Difference In IC50 Values Research Articles

In vitro antioxidant activity of alginate nanoparticles encapsulating the aqueous extract of Coccinia grandis L.

Bioactive compounds in medicinal plants are more susceptible to preventing oxidative stress. Encapsulation of herbal extracts has empowered the properties and characteristics of bioactive compounds. Nanoencapsulation allows the enhancement of the stability of extracts and targeted drug delivery. The present study aims to determine the antioxidant activity of alginate nanoparticles encapsulating the aqueous extract of Coccinia grandis L. (Family: Cucurbitaceae). The aqueous extract of C. grandis (AqCG) was prepared by using ultrasonication (40 °C, 20 min, 40 kHz) followed by refluxing (2½ h). The prepared AqCG (1-5 mg/mL) encapsulated alginate nanoparticles were synthesized by ionic gelation with the addition of extracts and CaCl2. Characterization of nanoparticles was performed via encapsulation efficiency (EE%), loading capacity (LC%), particle size (PS), scanning electron microscopy (SEM), zeta potential and Fourier transform infrared (FTIR) spectroscopy analysis. The antioxidant activity of the nanoparticles was evaluated in vitro by the ferric reducing antioxidant (FRAP) assay, 2,2-di-phenyl-1-picrylhydrazyl (DPPH) radical scavenging assay and 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical scavenging assay. One-way analysis of variance (ANOVA) followed by Tukey's posthoc test was used to analyze the data. Maximum LC% (3.07 ± 0.11) and average particle size (71 nm from SEM) were obtained for alginate nanoparticles encapsulated at 4 mg/mL extract concentration. The IC50 values for DPPH, ABTS, and FRAP were 6.49 ± 0.10 mg/mL, 0.24 ± 0.01 mg/mL, and 20.63 ± 0.28 mg Trolox equivalent/g of extract respectively for alginate nanoparticles encapsulating the AqCG. Nanoparticles have shown a significant difference in IC50 values compared to Trolox (p < 0.05). The successful encapsulation of the AqCG in the alginate matrix was evidenced by FTIR and SEM analysis. Encapsulation contributed to enhancing the antioxidant activity in terms of ABTS assay when compared to the AqCG. However, in vitro release and stability studies are warranted to facilitate the development of a commercially viable nanonutraceutical using alginate nanoparticles encapsulating the AqCG.

Enhanced detection and characterization of targetable EGFR and ERBB2 exon20 insertion mutations in urothelial carcinoma.

e16500 Background: EGFR and ERBB2 exon 20 insertion (exon20ins) driver mutations are well described in non-small cell lung cancer due to their resistance to early generation EGFR tyrosine kinase inhibitors. This has led to the development and ultimate approval of exon20ins specific inhibitors, such as mobocertinib. Previous studies have reported EGFR and ERBB2 exon20ins mutations in 0.15%-1.91% of urothelial carcinoma (UC) patients, but this is likely an underrepresentation as indel variants are often under detected by commonly used NGS-variant analysis tools. Additionally, little is known about the biological consequences of EGFR and ERBB2 exon20ins mutations in UC. In this study, we aimed to: 1) characterize the prevalence of EGFR and ERBB2 exon20ins mutations in UC; 2) assess how EGFR and ERBB2 exon20ins mutations impact malignant transformation; and 3) evaluate the sensitivity of UC cell lines with the exon20ins to mobocertinib. Methods: UC patient datasets were realigned using the indel caller, ABRA2, then EGFR and ERBB2 exon20ins frequencies were calculated. Next, parental KT1970 urothelial cells expressing either EGFR WT, ERBB2 WT, or exon20ins mutation constructs (EGFRinsH [insH] or ERBB2insYVMA [YVMA]) were generated and in vitro transformation assays were performed. Anchorage-independent growth was assessed with soft agar assay. Engineered urothelial organoids with various exon20ins variants were created to assess for their ability to differentiate. Finally, sensitivity to erlotinib and mobocertinib was determined. Results: ABRA2 identified a prevalence of ERBB2 and EGFR Exon20ins mutations in 2.5% (7/275) of urothelial tumors in the IMVigor210 patient cohort. ERBB2 insYVMA expressing organoids had the highest basal marker (KRT5) expression in proliferation media which decreased in differentiation media. In the soft agar assay, YVMA cells had a 9.26 fold increase in colony formation (CF) compared to the ERBB2 WT counterpart and insH had a 6.02 fold increase in CF over the EGFR WT counterpart. The IC50 for mobocertinib (M) was significantly lower than erlotinib (E) in the exon20ins cell lines (insH M: 0.123 uM, E:10.69 uM / YVMA M: 0.57 uM, E: 13.54 uM). The difference in IC50 values for mobocertinib vs erlotinib in the WT cells was less pronounced. Conclusions: The prevalence of EFGR and ERBB2 exon20 insertion mutations is likely unrepresented in urothelial carcinoma by current variant calling pipelines. The ERBB2 YVMA mutation showed a more aggressive phenotype and possible basal pattern in vitro which may have implications in terms of prognosis and treatment considerations. Both EGFR and ERBB2 exon20ins urothelial cells were more sensitive to mobocertinib. This study provides evidence that exon20ins specific inhibitors could offer additional targeted therapy options for patients with urothelial cancer who have EGFRinsH and ERBB2insYVMA mutations.

