UMLS:C0027651 - FACTA Search

Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Target Concepts:

Query: UMLS:C0027651 (tumor)
685,946 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Malignant brain tumors are the most common solid tumors in children. The overall prognosis for this group of patients is still poor, emphasizing the importance of more effective therapies. Betulinic acid (Bet A) has been described as a novel cytotoxic compound active against melanoma and neuroblastoma cells. Here we report that Bet A was active against medulloblastoma and glioblastoma cell lines. In addition, Bet A exerted cytotoxic activity against primary tumor cells cultured from patients in 4 of 4 medulloblastoma-tumor samples tested and in 20 of 24 glioblastoma-tumor samples. Since a small percentage of primary-glioblastoma-tumor cells (4/24) did not respond to Bet-A treatment, resistance to Bet A might occur. Induction of apoptosis by Bet A involved mitochondrial perturbations, since inhibition of the mitochondrial permeability transition by the mitochondrion-specific inhibitor bongkrekic acid (BA) reduced Bet-A-induced apoptosis. In addition, mitochondria undergoing Bet-A-induced permeability transition triggered DNA fragmentation in isolated nuclei. Cytochrome c was released from mitochondria of Bet-A-treated cells, and might be involved in activation of caspases. Following treatment with Bet A, caspase-8, caspase-3 and PARP were proteolytically processed. Inhibition of caspase cleavage by the broad-range caspase inhibitor zVAD.fmk strongly reduced Bet-A-induced apoptosis, indicating that apoptosis was mediated by activation of caspases. Since Bet A did not exhibit cytotoxicity against murine neuronal cells in vitro, these findings suggest that Bet A may be a promising new agent for the treatment of medulloblastoma and glioblastoma cells that clearly warrants further pre-clinical and clinical evaluation.
...
PMID:Betulinic acid: a new cytotoxic agent against malignant brain-tumor cells. 1039 62

Transduction of cancer cells with herpes simplex virus thymidine kinase gene (HSVtk) followed by prodrug ganciclovir (GCV) treatment has been shown to induce apoptosis. In this study, four murine tumors including B16F10 melanoma, NG4TL4 sarcoma, H6 hepatoma and 1MEA 7R.1 hepatoma were found to vary in sensitivity to this gene therapy strategy in vitro but, at effective doses of GCV, the HSVtk-transduced cells of all four tumors showed similar kinetics of early rise in p53 protein levels, then cell cycle S-/G2-phase arrest and finally signs of apoptosis. Immunoblot analyses revealed that Fas (CD95/APO-1), Fas ligand (FasL) and two downstream mediators, RIP and caspase-3, (CPP32, YAMA, Apopain) were increased in GCV-treated HSVtk-transduced tumor cells the cell cycle arrest and before apoptosis. Increased expression of FasL could also be observed in vivo in HSVtk-transduced tumors induced to regress by GCV treatment. Enzyme measurements using specific substrate showed that the caspase-3 activation followed kinetically the FasL expression. More than half of the HSVtk/GCV-induced cell death could be abrogated by addition to the cell culture medium of a specific antisense oligonucleotide to block FasL synthesis, a recombinant Fas/Fc chimeric protein to compete with Fas receptor for FasL binding, or cell-permeable specific tetrapeptide inhibitors of caspase-3 or caspase-8.
...
PMID:Involvement of Fas (CD95/APO-1) and Fas ligand in apoptosis induced by ganciclovir treatment of tumor cells transduced with herpes simplex virus thymidine kinase. 1043 92

Normal epithelial cells undergo apoptosis if integrinmediated matrix contacts are lost, in a process termed 'anoikis'. Anoikis prevents shed epithelial cells from colonizing elsewhere, and is thus essential for maintaining appropriate tissue organisation. Aberrant oncogenes or tumor suppressor genes can cause resistance to anoikis, thereby contributing substantially to malignancy. Apoptosis is mediated by a well-ordered signaling cascade, which involves activation of intracellular proteases known as caspases. However, the mechanism by which the caspase cascade is initiated following cell-matrix detachment is unknown. We have hypothesized that death receptor activation might be involved in anoikis. To test this hypothesis, we developed a transient assay for anoikis and used it to assay the effects of proteins that block the function of domains found within death receptors known as death domains. In this assay, silencer of death domains (SODD) and dominant-negative FAS-associated death domain protein (FADD) efficiently inhibited anoikis in Madin-Darby canine kidney (MDCK) cells. The protective activity of SODD required its BAG domain, which interacts with the heat shock proteins hsp70 and hsc70, and inhibits the chaperone activity of the latter. Both caspase 8, which physically associates with death receptors, and cleavage of the caspase-8 substrate BID, were activated by cell-matrix detachment. These findings indicate a role for death receptors or proteins with related death domains in triggering anoikis.
...
PMID:Evidence for a function of death-receptor-related, death-domain-containing proteins in anoikis. 1050 12

