Erratum: A novel selective AKR1C3-activated prodrug AST-3424/OBI-3424 exhibits broad anti-tumor activity.

[This corrects the article on p. 3645 in vol. 11, PMID: 34354865.].

Immunogenicity of a spike protein subunit-based COVID-19 vaccine with broad protection against various SARS-CoV-2 variants in animal studies.

SARS-CoV-2 pandemic has profound impacts on human life and global economy since the outbreak in 2019. With the new variants continue to emerge with greater immune escaping capability, the protectivity of the available vaccines is compromised. Therefore, development a vaccine that is capable of inducing immunity against variants including omicron strains is in urgent need. In this study, we developed a protein-based vaccine BCVax that is consisted of antigen delta strain spike protein and QS21-based adjuvant AB801 in nanoparticle immune stimulation complex format (AB801-ISCOM). Results from animal studies showed that high level of anti-S protein IgG was induced after two doses of BCVax and the IgG was capable of neutralizing multiple variants of pseudovirus including omicron BA.1 or BA.2 strains. In addition, strong Th1 response was stimulated after BCVax immunization. Furthermore, BCvax with AB801-ISCOM as the adjuvant showed significant stronger immunity compared with the vaccine using aluminum hydroxide plus CpG 1018 as the adjuvant. BCVax was also evaluated as a booster after two prior vaccinations, the IgG titers and pseudovirus neutralization activities against BA.2 or BA.4/BA.5 were further enhanced suggesting BCVax is a promising candidate as booster. Taken together, the pre-clinical data warrant BCVax for further development in clinic.

A novel selective AKR1C3-activated prodrug AST-3424/OBI-3424 exhibits broad anti-tumor activity.

AST-3424/OBI-3424 (denoted by 3424) is a novel prodrug bis-alkylating agent activated by AKR1C3. AKR1C3 is overexpressed in many types of cancer, particularly in liver, non-small cell lung, gastric, renal and CRPC cancer. Currently 3424 is being studied in phase 1/2 clinical trials for the treatment of solid and hematologic cancers, and it represents potentially a novel, selective anti-cancer agent for multiple indications. In this study, AKR1C3-dependent activation of 3424 was investigated in vitro using recombinant human AKR1C3. AKR1C3-dependent cytotoxicity of 3424 was determined in a wide range of human cancer cell lines with different AKR1C3 expression levels. In addition, anti-tumor activity of 3424 was also investigated in a broad panel of CDX and PDX models. AKR1C3-dependent activation of prodrug 3424 was evident by monitoring the decrease of 3424 and generation of the active form, 2660. Kinetic analysis indicated that AKR1C3 exhibited higher catalytic efficiency towards 3424 compared to the physiological substrates. There was a strong correlation between 3424 cytotoxic potency and AKR1C3 expression. The racemic mixture induced DNA cross-linking in a concentration dependent manner. Tumor growth inhibition of 3424 was shown to be better than or comparable to the standard of care chemotherapy at clinically achievable doses as a single agent in various CDX models with high expression of AKR1C3, including liver HepG2, lung H460, castration-resistant prostate VCaP, gastric SNU-16, and kidney A498 cancer cell lines. The excellent anti-tumor efficacy of 3424 was further demonstrated in PDX models which have high level of AKR1C3 expression, but not in a model with low level of AKR1C3 expression. In the combination therapy, we showed that 3424 could enhance the efficacy of the standard care of chemotherapy in the CDX models. The results described here highlight that 3424 exhibits AKR1C3-dependent cytotoxicity in vitro and anti-tumor activity in vivo in a wide range of human cancer types, which support further development of 3424 as an anti-cancer agent for treating different types of cancers and the use of AKR1C3 as a biomarker to profile cancer patients and further guide patient selection for therapy with 3424.

Preclinical Studies of OBI-999: A Novel Globo H-Targeting Antibody-Drug Conjugate.

