A fluorescent probe for selective detection of lysosomal β-hexosaminidase in live cells

Determining the activity of lysosomal β-hexosaminidase in cells is of great importance for understanding the roles that these enzymes play in pathophysiological events. Herein, we designed the new fluorescent probe, βGalNAc-Rhod-CM(NEt2), which consisted of a βGalNAc-linked rhodol unit serving as a β-hexosaminidase reactive fluorogenic moiety and a N,N'-diethylaminocoumarin (CM(NEt2)) group acting as a fluorescence marker for determining the degree of cell permeabilization. Treatment of βGalNAc-Rhod-CM(NEt2) with β-hexosaminidase promoted generation of Rhod-CM(NEt2), thereby leading to an increase in the intensity of fluorescence of Rhod. However, this probe did not respond to the functionally related glycosidase, O-GlcNAcase. The detection limit of βGalNAc-Rhod-CM(NEt2) for β-hexosaminidase was determined to be 0.52 nM, indicating that it has high sensitivity for this enzyme. Furthermore, the probe functioned as an excellent fluorogenic substrate for β-hexosaminidase with kcat and Km values of 17 sec-1 and 22 μM, respectively. The results of cell studies using βGalNAc-Rhod-CM(NEt2) showed that levels of β-hexosaminidase activity in cells can be determined by measuring the intensity of fluorescence arising from Rhod and that the intensity of fluorescence of CM(NEt2) can be employed to determine the degree of cell permeabilization of the probe. Utilizing the new probe, we assessed β-hexosaminidase activities in several types of cells and evaluated the effect of glucose concentrations in culture media on the activity of this enzyme.

A novel NLRP3 inhibitor as a therapeutic agent against monosodium urate-induced gout

Background

Since NEK7 is critical for NLRP3 inflammasome activation, NEK7 inhibitors could be employed as therapeutic agents against gout, a representative disease caused by NLRP3 inflammasome.

Methods

We designed NEK7 inhibitors based on biochemical kinome profiling of 2,7-substituted thieno[3,2-d]pyrimidine derivatives (SLC3031~3035 and SLC3037). Inflammasome activation was assessed by ELISA of IL-1b and immunoblotting of IL-1b maturation after treatment of bone marrow-derived macrophages with LPS+monosodium urate (MSU). NLPR3 binding to NEK7 and oligomerization were examined using immunoprecipitation and Blue Native gel electrophoresis, respectively. In vivo effect was investigated by studying gross and histopathological changes of food pad tissue of MSU-injected mice, together with assays of maturation of IL-1b and ASC speck in the tissue.

Results

SLC3037 inhibited inflammasome by MSU and other inflammasome activators through blockade of NLRP3 binding to NEK7 or oligomerization, and subsequent ASC oligomerization/phosphorylation. SLC3037 significantly reduced foot pad thickness and inflammation by MSU, which was superior to the effects of colchicine. SLC3037 significantly reduced content or maturation of IL-1b and ASC speck in the food pad. The number and height of intestinal villi were decreased by colchicine but not by SLC3037.

Conclusion

SLC3037, a NLRP3 inhibitor blocking NEK7 binding to NLRP3, could be a novel agent against diseases associated with NLRP3 inflammasome activation such as gout, cardiovascular diseases, metabolic syndrome or neurodegenerative diseases.

Engineering of cell-surface receptors for analysis of receptor internalization and detection of receptor-specific glycosylation

The epidermal growth factor receptor (EGFR) is a cell-surface glycoprotein that is involved mainly in cell proliferation. Overexpression of this receptor is intimately related to the development of a broad spectrum of tumors. In addition, glycans linked to the EGFR are known to affect its EGF-induced activation. Because of the pathophysiological significance of the EGFR, we prepared a fluorescently labeled EGFR (EGFR128-AZDye 488) on the cell surface by employing the genetic code expansion technique and bioorthogonal chemistry. EGFR128-AZDye 488 was initially utilized to investigate time-dependent endocytosis of the EGFR in live cells. The results showed that an EGFR inhibitor and antibody suppress endocytosis of the EGFR promoted by the EGF, and that lectins recognizing glycans of the EGFR do not enhance EGFR internalization into cells. Observations made in studies of the effects of appended glycans on the entry of the EGFR into cells indicate that a de-sialylated or de-fucosylated EGFR is internalized into cells more efficiently than a wild-type EGFR. Furthermore, by using the FRET-based imaging method of cells which contain an EGFR linked to AZDye 488 (a FRET donor) and cellular glycans labeled with rhodamine (a FRET acceptor), sialic acid residues attached to the EGFR were specifically detected on the live cell surface. Taken together, the results suggest that a fluorescently labeled EGFR will be a valuable tool in studies aimed at gaining an understanding of cellular functions of the EGFR.

