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Oncogenic Transformation (oncogenic + transformation)
Selected AbstractsOver-expression of Aurora-A targets cytoplasmic polyadenylation element binding protein and promotes mRNA polyadenylation of Cdk1 and cyclin B1GENES TO CELLS, Issue 7 2005Takashi Sasayama Aurora-A is a centrosomal serine-threonine kinase that regulates mitosis. Over-expression of Aurora-A has been found in a wide range of tumors and has been implicated in oncogenic transformation. However, how Aurora-A over-expression contributes to promotion of carcinogenesis remains elusive. Immunohistochemical analysis of breast tumors revealed that over-expressed Aurora-A is not restricted to the centrosomes but is also found in the cytoplasm. This over-expressed Aurora-A appeared to be phosphorylated on Thr288, which is known to be required for its enzymatic activation. In analogy to Aurora-A's role in oocyte maturation and the early embryonic cell cycle, here we investigated whether ectopically over-expressed Aurora-A can similarly stimulate polyadenylation of mRNA in human somatic cultured cells by interacting with a human ortholog of cytoplasmic polyadenylation element binding protein, h-CPEB. In vitro experiments revealed that Aurora-A binds directly to, and phosphorylates, h-CPEB. We found that polyadenylation of mRNA tails of cyclin B1 and Cdk1 was synergistically stimulated when Aurora-A and h-CPEB were over-expressed, and they were further promoted in the presence of an Aurora-A activator Ajuba. Our results suggest a function of ectopically over-expressed Aurora-A that might be relevant for carcinogenesis. [source] Deletion of the PDZ motif of HPV16 E6 preventing immortalization and anchorage-independent growth in human tonsil epithelial cellsHEAD & NECK: JOURNAL FOR THE SCIENCES & SPECIALTIES OF THE HEAD AND NECK, Issue 2 2008William C. Spanos MD Abstract Background Human papillomavirus 16 (HPV16) has been associated with head and neck squamous cell carcinoma (HNSCC) in up to 60% of sampled specimens. Methods To understand better the viral genes required to transform human tonsil epithelial cells (HTEC), we isolated HTEC's and transduced them with retroviral vectors containing HPV16 E6 and E7. Results Immortalization and anchorage-independent growth of HTEC's only occurred with expression of E6 and E7 with resultant degradation of p53. However, cells expressing E6 lacking the PSD-95/disc-large/Zo-1 (PDZ) motif did not immortalize or grow anchorage independent. Telomerase activity and degradation of p53 were similar for wild-type and mutant E6. Conclusion The mechanism of oncogenic transformation by E6 in HTEC's is dependent on the PDZ binding motif. Identification of pathways affected by the interaction of E6 and PDZ domain containing proteins will further our understanding of how HPV causes HNSCC and will provide potential therapeutic targets. © 2007 Wiley Periodicals, Inc. Head Neck, 2008 [source] Integrin signaling through FAK in the regulation of mammary stem cells and breast cancerIUBMB LIFE, Issue 4 2010Jun-Lin Guan Abstract Focal adhesion kinase (FAK) is a cytoplasmic tyrosine kinase identified as a key mediator of intracellular signaling by integrins, a major family of cell surface receptors for extracellular matrix, in the regulation of different cellular functions in a variety of cells. Upon activation by integrins through disruption of an autoinhibitory mechanism, FAK undergoes autophosphorylation and forms a complex with Src and other cellular proteins to trigger downstream signaling through its kinase activity or scaffolding function. A number of integrins are identified as surface markers for mammary stem cells (MaSCs), and both integrins and FAK are found to play crucial roles in the maintenance of MaSCs in studies using mouse models, suggesting that integrin signaling through FAK may serve as a functional marker for MaSCs. Consistent with previous studies linking increased expression and activation of FAK to human breast cancer, these findings suggest a novel cellular mechanism of FAK promotion of mammary tumorigenesis by maintaining the pools of MaSCs as targets of oncogenic transformation. Furthermore, FAK inactivation in mouse models of breast cancer also reduced the pool of mammary cancer stem cells (MaCSCs), decreased their self-renewal in vitro, and compromised their tumorigenicity and maintenance in