The human monoclonal antibody SC-1 induces apoptosis of stomach carcinoma cells and is currently used in a clinical Phase II trial. The antibody binds to a target molecule that is preferentially expressed on diffuse- and intestinal-type stomach cancer cells and shows a very restricted expression on other normal and malignant tissues. In this paper, we show that the SC-1 receptor is a stomach carcinoma-associated isoform of CD55 [membrane-bound decay-accelerating factor (DAF)-B] with a relative molecular mass of approximately 82 kDa. The antigenic site of SC-1 is an N-linked carbohydrate residue. Cross-linking of the DAF receptor increases apoptotic activity. SC-1 binding induces tyrosine phosphorylation of three proteins of approximately 60, 75, and 110 kDa, whereas a serine residue of an approximately 35-kDa protein is dephosphorylated. Expression of caspase-3 (CPP32) and caspase-8 (FLICE) is elevated, and activation of these caspases occurs. These data show that a tumor-specific variant form DAF is involved in apoptosis and can be used for adjuvant therapeutical purposes on gastric carcinoma.
...
PMID:Characterization of glycosylphosphatidylinositol-linked molecule CD55/decay-accelerating factor as the receptor for antibody SC-1-induced apoptosis. 1053 13

alpha-Fetoprotein (AFP) is an oncoembryonal protein with multiple cell growth regulating, differentiating and immunosuppressive activities. Previous studies have shown that treatment of tumor cells in vitro with 1-10 microM AFP produces significant suppression of tumor cell growth by inducing dose-dependent cytotoxicity, but the molecular mechanisms underlying these AFP functions are obscure. Here, we show that AFP cytotoxicity is closely related to apoptosis, as shown by cell morphology, nuclear DNA fragmentation and caspase-3-like activity resulting in cleavage of poly(ADP-ribose) polymerase. Apoptosis was significantly inhibited by a CPP32 family protease inhibitor whereas a general caspase inhibitor had no inhibitory effect, showing some enhancement of AFP-mediated cell death. Using fluorogenic caspase substrates, we found that caspase-3-like proteases were activated as early as 4 h after treatment of Raji cells with 15 microM AFP, whereas caspase-1, caspase-8, and caspase-9-like activity was not detected during the time interval 0.5-17 h. AFP treatment of Raji cells increased Bcl-2 protein, showing that AFP-induced apoptosis is not explained by downregulation of the Bcl-2 gene. This also suggests that AFP operates downstream of the Bcl-2-sensitive step. AFP notably decreased basal levels of soluble and membrane-bound Fas ligand. Incubation of AFP-sensitive tumor cells (HepG2, Raji) with neutralizing anti-Fas, anti-tumor necrosis factor receptor (TNFR)1 or anti-TNFR2 mAb did not prevent AFP-induced apoptosis, demonstrating its independence of Fas-dependent and TNFR-dependent signaling. In addition, it was found that cells resistant to TNF-induced (Raji) or Fas-induced (MCF-7) apoptosis are, nevertheless, sensitive to AFP-mediated cell death. In contrast, cells sensitive to Fas-mediated cell death (Jurkat) are completely resistant to AFP. Taken as a whole, our data demonstrate that: (a) AFP induces apoptosis in tumor cells independently of Fas/Fas ligand or TNFR/TNF signaling pathways, and (b) AFP-mediated cell death involves activation of the effector caspase-3-like proteases, but is independent of upstream activation of the initiator caspase-1, caspase-8, and caspase-9-like proteases.
...
PMID:alpha-fetoprotein causes apoptosis in tumor cells via a pathway independent of CD95, TNFR1 and TNFR2 through activation of caspase-3-like proteases. 1058 68