Glycosidase-targeting small molecules for biological and therapeutic applications

Glycosidases are ubiquitous enzymes that catalyze the hydrolysis of glycosidic linkages in oligosaccharides and glycoconjugates. These enzymes play a vital role in a wide variety of biological events, such as digestion of nutritional carbohydrates, lysosomal catabolism of glycoconjugates, and posttranslational modifications of glycoproteins. Abnormal glycosidase activities are associated with a variety of diseases, particularly cancer and lysosomal storage disorders. Owing to the physiological and pathological significance of glycosidases, the development of small molecules that target these enzymes is an active area in glycoscience and medicinal chemistry. Research efforts carried out thus far have led to the discovery of numerous glycosidase-targeting small molecules that have been utilized to elucidate biological processes as well as to develop effective chemotherapeutic agents. In this review, we describe the results of research studies reported since 2018, giving particular emphasis to the use of fluorescent probes for detection and imaging of glycosidases, activity-based probes for covalent labelling of these enzymes, glycosidase inhibitors, and glycosidase-activatable prodrugs.

O-GlcNAcylation of RIPK1 rescues red blood cells from necroptosis

Necroptosis is a type of cell death with excessive inflammation and organ damage in various human diseases. Although abnormal necroptosis is common in patients with neurodegenerative, cardiovascular, and infectious diseases, the mechanisms by which O-GlcNAcylation contributes to the regulation of necroptotic cell death are poorly understood. In this study, we reveal that O-GlcNAcylation of RIPK1 (receptor-interacting protein kinase1) was decreased in erythrocytes of the mouse injected with lipopolysaccharide, resulting in the acceleration of erythrocyte necroptosis through increased formation of RIPK1-RIPK3 complex. Mechanistically, we discovered that O-GlcNAcylation of RIPK1 at serine 331 in human (corresponding to serine 332 in mouse) inhibits phosphorylation of RIPK1 at serine 166, which is necessary for the necroptotic activity of RIPK1 and suppresses the formation of the RIPK1-RIPK3 complex in Ripk1 ^-/- MEFs. Thus, our study demonstrates that RIPK1 O-GlcNAcylation serves as a checkpoint to suppress necroptotic signaling in erythrocytes.

A fluorescent probe to simultaneously detect both O-GlcNAcase and phosphatase

O-GlcNAc modification of proteins often has crosstalk with protein phosphorylation. These posttranslational modifications are highly dynamic events that modulate a wide range of cellular processes. Owing to the physiological and pathological significance of protein O-GlcNAcylation and phosphorylation, we designed the fluorescent probe, βGlcNAc-CM-Rhod-P, to differentially detect activities of O-GlcNAcase (OGA) and phosphatase, enzymes that are responsible for these modifications. βGlcNAc-CM-Rhod-P was comprised of a βGlcNAc-conjugated coumarin (βGlcNAc-CM) acting as an OGA substrate, a phosphorylated rhodol (Rhod-P) as a phosphatase substrate and a piperazine bridge. Because the emission wavelength maxima of CM and Rhod liberated from the probe are greatly different (100 nm), spectral interference is avoided. The results of this study revealed that treatment of βGlcNAc-CM-Rhod-P with OGA promotes formation of the GlcNAc-cleaved probe, CM-Rhod-P, and a consequent increase in the intensity of fluorescence associated with free CM. Also, it was found that exposure of the probe to phosphatase produces a dephosphorylated probe, βGlcNAc-CM-Rhod, which displays strong fluorescence arising from free Rhod. On the other hand, when incubated with both OGA and phosphatase, βGlcNAc-CM-Rhod-P was converted to CM-Rhod which lacked both βGlcNAc and phosphoryl groups, in conjunction with increases in the intensities of fluorescence arising from both free CM and Rhod. This probe was employed to detect activities of OGA and phosphatase in cell lysates and to fluorescently image both enzymes in cells. Collectively, the findings indicate that βGlcNAc-CM-Rhod-P can be utilized as a chemical tool to simultaneously determine activities of OGA and phosphatase.

