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Tumor Suppressor Protein (tumor + suppressor_protein)
Selected AbstractsSEI family of nuclear factors regulates p53-dependent transcriptional activationGENES TO CELLS, Issue 8 2005Rie Watanabe-Fukunaga SEI family proteins, p34SEI-1 and SEI-2(TRIP-Br2), are nuclear factors that are implicated in cell cycle regulation through interaction with CDK4/CyclinD and E2F-1/DP-1 complexes. Here we report that the SEI family proteins regulate transcriptional activity of p53 tumor suppressor protein. Expression of SEI-1, SEI-2 or SEI-3 strongly stimulates p53-dependent gene activation in HeLa and U2OS cells but not in p53-deficient Saos2 or p53-knockdown HeLa cells. SEI proteins possess an intrinsic transactivation activity, interact with the coactivator CREB-binding protein, and cooperate synergistically with the ING family of chromatin-associated proteins to stimulate the transactivation function of p53. Doxycycline-induced expression of SEI proteins results in activation of the p21 gene and inhibition of cell growth, but the growth arrest was not suppressed by the siRNA-mediated knockdown of the endogenous p53 protein. These results indicate that the SEI family of nuclear proteins regulates p53 transcriptional activity and a p53-independent signaling pathway leading to growth inhibition. [source] Aberrant p53 alters DNA damage checkpoints in response to cisplatin: Downregulation of CDK expression and activityINTERNATIONAL JOURNAL OF CANCER, Issue 5 2004Katharine H. Wrighton Abstract The p53 tumor suppressor protein is a critical mediator of cell cycle arrest and apoptosis in response to genotoxic stress. Abrogation of p53 function is a major feature of tumor development and may result in a compromised DNA-damage response. In our study, we examined the effect of expressing a human p53 cDNA, encoding a histidine to leucine amino acid substitution at codon 179 (H179L), on the ability of wild-type p53-containing NIH3T3 cells to respond to treatment with the chemotherapeutic cisplatin. After 72 hr of cisplatin treatment control cells underwent apoptosis preceded by a combination of S- and G2 arrest, as judged by flow cytometry of propidium iodide-stained cells, and TUNEL and caspase-3 assays. This correlated with increased expression of the pro-apoptotic protein Bax. In contrast, cells stably expressing H179L-p53 arrested in S-phase following cisplatin treatment, which correlated with a marked decrease in the expression of cdc2, cyclin B1 and cyclin A, and a decrease in CDK2 and cyclin A-associated kinase activity. Interestingly, H179L p53 expressing cells underwent apoptosis earlier than control cells, indicating that this aberrant p53 may enhance cisplatin chemosensitivity. These data suggest that dominant-negative p53 can influence the expression and activity of CDK complexes, thereby modifying cell behavior following cisplatin-induced genotoxicity. © 2004 Wiley-Liss, Inc. [source] Mycosis fungoides associated with malignant melanoma and dysplastic nevus syndromeINTERNATIONAL JOURNAL OF DERMATOLOGY, Issue 2 2003J. A. Pielop MD Background The increased risk of second malignancies, including nonmelanoma skin cancers, in cutaneous T-cell lymphoma (CTCL) patients has been well documented. However, relatively few studies of malignant melanoma in CTCL patients have been reported. Methods A database of 250 CTCL patients registered over a 3-year period was searched to identify patients with diagnoses of both mycosis fungoides (MF) and malignant melanoma. Results We identified six cases of MF associated with malignant melanoma and one associated with dysplastic nevus syndrome, which is a marker of increased risk of melanoma. In four patients, melanoma was diagnosed along with or before MF. In the remaining two patients, MF was diagnosed prior to melanoma, although dysplastic nevi were noted at the time MF was diagnosed. These two patients received treatment for their MF (one with topical nitrogen mustard and another with radiation therapy and nitrogen mustard) prior to the histologic confirmation of melanoma. Six patients had early stages of MF (IA or IB), while one patient presented with simultaneous erythrodermic mycosis fungoides involving the lymph nodes as well as melanoma metastatic to the lymph nodes from an unknown primary. Conclusion There is an elevated prevalence of malignant melanoma in MF patients compared to the general US population (P < 0.00001) with a relative risk of 15.3 for observing malignant melanoma in MF patients (95% confidence interval 7.0,33.8). Possible pathologic links between the two diagnoses include effects of mycosis fungoides therapies, immunosuppression secondary to mycosis fungoides, and genetic alterations in the p16 tumor suppressor protein. [source] Nuclear accumulation of glycogen synthase kinase-3 during replicative senescence of human fibroblastsAGING CELL, Issue 5 2004Jaroslaw W. Zmijewski Summary Activation of the tumor suppressor protein p53 contributes to cellular senescence. As glycogen synthase kinase-3 (GSK3) was recently found to interact with p53 and contribute to the actions of p53, this study examined whether GSK3 accumulated in the nucleus and associated with p53 in senescent cells. Compared with young and middle-aged human WI-38 fibroblasts, senescent cells were found to contain increased nuclear levels of GSK3,, and also tended to accumulate in the nucleus