Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P10415 (Bcl-2)
 33,771 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We report the cloning and functional characterization of human cyclin L2, a novel member of the cyclin family. Human cyclin L2 shares significant homology to cyclin L1, K, T1, T2, and C, which are involved in transcriptional regulation via phosphorylation of the C-terminal domain of RNA polymerase II. The cyclin L2 protein contains an N-terminal "cyclin box" and C-terminal dipeptide repeats of alternating arginines and serines, a hallmark of the SR family of splicing factors. A new isoform and the mouse homologue of human cyclin L2 have also been cloned in this study. Human cyclin L2 is expressed ubiquitously in normal human tissues and tumor cells. We show here that cyclin L2 co-localizes with splicing factors SC-35 and 9G8 within nuclear speckles and that it associates with hyperphosphorylated, but not hypophosphorylated, RNA polymerase II and CDK p110 PITSLRE kinase via its N-terminal cyclin domains. It can also associate with the SC-35 and 9G8 through its RS repeat region. Recombinant cyclin L2 protein can stimulate in vitro mRNA splicing. Overexpression of human cyclin L2 suppresses the growth of human hepatocellular carcinoma SMMC 7721 cells both in vitro and in vivo, inducing cellular apoptosis. This process involves up-regulation of p53 and Bax and decreased expression of Bcl-2. The data suggest that cyclin L2 represents a new member of the cyclin family, which might regulate the transcription and RNA processing of certain apoptosis-related factors, resulting in tumor cell growth inhibition and apoptosis.
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PMID:Cyclin L2, a novel RNA polymerase II-associated cyclin, is involved in pre-mRNA splicing and induces apoptosis of human hepatocellular carcinoma cells. 3259 51

Mistletoe lectin has been reported to induce apoptosis in different cancer cell lines in vitro and to show antitumor activity against a variety of tumors in animal models. We previously demonstrated the Korean mistletoe lectin (Viscum album var. coloratum, VCA)-induced apoptosis by down-regulation of Bcl-2 and telomerase activity and by up-regulation of Bax through p53- and p21-independent pathway in hepatoma cells. In the present study, we observed the induction of apoptotic cell death through activation of caspase-3 and the inhibition of telomerase activity through transcriptional down-regulation of hTERT in the VCA-treated A253 cells. We also observed the inhibition of telomerase activity and induction of apoptosis resulted from dephosphorylation of Akt in the survival signaling pathways. In addition, combining VCA with the inhibitors of phosphatidylinositol 3-kinase (PI3-kinase) upstream of Akt, wortmannin and LY294002 showed an additive inhibitory effect of telomerase activity. In contrast, the inhibitor of protein phosphatase 2A (PP2A), okadaic acid inhibited VCA-induced dephosphorylation of Akt and inhibition of telomerase activity. Taken together, VCA induces apoptotic cell death through Akt signaling pathway in correlated with the inhibition of telomerase activity and the activation of caspase-3. From these results, together with our previous studies, we suggest that VCA triggers molecular changes that resulting in the inhibition of cell growth and the induction of apoptotic cell death of cancer cells, which suggest that VCA may be useful as chemotherapeutic agent for cancer cells.
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PMID:Mistletoe lectin induces apoptosis and telomerase inhibition in human A253 cancer cells through dephosphorylation of Akt. 1496 42

In this study we have investigated the mechanism underlying resistance to the chemotherapeutic drug paclitaxel in tumors of hepatocellular carcinoma (HCC) patients. Treatment with paclitaxel led to potent inhibition of growth of Hep3B hepatoma cells, but did not affect the growth properties of SNU-368 and SNU-398 cell lines that were established from primary HCC tumors. The growth inhibitory effect induced by paclitaxel correlated with levels of intracellular p21 and resulted in cell cycle arrest at the G2/M phase. However, paclitaxel treatment did not alter intracellular p53 levels. Instead, SNU-398 cells express high levels of the anti-apoptotic Bcl-2 and Bcl-x(L) proteins and the level of Bcl-x(L) could be further induced upon paclitaxel treatment. In contrast, Hep3B cells express pro-apoptotic members of the Bcl family and fail to induce Bcl-x(L) upon paclitaxel treatment. Therefore, these results strongly suggest that Bcl-2 and Bcl-x(L) play an important role in mediating resistance to paclitaxel.
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PMID:Bcl-2 and Bcl-xL are important for the induction of paclitaxel resistance in human hepatocellular carcinoma cells. 1497 68

