Identification and characterization of the binding sites of P-glycoprotein for multidrug resistance-related drugs and modulators

A major problem in cancer treatment is the development of resistance to multiple chemotherapeutic agents in tumor cells. A major mechanism of this multidrug resistance (MDR) is overexpression of the MDR1 product P-glycoprotein, known to bind to and transport a wide variety of agents. This review concentrates on the progress made toward understanding the role of this protein in MDR, identifying and characterizing the drug binding sites of P-glycoprotein, and modulating MDR by P-glycoprotein-specific inhibitors. Since our initial discovery that P-glycoprotein binds to vinblastine photoaffinity analogs, many P-glycoprotein-specific photoaffinity analogs have been developed and used to identify the particular domains of P-glycoprotein capable of interacting with these analogs and other P-glycoprotein substrates. Furthermore, significant advances have been made in delineating the drug binding sites of this protein by studying mutant P-glycoprotein. Photoaffinity labeling experiments and the use of site-directed antibodies to several domains of this protein have allowed the localization of the general binding domains of some of the cytotoxic agents and MDR modulators on P-glycoprotein. Moreover, site-directed mutagenesis studies have identified the amino acids critical for the binding of some of these agents to P-glycoprotein. Furthermore, equilibrium binding assays using plasma membranes from MDR cells and radioactive drugs have aided our understanding of the modes of drug interactions with P-glycoprotein. Based on the available data, a topological model of P-glycoprotein and the approximate locations of its drug binding sites, as well as a proposed classification of multiple drug binding sites of this protein, is presented in this review

Resistance to Cell Death and Its Modulation in Cancer Stem Cells

Accumulating evidence has demonstrated that human cancers arise from various tissues of origin that initiate from cancer stem cells (CSCs) or cancer-initiating cells. The extrinsic and intrinsic apoptotic pathways are dysregulated in CSCs, and these cells play crucial roles in tumor initiation, progression, cell death resistance, chemo- and radiotherapy resistance, and tumor recurrence. Understanding CSC-specific signaling proteins and pathways is necessary to identify specific therapeutic targets that may lead to the development of more efficient therapies selectively targeting CSCs. Several signaling pathways-including the phosphatidylinositol 3-kinase (PI3K)/Akt/mammalian target of rapamycin (mTOR), maternal embryonic leucine zipper kinase (MELK), NOTCH1, and Wnt/Β-catenin&and expression of the CSC markers CD133, CD24, CD44, Oct4, Sox2, Nanog, and ALDH1A1 maintain CSC properties. Studying such pathways may help to understand CSC biology and lead to the development of potential therapeutic interventions to render CSCs more sensitive to cell death triggered by chemotherapy and radiation therapy. Moreover, recent demonstrations of dedifferentiation of differentiated cancer cells into CSC-like cells have created significant complexity in the CSCs hypothesis. Therefore, any successful therapeutic agent or combination of drugs for cancer therapy must eliminate not only CSCs but differentiated cancer cells and the entire bulk of tumor cells. This review article expands on the CSC hypothesis and paradigm with respect to major signaling pathways and effectors that regulate CSC apoptosis resistance. Moreover, selective CSC apoptotic modulators and their therapeutic potential for making tumors more responsive to therapy are discussed. The use of novel therapies, including small-molecule inhibitors of specific proteins in signaling pathways that regulate stemness, proliferation and migration of CSCs, immunotherapy, and noncoding microRNAs may provide better means of treating CSCs