Glycan microarrays from construction to applications

Through their specific interactions with proteins, cellular glycans play key roles in a wide range of physiological and pathological processes. One of the main goals of research in the areas of glycobiology and glycomedicine is to understand glycan-protein interactions at the molecular level. Over the past two decades, glycan microarrays have become powerful tools for the rapid evaluation of interactions between glycans and proteins. In this review, we briefly describe methods used for the preparation of glycan probes and the construction of glycan microarrays. Next, we highlight applications of glycan microarrays to rapid profiling of glycan-binding patterns of plant, animal and pathogenic lectins, as well as other proteins. Finally, we discuss other important uses of glycan microarrays, including the rapid analysis of substrate specificities of carbohydrate-active enzymes, the quantitative determination of glycan-protein interactions, discovering high-affinity or selective ligands for lectins, and identifying functional glycans within cells. We anticipate that this review will encourage researchers to employ glycan microarrays in diverse glycan-related studies.

Identification of Pyridinyltriazine Derivatives as Potent panFGFR Inhibitors against Gatekeeper Mutants for Overcoming Drug Resistance

Although FGFR inhibitors hold promise in treating various cancers, resistance to the FGFR inhibitors caused by acquired secondary mutations has emerged. To discover novel FGFR inhibitors capable of inhibiting FGFR mutations, including gatekeeper mutations, we designed and synthesized several new pyridinyltriazine derivatives. A structure-activity relationship (SAR) study led to the identification of 17a as a highly potent panFGFR inhibitor against wild-type and mutant FGFRs. Notably, 17a is superior to infigratinib in terms of kinase-inhibitory and cellular activities, especially against V555M-FGFR3. Molecular dynamics simulations provide a clear understanding of why pyridinyltraizine derivative 17a possesses activity against V555M-FGFR3. Moreover, 17a significantly suppresses proliferation of cancer cells harboring FGFR mutations via FGFR signaling blockade, cell cycle arrest, and apoptosis. Furthermore, 17a and 17b exhibited remarkable efficacies in TEL-V555M-FGFR3 Ba/F3 xenograft mouse model and 17a is more efficacious than infigratinib. This study provides new insight into the design of novel FGFR inhibitors that are active against FGFR mutants.

Rhodamine-based cyclic hydrazide derivatives as fluorescent probes for selective and rapid detection of formaldehyde

We developed a fluorescent probe that is useful to monitor endogenous and exogenous formaldehyde in live cells.

A Thiol-Activated Fluorogenic Probe for Detection of a Target Protein

A novel fluorogenic probe for facile and efficient detection of a target protein that binds to a bioactive small molecule was developed. The probe was composed of a thiol-activated fluorogenic...

A fluorogenic probe targeting two spatially separated enzymes for selective imaging of cancer cells

We describe a fluorogenic probe BocLys(Ac)-AB-FC targeting both histone deacetylases (HDACs) and cathepsin L, which are overexpressed in spatially separated subcellular organelles of cancer cells. The results show that the...

Near-infrared (NIR) fluorescence-emitting small organic molecules for cancer imaging and therapy

We discuss recent advances made in the development of NIR fluorescence-emitting small organic molecules for tumor imaging and therapy.