A potent inhibitor of serine/threonine kinases, staurosporine exerts antiproliferative and apoptotic effects in many cancer cells, although the exact mechanism of its action is still unclear. This study examines the effects of staurosporine on Chang liver cells, an immortalized non-tumor cell line, in comparison with those caused in HuH-6 and HepG2 cells, two human hepatoma cell lines. Our results provide evidence that staurosporine promotes apoptosis in Chang liver cells as observed by flow cytometric analysis and acridine orange/ethidium bromide staining. The effect appeared already after 8 h of treatment and increased with treatment time and dose. After 48 h of exposure to 200 nM staurosporine clear apoptotic signs were observed in about 50% of the cells. Western blotting analysis showed that in Chang liver cells staurosporine induced a marked decrease in the levels of the antiapoptotic factors Bcl-2 (-75%) and Bcl-XL (-50%). Staurosporine also caused loss of mitochondrial transmembrane potential, release of cytochrome c from mitochondria and activation of caspase-3. The involvement of caspases in staurosporine-induced cell death was also suggested by the observation that the addition of z-VAD-fmk, a general inhibitor of caspases, suppressed apoptosis. In HuH-6 and HepG2 cells treatment with staurosporine induced the arrest of cells in G2/M phase of cell cycle. This effect was not modified by z-VAD-fmk and was not accompanied by the appearance of biochemical signs of apoptosis. We conclude that staurosporine induced apoptosis in Chang liver cells by a mitochondria-caspase-dependent pathway which was closely correlated with a decrease in Bcl-2 and Bcl-XL levels, while in HuH-6 and HepG2 hepatoma cells the drug caused only an antiproliferative effect.
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PMID:Staurosporine-induced apoptosis in Chang liver cells is associated with down-regulation of Bcl-2 and Bcl-XL. 1501 Aug 57

The central role of T cell activation in hepatocellular injury has been well documented. In this article, we provide evidence suggesting that T cells may also play a protective role in liver disease by releasing interleukin-22 (IL-22), a recently identified T cell-derived cytokine whose biological significance is unclear. IL-22 messenger RNA and protein expression are significantly elevated in T cell-mediated hepatitis induced by concanavalin A (ConA) but are less extensively elevated in the carbon tetrachloride-induced liver injury model. Activated CD3(+) T cells are likely responsible for the production of IL-22 in the liver after injection of ConA. The IL-22 receptor is normally expressed at high levels by hepatocytes and further induced after ConA injection. IL-22 blockade with a neutralizing antibody reduces signal transducer and activator of transcription factor 3 (STAT3) activation and worsens liver injury in T cell-mediated hepatitis, whereas injection of recombinant IL-22 attenuates such injury. In vitro treatment with recombinant IL-22 or overexpression of IL-22 promotes cell growth and survival in human hepatocellular carcinoma HepG2 cells. Stable overexpression of IL-22 in HepG2 cells constitutively activates STAT3 and induces expression of a variety of antiapoptotic (e.g., Bcl-2, Bcl-xL, Mcl-1) and mitogenic (e.g., c-myc, cyclin D1, Rb2, CDK4) proteins. Blocking STAT3 activation abolishes the antiapoptotic and mitogenic actions of IL-22 in hepatic cells. In conclusion, the T cell-derived cytokine IL-22 is a survival factor for hepatocytes; this suggests that T cell activation may also prevent and repair liver injury by releasing hepatoprotective cytokine IL-22 in addition to its previously documented central role in hepatocellular injury.
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PMID:Interleukin 22 (IL-22) plays a protective role in T cell-mediated murine hepatitis: IL-22 is a survival factor for hepatocytes via STAT3 activation. 1512 62