Photoswitchable Inhibitors to Optically Control Specific Kinase Activity.

Potent and selective small-molecule inhibitors are valuable tools to elucidate the functions of protein kinases within complex signaling networks. Incorporation of a photoswitchable moiety into the inhibitor scaffold offers the opportunity to steer inhibitor potency with temporal precision, while the challenge of selective inhibition can often be addressed by employing a chemical genetic approach, termed the analog-sensitive method. Here, we combine the perks of these two approaches and report photoswitchable azopyrazoles to target calcium-dependent protein kinase 1 (CDPK1) from Toxoplasma gondii, a kinase naturally susceptible to analog-sensitive kinase inhibitors due to its glycine gatekeeper residue. The most promising azopyrazoles display favorable photochemical properties, thermal stability, and a substantial difference in IC50 values between both photostationary states. Consequently, the CDPK1 kinase reaction can be controlled dynamically and reversibly by applying light of different wavelengths. Inhibition of CDPK1 by the azopyrazoles drastically relies on the nature of the gatekeeper residue as a successive increase in gatekeeper size causes a concurrent loss of inhibitory activity. Furthermore, two photoswitchable inhibitors exhibit activity against T. gondii and Cryptosporidium parvum infection in a cell culture model, making them a promising addition to the toolbox for dissecting the role of CDPK1 in the infectious cycle with high temporal control. Overall, this work merges the benefits of the analog-sensitive approach and photopharmacology without compromising inhibitory potency and thus holds great promise for application to other protein kinases in the future.

Abstract 3988: The role of HER3 mutations in the progression of colon cancer and modulation of drug sensitivity and resistance

Abstract Colorectal cancer is a disease of the colon and rectum that will claim about 52,580 American lives in2022. The most common treatment of colorectal cancer is surgery plus chemotherapy, although thereare some FDA approved targeted therapies such as regorafenib (targeting VEGF) or cetuximab (targetingEGFR). EGFR, along with HER2, HER3, and HER4 are members of the HER family of receptor tyrosinekinases that upon homo- or heterodimerization activate downstream signaling, growth, and survivalpathways. In recent years, more attention has been paid to HER2 and HER3’s roles in colorectal cancers,as they may cause resistance to targeted therapies. OWe are investigating naturally occurring mutantHER3’s role in colorectal cancer, as about 6% of all colorectal cancers contain a HER3 mutation. We arecurrently investigating how HER3 mutations may affect sensitivity to current therapies through HERfamily receptor dimerization and be involved in tumor metastasis. We are assessing the degree to whichmutant and wild-type HER3 have the ability to dimerize with EGFR, HER2, MET, and IGF1R the resultingeffects in colon cancer, as these receptor tyrosine kinases are HER3 binding partners. As HER3 bindingpartners are diverse, it may be that the pathway HER3 and its binding partner activate may influencetreatment strategy. It has been noted that mutant HER2 and HER3 could confer sensitivity to HER familyinhibitors, i.e. afatinib, in bladder cancer, and we have seen a difference in IC50 values of afatinibbetween cell lines containing wild-type or mutant HER3. If mutant HER3 is involved in therapeuticresistance or sensitivity and tumor progression, our findings may present a new biomarker for targetedtreatments in colorectal cancer with the eventual goal of increased overall patient survival. Citation Format: Mary K. Kilroy, Rosalin Mishra, Anastasia Stupecki, Wasim Feroz, Samar Alanazi, Joan T. Garrett. The role of HER3 mutations in the progression of colon cancer and modulation of drug sensitivity and resistance. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 3988.