Roles of c-FLIP in Apoptosis, Necroptosis, and Autophagy

Cellular FLICE (FADD-like IL-1β-converting enzyme)-inhibitory protein (c-FLIP) is a major antiapoptotic protein and an important cytokine and chemotherapy resistance factor that suppresses cytokine- and chemotherapyinduced apoptosis. c-FLIP is expressed as long (c-FLIPL), short (c-FLIPS), and c-FLIPR splice variants in human cells. c-FLIP binds to FADD and/or caspase-8 or -10 and TRAIL receptor 5 (DR5). This interaction in turn prevents Death-Inducing Signaling Complex (DISC) formation and subsequent activation of the caspase cascade. c-FLIPL and c-FLIPS are also known to have multifunctional roles in various signaling pathways, as well as activating and/ or upregulating several cytoprotective and pro-survival signaling proteins including Akt, ERK, and NF-κB. In addition to its role in apoptosis, c-FLIP is involved in programmed necroptosis (necrosis) and autophagy. Necroptosis is regulated by the Ripoptosome, which is a signaling intracellular cell death platform complex. The Ripoptosome contains receptor-interacting protein-1/Receptor-Interacting Protein-3 (RIP1), caspase-8, caspase-10, FADD, and c-FLIP isoforms involved in switching apoptotic and necroptotic cell death. c-FLIP regulates the Ripoptosome; in addition to its role in apoptosis, it is therefore also involved in necrosis. c-FLIPL attenuates autophagy by direct acting on the autophagy machinery by competing with Atg3 binding to LC3, thereby decreasing LC3 processing and inhibiting autophagosome formation. Upregulation of c-FLIP has been found in various tumor types, and its silencing has been shown to restore apoptosis triggered by cytokines and various chemotherapeutic agents. Hence, c-FLIP is an important target for cancer therapy. This review focuses on (1) the anti-apoptotic role of c-FLIP splice variants in preventing apoptosis and inducing cytokine and chemotherapy drug resistance, as well as its roles in necrosis and autophagy, and (2) modulation of c-FLIP expression as a means to enhance apoptosis and modulate necrosis and autophagy in cancer cells

Structural, biochemical, and inhibition studies of cell wall formation in the unicellular marine coccolithophorid alga Hymenomonas carterae

The wall in the coccolith-bearing stage of the life cycle of the marine coccolithophorid alga, Hymenomonas carterae, consists of several ultrastructurally distinct units: (1) columnar material, (2) glue , (3) crystalline vesicles , (4) 2-3 layers of scales, (5) coccoliths, and (6) coccolithonets. A technique based on the use of a nonionic detergent (Triton X-100) was developed to isolate the cell wall from coccolith-bearing cells. This cell wall was characterized with respect to its spatial arrangement, degradation, and the in vitro assembly of some of its components. The approach was to carefully describe the wall ultrastructure, partially solubilize and isolate the component parts, and biochemically characterize them. Treatment with 10 M LiCl and 10 mM EDTA dissociated the cell wall into soluble and insoluble fractions (SF and ISF). Cytochemical studies using ruthenium red and catonized ferritin as well as qualitative biochemical analysis (including EDTA extraction, colorimetric sugar determinations, pectinase digestion, and uronic acid assay) strongly suggested the presence of pectin-like acidic polysaccharides in the columnar material, glue , the periphery of scales, and the distal surface of the coccoliths. Such tests also indicated that the wall is held together by hydrogen bonds, hydrophobic links, and primarily ionic interactions. Acidic polysaccharides of the cell wall were isolated. These molecules possess sedimentation coefficients of 1.55, 1.82, and 4.25. Polyacrylamide gel electrophoresis patterns of the EDTA soluble fraction of coccoliths along with self-assembly characteristics and ultrastructural evidence indicated that the polyanionic carbohydrate molecule with a sedimentation coefficient of 1.82 is a part of the coccolith. This molecule demonstrated a crystalline lattice structure with center to center spacing of 60-65 (ANGSTROM) and appeared to be a proper candidate for subunits of the small Golgi product, the coccolithosomes, which participate in the formation of the calcareous coccolith rim;Cell wall regeneration and kinetics of wall formation were monitored by light and electron microscopy following wall removal. Protoplasts were released after enzymatic treatment with macerozyme and cellulase. Electron microscopic observations revealed that the entire cell wall had reappeared within about 24 hours after removal of the cells from the enzyme mixture. Cell wall formation was inhibited by coumarin (1,2-benzopyrone) and 2,6-dichlorobenzonitrile (DBN). In H. carterae, both compounds reversibly inhibit wall formation as well as cytokinesis. Coumarin affected protoplasts more drastically than DBN, although, in the presence of DBN, cytokinesis completely stopped while nuclear division was unaffected. In contrast, the antimitotic effect of coumarin stopped nuclear division