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) has been shown to exert potent cytotoxic activity against many tumor cell lines but not against normal cells. It has been hypothesized that this difference in TRAIL sensitivity between normal and transformed cells might be due to the expression of the non-death-inducing TRAIL receptors (TRAIL-R) TRAIL-R3 and TRAIL-R4, presumably by competition for limited amounts of TRAIL. To assess the regulation of resistance versus sensitivity to TRAIL in primary as well as transformed keratinocytes, we examined TRAIL sensitivity, TRAIL receptor expression, and intracellular signaling events induced by TRAIL. Although TRAIL induced apoptosis in primary as well as transformed keratinocytes, a marked difference in sensitivity could be observed with primary keratinocytes (PK) being 5-fold less sensitive to TRAIL than transformed keratinocytes (TK). Yet both cell types exhibited similar TRAIL receptor surface expression, suggesting that expression of TRAIL-R3 and TRAIL-R4 may not be the main regulator of sensitivity to TRAIL. Biochemical analysis of the signaling events induced by TRAIL revealed that PK could be sensitized for TRAIL and, similarly, for TRAIL-R1- and TRAIL-R2-specific apoptosis by pretreatment of the cells with cycloheximide (CHX). This sensitization concomitantly resulted in processing of caspase-8, which did not occur in TRAIL-resistant PK. These data indicate that an early block of TRAIL-induced apoptosis was present in PK compared with TK or PK treated with CHX. Interestingly, cellular FLICE inhibitory protein (cFLIP) levels, high in PK and low in TK and several other squamous cell carcinoma cell lines, decreased rapidly after treatment of PK with CHX, correlating with the increase in TRAIL sensitivity and caspase-8 processing. Furthermore, ectopic expression of cFLIP long (cFLIP(L)) in TK by transfection with a cFLIP(L) expression vector resulted in resistance to TRAIL-mediated apoptosis of these cells. Thus, our results demonstrate that TRAIL sensitivity in PK is primarily regulated at the intracellular level rather than at the receptor level.
...
PMID:Regulation of tumor necrosis factor-related apoptosis-inducing ligand sensitivity in primary and transformed human keratinocytes. 1067 36

Prostate apoptosis response-4 (Par-4) is a 38-kDa protein initially identified as the product of a gene upregulated in prostate tumor cells undergoing apoptosis. Par-4 contains both a death domain and a leucine zipper domain, and has been shown to interact with several proteins known to modulate apoptosis, including protein kinase Czeta, Bcl-2, and caspase-8. A rapid increase in Par-4 levels occurs in neurons undergoing apoptosis in a variety of paradigms, including trophic factor withdrawal, and exposure to oxidative and metabolic insults. Par-4, which can be induced at the translational level, acts at an early stage of the apoptotic cascade prior to caspase activation and mitochondrial dysfunction. The mechanism whereby Par-4 promotes apoptosis may involve inhibition of the antiapoptotic transcription factor NF-kappaB and suppression of Bcl-2 expression and/or function. Studies of postmortem tissues from patients and animal models of neurodegenerative disorders, including Alzheimer's, Parkinson's, and Huntington's diseases, amyotrophic lateral sclerosis (ALS), and HIV encephalitis, have documented increased levels of Par-4 in vulnerable neurons. Manipulations that block Par-4 expression or function prevent neuronal cell death in models of each disorder, suggesting a critical role for Par-4 in the neurodegenerative process. Interestingly, Par-4 levels rapidly increase in synaptic terminals following various insults, and such local increases in Par-4 levels appear to play important roles in synaptic dysfunction and degeneration. A better understanding of the molecular and cellular biology of Par-4 will help clarify mechanisms of neuronal apoptosis, and may lead to the development of novel preventative and therapeutic strategies for neurodegenerative disorders.
...
PMID:Par-4: an emerging pivotal player in neuronal apoptosis and neurodegenerative disorders. 1069 Dec 89