Novel Small Molecules Capable of Blocking mtRAS-Signaling Pathway

RAS mutants are involved in approximately 30% of all human cancers and have been regarded as undruggable targets owing to relatively smooth protein surface and obscure binding pockets. In our previous study, we have demonstrated that GNF-7, a multi-targeted kinase inhibitor, possesses potent anti-proliferative activity against Ba/F3 cells transformed with NRAS-G12D. Based on our further analysis using Ba/F3 cells transformed with mtRAS, we discovered a series of pyrimido[4,5-d]pyrimidin-2-one analogues as mtRAS-signaling pathway blockers. In addition, our efforts expanded the assessment to cancer cells with mtRAS, which revealed that these substances are also capable of strongly suppressing the proliferation of various cancer cells harboring KRAS-G12D (AsPC-1), KRAS-G12V (SW480, DU-145), KRAS-G12C (H358), KRAS-G13D (MDA-MB-231), KRAS-Q61L (HT-29), and NRAS-Q61L (OCI-AML3). We herein report novel and potent mtRAS-signaling pathway blockers, SIJ1795 and SIJ1772, possessing 2 to 10-fold increased anti-proliferative activities compared to those of GNF-7 on cancer cells harboring mtRAS as well as on Ba/F3 cells transformed with mtRAS. Both SIJ1795 and SIJ1772 attenuate phosphorylation of RAS downstream molecules (AKT and MEK) and induce apoptosis and G0/G1 cell cycle arrest on cancer cells with mtRAS. Moreover, both substances substantially suppress the migration, invasion, and colony formation of cancer cells harboring mtRAS. Taken together, this study led us to identification of SIJ1795 and SIJ1772 capable of strongly inhibiting mtRAS-signaling pathway on cancer cells harboring mtRAS.

Synthetic Na+/K+ exchangers promote apoptosis by disturbing cellular cation homeostasis

A number of artificial cation ionophores (or transporters) have been developed for basic research and biomedical applications. However, their mechanisms of action and the putative correlations between changes in intracellular cation concentrations and induced cell death remain poorly understood. Here, we show that three hemispherand-strapped calix[4]pyrrole-based ion-pair receptors act as efficient Na+/K+ exchangers in the presence of Cl- in liposomal models and promote Na+ influx and K+ efflux (Na+/K+ exchange) in cancer cells to induce apoptosis. Mechanistic studies reveal that these cation exchangers induce endoplasmic reticulum (ER) stress in cancer cells by perturbing intracellular cation homeostasis, promote generation of reactive oxygen species, and eventually enhance mitochondria-mediated apoptosis. However, they neither induce osmotic stress nor affect autophagy. This study provides support for the notion that synthetic receptors, which perturb cellular cation homeostasis, may provide new small molecules with potentially useful apoptotic activity.

Anti-cancer effects of 3,4-dihydropyrimido[4,5-d]pyrimidin-2(1H)-one derivatives on hepatocellular carcinoma harboring FGFR4 activation

Hepatocellular carcinoma (HCC) is disease with a high mortality rate and limited treatment options. Alterations of fibroblast growth factor receptor 4 (FGFR4) has been regarded as an oncogenic driver for HCC and a promising target for HCC therapeutics. Herein, we report that GNF-7, a multi-targeted kinase inhibitor, and its derivatives including SIJ1263 (IC₅₀ < 1 nM against FGFR4) are highly potent FGFR4 inhibitors and are capable of strongly suppressing proliferation of HCC cells and Ba/F3 cells transformed with wtFGFR4 or mtFGFR4. Compared with known FGFR4 inhibitors, both GNF-7 and SIJ1263 possess much higher (up to 100-fold) anti-proliferative activities via FGFR signaling blockade and apoptosis on HCC cells. Especially, SIJ1263 is 80-fold more potent (GI₅₀ = 24 nM) on TEL-FGFR4 V550E Ba/F3 cells than BLU9931, which suggests that SIJ1263 would be effective for overriding drug resistance. In addition, both substances strongly suppress migration/invasion and colony formation of HCC cells. It is worth noting that SIJ1263 is superior to GNF-7 with regards to the fact that activities of SIJ1263 are higher than those of GNF-7 in all assays performed in this study. Collectively, this study provides insight into designing highly potent FGFR4 inhibitors capable of potentially overcoming drug-resistance for the treatment of HCC patients.