Abstract 4762: Metabolome in 5-FU resistant gastric cancer organoids

Abstract Recent advances in metabolomics have deepened our understandings of the roles that specific modes of metabolism play in the maintenance of stem cells. Several pieces of evidence have demonstrated that cancer stem cells (CSCs) play a key role in the acquisition of drug resistance. Organoid is a novel 3D cell culture system through using the specific niche factors in a dish and is believed to harbor abundant stem cells; cancer organoid could possibly be useful for scrutinizing CSC biology. In this study, we successfully established 5-FU resistant gastric cancer organoids (GCOs) from patient-derived specimens, which were further confirmed by significant changes in the expression of molecules related to 5-FU metabolism. We then performed metabolome analysis using 3 pairs of 5-FU resistant/ parental GCOs and 10 pairs of non-neoplastic gastric organoid/ GCOs generated from the same patients. PCA plotting revealed that 5-FU resistant GCOs showed a distinct signature compared to those of their parental GCOs and 10 pairs of non-neoplastic gastric organoid/ GCOs. Among various significant changes in the metabolic pathways, we focused on the excessive reliance on the energy from TAC cycle in 5-FU resistant GCO because the difference was specifically seen in the comparison between 5-FU resistant and parental GCOs: not found in the comparison between 10 pairs of non-neoplastic gastric organoid and GCOs. We examined IC50 value for Tigecyclin and VLX600, both of which have an inhibitory effect on TCA cycle, by MTT assay using 5-FU resistant GCO and 2 gastric cancer cell lines (MKN-45 and MKN-74). Although there was almost no difference in IC50 values for Tigecyclin and VLX600 between 2 gastric cell lines and their 5-FU resistant cells, IC50 for both of TCA cycle inhibitors in 5-FU resistant GCO was significantly lower compared to that in parental GCO. Further studies are ongoing in order to verify the significance of dependency on TCA cycle, which could potentially lead to the development of new therapy for 5-FU resistant gastric cancer. Citation Format: Naoya Sakamoto, Kazuhito Naka, Shoichi Ukai, Ririno Honma, Daiki Taniyama, Tsuyoshi Takashima, Ryota Maruyama, Kazuaki Tanabe, Hideki Ohdan, Wataru Yasui. Metabolome in 5-FU resistant gastric cancer organoids [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 4762.

Angiotensin Converting Enzyme Inhibitory Activity of Blue Lupin (Lupinus angustifolius) Proteins

Abstract Objectives To evaluate the ACE inhibitory activity of protein hydrolysates derived from lupin Methods Methods used are spectrophotometer to assay the ACE activity, electrophoresis for estimation of protein molecular weight, and HPLC for determining products of ACE activity. Results The results revealed that the lupin flour was abundant in protein (43.3 g/100 g). Results from sequential Osborne extraction procedure showed that lupin protein comprised of 46% salt-soluble globulin, 27% water-soluble albumin, 18% alkaline-soluble glutelin and 7% alcohol-soluble prolamin fractions. Furthermore, lupin protein was rich in lysine but limiting in methionine. Hydrolysates prepared using Alcalase exhibited higher ACE inhibitory activities compared with those prepared using Flavourzyme, showing IC50 values ranging from 0.10 to 0.21 mg/mL. However, there was no significant difference in IC50 values between the hydrolysates prepared using Alcalase for 4, 10 and 16 h of hydrolysis times. Conclusions The results suggested that globulin was the major contributing protein fraction on ACE inhibitory effect in lupin protein. The lupin protein hydrolysates with potent ACE inhibitory activities can be incorporated into the daily diet to prevent hypertension. Funding Sources Ministry of Education Malaysia.

Evaluation of potential sodium-iodide symporter (NIS) inhibitors using a secondary Fischer rat thyroid follicular cell (FRTL-5) radioactive iodide uptake (RAIU) assay.

The Fischer rat thyroid follicular cell line (FRTL-5) endogenously expresses the sodium-iodide symporter (NIS) and has been used to identify environmental chemicals that perturb thyroid hormone homeostasis by disruption of NIS-mediated iodide uptake. Previously, a high-throughput radioactive iodide uptake (RAIU) screening assay incorporating the hNIS-HEK293T-EPA cell line was used to identify potential human NIS (hNIS) inhibitors in 1028 ToxCast Phase I (ph1_v2) and Phase II chemicals. In this study, the FRTL-5 cell line was evaluated and applied as a secondary RAIU assay coupled with cell viability assays to further prioritize highly active NIS inhibitors from the earlier screening. Assay validation with ten reference chemicals and performance assessment by chemical controls suggest the FRTL-5 based assays are robust and highly reproducible. Top-ranked chemicals from the ToxCast screening were then evaluated in both FRTL-5 and hNIS RAIU assays using newly sourced chemicals to strengthen the testing paradigm and to enable a rat vs. human species comparison. Eighteen of 29 test chemicals showed less than 1 order of magnitude difference in IC50 values between the two assays. Notably, two common perfluorinated compounds, perfluorooctanesulfonic acid (PFOS) and perfluorohexane sulfonate (PFHxS), demonstrated strong NIS inhibitory activity [IC50 -6.45 (PFOS) and -5.70 (PFHxS) log M in FRTL-5 RAIU assay]. In addition, several chemicals including etoxazole, methoxyfenozide, oxyfluorfen, triclocarban, mepanipyrim, and niclosamide also exhibited NIS inhibition with minimal cytotoxicity in both assays and are proposed for additional testing using short-term in vivo assays to characterize effects on thyroid hormone synthesis.

