A Simple Laser-Induced Breakdown Spectroscopy Method for Quantification and Classification of Edible Sea Salts Assisted by Surface-Hydrophilicity-Enhanced Silicon Wafer Substrates.

Salt, one of the most commonly consumed food additives worldwide, is produced in many countries. The chemical composition of edible salts is essential information for quality assessment and origin distinction. In this work, a simple laser-induced breakdown spectroscopy instrument was assembled with a diode-pumped solid-state laser and a miniature spectrometer. Its performances in analyzing Mg and Ca in six popular edible sea salts consumed in South Korea and classification of the products were investigated. Each salt was dissolved in water and a tiny amount of the solution was dropped and dried on the hydrophilicity-enhanced silicon wafer substrate, providing homogeneous distribution of salt crystals. Strong Mg II and Ca II emissions were chosen for both quantification and classification. Calibration curves could be constructed with limits-of-detection of 87 mg/kg for Mg and 45 mg/kg for Ca. Also, the Mg II and Ca II emission peak intensities were used in a k-nearest neighbors model providing 98.6% classification accuracy. In both quantification and classification, intensity normalization using a Na I emission line as a reference signal was effective. A concept of interclass distance was introduced, and the increase in the classification accuracy due to the intensity normalization was rationalized based on it. Our methodology will be useful for analyzing major mineral nutrients in various food materials in liquid phase or soluble in water, including salts.

Pharmacological Prevention of Ectopic Erythrophagocytosis by Cilostazol Mitigates Ferroptosis in NASH.

Hepatic iron overload (HIO) is a hallmark of nonalcoholic fatty liver disease (NAFLD) with a poor prognosis. Recently, the role of hepatic erythrophagocytosis in NAFLD is emerging as a cause of HIO. We undertook various assays using human NAFLD patient pathology samples and an in vivo nonalcoholic steatohepatitis (NASH) mouse model named STAMTM. To make the in vitro conditions comparable to those of the in vivo NASH model, red blood cells (RBCs) and platelets were suspended and subjected to metabolic and inflammatory stresses. An insert-coculture system, in which activated THP-1 cells and RBCs are separated from HepG2 cells by a porous membrane, was also employed. Through various analyses in this study, the effect of cilostazol was examined. The NAFLD activity score, including steatosis, ballooning degeneration, inflammation, and fibrosis, was increased in STAMTM mice. Importantly, hemolysis occurred in the serum of STAMTM mice. Although cilostazol did not improve lipid or glucose profiles, it ameliorated hepatic steatosis and inflammation in STAMTM mice. Platelets (PLTs) played an important role in increasing erythrophagocytosis in the NASH liver. Upregulated erythrophagocytosis drives cells into ferroptosis, resulting in liver cell death. Cilostazol inhibited the augmentation of PLT and RBC accumulation. Cilostazol prevented the PLT-induced increase in ectopic erythrophagocytosis in in vivo and in vitro NASH models. Cilostazol attenuated ferroptosis of hepatocytes and phagocytosis of RBCs by THP-1 cells. Augmentation of hepatic erythrophagocytosis by activated platelets in NASH exacerbates HIO. Cilostazol prevents ectopic erythrophagocytosis, mitigating HIO-mediated ferroptosis in NASH models.

Quantum Artificial Neural Network Approach to Derive a Highly Predictive 3D-QSAR Model for Blood-Brain Barrier Passage.

A successful passage of the blood-brain barrier (BBB) is an essential prerequisite for the drug molecules designed to act on the central nervous system. The logarithm of blood-brain partitioning (LogBB) has served as an effective index of molecular BBB permeability. Using the three-dimensional (3D) distribution of the molecular electrostatic potential (ESP) as the numerical descriptor, a quantitative structure-activity relationship (QSAR) model termed AlphaQ was derived to predict the molecular LogBB values. To obtain the optimal atomic coordinates of the molecules under investigation, the pairwise 3D structural alignments were conducted in such a way to maximize the quantum mechanical cross correlation between the template and a target molecule. This alignment method has the advantage over the conventional atom-by-atom matching protocol in that the structurally diverse molecules can be analyzed as rigorously as the chemical derivatives with the same scaffold. The inaccuracy problem in the 3D structural alignment was alleviated in a large part by categorizing the molecules into the eight subsets according to the molecular weight. By applying the artificial neural network algorithm to associate the fully quantum mechanical ESP descriptors with the extensive experimental LogBB data, a highly predictive 3D-QSAR model was derived for each molecular subset with a squared correlation coefficient larger than 0.8. Due to the simplicity in model building and the high predictability, AlphaQ is anticipated to serve as an effective computational screening tool for molecular BBB permeability.

