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Alexandru Almasan

Publications and source records attributed to Alexandru Almasan.

13 recordsLinked to original sources
PubMed2006

APO2 ligand/tumor necrosis factor-related apoptosis-inducing ligand in prostate cancer therapy.

Prostate cancer is one of the most common cancers in men and is the second leading cause of cancer-related death in the USA. Many anti-tumor agents against prostate cancer cells have been developed, but their unacceptable systemic toxicity to normal tissues usually limits their use in the clinic. Apo2 ligand (Apo2L), also called Tumor necrosis factor (TNF)-related apoptosis-inducing ligand (TRAIL), is one of several members of the TNF gene superfamily that induces apoptosis through engagement of death receptors. This protein has generated tremendous enthusiasm as a potential tumor-specific cancer therapeutic because, as a stable trimer, it selectively induces apoptosis in many transformed cells, but not in most normal cells. In this review we discuss its potential use in prostate cancer therapy, the mechanisms by which induces apoptosis or that underlie resistance to it, and strategies for sensitization to overcome them. Conventional chemotherapeutic and chemopreventive drugs, irradiation, and other therapeutic agents, such as histone deacetylase inhibitors or retinoids can sensitize Apo2L/TRAIL-resistant cells and tumors. Investigating the apoptotic effects of Apo2L/TRAIL, a unique tumor-specific cell death ligand, now in clinical trials, alone or in combination may not only help in understanding its antineoplastic role in prostate carcinoma but may also provide insights into basic mechanisms of apoptosis.

Androgens↗
PubMed2006

Apoptosis assays.

A large number of methods devoted to the identification of apoptotic cells and the analysis of the morphological, biochemical, and molecular changes that take place during this universal biological process have been developed. Apoptotic cells are recognized on the basis of their reduced DNA content and morphological changes that include nuclear condensation and which can be detected by flow cytometry (sub-G1 DNA content), Trypan Blue, or Hoechst staining. Changes in plasma membrane composition and function are detected by the appearance of phosphatidylserine on the plasma membrane, which reacts with Annexin V-fluorochrome conjugates. Combined with propidium iodide (PI) staining, this method can distinguish between the early and late apoptotic events. The best-recognized biochemical hallmarks of apoptosis are the activation of cysteine proteases (caspases), condensation of chromatin, and fragmentation of genomic DNA into nucleosomal fragments. Recognized by a variety of assays, activated caspases cleave many cellular proteins and the resulting fragments may serve as apoptosis markers. Finally, the mitochondria and the Bcl-2 family proteins play an important role in this process that can be recognized by translocation of apoptogenic factors, such as Bax and cytochrome c, in and out of mitochondria.

Annexin A5↗
PubMed2005

Proteolytic cleavage of the p65-RelA subunit of NF-kappaB during poliovirus infection.

Activation of NF-kappaB during viral infection is one of the critical elements in innate immune response. Several virus-specific factors, such as double-stranded RNA, can trigger host defense mechanisms by inducing NF-kappaB-mediated expression of cytokines and interferons. Early stages of poliovirus infection are also associated with degradation of IkappaB alpha and translocation of NF-kappaB into the nucleus. However, at later stages of poliovirus replication the p65-RelA component of the NF-kappaB complex undergoes a specific cleavage that coincides with the onset of intensive poliovirus protein synthesis and the appearance of the activity of poliovirus protease 3C. Indeed, the p65-RelA amino acid sequence contains the recognition site for 3C, and recombinant protein 3C was shown to be capable of proteolytic cleavage of p65-RelA, generating truncated product similar to that observed during poliovirus infection. Cleavage of p65-RelA occurs during replication of ECHO-1 and rhinovirus 14, suggesting that inactivation of NF-kappaB function by proteolytic cleavage of p65-RelA is the common mechanism by which picornaviruses suppress the innate immune response.

Amino Acid Sequence↗
PubMed2005

Superoxide dismutase inactivation in pathophysiology of asthmatic airway remodeling and reactivity.