Targeting the Anti-Apoptotic Protein c-FLIP for Cancer Therapy

Cellular FLICE (FADD-like IL-1beta-converting enzyme)-inhibitory protein (c-FLIP) is a major resistance factor and critical anti-apoptotic regulator that inhibits tumor necrosis factor-alpha (TNF-alpha), Fas-L, and TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis as well as chemotherapy-triggered apoptosis in malignant cells. c-FLIP is expressed as long (c-FLIPL), short (c-FLIPS), and c-FLIPR splice variants in human cells. c-FLIP binds to FADD and/or caspase-8 or -10 in a ligand-dependent and-independent fashion, which in turn prevents death-inducing signaling complex (DISC) formation and subsequent activation of the caspase cascade. Moreover, c-FLIPL and c-FLIPS are known to have multifunctional roles in various signaling pathways, as well as activating and/or upregulating several cytoprotective signaling molecules. Upregulation of c-FLIP has been found in various tumor types, and its downregulation has been shown to restore apoptosis triggered by cytokines and various chemotherapeutic agents. Hence, c-FLIP is an important target for cancer therapy. For example, small interfering RNAs (siRNAs) that specifically knockdown the expression of c-FLIPL in diverse human cancer cell lines augmented TRAIL-induced DISC recruitment and increased the efficacy of chemotherapeutic agents, thereby enhancing effector caspase stimulation and apoptosis. Moreover, small molecules causing degradation of c-FLIP as well as decreasing mRNA and protein levels of c-FLIPL and c-FLIPS splice variants have been found, and efforts are underway to develop other c-FLIP-targeted cancer therapies. This review focuses on (1) the functional role of c-FLIP splice variants in preventing apoptosis and inducing cytokine and drug resistance; (2) the molecular mechanisms that regulate c-FLIP expression; and (3) strategies to inhibit c-FLIP expression and function

The Fekete-Szegö problems for a subclass of m-fold symmetric bi-univalent functions

In this paper, we investigate a new subclass Pʰ˒ᵖ Σm(λ, γ) of m-fold symmetric bi-univalent functions. Moreover, for functions of this subclass, we obtain the coefficient estimates of the Taylor-Maclaurin coefficients |am+1|, |a2m+1| and Fekete-Szegö problems. The coefficients estimates presented in this paper would generalize and improve those in related works of several earlier authors.Publisher's Versio

Cellular FLICE-like inhibitory protein (C-FLIP): a novel target for cancer therapy

Cellular FLICE-like inhibitory protein (c-FLIP) has been identified as a protease-dead, procaspase-8-like regulator of death ligand-induced apoptosis, based on observations that c-FLIP impedes tumor necrosis factor-alpha (TNF-alpha), Fas-L, and TNF-related apoptosis-inducing ligand (TRAIL)-induced apoptosis by binding to FADD and/or caspase-8 or -10 in a ligand-dependent fashion, which in turn prevents death-inducing signaling complex (DISC) formation and subsequent activation of the caspase cascade. c-FLIP is a family of alternatively spliced variants, and primarily exists as long (c-FLIP(L)) and short (c-FLIP(S)) splice variants in human cells. Although c-FLIP has apoptogenic activity in some cell contexts, which is currently attributed to heterodimerization with caspase-8 at the DISC, accumulating evidence indicates an anti-apoptotic role for c-FLIP in various types of human cancers. For example, small interfering RNAs (siRNAs) that specifically knocked down expression of c-FLIP(L) in diverse human cancer cell lines, e.g., lung and cervical cancer cells, augmented TRAIL-induced DISC recruitment, and thereby enhanced effector caspase stimulation and apoptosis. Therefore, the outlook for the therapeutic index of c-FLIP-targeted drugs appears excellent, not only from the efficacy observed in experimental models of cancer therapy, but also because the current understanding of dual c-FLIP action in normal tissues supports the notion that c-FLIP-targeted cancer therapy will be well tolerated. Interestingly, Taxol, TRAIL, as well as several classes of small molecules induce c-FLIP downregulation in neoplastic cells. Efforts are underway to develop small-molecule drugs that induce c-FLIP downregulation and other c-FLIP-targeted cancer therapies. In this review, we assess the outlook for improving cancer therapy through c-FLIP-targeted therapeutics

