Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P06889 (Mol)
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p53 family proteins include p53 tumor suppressor, p63, and p73. Despite the high similarity in structure and function with p53, p63, and p73 function in tumor suppression is still controversial. Here, we show that TAp73alpha, a transcriptionally active p73 isoform, is able to synergize p53 tumor suppressor function in thyroid cancer cells. Indeed, depletion of p73 by small interfering RNA in thyroid cancer cells resulted in a reduced transcriptional activity of p53. Ectopic coexpression of both p53 and TAp73alpha in thyroid cancer cells resulted in increased transcription and tumor suppressor function compared with p53 or TAp73alpha alone, as well as in increased p53 protein levels. The enhancing effect of TAp73alpha on p53 activity is Mdm2 dependent because it is prevented by Mdm2 depletion by small interfering RNA. At least two mechanisms may explain the interference of TAp73alpha with p53 function. First, in thyroid cancer cells, TAp73alpha inhibits the effect of p53 on Mdm2 induction by antagonizing p53 at the Mdm2 promoter level. Second, a TAp73alpha mutant (G264W), which is devoid of DNA binding capability, is still able to increase p53 protein levels by competing with p53 for Mdm2 protein binding. Taken together, these results indicate that in thyroid cancer cells, TAp73alpha is able to increase p53 protein level and function by interfering with Mdm2-mediated p53 degradation. These results may be useful for designing gene therapies aimed at restoring a normal p53 function in thyroid cancer cells.
Mol Cancer Res 2008 Jan
PMID:TAp73 alpha increases p53 tumor suppressor activity in thyroid cancer cells via the inhibition of Mdm2-mediated degradation. 1823 63

p73 and p63 are members of the p53 gene family and have been shown to play an important role in development and homeostasis mainly by regulating the transcription of a variety of genes. A subset of these genes encodes secreted proteins and receptors that may be involved in the communication between adjacent cells. We report here that flotillin-2, a major hydrophobic protein on biomembrane microdomain lipid rafts, is a direct transcriptional target of the p53 family member genes. It has been suggested that such rafts could play an important role in many cellular processes including signal transduction, membrane trafficking, cytoskeletal organization, and pathogen entry. We found that the expression of flotillin-2 was specifically up-regulated by either TAp73beta or TAp63gamma, but not significantly by p53. In addition, flotillin-2 transcription is activated in response to cisplatin in a manner dependent on endogenous p73. By using small interference RNA designed to target p73, we showed that silencing endogenous p73 abolishes the induction of flotillin-2 transcription following cisplatin treatment. Furthermore, we identified a p73/p63-binding site located upstream of the flotillin-2 gene that is responsive to the p53 family members. This response element is highly conserved between humans and rodents. We also found that ectopic expression of TAp73 as well as TAp63 enhances signal transduction by assessing the interleukin-6-mediated phosphorylation of signal transducers and activators of transcription 3. Thus, in addition to direct transactivation, p53 family member genes enhance a set of cellular processes via lipid rafts.
Mol Cancer Res 2008 Mar
PMID:Identification of flotillin-2, a major protein on lipid rafts, as a novel target of p53 family members. 1829 50

Protein palmitoylation is the post-translational addition of the 16-carbon fatty acid palmitate to specific cysteine residues by a labile thioester linkage. Palmitoylation is mediated by a family of at least 23 palmitoyl acyltransferases (PATs) characterized by an Asp-His-His-Cys (DHHC) motif. Many palmitoylated proteins have been identified, but PAT-substrate relationships are mostly unknown. Here we present a method called palmitoyl-cysteine isolation capture and analysis (or PICA) to identify PAT-substrate relationships in a living vertebrate system and demonstrate its effectiveness by identifying CKAP4/p63 as a substrate of DHHC2, a putative tumor suppressor.
Mol Cell Proteomics 2008 Jul
PMID:Identification of CKAP4/p63 as a major substrate of the palmitoyl acyltransferase DHHC2, a putative tumor suppressor, using a novel proteomics method. 1829 95