Airway hyperresponsiveness and remodeling are defining features of asthma. We hypothesized that impaired superoxide dismutase (SOD) antioxidant defense is a primary event in the pathophysiology of hyperresponsiveness and remodeling that induces apoptosis and shedding of airway epithelial cells. Mechanisms leading to apoptosis were studied in vivo and in vitro. Asthmatic lungs had increased apoptotic epithelial cells compared to controls as determined by terminal dUTP nick-end labeling-positive cells. Apoptosis was confirmed by the finding that caspase-9 and -3 and poly (ADP-ribose) polymerase were cleaved. On the basis that SOD inactivation triggers cell death and low SOD levels occur in asthma, we tested whether SOD inactivation plays a role in airway epithelial cell death. SOD inhibition increased cell death and cleavage/activation of caspases in bronchial epithelial cells in vitro. Furthermore, oxidation and nitration of MnSOD were identified in the asthmatic airway, correlating with physiological parameters of asthma severity. These findings link oxidative and nitrative stress to loss of SOD activity and downstream events that typify asthma, including apoptosis and shedding of the airway epithelium and hyperresponsiveness.

Antioxidants↗
PubMed2004

Opposing roles of E2Fs in cell proliferation and death.

Progression through the cell cycle is dependent upon the temporal and spatial regulation of the various members of the E2F family of transcription factors. Two of these members, E2F1 and E2F4 have opposing roles in cell cycle progression, which were defined over a decade ago. While E2F1 is an activator of cell cycle progression, E2F4 functions as a transcriptional repressor. Recent data indicate that these transcription factors also play a role in the cellular response to DNA damage. In the case of E2F1, its overexpression leads to apoptosis. In contrast, the decreased expression of E2F4, in response to siRNA-mediated knockdown or to certain therapeutic agents, induces apoptosis. Conversely, increased levels of E2F4 may confer resistance to apoptosis-inducing therapies used in the clinic. The balance between the activities of these two proteins in tumor cells is of great interest. Directed control of E2F1 and E2F4 action may lead to better diagnosis of disease and improved therapeutic modalities.

Animals↗
PubMed2004

Effects of resveratrol on gene expression in renal cell carcinoma.

Studies have shown that Resveratrol (RE) can inhibit cancer initiation, promotion, and progression. However the gene expression profile in renal cell carcinoma (RCC) in response to RE treatment has never been reported. To understand the potential anticancer effect of RE on RCC at molecular level, we profiled and analyzed the expression of 2059 cancer-related genes in a RCC cell line RCC54 treated with RE. Biological functions of 633 genes were annotated based on biological process ontology and clustered into functional categories. Twenty-nine highly differentially expressed genes in RE treated RCC54 were identified and the potential implications of some gene expression alterations in RCC carcinogenesis were identified. RE was also shown to inhibit cell growth and induce cell death of RCC cells. The expression alterations of selected genes were validated using reverse transcription polymerase chain reaction. In addition, the gene expression profiles under different RE treatments were analyzed and visualized using singular value decomposition. The findings from this study support the hypothesis that RE induces differential expression of genes that are directly or indirectly related to the inhibition of RCC cell growth and induction of RCC cell death. In addition, it is apparent that the gene expression alterations due to RE treatment depend strongly on RE concentration. This study provides a general understanding of the overall genetic response of RCC54 to RE treatment and yields insights into the understanding of the cancer preventive mechanism of RE in RCC.

Angiogenesis Inhibitors↗
PubMed2004

Genotoxic stress induces expression of E2F4, leading to its association with p130 in prostate carcinoma cells.

The retinoblastoma (pRb), p107, and p130 pocket proteins bind to the E2F transcription factors to control gene expression. E2F4 protein levels increased and accumulated in the nuclei of prostate carcinoma cells subjected to ionizing radiation (IR). The IR-induced increase of E2F4 levels led to an increase in E2F4 binding to p130 but had no effect on E2F4/p107 or E2F5/p130 complexes. The increase in E2F4/p130 association after IR was observed in prostate carcinoma cells regardless of their sensitivity to androgens, but not in breast carcinoma cells. E2F4/p130 complex formation was dependent on dissociation of p130 from cyclin-dependent kinase 2 and p130 dephosphorylation. Disruption of E2F4 through small interfering RNA prevented p130/E2F4 complex formation and sensitized cells to IR-induced apoptosis, leading to caspase-3 activation, cleavage of its substrate, poly(ADP-ribose) polymerase, and nuclear condensation. The E2F4/p130 pocket protein complex emerges as a new target of radiation in prostate carcinoma cells.