Photodissociation Dynamics of Ortho-Substituted Thiophenols at 243 nm.

The photoinduced S-H (D) bond fission dynamics of four ortho-substituted thiophenols, 2-fluoro, 2-chloro, 2-bromo, and 2-methoxythiophenol at a pump wavelength of 243 nm, have been investigated by velocity-map imaging and high-level electronic structure calculations. The D atom images of the deuterated ortho-substituted thiophenols show much reduced X̃/à branching ratios of the cofragment radicals over that of bare thiophenol. The angular distributions of the D fragment display negative anisotropies, indicating that transition dipole moments are perpendicular to the fast dissociating S-D bond axis. Initial excitation at 243 nm occurs directly to the 1πσ* state or to the 21ππ* state followed by efficient coupling to the 1πσ* state. The calculated potential energy curves for the 1πσ* or 21ππ* excited states of the ortho-substituted thiophenols along the CCS-D torsion angle (ϕ) display minima at the nonplanar structures, whereas all of the states for bare thiophenol present minima at the planar geometries. This different topology of the ortho-substituted thiophenols in the excited states induces the wide spread of the reactive flux along the ϕ coordinate on the repulsive surface as it should experience significant torque with respect to ϕ during the fragmentation. This encourages the dissociating molecules to follow the adiabatic path at the conical intersection between the ground and the 1πσ* states at extended S-D bond lengths, giving rise to decreased X̃/à branching ratios, demonstrating that the excited-state molecular structure dictates the nonadiabatic transition probability.

Laser-induced breakdown spectroscopy for rapid accurate analysis of Mg, Ca, and K in edible sea salts.

A compact laser-induced breakdown spectroscopy (LIBS) instrument and a simple sample preparation method were developed for rapid on-site analysis of Mg, Ca, and K in edible sea salt products. The LIBS instrument was assembled using a small diode-pumped solid-state laser and a handheld spectrometer. Aqueous solutions of salts were prepared and sampled by using pieces of filter papers. The dried filter paper was attached on the flat surface of a silicon wafer and then analyzed by LIBS. Calibration curves were obtained using binary mixtures of ${\rm NaCl} {-} {{\rm MgSO}_4}$NaCl-MgSO4, ${\rm NaCl} {-} {{\rm CaCl}_2}$NaCl-CaCl2, and NaCl-KCl and used to estimate the concentrations of Mg, Ca, and K in 13 edible sea salt products. Matrix effects on the results from LIBS were identified in comparison with those from inductively coupled plasma optical emission spectroscopy. This indicates that the matrix of sea salt samples is significantly different from that of the binary mixture standards. The sea salts with known concentrations of Mg, Ca, and K were employed to match the matrices of samples and standards. This improved analysis accuracy remarkably. Furthermore, an alternative indirect method for estimating the concentration of K was suggested on the basis of the strong positive correlations observed between the concentrations of Mg and K in the sea salt samples.

Spatial Isolation of Conformational Isomers of Hydroquinone and Its Water Cluster Using the Stark Deflector.