Hepatocellular carcinoma (HCC) is one of the most common malignancies in Asia. HCC is often resistant to chemotherapy and the mechanism remains unclear. Mitochondrion-mediated pathway is critical in hepatocyte apoptosis, which suggests Bcl-2 family genes may play a role in the regulation of chemotherapy in HCC. In the present study, we investigated the role of BH3 domain-only protein Bid in HCC tissues, HCC-derived cell lines and how the expression of Bid was related to chemotherapeutic agent-induced apoptosis. Bid was differently expressed in HCC tissues and hepatoma cell lines. Hep3B, a Bid-abundant HCC cell line, was more sensitive to drug-induced cytotoxicity than PLC/PRF/5, a Bid-insufficient HCC cell line. The level of caspase activity induced by 5-fluorouracil (5-FU) was higher in Hep3B than in PLC/PRF/5 and a significant increase in the activity occurred at a rather late stage, after 48 h of the treatment. Similar to the activation of caspase, Bid cleavage and activation was only significant at 72 h after the treatment. Overexpression of Bid or tBid sensitized HCC cells to 5-FU and doxorubicin (Dox) treatments. We further demonstrated that such a sensitive effect could be offset by Bcl-xL, as Bid- or tBid-induced apoptosis was completely blocked by the over-expression of Bcl-xL. These results indicate the level of Bid expression is closely associated with the sensitivity of HCC cells to chemotherapeutic drugs, suggesting that Bid plays an important role in HCC management.
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PMID:Bid sensitizes apoptosis induced by chemotherapeutic drugs in hepatocellular carcinoma. 1528 66

Hepatoma is one of the most frequently occurring cancers worldwide. However, effective chemotherapeutic agents for this disease have not been developed. Acyclic retinoid, a novel synthetic retinoid, can reduce the incidence of postsurgical recurrence of hepatoma and improve the survival rate. OSI-461, a potent derivative of exisulind, can increase intracellular levels of cyclic GMP, which leads to activation of protein kinase G and induction of apoptosis in cancer cells. In the present study, we examined the combined effects of acyclic retinoid plus OSI-461 in the HepG2 human hepatoma cell line. We found that the combination of as little as 1.0 micromol/L acyclic retinoid and 0.01 micromol/L OSI-461 exerted synergistic inhibition of the growth of HepG2 cells. Combined treatment with low concentrations of these two agents also acted synergistically to induce apoptosis in HepG2 cells through induction of Bax and Apaf-1, reduction of Bcl-2 and Bcl-xL, and activation of caspase-3, -8, and -9. OSI-461 enhanced the G0-G1 arrest caused by acyclic retinoid, and the combination of these agents caused a synergistic decrease in the levels of expression of cyclin D1 protein and mRNA, inhibited cyclin D1 promoter activity, decreased the level of hyperphosphorylated forms of the Rb protein, induced increased cellular levels of the p21(CIP1) protein and mRNA, and stimulated p21(CIP1) promoter activity. Moreover, OSI-461 enhanced the ability of acyclic retinoid to induce increased cellular levels of retinoic acid receptor beta and to stimulate retinoic acid response element-chloramphenicol acetyltransferase activity. A hypothetical model involving concerted effects on p21(CIP1) and retinoic acid receptor beta expression is proposed to explain these synergistic effects. Our results suggest that the combination of acyclic retinoid plus OSI-461 might be an effective regimen for the chemoprevention and chemotherapy of human hepatoma and possibly other malignancies.
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PMID:Synergistic effects of acyclic retinoid and OSI-461 on growth inhibition and gene expression in human hepatoma cells. 1547 62

In the present work, we show that mithramycin A, a drug that is currently used for the treatment of patients with Paget's disease of the bone as well as with several forms of cancer, is a strong activator of the tumor suppressor p53 protein in human hepatoma cells. The time course of p53 activation by mithramycin A was similar to the known chemotherapeutic compound 5-fluorouracil (5-FU). Both 5-FU and mithramycin A induced site-specific phosphorylation of p53 at serine 15. However, in contrast to 5-FU, mithramycin A failed to activate p53 target genes including the cell cycle inhibitor p21Cip1 gene as well as the proapoptotic genes PUMA (p53-upregulated mediator of apotosis) and BAK (bcl2-homologous antagonist/killer) and blocked the induction of the above genes by 5-FU. Using transactivation assays in Sp1-deficient cells, we showed that mithramycin A inhibited the transcriptional activation of the p21Cip1 and PUMA promoters by Sp1 and p53. Using chromatin immunoprecipitation assays and a novel protein-protein interaction assay based on biotinylation in vivo, we established that 5-FU enhanced the formation of p53-Sp1 complexes in solution and the subsequent recruitment of both factors to the p21Cip1 promoter. Mithramycin A also enhanced the recruitment of p53 to the distal p21Cip1 promoter but totally blocked the recruitment of Sp1 to the proximal p21Cip1 promoter. Our findings suggest that inhibition of Sp1 binding to the promoters of several p53 target genes, such as the p21Cip1 gene as well as certain proapoptotic genes, by mithramycin A, prevents the transcriptional induction of these genes by p53 and propose a mechanism that could account for some of the tumor suppressing and antiapoptotic effects of mithramycin A.
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PMID:Inhibition of p53-mediated transcriptional responses by mithramycin A. 1548 92