Globo H (GH), a hexasaccharide, is expressed at low levels in normal tissues but is highly expressed in multiple cancer types, rendering it a promising target for cancer immunotherapy. OBI-999, a novel antibody-drug conjugate, is derived from a conjugation of a GH-specific mAb with a monomethyl auristatin E (MMAE) payload through a site-specific ThioBridge and a cleavable linker. OBI-999 high homogeneity with a drug-to-antibody ratio of 4 (>95%) was achieved using ThioBridge. OBI-999 displayed GH-dependent cellular internalization and trafficked to endosome and lysosome within 1 and 5 hours, respectively. Furthermore, OBI-999 showed low nanomolar cytotoxicity in the assay with high GH expression on tumor cells and exhibited a bystander killing effect on tumor cells with minimal GH expression. Tissue distribution indicated that OBI-999 and free MMAE gradually accumulated in the tumor, reaching maximum level at 168 hours after treatment, whereas OBI-999 and free MMAE decreased quickly at 4 hours after treatment in normal organs. Maximum MMAE level in the tumor was 16-fold higher than in serum, suggesting that OBI-999 is stable during circulation and MMAE is selectively released in the tumor. Excellent tumor growth inhibition of OBI-999 was demonstrated in breast, gastric, and pancreatic cancer xenograft or lung patient-derived xenograft models in a dose-dependent manner. The highest nonseverely toxic dose in cynomolgus monkeys is 10 mg/kg determined by a 3-week repeated-dose toxicology study demonstrating an acceptable safety margin. Taken together, these results support further clinical development of OBI-999, which is currently in a phase I/II clinical study in multiple solid tumors (NCT04084366). OBI-999, the first GH-targeting ADC, displayed excellent tumor inhibition in animal models across multiple cancer types, including breast, gastric, pancreatic, and lung cancers, warranting further investigation in the treatment of solid tumors.

Polygala tenuifolia extract inhibits lipid accumulation in 3T3-L1 adipocytes and high-fat diet-induced obese mouse model and affects hepatic transcriptome and gut microbiota profiles.

Obesity, the excessive accumulation of lipids in the body, is closely associated with many prevalent human disorders. Continued efforts to identify plant extracts that exhibit anti-obesity effects have drawn much attention. This study investigated whether a Polygala tenuifolia extract (PTE) possesses anti-obesity activity and how PTE may affect liver gene expression and gut microbiota. We used 3T3-L1 adipocytes and a high-fat diet-induced obese mouse model to determine the effects of PTE on lipid accumulation. Next-generation sequencing analysis of liver gene expression and gut microbiota profiles following PTE treatment were conducted to elucidate possible mechanisms. We found that treatment of fully differentiated 3T3-L1 adipocytes with PTE inhibited lipid accumulation in the cells through reducing lipid formation and triglyceride content and by increasing lipase activity. No cytotoxicity was observed from the PTE treatment. After 5 weeks of treatment with PTE, the increased body weight, elevated serum triglyceride content, and liver steatosis in the high-fat diet-induced obese mice were each reduced. Liver transcriptomic analysis revealed that expression of genes involved in lipid and cholesterol metabolism was significantly altered. The low-grade chronic inflammation of obesity caused by a high-fat diet was also decreased after PTE treatment. In addition, treatment with PTE improved the relatively low Bacteroidetes/Firmicutes ratio in the gut of high-fat diet-fed mice through enrichment of the Proteobacteria population and reduction of the Deferribacteres population. In conclusion, treatment with PTE inhibited lipid accumulation by inducing the expression of the master transcription factor PPARα, attenuated the low-grade chronic inflammation of obesity, and also altered gut microbiota profiles. These results indicate that PTE has the potential to be developed into an anti-obesity food supplement and therapy. Abbreviations: Abcg5: ATP-binding cassette subfamily G member 5; ALT: alanine aminotransferase; AMPK: adenosine monophosphate-activated protein kinase; AST: aspartate aminotransferase; B/F: Bacteroidetes to Firmicutes [ratio]; C/EBPα: CCAAT/enhancer-binding protein alpha; CR: creatinine; Cyp51: cytochrome P450 family 51; DMEM: Dulbecco's modified Eagle's medium; Fabp5: fatty acid-binding protein 5; FBS: fetal bovine serum; Fdps: farnesyl diphosphate synthase; Glc: Glucose; HFD: high-fat diet; GO: gene ontology; HPRT: hypoxanthine guanine phosphoribosyl transferase; IBMS: 3-isobutyl-1-methylxanthine; Idi1: isopentenyl-diphosphate delta isomerase 1; IL-1ß: interleukin-1-beta; Lpin1: phosphatidic acid phosphohydrolase; LPS: lipopolysaccharide; Mvd: mevalonate diphosphate decarboxylase; ND: normal diet; OTU: operational taxonomic units; Pcsk9: proprotein convertase subtilisin/kexin 9; Pctp: phosphatidylcholine transfer protein; PPARα: peroxisome proliferator-activated receptor alpha; PPARγ: peroxisome proliferator-activated receptor gamma; PTE: Polygala tenuifolia extract; Saa1: serum amyloid A1; SD: standard deviation; SEM: standard error of the mean; Serpina12: serpin family member 12; Sqle: squalene monooxygenase; SREBP1C: sterol regulatory element-binding protein 1C; TCHO: total cholesterol; TG: triglyceride.