Leishmania infantum isolates exhibit high infectivity and reduced susceptibility to amphotericin B.

Leishmaniasis is a neglected disease caused by a protozoan parasite of the Leishmania species in over 98 countries in five continents. Visceral leishmaniasis is one of the main forms of the disease and is mainly caused by Leishmania infantum, whose main vector is the dipteran Lutzomyia longipalpis. The presence of the vector in Uruguay was recorded for the first time in 2010 and an autochthonous outbreak of canine visceral leishmaniasis occurred in the northern locality of the country in 2015. We report the isolation in blood-free FBS-supplemented defined media of five isolates responsible for the referred outbreak, and characterize them in terms of their growth as promastigotes, infectivity and replication in human derived monocytes and drug resistance. Results indicate similar promastigote growth among the strains, enhanced infectivity and replication for the five strains isolated from the Uruguayan outbreak when compared with reference strains from South America, equivalent drug susceptibility for miltefosine and nifurtimox and a significant difference in IC50 values for amphotericin B between the Uruguayan strains, 3-4 fold higher than the reference strain.

Screening and characterization of a novel high-efficiency tumor-homing cell-penetrating peptide from the buffalo cathelicidin family.

Targeted delivery of antitumor drugs is especially important for tumor therapy. Cell-penetrating peptides (CPPs) have been shown to be very effective drug carriers for tumor therapy. However, most CPPs lack tumor cell specificity. Here, we identified a highly efficient CPP, CAT, from the newly identified buffalo-derived cathelicidin family, which exhibits a preferential binding capacity for multiple tumor cell lines and delivers carried drug molecules into cells. CAT showed an approximately threefold to sixfold higher translocation efficiency than some reported cell-penetrating antimicrobial peptides, including the well-known classical CPP TAT. Moreover, the delivery efficiency of CAT was greater in a variety of tested tumor cells than in normal cells, especially for the human hepatoma cell line SMMC-7721, for which delivery was 7 times more efficient than the normal human embryonic lung cell line MRC-5, according to fluorescent labeling experiment results. CAT was conjugated to the Momordica charantia-derived type-I ribosome-inactivating protein MAP 30, and the cytotoxicity of the MAP 30-CAT fusion protein in the tumor cell line SMMC-7721 was significantly enhanced compared with that of the unconjugated MAP 30. The IC50 value of MAP 30-CAT was approximately 83 times lower than the IC50 value of the original MAP 30. Interestingly, the IC50 value of MAP 30 alone for MRC-5 was approximately twofold higher than the value for SMMC-7721, showing a small difference. However, when MAP 30 was conjugated to CAT, the difference in IC50 values between the two cell lines was significantly increased by 38-fold. The results of the flow cytometric detection of apoptosis revealed that the increase in cytotoxicity after CAT conjugation was mainly caused by the increased induction of apoptosis by the fusion protein. These results suggest that CAT, as a novel tumor-homing CPP, has great potential in drug delivery applications in vivo and will be beneficial to the development of tumor therapeutics.

The impact of azole antifungal drugs on imatinib metabolism in human liver microsomes