Apoptosis↗
PubMed2004

Microarray gene expression profiling and analysis in renal cell carcinoma.

BACKGROUND: Renal cell carcinoma (RCC) is the most common cancer in adult kidney. The accuracy of current diagnosis and prognosis of the disease and the effectiveness of the treatment for the disease are limited by the poor understanding of the disease at the molecular level. To better understand the genetics and biology of RCC, we profiled the expression of 7,129 genes in both clear cell RCC tissue and cell lines using oligonucleotide arrays. METHODS: Total RNAs isolated from renal cell tumors, adjacent normal tissue and metastatic RCC cell lines were hybridized to affymatrix HuFL oligonucleotide arrays. Genes were categorized into different functional groups based on the description of the Gene Ontology Consortium and analyzed based on the gene expression levels. Gene expression profiles of the tissue and cell line samples were visualized and classified by singular value decomposition. Reverse transcription polymerase chain reaction was performed to confirm the expression alterations of selected genes in RCC. RESULTS: Selected genes were annotated based on biological processes and clustered into functional groups. The expression levels of genes in each group were also analyzed. Seventy-four commonly differentially expressed genes with more than five-fold changes in RCC tissues were identified. The expression alterations of selected genes from these seventy-four genes were further verified using reverse transcription polymerase chain reaction (RT-PCR). Detailed comparison of gene expression patterns in RCC tissue and RCC cell lines shows significant differences between the two types of samples, but many important expression patterns were preserved. CONCLUSIONS: This is one of the initial studies that examine the functional ontology of a large number of genes in RCC. Extensive annotation, clustering and analysis of a large number of genes based on the gene functional ontology revealed many interesting gene expression patterns in RCC. Most notably, genes involved in cell adhesion were dominantly up-regulated whereas genes involved in transport were dominantly down-regulated. This study reveals significant gene expression alterations in key biological pathways and provides potential insights into understanding the molecular mechanism of renal cell carcinogenesis.

Adenocarcinoma, Clear Cell↗
PubMed2004

Apoptosis of multiple myeloma.

Multiple myeloma (MM) is a malignancy of terminally differentiated plasma cells. MM cells localize to the bone marrow, where cell adhesion-mediated autocrine or paracrine activation of various cytokines, such as interleukin 6, insulin-like growth factor 1, and interferon alpha, results in their accumulation mainly because of loss of critical apoptotic controls. Resistance to apoptosis, a genetically regulated cell death process, may play a critical role in both pathogenesis and resistance to treatment of MM. Abnormalities in regulation and execution of apoptosis can contribute to tumor initiation, progression, as well as to tumor resistance to various therapeutic agents. Apoptosis is executed via 2 main pathways that lead to activation of caspases: the death receptor (extrinsic) pathway and the mitochondrial (intrinsic) pathway. Ionizing radiation and chemotherapeutic agents act primarily through the intrinsic pathway, in which mitochondria play the central role. Various therapeutic modalities that are effective in MM modulate levels of the proapoptotic and antiapoptotic Bcl-2 family of proteins and of inhibitors of apoptosis, expression of which is primarily regulated by p53, nuclear factor KB, and STAT (signal transducers and activators of transcription) factors. This review focuses on the key concepts and some of the most recent studies of signaling pathways regulated in MM and summarizes what is known about the clinical role of these pathways.

Apoptosis↗
PubMed2003

Role of Apo2L/TRAIL and Bcl-2-family proteins in apoptosis of multiple myeloma.