Insights into the coordinated interplay of the sHP hairpin and its co-existing and mutually-exclusive dengue virus terminal RNA elements for viral replication.

Terminal RNA elements of the dengue virus (DENV) genome are necessary for balanced stability of linear and circular conformations during replication. We examined the small hairpin (sHP) and co-existing and mutually-exclusive terminal RNA elements by mutagenesis analysis, compensatory mutation screening, and by probing with RNA fragments to explore localized RNA folding and long-range RNA interactions. We found that the first base pair of the sHP and the stability of SLB and the 3'SL bottom stem affected circularization; sHPgc/C10631G+G10644C prohibited circularization, sHPuG accelerated and stabilized 5'-to-3' RNA hybridization, while C94A and A97G and C10649 mutations loosened SLB and 3'SL, respectively, for circularization. sHPuG+C10649G induced circularization and impeded replication, whereas point mutations that loosened the UAR or DAR ds region, strengthened the sHP, or reinforced the 3'SL bottom stem, rescued the replication deficiency. Overall, we reveal structural and sequence features and interplay of DENV genome terminal RNA elements essential to viral replication.

Identification of Heat Shock Transcription Factor Genes Involved in Thermotolerance of Octoploid Cultivated Strawberry.

Heat shock transcription factors (HSFs) are mainly involved in the activation of genes in response to heat stress as well as other abiotic and biotic stresses. The growth, development, reproduction, and yield of strawberry are strongly limited by extreme temperatures and droughts. In this study, we used Illumina sequencing and obtained transcriptome data set from Fragaria × ananassa Duchessne cv. Toyonoka. Six contigs and three unigenes were confirmed to encode HSF proteins (FaTHSFs). Subsequently, we characterized the biological functions of two particularly selected unigenes, FaTHSFA2a and FaTHSFB1a, which were classified into class A2 and B HSFs, respectively. Expression assays revealed that FaTHSFA2a and FaTHSFB1a expression was induced by heat shock and correlated well with elevated ambient temperatures. Overexpression of FaTHSFA2a and FaTHSFB1a resulted in the activation of their downstream stress-associated genes, and notably enhanced the thermotolerance of transgenic Arabidopsis plants. Besides, both FaTHSFA2a and FaTHSFB1a fusion proteins localized in the nucleus, indicating their similar subcellular distributions as transcription factors. Our yeast one-hybrid assay suggested that FaTHSFA2a has trans-activation activity, whereas FaTHSFB1a expresses trans-repression function. Altogether, our annotated transcriptome sequences provide a beneficial resource for identifying most genes expressed in octoploid strawberry. Furthermore, HSF studies revealed the possible insights into the molecular mechanisms of thermotolerance, thus rendering valuable molecular breeding to improve the tolerance of strawberry in response to high-temperature stress.

Antiangiogenic and antihepatocellular carcinoma activities of the Juniperus chinensis extract.