1. Imatinib is widely used for the treatment of hematologic malignancies. It is common that imatinib is clinically co-prescribed with azole antifungal agents since these patients are more prone to invasive antifungal infection. The present study was to investigate the effects of azole antifungal drugs, including ketoconazole, fluconazole, voriconazole, itraconazole and posaconazole on imatinib metabolism.2. The main metabolites, 1-OH midazolam and N-desmethyl imatinib, were determined in the absence and in the presence of various levels of ketoconazole, fluconazole, voriconazole, itraconazole and posaconazole. The relevant assay was also performed to screen mechanism-based inhibitors (MBI).3. The inhibition ability of 1-OH midazolam formation from midazolam based on IC50 values was ketoconazole (0.09 µM)>itraconazole (0.31 µM)> posaconazole (0.68 µM)>voriconazole (2.10 µM) > fluconazole (8.90 µM). Similarly, the rank order of inhibitory effects on formation of N-desmethyl imatinib from imatinib was ketoconazole (4.58 µM)>itraconazole (17.45 µM)> posaconazole (31.02 µM)> voriconazole (367.9 µM) >fluconazole (1.11 mM). Posaconazole and itraconazole displayed evidence of MBI. Additionally, imatinib was also shown as a MBI of CYP3A with IC50 value of 5.40 µM against the midazolam.4. The significant difference in IC50 values of midazolam and imatinib inhibited by azole antifungal agents was observed. The role of CYP2C8 in imatinib metabolism and imatinib autoinhibits CYP3A activity may explain this difference. Our findings suggest that the azole antifungal agents might have limited impacts on imatinib exposure by CYP3A activity.

Effects of polymyxin-B on TNF-α production in equine whole blood stimulated with three different bacterial toxins.

Polymyxin-B is used to treat equine systemic inflammation. Bacterial toxins other than lipopolysaccharide (LPS) contribute to systemic inflammation but the effects of polymyxin-B on these are poorly defined. Whole blood aliquots from six healthy horses diluted 1:1 with RPMI were incubated for 21hr with 1μg/ml of LPS, lipoteichoic acid (LTA) or peptidoglycan (PGN) in the presence of increasing concentrations of polymyxin-B (10-3000μg/ml). A murine L929 fibroblast bioassay was used to measure TNF-α activity. Polymyxin-B significantly inhibited the effects of all three bacterial toxins. Analysis of variance showed the IC50 value for polymyxin-B for TNF-α inhibition caused by LTA (11.19±2.89μg/ml polymyxin-B) was significantly lower (p=.009) than the values for LPS (46.48±9.93μg/ml) and PGN (54.44±8.97μg/ml). There was no significant difference in IC50 values between LPS and PGN (p>.05). Maximum inhibition of TNF-α was 77.4%, 73.0% and 82.7% for LPS, PGN and LTA, respectively and was not significantly different between toxins. At the two highest concentrations of polymyxin-B, TNF-α began to increase. These data suggest that polymyxin-B may inhibit the effects of bacterial toxins other than LPS and might be a more potent inhibitor of LTA than LPS or PGN.

Screening Indigenous Medicinal Plants of Northeast India for Their Anti-Alzheimer’s Properties

Introduction: Alzheimer’s disease (AD) is a progressive neurologic disease of the brain that affects intellectual abilities, reasoning and memory. Acetylcholine (ACh) is involved in the maintenance of cognitive process. Pathologically, ACh production is compromised in the brains of AD affected people. Presence of acetylcholinesterase (AChE) in the synaptic cleft, which hydrolyzes ACh, further decreases the ACh-levels, and thereby, additionally compromises cognition. The tribal people of North East India have been using indigenous plants as traditional medicine for brain disorders. We assayed whether the plants used in the traditional tribal knowledge for the treatment of brain disorders might contain better AChE-inhibitors. Methods: We collected 10 traditional medicinal plants from Northeast India. A total of 39 plant extracts were prepared using three solvent systems. The Acetylcholinesterase (AChE) activity was measured with Ellman method. The experiment was done in triplicate for each level of inhibitor. The activity was measured at 412 nm wavelength using Plate Reader. The standard student t-test was used to show significant difference in IC50 values between extracts. Results: The result are reported based on Km, Vmax, IC50 (μg/μl), percentage inhibition and inhibition pattern. Two extracts had competitive inhibition, 11 extracts had mixed inhibition, 2 extracts had non-competitive inhibition, 11 extracts had uncompetitive inhibition and 4 extracts did not provide any proper pattern. The IC50 for these plant extracts were at the range of 0.51-12.4 μg/μl. Notably, Cinnamomum camphora (leaf: chloroform), Litsea glutinosa (stem; chloroform), and Litsea glutinosa (stem; methanol) showed IC50 values of 0.51, 0.53 & 0.81 μg/μl, respectively.

Impact of Dendrimer Terminal Group Chemistry on Blockage of the Anthrax Toxin Channel: A Single Molecule Study.

