Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0006826 (cancer)
 1,092,456 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The cyclin-dependent kinase inhibitor p27Kip1 is a negative regulator of cell proliferation. Its expression is known to be altered in a proteasome-dependent manner without changes in DNA level. Reduced expression of p27Kip1 is associated with aggressive behavior in a variety of human cancers. We investigated expression of p27Kip1 protein in human breast cancer using immunohistochemistry to assess its biologic implication along with cell-cycle analysis by flow cytometry. A total of 68 patients with invasive ductal cancer received adjuvant chemotherapy with cyclophosphamide, methotrexate, and 5-FU every 3 weeks for six cycles. In epithelial cells of normal and benign breast disease, expression of p27Kip1 was well preserved while its expression markedly decreased in breast cancer (45 of 68). Expression of p27Kip1 is significantly reduced in poorly differentiated cancers and in the advanced stage of the disease. Levels of p27Kip1 expression correlated with cell populations in G0/G1 phase of the cell cycle. In survival analysis, p27Kip1 was useful to predict disease free survival but not overall survival of the patients after adjuvant chemotherapy. In summary, p27Kip1 seems to have a role in the cell proliferation and differentiation process during carcinogenesis of breast cancer. The results of the present study suggest that p27Kip1 can be used in predicting response to systemic chemotherapy in a subset of patients with breast cancer.
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PMID:Reduced expression of p27Kip1 protein is associated with poor clinical outcome of breast cancer patients treated with systemic chemotherapy and is linked to cell proliferation and differentiation. 1048 43

The sustained cytotoxicity conferred by proteasome inhibitors against a broad spectrum of human cancer cells is mediated by a delicate mechanism of programmed cell death. Similar to microtubule disarraying agents, the cell death induced by these potent antitumor agents precedes blocking in cell cycle transition at G2-M phase. The microtubule damaging antineoplastic drugs can kill tumor cells by inducing phosphorylation of antiapoptotic proteins such as Bcl2, Bcl-xL or MCL-1. The simultaneous apoptosis with Bcl2 phosphorylation was evident in cancer cells challenged with the proteasome inhibitor, MG132. Our studies suggest that the proteasome inhibitor MG132 induced tumor cell killing is mediated through Bcl2 phosphorylation.
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PMID:Potent antitumor agent proteasome inhibitors: a novel trigger for Bcl2 phosphorylation to induce apoptosis. 1049 41

The anticancer activity of the boronic acid dipeptide proteasome inhibitor PS-341 was examined in vitro and in vivo. PS-341 was a potent cytotoxic agent toward MCF-7 human breast carcinoma cells in culture, producing an IC90 of 0.05 microM on 24 h of exposure to the drug. In the EMT-6 tumor cell survival assay, PS-341 was equally cytotoxic administered p.o. or by i.p. injection up to a dose of 2 mg/kg. PS-341 was also toxic to the bone marrow colony-forming unit-granulocyte macrophage. PS-341 increased the tumor cell killing of radiation therapy, cyclophosphamide, and cisplatin in the EMT-6/Parent tumor, but was not able to overcome the in vivo resistance of the EMT-6/CTX and EMT-6/CDDP tumors. In the tumor growth delay assay, PS-341 administered p.o. had antitumor activity against the Lewis lung carcinoma, both primary and metastatic disease. In combination, regimens with 5-fluorouracil, cisplatin, Taxol and adriamycin, PS-341 seemed to produce primarily additive tumor growth delays against the s.c. tumor and was highly effective against disease metastatic to the lungs. The proteasome is an interesting new target for cancer therapy, and the proteasome inhibitor PS-341 warrants continued investigation in cancer therapy.
Clin Cancer Res 1999 Sep
PMID:The proteasome inhibitor PS-341 in cancer therapy. 1049 43