Conformational isomers of hydroquinone and their 1:1 clusters with water have been spatially separated using a Stark deflector in a supersonic jet. trans-Hydroquinone (HyQ) conformer with zero dipole moment is little influenced by inhomogeneous electric fields, whereas cis conformer with nonzero dipole moment (2.38 D) is significantly deflected from the molecular beam axis into the direction along which the strong field gradient is applied. Resonant two photon ionization carried out by shifting the laser position perpendicular to the molecular beam axis after the Stark deflector then gives an exclusive S1-S0 excitation spectrum of the cis conformer only, making possible immaculate conformer-specific spectroscopy and dynamics. As the spatial separation is apparently proportional to the effective dipole moment strength, conformational assignment could be absolute in the Stark deflector, which contrasts with the hole-burning spectroscopic technique where identification of a conformational isomer is intrinsically not unambiguous. trans- and cis-HyQ-H2O clusters have also been spatially separated according to their distinct effective dipole moment strengths to give absolute spectroscopic identification of each cluster isomer, nailing down the otherwise disputable conformational assignment. This is the first report for the spatial separation of conformational cluster isomers.

Structural insights into the binding of lauric acid to CYP107L2 from Streptomyces avermitilis.

Streptomyces avermitilis is an actinobacterium known to produce clinically useful macrolides including avermectins. CYP107L2 from S. avermitilis shares a high sequence similarity with the PikC (CYP107L1) from S. venezuelae. To elucidate the structural features of CYP107L2, we conducted biochemical and structural characterization of CYP107L2 from S. avermitilis. The CYP107L2 gene was cloned, and its recombinant protein was expressed and purified. The CYP107L2 showed a low-spin state of heme, and the reduced form yielded the CO difference spectra with a maximal absorption at 449 nm. Binding of pikromycin and lauric acid yielded the typical type I spectra with Kd values of 4.8 ± 0.3 and 111 ± 9 µM, respectively. However, no metabolic product was observed in the enzyme reaction. X-ray crystal structures of the ligand-free CYP107L2 and its complex with lauric acid were determined at the resolution of 2.6 and 2.5 Å, respectively. CYP107L2 showed a well-conserved CYP structure with a wide-open substrate-binding cavity. The lauric acid is bound mainly via hydrophobic interactions with the carboxylate group of lauric acid coordinated to the heme of P450. Glu-40 and Leu-382 residues in the CYP107L2 complex with lauric acid showed significant conformational changes to provide plentiful room for the lauric acid in the substrate-binding site.

Systemic inflammation is associated with the density of immune cells in the tumor microenvironment of gastric cancer.

BACKGROUND: The neutrophil-lymphocyte ratio (NLR) and the prognostic nutritional index (PNI) are markers of systemic inflammation known to be useful prognostic indicators of malignancy. However, little evidence has defined the influence of inflammation on the tumor microenvironment. METHODS: Two hundred eighty-eight patients who underwent curative surgery for gastric cancer were included. Preoperative peripheral blood samples were used to analyze the NLR and PNI. The optimal cutoff levels for the NLR and PNI were defined by receiver operating characteristic curve analysis for survival (NLR = 2.7, PNI = 47.7). The densities of specific immune cells (CD3+, CD4+, CD8+) within the tumor microenvironment were measured in tumor microarrays by immunohistochemical analysis. RESULTS: Two hundred thirty-five patients (81.6 %) had a low NLR and 53 patients (18.4 %) had a high NLR. One hundred seventeen patients (40.6 %) had a low PNI and 171 patients (59.4 %) had a high PNI. CD3+ and CD8+ immune cell density were not associated with the NLR and PNI. However, in the high-NLR group compared with the low-NLR group, CD4+ immune cell density was significantly decreased (P < 0.001). Similarly, the density of CD4+ immune cells was also significantly decreased in the low-PNI group compared with the high-PNI group (P = 0.007). A high NLR and a low PNI were correlated with worse overall survival in multivariate analysis (P = 0.028 and P = 0.002 respectively). CONCLUSIONS: The NLR and PNI are associated with the density of CD4+ immune cells in the tumor microenvironment, which leads to prognostic values of systemic inflammation in gastric cancer.

Inhibition of hepatitis C virus in mouse models by lipidoid nanoparticle-mediated systemic delivery of siRNA against PRK2.

