was shown by Western analysis. Acetyl-Tyr-Val-Ala-Asp-chloromethylketone and benzyloxycarbonyl-Asp(OMe)-Glu(OMe)-Val-Asp(OMe)-fluoromethylketone, tetrapeptide inhibitors of caspase-1– and caspase-3–like proteases, respectively, failed to block Fas-induced apoptosis. Unexpectedly, the broad-spectrum caspase inhibitors benzyloxycarbonyl-Val-Ala-Asp(OMe)-fluoromethylketone and benzyloxycarbonyl-Asp(OMe)-fluoromethylketone rendered the cells even more sensitive to Fas-mediated cell death, as measured after 18 h incubation. However, when the process was followed microscopically, it became clear that anti-Fas–induced apoptosis of Fas-transfected L929 cells was blocked during the first 3 h, and subsequently the cells died by necrosis. As in tumor necrosis factor (TNF)-induced necrosis, Fas treatment led to accumulation of reactive oxygen radicals, and Fas-mediated necrosis was inhibited by the oxygen radical scavenger butylated hydroxyanisole. However, in contrast to TNF, anti-Fas did not activate the nuclear factor κB under these necrotic conditions. These results demonstrate the existence of two different pathways originating from the Fas receptor, one rapidly leading to apoptosis, and, if this apoptotic pathway is blocked by caspase inhibitors, a second directing the cells to necrosis and involving oxygen radical production.     

Kinetics of soluble TNF-receptors and soluble adhesion molecules ICAM-1, E-selectin and VCAM-1 under systemic rhTNFα therapy

Cytostatic as well as cytotoxic effects of tumour necrosis factor alpha (TNF-α) therapy have been shown in vitro and in experimental in vivo models. Nevertheless, the mechanism of anti-tumour activity in humans in vivo remains unclear. To determine the role of the vascular lining endothelial cells as important mediators of several immunological interactions, we investigated changes in the levels of the soluble endothelial cell adhesion molecules intercellular adhesion molecule 1, E-selectin and vascular cell adhesion molecule 1 as well as of soluble TNF receptors I and II during systemic therapy with recombinant human rhTNF-α (rhTNF-α). All tests were performed by enzyme-linked immunosorbent assays (ELISAs). The clinical efficacy of the intravenous rhTNF-α therapy was poor. Only one patient with isolated intra-arterial limb perfusion had a delayed, marked, but only temporary necrosis of tumour cells. In contrast, we found a marked, significant and (during therapy) undulating augmented increase in the levels of soluble adhesion molecules as well as of the soluble TNF receptors. Taken together, these data support the hypothesis that a sufficient tumour-specific cellular immunity is required to achieve a clinically apparent efficacy of systemic rhTNF-α therapy in addition to cytokine-dependent inducible activation mechanisms. In this context, the vascular lining endothelial cells might play an important role as mediators of the complex immunological antitumoral activity.