A HYBRID DEEP LEARNING APPROACH FOR SENTIMENT ANALYSIS IN PRODUCT REVIEWS

Product reviews play a crucial role in providing valuable insights to consumers and producers. Analyzing the vast amount of data generated around a product, such as posts, comments, and views, can be challenging for business intelligence purposes. Sentiment analysis of this content helps both consumers and producers gain a better understanding of the market status, enabling them to make informed decisions. In this study, we propose a novel hybrid approach based on deep neural networks (DNNs) for sentiment analysis in product reviews, focusing on the classification of sentiments expressed. Our approach utilizes the recursive neural network (RNN) algorithm for sentiment classification. To address the imbalanced distribution of positive and negative samples in social network data, we employ a resampling technique that balances the dataset by increasing samples from the minority class and decreasing samples from the majority class. We evaluate our approach using Amazon data, comprising four product categories: clothing, cars, luxury goods, and household appliances. Experimental results demonstrate that our proposed approach performs well in sentiment analysis for product reviews, particularly in the context of digital marketing. Furthermore, the attention-based RNN algorithm outperforms the baseline RNN by approximately 5%. Notably, the study reveals consumer sentiment variations across different products, particularly in relation to appearance and price aspects

Human β-galactoside α-2,3-sialyltransferase (ST3Gal III) attenuated Taxol-induced apoptosis in ovarian cancer cells by downregulating caspase-8 activity

Taxol triggers apoptosis in a variety of cancer cells, but it also upregulates cytoprotective proteins and/or pathways that compromise its therapeutic efficacy. In this report, we found that Taxol treatment resulted in caspase-8-dependent apoptosis in SKOV3 human ovarian cancer cells. Moreover, Taxol-induced apoptosis was associated with caspase-3 activation. Interestingly, Taxol treatment upregulated α-2,3-sialyltransferase (ST3Gal III) expression and forced expression of ST3Gal III attenuated Taxol-induced apoptosis. Furthermore, ST3Gal III overexpression inhibited Taxol-ttiggered caspase-8 activation, indicating that ST3Gal III upregulation produces cellular resistance to Taxol and hence reduces the efficacy of Taxol therapy

Human GM3 Synthase Attenuates Taxol-Triggered Apoptosis Associated with Downregulation of Caspase-3 in Ovarian Cancer Cells

BACKGROUND: Taxol (paclitaxel) inhibits proliferation and induces apoptosis in a variety of cancer cells, but it also upregulates cytoprotective proteins and/or pathways that compromise its therapeutic efficacy. MATERIALS AND METHOD: The roles of GM3 synthase (α2,3-sialyltransferase, ST3Gal V) in attenuating Taxol-induced apoptosis and triggering drug resistance were determined by cloning and overexpressing this enzyme in the SKOV3 human ovarian cancer cell line, treating SKOV3 and the transfectants (SKOV3/GS) with Taxol and determining apoptosis, cell survival, clonogenic ability, and caspase-3 activation. RESULTS: In this report, we demonstrated that Taxol treatment resulted in apoptosis which was associated with caspase-3 activation. Taxol treatment upregulated the expression of human GM3 synthase, an enzyme that transfers a sialic acid to lactosylceramide. Moreover, we cloned the full-length GM3 synthase gene and showed for the first time that forced expression of GM3 synthase attenuated Taxol-induced apoptosis and increased resistance to Taxol in SKOV3 cells. CONCLUSIONS: GM3 synthase overexpression inhibited Taxol-triggered caspase-3 activation, revealing that upregulation of GM3 synthase prevents apoptosis and hence reduces the efficacy of Taxol therapy