The identification of molecular events relevant in the biology of cancer cells and the possibility of defining the molecular profile of cancer cell lines have radically changed the process of cancer-drug development. Cancer drug discovery relies now mainly on the National Cancer Institute cell line screening program; this screening system allows the selection of compounds with well-defined molecular mechanisms of action by screening them on cell lines characterised at the molecular level and by comparing their cytotoxicity through a computer-based analysis of the response profile. Biologically targeted drugs, which should hit specific molecular or biochemical targets, can be classified by a specific target, such as farnesyltransferase inhibitors, or by general mechanism of action. The clinical development of these new anti-cancer agents presents a significant challenge because clinical studies should comply with the molecular premises and be devised in order to provide the "proof of principle", that is the ability of the drug to interact with and activate or block the molecular target. After a summary of the main features and problems faced in the clinical development of biologically targeted anti-cancer therapies, the pre-clinical and clinical data available for some cell-cycle modulators, signal transduction inhibitors, drugs acting on the mitochondria and proteasome inhibitors will be reviewed.
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PMID:Developing new anti-cancer drugs: novel targets and methodological problems. 1050 68

The human multidrug resistance P-glycoprotein (P-gp) contributes to the phenomenon of multidrug resistance during cancer and AIDS chemotherapy. A potential novel strategy to circumvent the effects of P-gp during chemotherapy is to prevent maturation of P-gp during biosynthesis so that the transporter does not reach the cell surface. Here we report that immature, core-glycosylated P-gp that is prevented from reaching the cell surface by processing mutations or by proteasome inhibitors such as lactacystin or MG-132 exhibited no detectable drug-stimulated ATPase activity. Disulfide cross-linking analysis also showed that the immature P-gp did not exhibit ATP-induced conformational changes as found in the mature enzyme. In addition, the immature P-gp was more sensitive to trypsin than the mature enzyme. These results suggest that P-gp is unlikely to be functional immediately after synthesis. These differences in the structural and enzymatic properties of the mature and core-glycosylated, immature P-gp could potentially be used during chemotherapy, and should result in the search for compounds that can specifically inhibit the maturation of P-gp.
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PMID:The human multidrug resistance P-glycoprotein is inactive when its maturation is inhibited: potential for a role in cancer chemotherapy. 1050 75

p107 protein, a member of the retinoblastoma family protein, suppresses growth promotion in cancer cells. We have already reported evidence that calpain, a calcium dependent protease is involved in the cleavage of p107 protein. We show here that p107 protein can also be a substrate for ubiquitination. A negative growth regulator, the HMG-CoA reductase inhibitor lovastatin was found to induce loss of p107 protein which was reversible by a specific protease inhibitor lactacystin as well as calpain inhibitor. Following treatment with lovastatin higher molecular weight ubiquitinated forms of p107 were detected by anti-p107 immunoprecipitation and anti-ubiquitin Western blotting. These forms further increased when lactacystin was added to culture medium. These results indicate that ubiquitin-proteasome pathway plays a potential role in the degradation as well as calpain. The data presented here suggest a model in which calpain and ubiquitin-proteasome system possibly play a cooperative role in targeting the protein under certain conditions.
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PMID:Proteolytic degradation of the retinoblastoma family protein p107: A putative cooperative role of calpain and proteasome. 1053 70