vivo, suggesting a potential role of integrin signaling through FAK in breast cancer growth and progression through its functions in MaCSCs. This review discusses these recent advances and future studies into the mechanism of integrin signaling through FAK in breast cancer through regulation of MaCSCs that may lead to development of novel therapies for this deadly disease. © 2010 IUBMB IUBMB Life, 62(4): 268,276, 2010 [source] A novel splice variant of the ,-tropomyosin (TPM2) gene in prostate cancerMOLECULAR CARCINOGENESIS, Issue 6 2010Stephen J. Assinder Abstract Decreased expression of high molecular weight isoforms of tropomyosin (Tm) is associated with oncogenic transformation and is evident in cancers, with isoform Tm1 seemingly an important tumor suppressor. Tm1 expression in prostate cancer has not previously been described. In this study, while demonstrating suppressed levels of Tm1 in the prostate cancer cell lines LNCaP, PC3, and DU-145 compared to normal prostate epithelial cell primary isolates (PrEC), a novel splice variant of the TPM2 gene was identified. Quantitative RT-PCR determined significantly greater levels of the transcript variant in all three prostate cancer cell lines than in normal prostate epithelial cells. Characterization of this novel variant demonstrated it to include exon 6b, previously thought unique to the muscle-specific ,-Tm isoform, with an exon arrangement of 1,2,3,4,5,6a,6b,7,8,10. Inclusion of exon 6b introduces a premature stop codon directly following the 6a,6b exon boundary. Western blot analysis demonstrated the presence of a truncated protein in prostate cancer cell lines that was absent in normal prostate epithelial cells. It is hypothesized that this truncated protein will result in suppression of Tm1 polymer formation required for actin filament association. The lack of Tm polymer,actin association will result in loss of the stable actin microfilament organization and stress fiber formation, a state associated with cell transformation. Mol. Carcinog. © 2010 Wiley-Liss, Inc. [source] Protein phosphatase 1, activity prevents oncogenic transformationMOLECULAR CARCINOGENESIS, Issue 9 2006Cathy W.Y. Liu Abstract Cyclin-dependent kinase 2 (Cdk2) phosphorylates Thr320 of protein phosphatase 1, (PP1,) in late G1, thereby inhibiting its activity. Phosphorylation-resistant PP1,T320A, acting as a constitutively active (CA) mutant, causes a late G1 arrest by preventing the phosphorylation and inactivation of the retinoblastoma protein (pRb). Both PP1,-mediated G1 arrest and PP1, phosphorylation in late G1 require the presence of pRb, indicating that PP1, is a crucial regulator of the pRb pathway, which is almost invariably mutated in human cancer. These findings prompted us to investigate whether PP1, interferes with oncogenic transformation. The ability of NIH 3T3 cells to form foci after transformation with ras/cyclin D1 was significantly inhibited by co-transfection with PP1,T320A, but not PP1,. Likewise, cells expressing PP1,T320A or PP1,T320A fused to green fluorescent protein (GFP) were unable to form colonies in soft agar, regardless of whether PP1, constructs were co-transfected with ras/cyclin D1 or transfected into stably transformed cells. Overexpressed wild-type (Wt) PP1, and GFP-PP1, were phosphorylated in Thr320, most likely explaining its lack of effect. Expression of GFP-PP1,T320A was associated with caspase-cleaved pRb in Western blots (WB) and morphological signs of cell death. These findings demonstrate that PP1, activity can override oncogenic signaling by causing cell-cycle arrest and/or apoptosis rather than restoring contact inhibition or anchorage dependence. © 2006 Wiley-Liss, Inc. [source] Searching cell-secreted proteomes for potential urinary bladder tumor markersPROTEINS: STRUCTURE, FUNCTION AND BIOINFORMATICS, Issue 15 2006Chiao-Yun Lin Abstract To search for biomarkers critical for bladder carcinoma diagnosis and prognosis, secreted proteomes of highly malignant U1 and pre-malignant U4 cell lines were initially analyzed. Proteins in the culture media of the U1 and U4 cell lines were systematically examined by SDS-PAGE combined with MALDI-TOF MS. Among them, expression of pro-u-plasminogen activator (pro-u-PA) was confirmed by Western blot analysis and further evaluated. In analyzing urine samples from bladder cancer patients and normal subjects, we established a statistically