Malignant pleural mesothelioma (MPM) is a rare cancer that metastasizes to mediastinal lymph nodes (MLNs). The diagnosis of MPM metastatic to MLNs may not be straightforward. We describe 3 cases to highlight unusual entities of MPM metastatic to MLNs as follows. One patient with a history of T3N1M0, poorly differentiated esophageal adenocarcinoma and malignant melanoma presented with shortness of breath, mediastinal lymphadenopathy, and pleural effusion; metastatic disease was clinically suspected. Unexpectedly, immunohistochemical studies supported the diagnosis of MPM metastatic to the MLN on biopsy. In another case, mesothelial cell inclusions were initially diagnosed based on the light microscopy, immunohistochemistry, and lack of pleural thickening on computed tomography studies. Subsequent fine needle aspiration of an enlarged cervical lymph node found an atypical mesothelial proliferation, and metastatic mesothelioma was strongly suspected. Video-assisted thoracoscopic examination showed small visceral nodules, and pleural biopsy was diagnosed as malignant epithelioid mesothelioma. The mediastinal and cervical lymph node biopsies were reinterpreted as positive for MPM. In the last case, MLN biopsy showed a malignant epithelioid cell proliferation. Calretinin, CK5/6, WT-1, D2-40, p63, and CD5 were immunohistochemically detected in the tumor but epithelial markers and TTF-1 were negative. Metastatic mesothelioma was considered based on immunohistochemistry and computerized tomography finding of pleural thickening even though p63 and CD5 positivity were unusual. In summary, MPM may present as mediastinal lymphadenopathy with metastases or it may be a concurrent neoplasm with other malignancies or shows an unusual immunohistochemical staining pattern. Caution should be used when diagnosing mesothelial cell inclusions in MLNs.
Appl Immunohistochem Mol Morphol 2008 May
PMID:Unusual features of malignant pleural mesothelioma metastatic to the mediastinal lymph nodes. 1830 Dec 36

The distinction between sarcomatoid carcinoma (SC) and bona fide sarcoma can be difficult using conventional immunohistochemical markers. Epithelial-mesenchymal transition (EMT) has been proposed as a histogenetic mechanism for the development of SC. Expression of selected markers of EMT (Twist and Slug) was compared with other markers of epithelial differentiation in SC and spindle cell sarcoma to determine the utility of these antigens in this differential diagnosis. Twenty-seven cases of SC (excluding those of gynecologic origin) were stained by immunohistochemistry for cytokeratins (AE1/AE3, 5D3, CK5/6, and 34betaE12), p63, claudin-1, claudin-7, epithelial cadherin, placental cadherin, epithelial cell adhesion molecule/epithelial-specific antigen, 14-3-3sigma, Twist, and Slug. A comparison group of 21 spindle or pleomorphic spindle cell sarcomas was also studied. Immunohistochemical stains were scored in a semiquantitative manner and subsequent exploratory analyses were performed using logistic regression and chi2 tests. Only cytokeratin AE1/AE3 specifically labeled SC in a statistically significant manner. Other epithelial-specific markers tested did not distinguish SC from sarcoma primarily owing to low sensitivity. However, when positive, immunostains such as CK5/6, membranous epithelial cadherin, and nuclear p63 may aid in the distinction of SC from sarcoma. EMT markers were expressed in most cases of both SC and sarcoma, and were not useful in making a differential diagnosis between these neoplasms.
Appl Immunohistochem Mol Morphol 2008 May
PMID:Markers of epithelial-mesenchymal transition and epithelial differentiation in sarcomatoid carcinoma: utility in the differential diagnosis with sarcoma. 1830 Dec 44