Our recent studies suggest that human squamous cell carcinoma of the head and neck (SCCHN) is capable of activating an intrinsic mechanism of programmed-cell death in interacting lymphocytes in situ and in vitro. The current study used Jurkat T-cell line as a model to investigate intracellular apoptotic events in T cells interacting with SCCHN. Apoptosis induced in T lymphocytes by tumor cells was in part Fas-mediated, since it was partially, but significantly, inhibited in the presence of anti-Fas ligand Ab or in Fas-resistant Jurkat cells. The synthetic caspase inhibitors, N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethyl ketone (Z-VAD-FMK) and N-benzyloxycarbonyl-Asp-glu-Val-Asp-fluoromethyl ketone (Z-DEVD-FMK), effectively blocked apoptosis of Jurkat cells co-incubated with SCCHN cell lines, suggesting the involvement of caspases in tumor-induced apoptosis of lymphocytes. Overexpression of CrmA, an inhibitor of caspase-1 and caspase-8, partially inhibited tumor-induced T-cell death. Caspase-8 and caspase-3 were identified as effector molecules in the execution of tumor-induced T-cell death, since the proform enzymes were processed into active subunits during co-incubation of T cells with tumor cells. Furthermore, co-incubation with tumor cells resulted in cleavage of poly(ADP-ribose) polymerase (PARP), a common caspase-3 substrate, and in cleavage of TcR-zeta chain, shown by us to be a T-cell specific caspase-3 substrate. Overexpression of Bcl-2 did not provide protection of T cells from SCCHN-induced DNA degradation. Instead, the Bcl-2 protein was cleaved in the target T cells during their co-incubation with tumor cells. These findings demonstrate that tumor cells can trigger in T lymphocytes caspase-dependent apoptotic cascades, which are not effectively protected by Bcl-2. (Blood. 2000;95:2015-2023)
...
PMID:Tumor-induced apoptosis of T lymphocytes: elucidation of intracellular apoptotic events. 1070 69

A CTL clone that recognizes autologous tumor cells was previously isolated from the blood of a head-and-neck cancer patient. The Ag was identified as peptide FPSDSWCYF presented by autologous HLA-B*3503 molecules. This peptide was encoded by a mutated CASP-8 gene, which is implicated in the triggering of apoptosis. Here, we show that this CTL clone, which expresses a single TCR, also recognizes two unrelated peptides on allogeneic HLA-B*3501 molecules. One peptide, HIPDVITY, is encoded by squalene synthase, and the other one, QFADVIVLF, is encoded by 2-hydroxyphytanoyl-CoA lyase. Both genes are expressed ubiquitously. These antigenic peptides are processed and presented by HLA-B*3501 cells. The two HLA-B35 alleles are closely related. Our results might reinforce the notion that the recognition of allogeneic HLA molecules depends on the presence in their groove of a limited number of peptides processed from ubiquitous proteins.
...
PMID:A human CTL recognizes a caspase-8-derived peptide on autologous HLA-B*3503 molecules and two unrelated peptides on allogeneic HLA-B*3501 molecules. 1075 7

Growth factor deprivation-induced apoptosis plays an important role in several cellular systems. However, knowledge of the molecular mechanisms involved are restricted to a few murine models or tumor cell lines. Therefore, we aimed studying signaling pathways leading to apoptosis in activated human peripheral T cells after IL-2 withdrawal. Lymphoblasts from patients with CD 95 (Fas/APO-1)-deficiency revealed that functional CD95 was not required to induce apoptosis after IL-2 withdrawal. Moreover, apoptosis induction in response to various cytotoxic stimuli was found to be mediated in the absence of functional CD95 but was affirmatorily influenced by IL-2 signaling. Immunoblots showed no downregulation of Bcl-2 or Bcl-xL and no upregulation of Bax, whereas decreased mitochondrial membrane potential was readily measurable 24 h after cytokine deprivation. Tetrapeptide inhibitors showed limited efficacy in preventing apoptosis whereas the caspase inhibitor zVAD-FMK potently blocked induction of apoptosis. Cleavage of different fluorogenic substrates revealed multiple caspase enzyme activities in lymphoblasts, which were not negatively affected by the fas mutation. Starting at 8 h after IL-2 withdrawal, upregulation of active caspase-3 but not of caspase-8 could be detected. Taken together, our data argue for molecular mechanisms of cytokine deprivation-induced apoptosis in activated human lymphocytes independent of CD95.
...
PMID:CD 95-independent mechanisms of IL-2 deprivation-induced apoptosis in activated human lymphocytes. 1082 77

<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>