Wingless/Wnt signaling directs cell-fate choices during embryonic development. In Drosophila, Wingless signaling mediates endoderm induction and the establishment of segment polarity in the developing embryo. The fly Wingless cascade is strikingly similar to the vertebrate Wnt signaling pathway, which controls a number of key developmental decisions such as dorsal-ventral patterning in Xenopus. Factors of the TCF/LEF HMG domain family (Tcfs) have recently been established as the downstream effectors of the Wingless/Wnt signal transduction pathways. Upon Wingless/Wnt signaling, a cascade is initiated that results in the accumulation of cytoplasmic beta-catenin (or its fly homolog, Armadillo). There is also a concomitant translocation of beta-catenin/Armadillo to the nucleus, where it interacts with a specific sequence motif at the N terminus of Tcfs to generate a transcriptionally active complex. This bipartite transcription factor is targeted to the upstream regulatory regions of Tcf target genes including Siamois and Nodal related gene-3 in Xenopus, engrailed and Ultrabithorax in Drosophila via the sequence-specific HMG box, and mediates their transcriptional activation by virtue of transactivation domains contributed by beta-catenin/Armadillo. In the absence of Wingless/Wnt signals, a key negative regulator of the pathway, GSK3 beta, is activated, which mediates the downregulation of cytoplasmic beta-catenin/Armadillo via the ubiquitin-proteasome pathway. In the absence of nuclear beta-catenin, the Tcfs recruit the corepressor protein Groucho to the target gene enhancers and actively repress their transcription. An additional corepressor protein, CREB-binding protein (CBP), may also be involved in this repression of Tcf target gene activity. Several other proteins, including adenomatous polyposis coli (APC), GSK3 beta, and Axin/Conductin, are instrumental in the regulation of beta-catenin/Armadillo. In APC-deficient colon carcinoma cell lines, beta-catenin accumulates and is constitutively complexed with nuclear Tcf-4. A proportion of APC wild-type colon carcinomas and melanomas also contains constitutive nuclear Tcf-4/beta-catenin complexes as a result of dominant mutations in the N terminus of beta-catenin that render it insensitive to downregulation by APC, GSK3 beta, and Axin/Conductin. This results in the unregulated expression of Tcf-4 target genes such as c-myc. Based on the established role for Tcf-4 in maintaining intestinal stem cells it is likely that deregulation of c-myc expression as a result of constitutive Tcf-4/beta-catenin activity promotes uncontrolled intestinal cell proliferation. This would readily explain the formation of intestinal polyps during colon carcinogenesis. Similar mechanisms leading to deregulation of Tcf target gene activity are likely to be involved in melanoma and other forms of cancer.
Adv Cancer Res 2000
PMID:The Yin-Yang of TCF/beta-catenin signaling. 1054 54

This study deals with the apoptotic effect exerted on human retinoblastoma Y79 cells by both sodium butyrate and an inhibitor of 26S proteasome [z-Leu-Leu-Leu-CHO (MG132)] and their synergistic effect. Exposure to sodium butyrate (1-4 mM) induced an accumulation of cells in the G2-M phase that was already visible after 24 h of treatment, when morphological and biochemical signs of apoptosis appeared only in a small number of cells (5-10%). Thereafter, the apoptotic effects increased progressively with slow kinetics, reaching a maximum after 72 h of exposure, when they concerned a large fraction of cells (>75% with 4 mM sodium butyrate). Sodium butyrate stimulated the conversion of procaspase-3 into caspase-3 and also induced the cleavage of poly-(ADP-ribose) polymerase and lamin B, two hallmarks of apoptosis. All of the apoptotic signals were suppressed by benzyloxy carbonyl-Val-Ala-Asp-fluoromethylketone (a general inhibitor of caspase activities), whereas acetyl-Asp-Glu-Val-Asp aldehyde, a specific inhibitor of caspase-3 activity, only induced a partial reversion of the apoptotic effects. Sodium butyrate also decreased the Bcl-2 level, whereas it increased the Bax level and stimulated the release of cytochrome c from the mitochondria, an event that was most likely responsible for the activation of caspase-3. Finally, sodium butyrate activated 26S proteasome, the major extralysosomal degradative machinery, which is responsible for the degradation of short-lived proteins. Consequently, the levels of p53, N-myc, and IkappaBalpha (factors that play regulatory roles in apoptosis) diminished, whereas the nuclear level of nuclear factor kappaB concomitantly increased. Treatment of Y79 cells with MG132 induced apoptosis with more rapid kinetics than with sodium butyrate. The effects appeared after 8 h of incubation, reaching a maximum at 24 h, and they were accompanied by increased levels of N-myc, p53, and IkappaBalpha. MG132 also favored the release of cytochrome c from the mitochondria and increased the activity of caspase-3. When Y79 cells were exposed to combinations of sodium butyrate and MG132, the latter compound suppressed the decreasing effect induced by sodium butyrate on the levels of p53, N-myc, and IkappaBalpha and the increasing effect on the nuclear level of nuclear factor kappaB. Moreover, an increase in the level of Bax and an enhancement in the release of cytochrome c from the mitochondria were observed. Clear synergistic effects concerning the activation of both caspase-3 and apoptosis were induced by a combination of suboptimal doses of sodium butyrate and MG132. The results support the conclusion that MG132 potentiates the apoptotic effect of sodium butyrate by suppressing its stimulatory effect on 26S proteasome activity. Synergistic interactions between butyrate and inhibitors of proteasome could represent a new important tool in tumor therapy and, in particular, the treatment of retinoblastoma.
Cancer Res 1999 Nov 01
PMID:The apoptotic effects and synergistic interaction of sodium butyrate and MG132 in human retinoblastoma Y79 cells. 1055 39