Host-targeting antivirals have an advantage over direct-acting antivirals in that they have a high genetic barrier to resistance. Here, we describe in vivo anti-hepatitis C virus (HCV) efficacy of a potent siRNA targeting the protein kinase C-related kinase 2 (PRK2), which phosphorylates HCV NS5B RNA-dependent RNA polymerase and promotes HCV replication. PRK2-silencing reduced the phosphorylated NS5B level and resulted in inhibition of NS5B RdRp activity to decrease HCV genome abundance. Systemic administration of lipidoid nanoparticle-formulated PRK2 siRNA (once every three days for a total of three injections at a dose of 3mgkg(-1)) resulted in a 3.72 and 1.96 log10 reduction in serum HCV RNA titer, in mouse subcutaneous and orthotopic xenograft models for HCV replication, respectively. Our results verify the essential role of PRK2 in HCV replication and offer a host-targeting anti-HCV siRNA therapy that might be beneficial for non-responders to current treatment regimens.

Metformin enhances the anti-adipogenic effects of atorvastatin via modulation of STAT3 and TGF-ß/Smad3 signaling.

Adipocyte accumulation is associated with the development of obesity and obesity-related diseases. Interactions of master transcription factors and signaling cascades are required for adipogenesis. Regulation of excessive adipogenic processes may be an attractive therapeutic for treatment of obesity and obesity-related diseases. In this study, we found that atorvastatin exerts an anti-adipogenic activity in 3T3-L1 pre-adipocytes, and that this activity is elevated in combination with metformin. Expression of the adipogenic master regulators PPARγ and C/EBPα, and their target gene aP2, was suppressed by atorvastatin. Furthermore, atorvastatin treatment resulted in increased activation of the key master regulator of cellular energy homeostasis, AMPK. These biological activities of atorvastatin were elevated in combination with metformin. These anti-adipogenic activities were associated with regulation of the STAT3 and TGF-ß signaling cascades, resulting in the regulation of the expression of STAT3 target genes, such as KLF5, p53, and cyclin D1, and TGF-ß signaling inhibitory genes, such as SMAD7. Our results suggest that combination therapy with atorvastatin and metformin may have therapeutic potential for the treatment of obesity and obesity-related diseases caused by excessive adipogenesis.

Phosphorylation of hepatitis C virus RNA polymerases ser29 and ser42 by protein kinase C-related kinase 2 regulates viral RNA replication.

UNLABELLED: Hepatitis C virus (HCV) nonstructural protein 5B (NS5B), an RNA-dependent RNA polymerase (RdRp), is the key enzyme for HCV RNA replication. We previously showed that HCV RdRp is phosphorylated by protein kinase C-related kinase 2 (PRK2). In the present study, we used biochemical and reverse-genetics approaches to demonstrate that HCV NS5B phosphorylation is crucial for viral RNA replication in cell culture. Two-dimensional phosphoamino acid analysis revealed that PRK2 phosphorylates NS5B exclusively at its serine residues in vitro and in vivo. Using in vitro kinase assays and mass spectrometry, we identified two phosphorylation sites, Ser29 and Ser42, in the Δ1 finger loop region that interacts with the thumb subdomain of NS5B. Colony-forming assays using drug-selectable HCV subgenomic RNA replicons revealed that preventing phosphorylation by Ala substitution at either Ser29 or Ser42 impairs HCV RNA replication. Furthermore, reverse-genetics studies using HCV infectious clones encoding phosphorylation-defective NS5B confirmed the crucial role of these PRK2 phosphorylation sites in viral RNA replication. Molecular-modeling studies predicted that the phosphorylation of NS5B stabilizes the interactions between its Δ1 loop and thumb subdomain, which are required for the formation of the closed conformation of NS5B known to be important for de novo RNA synthesis. Collectively, our results provide evidence that HCV NS5B phosphorylation has a positive regulatory role in HCV RNA replication. IMPORTANCE: While the role of RNA-dependent RNA polymerases (RdRps) in viral RNA replication is clear, little is known about their functional regulation by phosphorylation. In this study, we addressed several important questions about the function and structure of phosphorylated hepatitis C virus (HCV) nonstructural protein 5B (NS5B). Reverse-genetics studies with HCV replicons encoding phosphorylation-defective NS5B mutants and analysis of their RdRp activities revealed previously unidentified NS5B protein features related to HCV replication and NS5B phosphorylation. These attributes most likely reflect potential structural changes induced by phosphorylation in the Δ1 finger loop region of NS5B with two identified phosphate acceptor sites, Ser29 and Ser42, which may transiently affect the closed conformation of NS5B. Elucidating the effects of dynamic changes in NS5B phosphorylation status during viral replication and their impacts on RNA synthesis will improve our understanding of the molecular mechanisms of NS5B phosphorylation-mediated regulation of HCV replication.