The limbal region of the adult cornea contains stem cells which are ultimately responsible for regeneration of the corneal epithelium during wound repair. However, primarily-isolated murine corneal/limbal epithelial cells rapidly senesce on plastic in a serum-free low [Ca(2+)] medium, suggesting only transit amplifying cells are promoted. We developed a novel expansion method by seeding at a low cell density (<500 cells/cm(2)) and prolonging each culture time beyond the lifespan of transit amplifying cells (4 weeks). Expanded cells were uniformly small, negative to K12 keratin, but positive for p63 nuclear staining, and could be subcultured beyond 100 passages. After limiting dilution, one clone (TKE2) was selected that exhibited single cell clonal expansion with a doubling time of 34.2 hrs, and had normal karyotyping, but no anchorage-independent growth. A single cell could be continually expanded to a confluent monolayer on denuded amniotic membrane and became stratified by exposing to the air-medium interface. The resultant stratified epithelium expressed K14 keratin, involucrin, connexin 43 and p63, but not K12 keratin or Pax 6. However, expression of K12 could be up-regulated by increasing extracellular calcium concentration and addition of foetal bovine serum (FBS) at P12, but less so at P85. Therefore, this murine lim-bal/corneal epithelium-derived progenitor cell line still retained the plasticity for adopting corneal lineage differentiation, could be useful for investigating limbal niche cues that may promote corneal epithelial fate decision.
J Cell Mol Med 2008 Aug
PMID:Stratified epithelial sheets engineered from a single adult murine corneal/limbal progenitor cell. 1831 92

Missense mutations in the 3' end of the p63 gene are associated with either RHS (Rapp-Hodgkin syndrome) or AEC (Ankyloblepharon Ectodermal defects Cleft lip/palate) syndrome. These mutations give rise to mutant p63alpha protein isoforms with dominant effects towards their wild-type counterparts. Here we report four RHS/AEC-like patients with mutations (p.Gln9fsX23, p.Gln11X, p.Gln16X), that introduce premature termination codons in the N-terminal part of the p63 protein. These mutations appear to be incompatible with the current paradigms of dominant-negative/gain-of-function outcomes for other p63 mutations. Moreover it is difficult to envisage how the remaining small N-terminal polypeptide contributes to a dominant disease mechanism. Primary keratinocytes from a patient containing the p.Gln11X mutation revealed a normal and aberrant p63-related protein that was just slightly smaller than the wild-type p63. We show that the smaller p63 protein is produced by translation re-initiation at the next downstream methionine, causing truncation of a non-canonical transactivation domain in the DeltaN-specific isoforms. Interestingly, this new DeltaDeltaNp63 isoform is also present in the wild-type keratinocytes albeit in small amounts compared with the p.Gln11X patient. These data establish that the p.Gln11X-mutation does not represent a null-allele leading to haploinsufficiency, but instead gives rise to a truncated DeltaNp63 protein with dominant effects. Given the nature of other RHS/AEC-like syndrome mutations, we conclude that these mutations affect only the DeltaNp63alpha isoform and that this disruption is fundamental to explaining the clinical characteristics of these particular ectodermal dysplasia syndromes.
Hum Mol Genet 2008 Jul 01
PMID:A novel translation re-initiation mechanism for the p63 gene revealed by amino-terminal truncating mutations in Rapp-Hodgkin/Hay-Wells-like syndromes. 1836 88

Carcinosarcomas are malignant tumors with a mixture of carcinomatous and differentiated sarcomatous elements. We investigate the morphology, immunohistochemistry, and comparative genomic hybridization analysis of 3 mixed squamous carcinoma and osteosarcoma of the lung. All patients were male and their ages were 72, 43, and 58 years. The sizes of the neoplasms were 7, 5, and 5 cm in maximum diameter, respectively. Two patients died of the disease 9 and 14 months after surgery; and one is alive 6 months later. By light microscopy, all cases had both squamous and osteosarcomatous structures. Immunohistochemistry was positive for AE3AE1, p63, 34 E12, CAM 5.2 (2/3 cases), CK-7 (2/3 cases), epithelial membrane antigen, E-cadherin, p53, and carcinogenic embryonic antigen in carcinomatous areas, and for vimentin and CD-68 in sarcomatous component. Areas of transition positive for both cytokeratins and vimentin were seen in all cases. A total of 55 copy number changes were detected with a median of 18 abnormalities per case: 48 gains, 6 losses, and 1 high-level amplification. Chromosome alterations in osteosarcomatous areas were similar to those found in lung metastatic osteosarcoma, comparable to those found in carcinomatous areas and to lung squamous carcinomas. Coincidences between carcinomatous areas and osteosarcomatous zones were found as gains in chromosomes 1q, 3q, 5p, 8q, and 12p. These findings provide arguments that favor a common origin for both types of cells, supported by the mixture of cells, the existence of undifferentiated cells positive to both cytokeratin and vimentin markers, and the CGH overlaps of chromosomal gains between carcinomatous and sarcomatous areas.
Diagn Mol Pathol 2008 Sep
PMID:Primary mixed squamous carcinoma and osteosarcoma (carcinosarcomas) of the lung have a CGH mapping similar to primitive squamous carcinomas and osteosarcomas. 1838 57