the other isoform of GSK3, GSK3,. Co-immunoprecipitation experiments demonstrated that GSK3, and p53 formed a complex in the nucleus. Further experiments tested whether inhibition of GSK3 altered the development of senescence using long-term treatment with the selective GSK3 inhibitor lithium. Lithium treatment reduced the senescence-associated accumulation of p53 and caused cells to enter a reversible quiescent state. These results indicate that a portion of the p53 that is activated in senescent cells is modulated by its association with GSK3, in the nucleus, an association that is known to facilitate the actions of p53 and that may contribute to senescence. [source] Isolation and functional analysis of five HPVE6 variants with respect to p53 degradationJOURNAL OF MEDICAL VIROLOGY, Issue 3 2008Thomas Hiller Abstract Persistent infection with high risk human papillomavirus is a necessary risk factor in the etiology of invasive cervical carcinoma. With regard to molecular details, the best studied types are HPV16 and HPV18 which are found in 70% of cervical cancer worldwide, however factors associated with the progression of individual cervical intraepithelial neoplasias into cancer are still poorly understood. Intratype amino acid variations in the immortalizing and transforming early proteins E6 and E7 were described to be associated with progressive disease and linked to increased viral persistence or progression. One of the key actions of high risk HPVE6 proteins is the inhibition of the function of p53, a tumor suppressor protein, by enhancing its degradation through the ubiquitin pathway. In this study, variants of five HPV type E6 proteins (HPV35, 53, 56, 66, and 70) isolated from patient materials are described and functional analysis of them were done with respect to p53 degradation. Interestingly the E6 protein of HPV type 53, which has no consistent risk classification in the literature showed the highest variability in our study. The analysis of all variants revealed no differences with regard to the degradation ability for p53 compared to the prototype E6 proteins, suggesting that the variants tested revealed no altered functions related to the carcinogenicity of the respective HPV types. It therefore seems more likely that variations in the E6 gene sequence may allow evasion from the hosts immune system, supporting increased viral persistence. J. Med. Virol. 80:478,483, 2008. © 2008 Wiley-Liss, Inc. [source] The tumor suppressor parafibromin is required for posttranscriptional processing of histone mRNAMOLECULAR CARCINOGENESIS, Issue 3 2010Leslie J. Farber Abstract Parafibromin, encoded by the gene HRPT2, is a tumor suppressor protein associated with the RNA polymerase II-associated complex, Paf1 complex. HRPT2 mutations were first identified in patients with the multiple endocrine neoplasia syndrome, hyperparathyroidism-jaw tumor (HPT-JT) syndrome, and have also been found in sporadic parathyroid and renal tumors. However, the mechanisms by which parafibromin suppresses tumor formation remain unknown. In this study, we identify a novel role of parafibromin in the regulation of replication-dependent histones. Both in vitro and in vivo analyses reveal a posttranscriptional role of parafibromin in histone mRNA processing. Downregulation of parafibromin through RNA interference or in vivo mutations lead to uncleaved histone mRNA with polyadenylated tails. These results indicate that parafibromin regulates the 3, processing of histone RNA, an essential component of the cell cycle. © 2009 Wiley-Liss, Inc. [source] Differential protein expression in human gliomas and molecular insightsPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 4 2005Vaibhav C. Chumbalkar Abstract Gliomas are the most common of the primary intracranial tumors with astrocytomas constituting about 40%. Using clinically and histologically assessed astrocytomas, we have studied their protein profiles using a two-dimensional gel electrophoresis-mass spectrometry approach and identified differentially expressed proteins which may be useful molecular indicators to understand these tumors. Examination of the protein profiles of 27,astrocytoma samples of different grades revealed 72,distinct, differentially expressed proteins belonging to various functional groups such as cytoskeleton and intermediate filament proteins, heat shock proteins (HSPs), enzymes and regulatory proteins. Based on the consistency of their differential expression, 29,distinct proteins could be short-listed and may have a role in the pathology of astrocytomas. Some were found to be differentially expressed in both Grade,III and IV astrocytomas while others were associated with a particular grade. A notable observation was underexpression of Prohibitin, a potential tumor suppressor protein, Rho-GDP dissociation inhibitor, Rho-GDI, a regulator of Rho GTPases and HSPs as well as destabilization of glial fibrillary acidic protein, GFAP, major protein of the glial filaments, in Grade,III malignant tumors. We attempt to explain glioma malignancy and progression in terms of their combined role. [source] Genotyping single nucleotide polymorphisms using intact polymerase chain reaction products by electrospray quadrupole mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 18 2001James J. Walters Both single nucleotide polymorphisms (SNPs) and mutations are commonly observed in the gene encoding the