Mutant-type p53 (mt p53) is largely accumulated in cancer cells due to its increased stability. To elucidate the mechanism of mt p53 stabilization, we analysed the turnover of p53 mutated at codon 248 whose alteration is most frequently found in human cancers. Proteasome inhibition induced the accumulation of ubiquitinated mt p53, indicating that the ubiquitinated forms were essentially unstable and degraded by the proteasome. The presence of a small amount of the ubiquitinated mt p53 relative to the abundant non-ubiquitinated form suggested that the mt p53 ubiquitination was a rate-limiting process in the slow turnover. Two phenomena destabilizing mt p53 via the ubiquitin-proteasome degradation were proved to be independent. First, the coexpression of wild-type p53 (wt p53) promoted mt p53 destabilization as feedback regulation. Second, geldanamycin also induced mt p53 destabilization through the dissociation of the protein from hsp90 but not through the restoration of wt p53 function. Neither the mutant-specific conformation nor the N-terminal phosphorylation seemed to contribute directly to the mt p53 stabilization. Further, a two-dimensional gel electrophoresis revealed that most of the post-translationally modified mt p53 was equally subjected to ubiquitination and subsequent proteasomal degradation. These findings are evidence that mt p53 stabilization depends on the impaired ubiquitination due to both the loss of wt p53 function and the hsp90 association.
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PMID:The stabilization mechanism of mutant-type p53 by impaired ubiquitination: the loss of wild-type p53 function and the hsp90 association. 1055 93

Overexpression or activation of insulin-like growth factor I receptor (IGF-IR) has been observed in many human cancers including breast, lung, colon and gastric carcinomas. We demonstrate that inhibition of the endogenous insulin-like growth factor I receptor by stable expression of a dominant-negative IGF-IR represses the transforming activity in vitro and tumorigenicity of human lung carcinoma cells A549 in vivo. The suppression of tumorigenicity in nude mice is correlated with the induction of glandular differentiation. In addition, functional inhibition of the endogenous receptor dramatically increases the sensitivity of A549 cells to a variety of apoptotic signals including UV irradiation and proteasome inhibitors. These effects are due to the formation of a stable heterocomplex of the dominant-negative receptor with the endogenous wild type receptor which reduces the kinase activity of the latter by twofold. Thus, inhibition of the IGF-IR signaling pathway not only suppresses tumorigenicity but also enhances sensitivity to apoptosis-inducing agents. Antagonizing IGF-IR signaling by promoting tumor differentiation and enhancing sensitivity to apoptotic death are potential cancer therapeutic approaches.
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PMID:Induction of tumor suppression and glandular differentiation of A549 lung carcinoma cells by dominant-negative IGF-I receptor. 1055 96


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