Nearly all the cationic molecules tested so far have been shown to reversibly block K+ current through the cation-selective PA63 channels of anthrax toxin in a wide nM–mM range of effective concentrations. A significant increase in channel-blocking activity of the cationic compounds was achieved when multiple copies of positively charged ligands were covalently linked to multivalent scaffolds, such as cyclodextrins and dendrimers. Even though multivalent binding can be strong when the individual bonds are relatively weak, for drug discovery purposes we often strive to design multivalent compounds with high individual functional group affinity toward the respective binding site on a multivalent target. Keeping this requirement in mind, here we perform a single-channel/single-molecule study to investigate kinetic parameters of anthrax toxin PA63 channel blockage by second-generation (G2) poly(amido amine) (PAMAM) dendrimers functionalized with different surface ligands, including G2-NH2, G2-OH, G2-succinamate, and G2-COONa. We found that the previously reported difference in IC50 values of the G2-OH/PA63 and G2-NH2/PA63 binding was determined by both on- and off-rates of the reversible dendrimer/channel binding reaction. In 1 M KCl, we observed a decrease of about three folds in and a decrease of only about ten times in with G2-OH compared to G2-NH2. At the same time for both blockers, and increased dramatically with transmembrane voltage increase. PAMAM dendrimers functionalized with negatively charged succinamate, but not carboxyl surface groups, still had some residual activity in inhibiting the anthrax toxin channels. At 100 mV, the on-rate of the G2-succinamate binding was comparable with that of G2-OH but showed weaker voltage dependence when compared to G2-OH and G2-NH2. The residence time of G2-succinamate in the channel exhibited opposite voltage dependence compared to G2-OH and G2-NH2, increasing with the cis-negative voltage increase. We also describe kinetics of the PA63 ion current modulation by two different types of the “imperfect” PAMAM dendrimers, the mixed-surface G2 75% OH 25% NH2 dendrimer and G3-NH2 dendron. At low voltages, both “imperfect” dendrimers show similar rate constants but significantly weaker voltage sensitivity when compared with the intact G2-NH2 PAMAM dendrimer.

DDIS-05. TARGETING MESENCHYMAL GLIOBLASTOMA THROUGH INHIBITION OF DIACYLGLYCEROL KINASE ALPHA

Recent studies have shown that glioblastoma (GBM) can be classified into distinct subtypes based on gene expression signatures: classical, proneural, and mesenchymal. Of these, the mesenchymal subtype is relatively more aggressive and resistant to therapy, and is thought to be a primary driver of recurrence. The diacylglycerol kinase alpha (DGKα) signaling pathway has extensive connections to oncogenic pathways/proteins. Recently, we identified ritanserin, an abandoned serotonin receptor 5-HT2 inhibitor originally developed for schizophrenia, as a novel DGKα inhibitor. Compared to a known DGKα inhibitor, R59022, ritanserin is more potent and has favorable pharmacologic features such as long plasma half-life and known BBB penetration. Based on the TCGA database, we have determined that DGKα expression level is highest in the mesenchymal subtype. DGKα inhibition with ritanserin revealed a significant difference in IC50 values, with a 3-4 fold increase in sensitivity, of all mesenchymal GBM stem cell (GSC) lines tested versus all non-mesenchymal lines. In vivo, daily oral ritanserin increased mice survival significantly with two mesenchymal GSC lines, while there was no survival benefit with a proneural GSC line. With an EMT model, both lung and pancreatic carcinoma cells became more sensitive to ritanserin after the acquisition of mesenchymal phenotype. Ritanserin reduces NF-κB activity significantly and suppresses geranylgeranylation of proteins by inhibiting geranylgeranyltransferase I. Exogenous phosphatidic acid, the DGKα enzymatic product, substantially rescued GBM cells from ritanserin toxicity while exogenous 5-HT2 receptor agonist, 5-hydroxytryptamine, showed a small rescue from ritanserin toxicity. In keeping with its anti-mesenchymal activity, ritanserin functions as a radiosensitizer, with suppression of the DNA damage response and shows significant synergy with radiation. Our work is the first to show in vitro and in vivo that a clinically practical agent has strong preferential toxicity for the mesenchymal GBM subtype, with potential therapeutic implications for GBM and other cancers as well.

Identification and Biochemical Properties of Two New Acetylcholinesterases in the Pond Wolf Spider (Pardosa pseudoannulata).