Real-Time Spatial and Temporal Analysis of the Translocation of the Apoptosis-Inducing Factor in Cells

Translocation of the apoptosis-inducing factor (AIF) from the mitochondria to the nucleus is crucial for AIF-mediated apoptosis. However, the lack of methods for real-time spatial and temporal analysis of translocation of functional AIF is a large hurdle to gain a detailed understanding of this process. In this study, a genetic code expansion technique was developed to overcome this hurdle. Specifically, this technique was utilized to construct ANAP-AIF containing a small fluorescent amino acid (ANAP) at a specific site in cells. Additionally, we developed efficient fluorescence resonance energy-transfer systems consisting of ANAP-AIF and either yellow fluorescent protein (YFP)-fused cyclophilin A (CypA) or Hsp70, respective positive and negative regulators for AIF translocation to the nucleus. We found that apoptosis inducers, including apoptozole, 2-phenylethynesulfonamide (PES), myricetin, Bam7, reactivating p53 and inducing tumor apoptosis (RITA), brefeldin A, and carbonyl cyanide-p-trifluoromethoxyphenylhydrazone (FCCP) promote translocation of mitochondrial AIF to the cytosol after 4 h incubation, reaching a maximum after 6-7 h. However, these substances did not enhance AIF translocation to the nucleus through the interaction of AIF with Hsp70 in the cytosol. On the other hand, treatment with apoptosis inducers, such as paclitaxel, silibinin, doxorubicin, actinomycin D, and camptothecin caused AIF translocation to the nucleus after 4 h incubation through AIF binding to CypA, reaching saturation after 6-7 h. It was also found that Hsp70 and CypA regulate AIF translocation in a mutually exclusive manner because they do not interact with AIF simultaneously in cells undergoing apoptosis. The results demonstrate clearly that ANAP-incorporated proteins are powerful to obtain a more in-depth understanding of protein translocation.

Efficient Preparation and Bioactivity Evaluation of Glycan-Defined Glycoproteins

Owing to the generation of heterogeneous glycoproteins in cells, it is highly difficult to study glycoprotein-mediated biological events and to develop biomedical agents. Thus, general and efficient methods to prepare homogeneous glycoproteins are in high demand. Herein, we report a general method for the efficient preparation of homogeneous glycoproteins that utilizes a combination of genetic code expansion and chemoselective ligation techniques. In the protocol to produce glycan-defined glycoproteins, an alkyne tag-containing protein, generated by genetic encoding of an alkynylated unnatural amino acid, was quantitatively coupled via click chemistry to versatile azide-appended glycans. The glycoproteins produced by the present strategy were found to recognize mammalian cell-surface lectins and enter the cells through lectin-mediated internalization. Also, cell studies exhibited that the glycoprotein containing multiple mannose-6-phosphate residues enters diseased cells lacking specific lysosomal glycosidases by binding to the cell-surface M6P receptor, and subsequently migrates to lysosomes for efficient degradation of stored glycosphingolipids.

A triple-targeting delivery system carrying two anticancer agents

To improve tumor selectivity, a triple-targeting delivery system (Oct-FK(PBA-Az)-Dox) carrying two anticancer agents (apoptozole (Az) and doxorubicin (Dox)) was designed and synthesized. The results showed that both anticancer agents in Oct-FK(PBA-Az)-Dox are liberated in the presence of both H₂O₂ and cathepsin B, which are normally present at high levels in tumors.

Identification of Thieno[3,2-d]pyrimidine Derivatives as Dual Inhibitors of Focal Adhesion Kinase and FMS-like Tyrosine Kinase 3

Focal adhesion kinase (FAK) is overexpressed in highly invasive and metastatic cancers. To identify novel FAK inhibitors, we designed and synthesized various thieno[3,2-d]pyrimidine derivatives. An intensive structure-activity relationship (SAR) study led to the identification of 26 as a lead. Moreover, 26, a multitargeted kinase inhibitor, possesses excellent potencies against FLT3 mutants as well as FAK. Gratifyingly, 26 remarkably inhibits recalcitrant FLT3 mutants, including F691L, that cause drug resistance. Importantly, 26 is superior to PF-562271 in terms of apoptosis induction, anchorage-independent growth inhibition, and tumor burden reduction in the MDA-MB-231 xenograft mouse model. Also, 26 causes regression of tumor growth in the MV4-11 xenograft mouse model, indicating that it could be effective against acute myeloid leukemia (AML). Finally, in an orthotopic mouse model using MDA-MB-231, 26 remarkably prevents metastasis of orthotopic tumors to lymph nodes. Taken together, the results indicate that 26 possesses potential therapeutic value against highly invasive cancers and relapsed AML.