A new anticancer tripeptide, L-proline-m-bis (2-chloroethyl) amino-L-phenylalanyl-L-norvaline ethyl ester hydrochloride (MF13), was investigated for its activity and mechanism in human hepatocellular carcinoma (HCC) cell lines. MF13 showed antiproliferative activities in the panel of 7 human HCC cell lines with IC50 in the range of 0.08-2.32 microM. A significant blockade in the S-phase occurred in tumor cells 12 h after their exposure to MF13. The inactivated Rb (phosphorylated Rb, pRb), which is present in the S-phase, was increased within 6 h of treatment. Bcl-2 expression was without change in hepatocarcinoma cells treated with MF13; however, a significant increase of bax was observed, resulting in a decreased ratio of bcl-2/bax. Increased activity of caspase-9, -8 and -3 was detected in the MF13 treated cells, indicating an activated pathway of apoptosis by MF13. Morphological examination as well as DNA gel electrophoresis demonstrated a nuclear fragmentation and DNA degradation in the form of multiple-unit DNA ladder in MF13 treated tumor cells. MF13 alone at 10 mg/kg (i.p.) inhibited HepG2 tumor in nude mice by more than 94% in volume. Bel-7402 tumor originated from a Chinese patient with HCC exhibited a sensitivity to MF13 similar to HepG2 in vivo. Antitumor effect of MF13 in the nude mice bearing human hepatocarcinoma (Bel-7402 or HepG2) was stronger than mitomycin C as well as its precursor m-sarcolysin (p<0.01), and comparable with cyclophosphamide. We believe MF13 merits consideration for further investigation as an agent against human hepatocellular carcinoma.
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PMID:Inhibition of human hepatocellular carcinoma by L-proline-m-bis (2-chloroethyl) amino-L-phenylalanyl-L-norvaline ethyl ester hydrochloride (MF13) in vitro and in vivo. 1549 17

Cell-cycle deregulation is an early event of hepatocarcinogenesis. We evaluated the role of changes in activity of nuclear factor kappaB (NF-kappaB) and some related pathways in this alteration, and the interference of N-(4-hydroxyphenyl)retinamide (HPR), a retinoid chemopreventive for various cancer types, with these molecular mechanisms and the evolution of preneoplastic liver to cancer. Male F344 rats, initiated according to the 'resistant hepatocyte' model of liver carcinogenesis, received weekly 840 nmol of liposomal HPR (SL-HPR)/100 g body wt or empty liposomes, between 5 and 25 weeks after initiation. Inhibition of DNA synthesis and induction of apoptosis occurred in pre-cancerous lesions, 7-147 days after starting SL-HPR, and a decrease in carcinoma incidence and multiplicity was observed 25 weeks after arresting treatment. An increase in NF-kappaB expression and binding activity, and under-expression of the inhibitor kappaB-alpha (IkappaB-alpha) were found in preneoplastic liver and neoplastic nodules, 5 and 25 weeks after initiation, respectively. These lesions also showed low expression of Mat1A and low activity of methionine adenosyltransferase I/III, whose reaction product, S-adenosyl-l-methionine, enhances IkappaB-alpha expression. SL-HPR prevented these changes and induced a decrease in expression of iNos, c-myc, cyclin D1 and Vegf-A genes, that were over-expressed in preneoplastic liver and nodules, and a decrease in Bcl-2/Bax, Bcl-2/Bad and Bcl-xL/Bax mRNA ratios with respect to the lesions of control rats. Liposomes alone did not influence the parameters tested. These results indicate that signal transduction pathways controlled by NF-kappaB, nitric oxide and S-adenosyl-l-methionine are deregulated in pre-cancerous lesions. Recovery from these alterations by SL-HPR is associated with chemoprevention of hepatocarcinogenesis. Overall, these studies elucidate some molecular changes, in early stages of hepatocarcinogenesis, and underline their pathogenetic role. Moreover, they demonstrate a partially new mechanism of HPR chemopreventive effect and indicate the potential clinical relevance of this compound for prevention of hepatocellular carcinoma.
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PMID:Chemopreventive N-(4-hydroxyphenyl)retinamide (fenretinide) targets deregulated NF-{kappa}B and Mat1A genes in the early stages of rat liver carcinogenesis. 1549 86


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