Acetylcholinesterase (AChE), an important neurotransmitter hydrolase in both invertebrates and vertebrates, is targeted by organophosphorus and carbamate insecticides. In this study, two new AChEs were identified in the pond wolf spider Pardosa pseudoannulata, an important predatory natural enemy of several insect pests. In total, four AChEs were found in P. pseudoannulata (including two AChEs previously identified in our laboratory). The new putative AChEs PpAChE3 and PpAChE4 contain most of the common features of the AChE family, including cysteine residues, choline binding sites, the conserved sequence ‘FGESAG’ and conserved aromatic residues but with a catalytic triad of ‘SDH’ rather than ‘SEH’. Recombinant enzymes expressed in Sf9 cells showed significant differences in biochemical properties compared to other AChEs, such as the optimal pH, substrate specificity, and catalytic efficiency. Among three test substrates, PpAChE1, PpAChE3 and PpAChE4 showed the highest catalytic efficiency (Vmax/KM) for ATC (acetylthiocholine iodide), with PpAChE3 exhibiting a clear preference for ATC based on the VmaxATC/VmaxBTC ratio. In addition, the four PpAChEs were more sensitive to the AChE-specific inhibitor BW284C51, which acts against ATC hydrolysis, than to the BChE-specific inhibitor ISO-OMPA, which acts against BTC hydrolysis, with at least a 8.5-fold difference in IC50 values for each PpAChE. PpAChE3, PpAChE4, and PpAChE1 were more sensitive than PpAChE2 to the tested Carb insecticides, and PpAChE3 was more sensitive than the other three AChEs to the tested OP insecticides. Based on all the results, two new functional AChEs were identified from P. pseudoannulata. The differences in AChE sequence between this spider and insects enrich our knowledge of invertebrate AChE diversity, and our findings will be helpful for understanding the selectivity of insecticides between insects and natural enemy spiders.

X-Ray Structure and Inhibition of 3C-like Protease from Porcine Epidemic Diarrhea Virus.

Porcine epidemic diarrhea virus (PEDV) is a coronavirus that infects pigs and can have mortality rates approaching 100% in piglets, causing serious economic impact. The 3C-like protease (3CLpro) is essential for the coronaviral life cycle and is an appealing target for the development of therapeutics. We report the expression, purification, crystallization and 2.10 Å X-ray structure of 3CLpro from PEDV. Analysis of the PEDV 3CLpro structure and comparison to other coronaviral 3CLpro’s from the same alpha-coronavirus phylogeny shows that the overall structures and active site architectures across 3CLpro’s are conserved, with the exception of a loop that comprises the protease S2 pocket. We found a known inhibitor of severe acute respiratory syndrome coronavirus (SARS-CoV) 3CLpro, (R)-16, to have inhibitor activity against PEDV 3CLpro, despite that SARS-3CLpro and PEDV 3CLpro share only 45.4% sequence identity. Structural comparison reveals that the majority of residues involved in (R)-16 binding to SARS-3CLpro are conserved in PEDV-3CLpro; however, the sequence variation and positional difference in the loop forming the S2 pocket may account for large observed difference in IC50 values. This work advances our understanding of the subtle, but important, differences in coronaviral 3CLpro architecture and contributes to the broader structural knowledge of coronaviral 3CLpro’s.

Usefulness of A Model-Based Approach for Estimating In Vitro P-Glycoprotein Inhibition Potency in a Transcellular Transport Assay

In vitro half-maximal inhibitory concentration (IC50) is a key parameter for accurately predicting the potential risk for P-glycoprotein (P-gp)–mediated drug–drug interactions. We aimed to compare the IC50 values estimated by different approaches and determine the usefulness of model-based approaches. Transcellular transport of digoxin across Caco-2 monolayer was investigated using various concentrations of P-gp inhibitors, quinidine, verapamil, and zosuquidar. To calculate IC50 values, 3 traditional parameters were used: apical-to-basal (AtoB) and basal-to-apical (BtoA) clearance (CL) with inhibitors (CLAtoB,i and CLBtoA,i) and the difference between the efflux ratios (ERs) with P-gp inhibitors (ERi) and those under complete P-gp inhibition [ER(−P-gp)]. Furthermore, a new model-based approach was applied that uses the difference between the reciprocals of CLAtoB with P-gp inhibitors (1/CLAtoB,i) and those under complete P-gp inhibition [1/CLAtoB(−P-gp)] as parameters. IC50 values obtained from 2 model-based approaches [ERi − ER(−P-gp) and 1/CLAtoB,i − 1/CLAtoB(−P-gp)] were comparable, whereas 2.6- to 6.6-fold larger IC50 values were estimated from empirical approaches (CLAtoB,i and CLBtoA,i). The reason for such difference in IC50 values is that indicators for model-based approaches, but not empirical approaches, directly reflect the P-gp function. Our new approach [1/CLAtoB,i − 1/CLAtoB(−P-gp)] based on only AtoB transcellular transport could substitute for current estimation methods using ER.

5'-β,γ-CHF-ATP diastereomers: synthesis and fluorine-mediated selective binding by c-Src protein kinase.