Bright attosecond soft X-ray pulse trains by transient phase-matching in two-color high-order harmonic generation.

We study two-color high-order harmonic generation in Neon with 790 nm and 1300 nm driving laser fields and observe an extreme-ultraviolet continuum that extends to photon energies of 160 eV. Using a 6-mm-long, high pressure gas cell, we optimize the HHG yield at high photon energies and investigate the effect of ionization and propagation under phase-matching conditions that allow us to control the temporal structure of the XUV emission. Numerical simulations that include the 3D propagation of the two-color laser pulse show that a bright isolated attosecond pulse with exceptionally high photon energies can be generated in our experimental conditions due to an efficient hybrid optical and phase-matching gating mechanism.

Functional characterization of CYP107W1 from Streptomyces avermitilis and biosynthesis of macrolide oligomycin A.

Streptomyces avermitilis contains 33 cytochrome P450 genes in its genome, many of which play important roles in the biosynthesis process of antimicrobial agents. Here, we characterized the biochemical function and structure of CYP107W1 from S. avermitilis, which is responsible for the 12-hydroxylation reaction of oligomycin C. CYP107W1 was expressed and purified from Escherichia coli. Purified proteins exhibited the typical CO-binding spectrum of P450. Interaction of oligomycin C and oligomycin A (12-hydroxylated oligomycin C) with purified CYP107W1 resulted in a type I binding with Kd values of 14.4 ± 0.7 µM and 2.0 ± 0.1 µM, respectively. LC-mass spectrometry analysis showed that CYP107W1 produced oligomycin A by regioselectively hydroxylating C12 of oligomycin C. Steady-state kinetic analysis yielded a kcat value of 0.2 min(-1) and a Km value of 18 µM. The crystal structure of CYP107W1 was determined at 2.1 Å resolution. The overall P450 folding conformations are well conserved, and the open access binding pocket for the large macrolide oligomycin C was observed above the distal side of heme. This study of CYP107W1 can help a better understanding of clinically important P450 enzymes as well as their optimization and engineering for synthesizing novel antibacterial agents and other pharmaceutically important compounds.

Dynamic role of the intramolecular hydrogen bonding in nonadiabatic chemistry revealed in the UV photodissociation reactions of 2-fluorothiophenol and 2-chlorothiophenol.

The dynamic interplay between the intramolecular hydrogen bonding and intramolecular vibrational redistribution is found to be critical in nonadiabatic reaction dynamics. Herein, it has been demonstrated that the molecular planarity, directed by the intramolecular hydrogen bonding, plays an important role in the nonadiabatic passage of the reactive flux at the conical intersection in the photodissociation reactions of 2-fluorothiophenol and 2-chlorothiophenol. As the internal energy increases in the excited state, the intramolecular hydrogen bonding of 2-fluorothiophenol loosens. The floppiness brought into the molecular structure then modifies the dynamic path of the reactive flux, leading to the diminishment of the nonadiabatic transition probability at the conical intersection. On the contrary, for 2-chlorothiophenol having the relatively stronger intramolecular hydrogen bonding, the reactive flux seems to retain the molecular planarity even with the increase of the internal energy as manifested by the constant nonadiabatic transition probability over the wide range of the S1 internal energy. The effect of the intramolecular hydrogen bonding on the molecular structure and its relation to the nonadiabatic dynamics along the tunneling path has been experimentally demonstrated.

Conical intersection seam and bound resonances embedded in continuum observed in the photodissociation of thioanisole-d3.