BACKGROUND: To identify a novel therapeutic agent for hepatocellular carcinoma (HCC), for which no promising therapeutic agent exists, we screened a panel of plants and found that Juniperus chinensis exhibited potential antiangiogenic and anti-HCC activities. We further investigated the antiangiogenic and anti-HCC effects of the active ingredient of J. chinensis extract, CBT-143-S-F6F7, both in vitro and in vivo. METHODS: A tube formation assay conducted using human umbilical vein endothelial cells (HUVECs) was first performed to identify the active ingredient of CBT-143-S-F6F7. A series of angiogenesis studies, including HUVEC migration, Matrigel plug, and chorioallantoic membrane (CAM) assays, were then performed to confirm the effects of CBT-143-S-F6F7 on angiogenesis. The effects of CBT-143-S-F6F7 on tumor growth were investigated using a subcutaneous and orthotopic mouse model of HCC. In vitro studies were performed to investigate the effects of CBT-143-S-F6F7 on the cell cycle and apoptosis in HCC cells. Moreover, protein arrays for angiogenesis and apoptosis were used to discover biomarkers that may be influenced by CBT-143-S-F6F7. Finally, nuclear magnetic resonance analysis was conducted to identify the compounds of CBT-143-S-F6F7. RESULTS: CBT-143-S-F6F7 showed significantly antiangiogenic activity in various assays, including HUVEC tube formation and migration, CAM, and Matrigel plug assays. In in vivo studies, gavage with CBT-143-S-F6F7 significantly repressed subcutaneous Huh7 tumor growth in severe combined immunodeficient (SCID) mice, and prolonged the survival of orthotopic Huh7 tumor-bearing SCID mice (a 40 % increase in median survival duration compared with the vehicle-treated mice). Immunohistochemical staining of subcutaneous Huh7 tumors in CBT-143-S-F6F7-treated mice showed a significantly decrease in the cell cycle regulatory protein cyclin D1, cellular proliferation marker Ki-67, and endothelial marker CD31. CBT-143-S-F6F7 caused arrest of the G2/M phase and induced Huh7 cell apoptosis, possibly contributing to the inhibition of HCC tumors. Protein array analysis revealed that several angiogenic and antiapoptotic factors were suppressed in CBT-143-S-F6F7-treated Huh7 cells. Finally, five compounds from CBT-143-S-F6F7 were identified. CONCLUSIONS: According to these results, we report for the first time the antiangiogenic and anti-HCC activities of CBT-143-S-F6F7, the active fractional extract of J. chinensis. We believe that CBT-143-S-F6F7 warrants further evaluation as a new anti-HCC drug.

Differential proteomic analysis of cancer stem cell properties in hepatocellular carcinomas by isobaric tag labeling and mass spectrometry.

Malignant tumors are relatively resistant to treatment due to their heterogeneous nature, drug resistance, and tendency for metastasis. Recent studies suggest that a subpopulation of cancer cells is responsible for the malignant outcomes. These cells are considered as cancer stem cells (CSC). Although a number of molecules have been identified in different cancer cells as markers for cancer stem cells, no promising markers are currently available for hepatocellular carcinoma cells. In this study, two clones of Hep3B cell lines were functionally characterized as control or CSC-like cells, based on properties including spheroid formation, drug resistance, and tumor initiation. Furthermore, their protein expression profiles were investigated by isobaric tags for relative and absolute quantitation (iTRAQ), and a total of 1,127 proteins were identified and quantified from the combined fractions; 50 proteins exhibited at least 2-fold differences between these two clones. These 50 proteins were analyzed by GeneGo and were found to be associated with liver neoplasms, hepatocellular carcinoma (HCC), and liver diseases. They were also components of metabolic pathways, immune responses, and cytoskeleton remodeling. Among these proteins, the expressions of S100P, S100A14, and vimentin were verified in several HCC cell lines, and their expressions were correlated with tumorigenicity in HCC cell lines. The functional significance of vimentin and S100A14 were also investigated and verified.

Identification of a small-molecule inhibitor of dengue virus using a replicon system.

Dengue virus (DENV) is a mosquito-borne human pathogen that causes a serious public-health threat in tropical and subtropical regions of the world. Neither a vaccine to prevent nor an effective therapeutic agent to treat DENV infection is currently available. We established a stable cell line harboring a luciferase-reporting DENV subgenomic replicon to screen for inhibitors of DENV. A total of 14,400 small-molecule (MW < 500 Da) chemicals were evaluated for their ability to reduce luciferase reporter activity in cell lysates. One effective compound was identified from the screening. This compound was found to reduce virus production but did not block virus entry in virus-based assay. Mode-of-action analysis revealed that this inhibitor suppressed viral RNA replication but did not affect replicon translation. This compound potentially could be developed as an anti-DENV agent and might be useful for dissecting the molecular mechanism of DENV replication.

Development of novel 3D-QSAR combination approach for screening and optimizing B-Raf inhibitors in silico.