Multivalent glycans for biological and biomedical applications

Recognition of glycans by proteins plays a crucial role in a variety of physiological processes in cells and living organisms. In addition, interactions of glycans with proteins are involved in the development of diverse diseases, such as pathogen infection, inflammation and tumor metastasis. It is well-known that multivalent glycans bind to proteins much more strongly than do their monomeric counterparts. Owing to this property, numerous multivalent glycans have been utilized to elucidate glycan-mediated biological processes and to discover glycan-based biomedical agents. In this review, we discuss recent advances (2014-2020) made in the development and biological and biomedical applications of synthetic multivalent glycans, including neoglycopeptides, neoglycoproteins, glycodendrimers, glycopolymers, glyconanoparticles and glycoliposomes. We hope this review assists researchers in the design and development of novel multivalent glycans with predictable activities.

Maintenance of the Neuroprotective Function of the Amino Group Blocked Fluorescence-Agmatine

Agmatine, an endogenous derivative of arginine, has been found to be effective in treating idiopathic pain, convulsion, stress-mediated behavior, and attenuate the withdrawal symptoms of drugs like morphine. In the early stages of ischemic brain injury in animals, exogenous agmatine treatment was found to be neuroprotective. Agmatine is also considered as a putative neurotransmitter and is still an experimental drug. Chemically, agmatine is called agmatine 1-(4-aminobutyl guanidine). Crystallographic study data show that positively-charged guanidine can bind to the protein containing Gly and Asp residues, and the amino group can interact with the complimentary sites of Glu and Ser. In this study, we blocked the amino end of the agmatine by conjugating it with FITC, but the guanidine end was unchanged. We compared the neuroprotective function of the agmatine and agmatine-FITC by treating them in neurons after excitotoxic stimulation. We found that even the amino end blocked neuronal viability in the excitotoxic condition, by NMDA treatment for 1 h, was increased by agmatine-FITC, which was similar to that of agmatine. We also found that the agmatine-FITC treatment reduced the expression of nitric oxide production in NMDA-treated cells. This study suggests that even if the amino end of agmatine is blocked, it can perform its neuroprotective function.

An Autophagy-Disrupting Small Molecule Promotes Cancer Cell Death via Caspase Activation

A novel autophagy inhibitor, autophazole (Atz), which promoted cancer cell death via caspase activation, is described. This compound was identified from cell-based high-content screening of an imidazole library. The results showed that Atz was internalized into lysosomes of cells where it induced lysosomal membrane permeabilization (LMP). This process generated nonfunctional autolysosomes, thereby inhibiting autophagy. In addition, Atz was found to promote LMP-mediated apoptosis. Specifically, LMP induced by Atz caused release of cathepsins from lysosomes into the cytosol. Cathepsins in the cytosol cleaved Bid to generate tBid, which subsequently activated Bax to induce mitochondrial outer membrane permeabilization (MOMP). This event led to cancer cell death via caspase activation. Overall, the findings suggest that Atz will serve as a new chemical probe in efforts aimed at gaining a better understanding of the autophagic process.

Cancer cell death using metabolic glycan labelling techniques

Herein we describe a method for inducing cancer cell death, which relies on the use of a H2O2-responsive glycan metabolic precursor in conjunction with antibody-dependent cellular cytotoxicity (ADCC) or photodynamic therapy (PDT).

Development and Validation of a Deep Learning-Based Model to Distinguish Glioblastoma from Solitary Brain Metastasis Using Conventional MR Images

BACKGROUND AND PURPOSE

Differentiating glioblastoma from solitary brain metastasis preoperatively using conventional MR images is challenging. Deep learning models have shown promise in performing classification tasks. The diagnostic performance of a deep learning-based model in discriminating glioblastoma from solitary brain metastasis using preoperative conventional MR images was evaluated.