Herein, the multi-dimensional nature of the conical intersection seam has been experimentally revealed in the photodissociation reaction of thioanisole-d3 (C6H5SCD3) excited on S1, giving C6H5S·(à or X̃]) +·CD3 products. The translational energy distribution of the nascent·CD3 fragment, reflecting the relative yields of the C6H5S·(Ã) and C6H5S·(X̃) products, was measured at each S1 vibronic band using the velocity map ion imaging technique. Direct access of the reactant flux to the conical intersection seam leads to the increase of the nonadiabatic transition probability resulting in sharp resonances in the X̃/ÃC6H5S·product branching ratio at several distinct S1 vibronic bands. The nature of the S1 vibronic bands associated with such dynamic resonances was clarified by the mass-analyzed threshold ionization spectroscopy. The bound state embedded in continuum generated by the conical intersection is observed as a distinct dynamic resonance, revealing the nature of the nuclear motion responsible for the nonadiabatic coupling of two potential energy surfaces at the conical intersection. The multi-dimensional facets of the conical intersection seam in terms of its detailed structure and dynamic role are discussed with the aid of theoretical calculations.

Directed-evolution analysis of human cytochrome P450 2A6 for enhanced enzymatic catalysis.

Cytochrome P450 2A6 (P450 2A6) is the major enzyme responsible for the oxidation of coumarin, nicotine, and tobacco-specific nitrosamines in human liver. In this study, the catalytic turnover of coumarin oxidation was improved by directed-evolution analysis of P450 2A6 enzyme. A random mutant library was constructed using error-prone polymerase chain reaction (PCR) of the open reading frame of the P450 2A6 gene and individual mutant clones were screened for improved catalytic activity in analysis of fluorescent coumarin 7-hydroxylation. Four consecutive rounds of random mutagenesis and screening were performed and catalytically enhanced mutants were selected in each round of screening. The selected mutants showed the sequentially accumulated mutations of amino acid residues of P450 2A6: B1 (F209S), C1 (F209S, S369G), D1 (F209S, S369G, E277K), and E1 (F209S, S369G, E277K, A10V). E1 mutants displayed approximately 13-fold increased activity based on fluorescent coumarin hydroxylation assays at bacterial whole cell level. Steady-state kinetic parameters for coumarin 7-hydroxylation and nicotine oxidation were measured in purified mutant enzymes and indicated catalytic turnover numbers (kcat) of selected mutants were enhanced up to sevenfold greater than wild-type P450 2A6. However, all mutants displayed elevated Km values and therefore catalytic efficiencies (kcat/Km) were not improved. The increase in Km values was partially attributed to reduction in substrate binding affinities measured in the analysis of substrate binding titration. The structural analysis of P450 2A6 indicates that F209S mutation is sufficient to affect direct interaction of substrate at the active site.

Characterizing the Tumor Microenvironment and Its Correlation with cDC1-Related Gene Expression in Gastric Cancer.

Materials and Methods: We analyzed RNA-seq data from the Cancer Genome Atlas (TCGA-STAD) and Gene Expression Omnibus (GEO) datasets, focusing on five cDC1-related genes. The cDC1-related signature was defined and divided into high and low expression groups. We employed gene set variation analysis (GSVA) for oncogenic signaling pathways and conducted comprehensive statistical analyses, including Kaplan-Meier and Cox proportional hazards models. Results: The high cDC1-related gene signature group was associated with poorer overall and disease-free survival in the TCGA-STAD cohort. Significant differences in CD8+ T cell infiltration and cytotoxic capabilities were observed between high and low CDC1-related signature groups. The study also revealed a strong correlation between CDC1-related signature and increased expression of immune checkpoint proteins and oncogenic pathways, suggesting a complex immunosuppressive tumor microenvironment. Conclusions: Our findings indicate the potential of the cDC1-related signature as a prognostic marker in GC, offering insights into the tumor-immune interplay. The study underscores the importance of cDC1s in shaping the tumor microenvironment and their influence on patient prognosis in GC. These results may contribute to the development of novel therapeutic strategies targeting the immune microenvironment in GC.

Targeting the CSF-1/CSF-1R Axis: Exploring the Potential of CSF1R Inhibitors in Neurodegenerative Diseases.