Apo2 Ligand or Tumour Necrosis Factor (TNF)-Related Apoptosis-Inducing Ligand (Apo2L/TRAIL) is a member of the TNF gene superfamily that selectively induces apoptosis in tumor cells of diverse origins through engagement of death receptors. We have recently demonstrated that Type I interferons (IFN-alpha and beta) induce apoptosis in multiple myeloma (MM) cell lines and in plasma cells from MM patients. Moreover, Apo2L selectively induces apoptosis of patient MM tumor cells while sparing non-malignant cells. Apo2L induction is one of the earliest events following IFN administration in these cells. IFNs activate Caspases and the mitochondrial-dependent apoptotic pathway mediated by Apo2L production. Cell death induced by IFNs and Apo2L can be blocked by a dominant-negative Apo2L receptor, DRS, and is regulated by members of the Bcl-2 family of proteins. This review is focused on the apoptotic signaling pathways regulated by Apo2L and Bcl-2-family proteins and summarizes what is known about their clinical role.

Apoptosis↗
PubMed2002

Proteolytic cleavage of cyclin E leads to inactivation of associated kinase activity and amplification of apoptosis in hematopoietic cells.

Cyclin E/Cdk2 is a critical regulator of cell cycle progression from G(1) to S in mammalian cells and has an established role in oncogenesis. Here we examined the role of deregulated cyclin E expression in apoptosis. The levels of p50-cyclin E initially increased, and this was followed by a decrease starting at 8 h after treatment with genotoxic stress agents, such as ionizing radiation. This pattern was mirrored by the cyclin E-Cdk2-associated kinase activity and a time-dependent expression of a novel p18-cyclin E. p18-cyclin E was induced during apoptosis triggered by multiple genotoxic stress agents in all hematopoietic tumor cell lines we have examined. The p18-cyclin E expression was prevented by Bcl-2 overexpression and by the general caspase and specific caspase 3 pharmacologic inhibitors zVAD-fluoromethyl ketone (zVAD-fmk) and N-acetyl-Asp-Glu-Val-Asp-aldehyde (DEVD-CHO), indicating that it was linked to apoptosis. A p18-cyclin E(276-395) (where cyclin E(276-395) is the cyclin E fragment containing residues 276 to 395) was reconstituted in vitro, with mutagenesis experiments, indicating that the caspase-dependent cleavage was at amino acid residues 272 to 275. Immunoprecipitation analyses of the ectopically expressed cyclin E(1-275), cyclin E(276-395) deletion mutants, and native p50-cyclin E demonstrated that caspase-mediated cyclin E cleavage eliminated interaction with Cdk2 and therefore inactivated the associated kinase activity. Overexpression of cyclin E(276-395), but not of several other cyclin E mutants, specifically induced phosphatidylserine exposure and caspase activation in a dose-dependent manner, which were inhibited in Bcl-2-overexpressing cells or in the presence of zVAD-fmk. Apoptosis and generation of p18-cyclin E were significantly inhibited by overexpressing the cleavage-resistant cyclin E mutant, indicating a functional role for caspase-dependent proteolysis of cyclin E for apoptosis of hematopoietic tumor cells.

Apoptosis↗
PubMedDate not supplied

Apo2L/TRAIL: apoptosis signaling, biology, and potential for cancer therapy.

Apo2 ligand or tumor necrosis factor (TNF)-related apoptosis-inducing ligand (Apo2L/TRAIL) is one of several members of the TNF gene superfamily that induce apoptosis through engagement of death receptors. Apo2L/TRAIL is unusual as compared to any other cytokine as it interacts with a complex system of receptors: two pro-apoptotic death receptors and three anti-apoptotic decoys. This protein has generated tremendous excitement as a potential tumor-specific cancer therapeutic because, as a stable soluble trimer, it selectively induces apoptosis in many transformed cells but not in normal cells. Transcriptional activation of Apo2L/TRAIL by interferons (IFNs) through specific regulatory elements in its promoter, and possibly by a number of other cytokines, reveals its possible involvement in the activation of natural killer cells, cytotoxic T lymphocytes, and dendritic cells. In this review, we focus on the apoptosis signaling pathways stimulated by Apo2L/TRAIL, summarize what is known to date about the physiological role of this ligand and the potential for its application to cancer therapy.

Animals↗