B-Raf is a member of the RAF family of serine/threonine kinases: it mediates cell division, differentiation, and apoptosis signals through the RAS-RAF-MAPK pathway. Thus, B-Raf is of keen interest in cancer therapy, such as melanoma. In this study, we propose the first combination approach to integrate the pharmacophore (PhModel), CoMFA, and CoMSIA models for B-Raf, and this approach could be used for screening and optimizing potential B-Raf inhibitors in silico. Ten PhModels were generated based on the HypoGen BEST algorithm with the flexible fit method and diverse inhibitor structures. Each PhModel was designated to the alignment rule and screening interface for CoMFA and CoMSIA models. Therefore, CoMFA and CoMSIA models could align and recognize diverse inhibitor structures. We used two quality validation methods to test the predication accuracy of these combination models. In the previously proposed combination approaches, they have a common factor in that the number of training set inhibitors is greater than that of testing set inhibitors. In our study, the 189 known diverse series B-Raf inhibitors, which are 7-fold the number of training set inhibitors, were used as a testing set in the partial least-squares validation. The best validation results were made by the CoMFA09 and CoMSIA09 models based on the Hypo09 alignment model. The predictive r(2)(pred) values of 0.56 and 0.56 were derived from the CoMFA09 and CoMSIA09 models, respectively. The CoMFA09 and CoMSIA09 models also had a satisfied predication accuracy of 77.78% and 80%, and the goodness of hit test score of 0.675 and 0.699, respectively. These results indicate that our combination approach could effectively identify diverse B-Raf inhibitors and predict the activity.

HCV NS3 protein helicase domain assists RNA structure conversion.

NS3H, the helicase domain of HCV NS3, possesses RNA-stimulated ATPase and ATP hydrolysis-dependent dsRNA unwinding activities. Here, the ability of NS3H to facilitate RNA structural rearrangement is studied using relatively long RNA strands as the model substrates. NS3H promotes intermolecular annealing, resolves three-stranded RNA duplexes, and assists dsRNA and ssRNA inter-conversions to establish a steady state among RNA structures. NS3H facilitates RNA structure conversions in a mode distinct from an ATP-independent RNA chaperone. These findings expand the known function of HCV NS3 helicase and reveal a role for viral helicase in assisting RNA structure conversions during virus life cycle.

Analysis of the nucleoside triphosphatase, RNA triphosphatase, and unwinding activities of the helicase domain of dengue virus NS3 protein.

The helicase domain of dengue virus NS3 protein (DENV NS3H) contains RNA-stimulated nucleoside triphosphatase (NTPase), ATPase/helicase, and RNA 5'-triphosphatase (RTPase) activities that are essential for viral RNA replication and capping. Here, we show that DENV NS3H unwinds 3'-tailed duplex with an RNA but not a DNA loading strand, and the helicase activity is poorly processive. The substrate of the divalent cation-dependent RTPase activity is not restricted to viral RNA 5'-terminus, a protruding 5'-terminus made the RNA 5'-triphosphate readily accessible to DENV NS3H. DENV NS3H preferentially binds RNA to DNA, and the functional interaction with RNA is sensitive to ionic strength.

Nucleic acid binding properties of the nucleic acid chaperone domain of hepatitis delta antigen.

The N terminal region of hepatitis delta antigen (HDAg), referred to here as NdAg, has a nucleic acid chaperone activity that modulates the ribozyme activity of hepatitis delta virus (HDV) RNA and stimulates hammerhead ribozyme catalysis. We characterized the nucleic acid binding properties of NdAg, identified the structural and sequence domains important for nucleic acid binding, and studied the correlation between the nucleic acid binding ability and the nucleic acid chaperone activity. NdAg does not recognize the catalytic core of HDV ribozyme specifically. Instead, NdAg interacts with a variety of nucleic acids and has higher affinities to longer nucleic acids. The studies with RNA homopolymers reveal that the binding site size of NdAg is around nine nucleotides long. The extreme N terminal portion of NdAg, the following coiled-coil domain and the basic amino acid clusters in these regions are important for nucleic acid binding. The nucleic acid-NdAg complex is stabilized largely by electrostatic interactions. The formation of RNA-protein complex appears to be a prerequisite for facilitating hammerhead ribozyme catalysis of NdAg and its derivatives. Mutations that reduce the RNA binding activity or high ionic strength that destabilizes the RNA-protein complex, reduce the nucleic acid chaperone activity of NdAg.