We report herein the potential of colony-stimulating factor-1 receptor (CSF1R) inhibitors as therapeutic agents in neuroinflammatory diseases, with a focus on Alzheimer's disease (AD). Employing a carefully modified scaffold, N-(4-heterocycloalkyl-2-cycloalkylphenyl)-5-methylisoxazole-3-carboxamide, we identify highly selective and potent CSF1R inhibitors─7dri and 7dsi. Molecular docking studies shed light on the binding modes of these key compounds within the CSF1R binding site. Remarkably, kinome-wide selectivity assessment underscores the impressive specificity of 7dri for CSF-1R. Notably, 7dri emerges as a potent CSF-1R inhibitor with favorable cellular activity and minimal cytotoxicity among the synthesized compounds. Demonstrating efficacy in inhibiting CSF1R phosphorylation in microglial cells and successfully mitigating neuroinflammation in an in vivo LPS-induced model, 7dri establishes itself as a promising antineuroinflammatory agent.

BST-2 is a potential activator of invasion and migration in tamoxifen-resistant breast cancer cells.

Bone marrow stromal cell antigen 2 (BST-2) is a type II transmembrane protein that is known to be a therapeutic target in several types of cancer. However, despite its clinical importance, the roles of BST-2 expression have remained elusive. Here, we found that BST-2 expression is up-regulated in tamoxifen-resistant MCF-7 human breast cancer (TRM-7) cells, resulting in enhanced invasiveness and migration. Matrigel and wound healing assays also showed that overexpression of BST-2 increased invasion and migration in MCF-7 cells, whereas invasion and migration were decreased by the silencing of BST-2 in TRM-7 cells. In addition, B16F10 cells expressing BST-2 showed increased metastatic melanoma nodule growth in a lung metastasis mouse model. Furthermore, BST-2 expression and promoter activity were regulated by activated signal transducer and activator of transcription 3 (STAT3). Taken together, our results indicate that BST-2 is an important factor in the invasiveness and motility of tamoxifen-resistant breast cancer cells, and that its expression and activity are regulated by activated STAT3. Therefore, regulation of BST-2 is a potential therapeutic target for tamoxifen-resistant breast cancer.

A cancer-specific variant of the SLCO1B3 gene encodes a novel human organic anion transporting polypeptide 1B3 (OATP1B3) localized mainly in the cytoplasm of colon and pancreatic cancer cells.

OATP1B3 is a member of the OATP (organic anion transporting polypeptides) superfamily, responsible for mediating the transport of numerous endogenous and xenobiotic substances. Although initially reported to be exclusively expressed in the liver, several studies reported that OATP1B3 is frequently expressed in multiple types of cancers and may be associated with differing clinical outcomes. However, a detailed investigation on the expression and function of OATP1B3 protein in cancer has been lacking. In this study, we confirmed that colon and pancreatic cancer cells express variant forms of OATP1B3, different from OATP1B3 wild-type (WT) expressed in the normal liver. OATP1B3 variant 1 (V1), the most prevalent form among the variants, contains alternative exonic sequences (exon 2a) instead of exons 1 and 2 present in OATP1B3 WT. The translated product of OATP1B3 V1 is almost identical to OATP1B3 WT, with exception to the first 28 amino acids at the N-terminus. Exogenous expression of OATP1B3 V1 revealed that OATP1B3 V1 undergoes post-translational modifications and proteasomal degradation to a differing extent compared to OATP1B3 WT. OATP1B3 V1 showed only modest transport activity toward cholecystokin-8 (CCK-8, a prototype OATP1B3 substrate) in contrast to OATP1B3 WT showing a markedly efficient uptake of CCK-8. Consistent with these results, OATP1B3 V1 was localized mainly in the cytoplasm with a much lower extent of trafficking to the surface membrane compared to OATP1B3 WT. In summary, our results demonstrate that colon and pancreatic cancer cells express variant forms of OATP1B3 with only limited transport activity and different subcellular localization compared to OATP1B3 WT. These observed differences at the molecular and functional levels will be important considerations for further investigations of the biological and clinical significance of OATP1B3 expression in cancer.