tumor suppressor protein, p53. SNPs occur at specific locations within genes whereas mutations may be distributed across large regions of genes. When determining nucleotide differences, mass spectrometry is the only method other than Sanger sequencing which offers direct structural information. Electrospray ionization (ESI) quadrupole mass spectrometry (MS) analysis of intact polymerase chain reaction (PCR) products was performed following a simple purification and on-line heating to limit ion adduction. The PCR products were amplified directly from genomic DNA rather than plasmids, as in our previous work. Two known polymorphisms of the p53 gene were genotyped. A cytosine (C) or guanine (G) transversion, designated C,,,G (G,,,C on the opposite strand), were each detected by a 40.0,Da change upon ESI quadrupole MS analysis. Using known PCR products as standards, the genotypes determined for 10 human samples corresponded with restriction fragment length polymorphism (RFLP) analysis. Cytosine/thymine (T) transitions, designated C,,,T (G,,,A on the opposite strand), were also genotyped by ESI-MS. This SNP is discriminated by a 15.0,Da change on one strand (C,,,T) and a 16.0,Da change on the other (G,,,A). Appropriate sample preparation and instrumental configuration (including heated sample inlet syringe and MS source), to limit adducts, are both vital for successful ESI quadrupole MS analysis of intact PCR products. Copyright © 2001 John Wiley & Sons, Ltd. [source] Synthetic small interfering RNA targeting heat shock protein 105 induces apoptosis of various cancer cells both in vitro and in vivoCANCER SCIENCE, Issue 7 2006Seiji Hosaka We previously reported that heat shock protein 105 (HSP105), identified by serological analysis of a recombinant cDNA expression library (SEREX) using serum from a pancreatic cancer patient, was overexpressed in various human tumors and in the testis of adult men by immunohistochemical analysis. In the present study, to elucidate the biological function of the HSP105 protein in cancer cells, we first established NIH3T3 cells overexpressing murine HSP105 (NIH3T3-HSP105). The NIH3T3-HSP105 cells acquired resistance to apoptosis induced by heat shock or doxorubicin. The small interfering RNA (siRNA)-mediated suppression of HSP105 protein expression induced apoptosis in human cancer cells but not in fibroblasts. By a combination of siRNA introduction and doxorubicin or heat shock treatment, apoptosis was induced synergistically in a human colon cancer cell line, HCT116. In vivo, siRNA inoculation into the human gastric cancer cell line KATO-3 established in the flank of an NOD SCID mouse suppressed the tumor growth. This siRNA-induced apoptosis was mediated through caspases, but not the p53 tumor suppressor protein, even though the HSP105 protein was bound to wild-type p53 protein in HCT116 cells. These findings suggest that the constitutive overexpression of HSP105 in cancer cells is involved in malignant transformation by protecting tumor cells from apoptosis. HSP105 may thus be a novel target molecule for cancer therapy and a treatment regimen using synthetic siRNA to suppress the expression of HSP105 protein may provide a new strategy for cancer therapy. (Cancer Sci 2006; 97: 623,632) [source] Jostling for Position: Optimizing Linker Location in the Design of Estrogen Receptor-Targeting PROTACsCHEMMEDCHEM, Issue 7 2010Kedra Cyrus Dr. Abstract Estrogen receptor-, (ER) antagonists have been widely used for breast cancer therapy. Despite initial responsiveness, hormone-sensitive ER-positive cancer cells eventually develop resistance to ER antagonists. It has been shown that in most of these resistant tumor cells, the ER is expressed and continues to regulate tumor growth. Recent studies indicate that tamoxifen initially acts as an antagonist, but later functions as an ER agonist, promoting tumor growth. This suggests that targeted ER degradation may provide an effective therapeutic approach for breast cancers, even those that are resistant to conventional therapies. With this in mind, we previously demonstrated that proteolysis targeting chimeras (PROTACs) effectively induce degradation of the ER as a proof-of-concept experiment. Herein we further refined the PROTAC approach to target the ER for degradation. The ER-targeting PROTACs are composed of an estradiol on one end and a hypoxia-inducing factor,1, (HIF-1,)-derived synthetic pentapeptide on the other. The pentapeptide is recognized by an E3 ubiquitin ligase called the von,Hippel Lindau tumor suppressor protein (pVHL), thereby recruiting the ER to this E3 ligase for ubiquitination and degradation. Specifically, the pentapeptide is attached at three different locations on estradiol to generate three different PROTAC types. With the pentapeptide linked through the C7, position of estradiol, the resulting PROTAC shows the most effective ER degradation and highest affinity for the estrogen receptor. This result provides an opportunity to develop a novel type of ER antagonist that may overcome the resistance of breast tumors to conventional drugs such as tamoxifen and fulvestrant (Faslodex). [source] Synthesis and Biological Characterization of Argyrin,FCHEMMEDCHEM, Issue 6 2010Leila Bülow Argyrin,F unfolds its promising antitumor activity twice: First through stabilization of the tumor suppressor protein p27 and second by vascular damage. [source] | ||||||||||||||||