Therapeutic replacement of the wild-type p53 gene has been pursued as a potential gene therapy strategy in a variety of cancer types; however, some cancer models are resistant to p53 in vivo and in vitro. Therefore, to improve p53 gene therapy, it is important to overcome the resistance to p53-mediated apoptosis. Histone deacetylase inhibitors are a novel class of chemotherapeutic agents that are able to reverse the malignant phenotype of transformed cells. A natural histone deacetylase inhibitor, FK228, is reported to enhance adenovirus infection due in part to the up-regulation of coxsackievirus adenovirus receptor expression. In this study, preclinical experiments were done to establish a mechanistic rationale for the combination of adenovirus-mediated p53 family gene transfer and FK228 pretreatment in future clinical trials. Pretreatment with FK228 enhanced apoptosis in human cancer cells through enhanced transduction of Ad-p53. FK228 also induced hyperacetylation of the p53 protein and specifically enhanced p53-mediated Noxa expression. Additionally, the combination of FK228 and Ad-p53 induced Bax translocation to the mitochondria. The double knockdown of Bax and Noxa expression by small interfering RNA antagonized the synergistic effect of Ad-p53 and FK228 on apoptosis induction. In human cancer xenograft models, FK228 significantly increased the therapeutic effectiveness of p53 as well as p63 gene therapy. These results provide a strong rationale for combining p53 gene therapy and FK228 pretreatment in cancer therapy.
Mol Cancer Ther 2008 Apr
PMID:Histone deacetylase inhibitor FK228 enhances adenovirus-mediated p53 family gene therapy in cancer models. 1841 92

Metaplastic breast carcinoma, a rare tumor composed of adenocarcinomatous and nonglandular growth patterns, is characterized by a propensity for distant metastases and resistance to standard anticancer therapies. We sought confirmation that this tumor is a basal-like breast cancer, expressing epidermal growth factor receptor (EGFR) and stem cell factor receptor (KIT). EGFR activating mutations and high copy number (associated with response to tyrosine kinase inhibitor gefitinib) and KIT activating mutations (associated with imatinib sensitivity) were then investigated. Seventy-seven metaplastic cases were identified (1976-2006); 38 with tumor blocks available underwent pathologic confirmation before EGFR and KIT immunohistochemical analyses. A tissue microarray of malignant glandular and metaplastic elements was constructed and analyzed immunohistochemically for cytokeratin 5/6, estrogen receptor, progesterone receptor, and p63, and by fluorescence in situ hybridization for EGFR and HER-2/neu. DNA isolated from individual elements was assessed for EGFR and KIT activating mutations. All assessable cases were negative for estrogen receptor, progesterone receptor, and (except one) HER2. The majority were positive for cytokeratin 5/6 (58%), p63 (59%), and EGFR overexpression (66%); 24% were KIT positive. No EGFR or KIT activating mutations were present; 26% of the primary metaplastic breast carcinomas were fluorescence in situ hybridization-positive, displaying high EGFR copy number secondary to aneusomy (22%) and amplification (4%). We report here that metaplastic breast carcinoma is a basal-like breast cancer lacking EGFR and KIT activating mutations but exhibiting high EGFR copy number (primarily via aneusomy), suggesting that EGFR tyrosine kinase inhibitors should be evaluated in this molecular subset of breast carcinomas.
Mol Cancer Ther 2008 Apr
PMID:Molecular analysis of metaplastic breast carcinoma: high EGFR copy number via aneusomy. 1841 8


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