The first preparation of the individual β,γ-CHF-ATP stereoisomers 12a and 12b is reported. Configurationally differing solely by the orientation of the C-F fluorine, 12a and 12b have discrete (31)P (202 MHz, pH 10.9, ΔδPα 6 Hz, ΔδPβ 4 Hz) and (19)F NMR (470 MHz, pH 9.8, ΔδF 25 Hz) spectral signatures and exhibit a 6-fold difference in IC50 values for c-Src kinase, attributed to a unique interaction of the (S)-fluorine of bound 12b with R388 in the active site.

Four years’ monitoring of in vitro sensitivity and candidate molecular markers of resistance of Plasmodium falciparum to artesunate-mefloquine combination in the Thai-Myanmar border

BackgroundThe decline in efficacy of artesunate (AS) and mefloquine (MQ) is now the major concern in areas along the Thai-Cambodian and Thai-Myanmar borders.MethodsThe correlation between polymorphisms of pfatp6, pfcrt, pfmdr1 and pfmrp1 genes and in vitro sensitivity of Plasmodium falciparum isolates to the artemisinin-based combination therapy (ACT) components AS and MQ, including the previously used first-line anti-malarial drugs chloroquine (CQ) and quinine (QN) were investigated in a total of 119 P. falciparum isolates collected from patients with uncomplicated P. falciparum infection during 2006–2009.ResultsReduced in vitro parasite sensitivity to AS [median (95% CI) IC50 3.4 (3.1-3.7) nM] was found in 42% of the isolates, whereas resistance to MQ [median (95% CI) IC50 54.1 (46.8-61.4) nM] accounted for 58% of the isolates. Amplification of pfmdr1 gene was strongly associated with a decline in susceptibility of P. falciparum isolates to AS, MQ and QN. Significant difference in IC50 values of AS, MQ and QN was observed among isolates carrying one, two, three, and ≥ four gene copies [median (95% CI) AS IC50: 1.6 (1.3-1.9), 1.8 (1.1-2.5), 2.9 (2.1-3.7) and 3.1 (2.5-3.7) nM, respectively; MQ IC50: 19.2 (15.8-22.6), 37.8 (10.7-64.8), 55.3 (47.7-62.9) and 63.6 (49.2-78.0) nM, respectively; and QN IC50: 183.0 (139.9-226.4), 256.4 (83.7-249.1), 329.5 (206.6-425.5) and 420.0 (475.2-475.6) nM, respectively]. The prevalence of isolates which were resistant to QN was reduced from 21.4% during the period 2006–2007 to 6.3% during the period 2008–2009. Pfmdr1 86Y was found to be associated with increased susceptibility of the parasite to MQ and QN. Pfmdr1 1034C was associated with decreased susceptibility to QN. Pfmrp1 191Y and 1390I were associated with increased susceptibility to CQ and QN, respectively.ConclusionHigh prevalence of CQ and MQ-resistant P. falciparum isolates was observed during the four-year observation period (2006–2009). AS sensitivity was declined, while QN sensitivity was improved. Pfmdr1 and pfmrp1 appear to be the key genes that modulate multidrug resistance in P. falciparum.

Carbohydrate-appended photocytotoxic (imidazophenanthroline)-oxovanadium(iv) complexes for cellular targeting and imaging

Oxovanadium(IV) complexes [VO(aip)(L)](ClO4)2 (L = phtpy, 1; stpy, 2) and [VO(pyip)(L)](ClO4)2 (L = phtpy, 3; stpy, 4), where aip is 2-(9-anthryl)-1H-imidazo[4,5-f][1,10]phenanthroline, pyip is [2-(1-pyrenyl)-1H-imidazo[4,5-f][1,10]phenanthroline, phtpy is (4'-phenyl)-2,2':6',2''-terpyridine and stpy is (2,2':6',2''-terpyridin-4'-oxy)ethyl-β-D-glucopyranoside, were prepared, characterized and their DNA binding and photocleavage activity, cellular uptake and photocytotoxicity in visible light were studied. The complexes are avid binders to calf thymus DNA (K(b) ~10(5) mol(-1)). They efficiently cleave pUC19 DNA in red light of 705 nm via the formation of HO˙ species. The glucose appended complexes 2 and 4 showed higher photocytotoxicity in HeLa and Hep G2 cells over the normal HEK 293T cells. No such preference was observed for the phtpy complexes 1 and 3. No significant difference in IC50 values was observed for the HEK 293T cells. Cell cycle analysis showed that the glucose appended complexes 2 and 4 are more photocytotoxic in cancer cells than in normal cells. Fluorescence microscopy was done to study the cellular localization of complex 4 having a pendant pyrenyl group.