significant relationship between the low level and absence of pro-u-PA in urine with high stages and grades of the tumor samples. Constitutive expression of Ras dominant negative protein led to increased expression of pro-u-PA in culture media, indicating that the loss of pro-u-PA is associated with oncogenic transformation. Analysis of cancer-secreted proteomes can be a feasible, non-invasive and efficient strategy for searching potential bladder tumor biomarkers. Our work also has identified the loss of pro-u-PA in urine as potential marker of more advanced bladder carcinoma. [source] Regulating p73 isoforms in human tumoursTHE JOURNAL OF PATHOLOGY, Issue 4 2006PJ Coates Abstract Although mutations in the TP73 gene are extremely rare in human tumours, altered expression is common. In some tumours, most notably leukaemias and lymphomas, expression of TP73 is reduced, suggesting a tumour suppressor role. In contrast, TP73 is over-expressed in many other tumour types, implying that it has oncogenic functions in human tumourigenesis. These conflicting scenarios can be reconciled by the observations that the TP73 gene produces p53-like isoforms (TAp73) and anti-p53 isoforms (,TAp73). Thus, loss of TAp73 or over-expression of ,TAp73 should each promote oncogenic transformation, and the balance of expression of the opposing isoforms is the crucial factor. The mechanisms that regulate expression of TP73 isoforms are therefore of great interest. Recent data provide evidence for interacting roles of ZEB1, p300, and a polymorphic 73 bp deletion in intron 1 of the human TP73 gene in this process. Importantly, alterations to the proposed regulatory pathway for controlling TP73 isoform expression in colorectal cancer are associated with adverse clinico-pathological characteristics. Because p73 is also associated with tumour chemosensitivity, these new findings should provide prognostic information and have the potential to guide future therapeutic decisions. Copyright © 2006 Pathological Society of Great Britain and Ireland. Published by John Wiley & Sons, Ltd. [source] Role of Network Branching in Eliciting Differential Short-Term Signaling Responses in the Hypersensitive Epidermal Growth Factor Receptor Mutants Implicated in Lung CancerBIOTECHNOLOGY PROGRESS, Issue 3 2008Jeremy Purvis We study the effects of EGFR inhibition in wild-type and mutant cell lines upon tyrosine kinase inhibitor TKI treatment through a systems level deterministic and spatially homogeneous model to help characterize the hypersensitive response of the cancer cell lines harboring constitutively active mutant kinases to inhibitor treatment. By introducing a molecularly resolved branched network systems model (the molecular resolution is introduced for EGFR reactions and interactions in order to distinguish differences in activation between wild-type and mutants), we are able to quantify differences in (1) short-term signaling in downstream ERK and Akt activation, (2) the changes in the cellular inhibition EC50 associated with receptor phosphorylation (i.e., 50% inhibition of receptor phosphorylation in the cellular context), and (3) EC50 for the inhibition of activated downstream markers ERK-(p) and Akt-(p), where (p) denotes phosphorylated, upon treatment with the inhibitors in cell lines carrying both wild-type and mutant forms of the receptor. Using the branched signaling model, we illustrate a possible mechanism for preferential Akt activation in the cell lines harboring the oncogenic mutants of EGFR implicated in non-small-cell lung cancer and the enhanced efficacy of the inhibitor erlotinib especially in ablating the cellular Akt-(p) response. Using a simple phenomenological model to describe the effect of Akt activation on cellular decisions, we discuss how this preferential Akt activation is conducive to cellular oncogene addiction and how its disruption can lead to dramatic apoptotic response and hence remarkable inhibitor efficacies. We also identify key network nodes of our branched signaling model through sensitivity analysis as those rendering the network hypersensitive to enhanced ERK-(p) and Akt-(p); intriguingly, the identified nodes have a strong correlation with species implicated in oncogenic transformations in human cancers as well as in drug resistance mechanisms identified for the inhibitors in non-small-cell lung cancer therapy. [source] | |||||||||||||