MATERIALS AND METHODS

Records of 598 patients with histologically confirmed glioblastoma or solitary brain metastasis at our institution between February 2006 and December 2017 were retrospectively reviewed. Preoperative contrast-enhanced T1WI and T2WI were preprocessed and roughly segmented with rectangular regions of interest. A deep neural network was trained and validated using MR images from 498 patients. The MR images of the remaining 100 were used as an internal test set. An additional 143 patients from another tertiary hospital were used as an external test set. The classifications of ResNet-50 and 2 neuroradiologists were compared for their accuracy, precision, recall, F1 score, and area under the curve.

RESULTS

The areas under the curve of ResNet-50 were 0.889 and 0.835 in the internal and external test sets, respectively. The area under the curve of neuroradiologists 1 and 2 were 0.889 and 0.768 in the internal test set and 0.857 and 0.708 in the external test set, respectively.

CONCLUSIONS

A deep learning-based model may be a supportive tool for preoperative discrimination between glioblastoma and solitary brain metastasis using conventional MR images.

Synthesis of an Hsp70 inhibitor and its assessment of lysosomal membrane permeabilization

Hsp70 inhibitors have great potential as chemical probes and anticancer agents. Thus, it is important to elucidate their modes of action on cancer cell death. This protocol describes a step-by-step process for the synthesis of apoptozole as an inhibitor of Hsp70, analysis of internalization of apoptozole into lysosomes, and assessment of lysosomal membrane permeabilization induced by apoptozole. The current protocol can be used for detailed mechanistic studies of Hsp70 inhibitors and further substances targeting lysosomal proteins on cancer cell death.

For complete information on the use and execution of this protocol, please refer to Park et al. (2018).

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Synthesis of apoptozole as an Hsp70 inhibitor

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Internalization study of an Hsp70 inhibitor into lysosomes

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Assessment of lysosomal membrane permeabilization induced by an Hsp70 inhibitor

Anti-glioma effects of 2-aminothiophene-3-carboxamide derivatives, ANO1 channel blockers

Anoctamin1 (ANO1), a calcium-activated chloride ion channel (CaCC), is associated with various physiological functions including cancer progression and metastasis/invasion. ANO1 has been considered as a promising target for cancer therapeutics as ANO1 is over-expressed in a variety of cancers including glioblastoma (GBM) and inhibition of ANO1 has been reported to suppress cell proliferation, migration and invasion in GBM. GBM is one of the most common and aggressive cancers with poor prognosis with median survival for 15 months. Lack of effective treatment options against GBM emphasizes urgent necessity of effective GBM therapeutics. In an effort to discover potent and selective ANO1 inhibitors capable of inhibiting GBM cells, we have designed and synthesized a series of new 2-aminothiophene-3-carboxamide derivatives and performed SAR studies using both fluorescent cellular membrane potential assay and whole-cell patch-clamp recording. We observed that among these substances, 9c and 10q strongly suppress ANO1 channel activities and possess remarkable selectivity over ANO2. Unique structural feature of 10q, a cyclopentane-fused thiophene-3-carboxamide derivative, is the presence of benzoylthiourea functionality which dramatically contributes to activity. Both 9c and 10q suppress more strongly proliferation of GBM cells than four reference compounds including 3, Ani-9 and are also capable of inhibiting much more strongly colony formation than reference compounds in both 2D colony formation assay and 3D soft agar assay using U251 glioma cells. In addition, 9c and 10q suppress far more strongly migration/invasion of GBM cells than reference compounds. We, for the first time, found that the combination of ANO1 inhibitor (9c or 3) and temozolomide (TMZ) brings about remarkable synergistic effects in suppressing proliferation of GBM cells. Our study may provide an insight into designing selective and potent ANO1 inhibitors aiming at GBM treatment.

Bacterial Lectin-Targeting Glycoconjugates for Selective Elimination of Pathogenic Bacteria

Herein we report a strategy to eradicate pathogenic bacteria selectively, which utilizes bacterial lectin-targeting glycoconjugates that contain an epitope or a photosensitizer to promote antibody-dependent cellular cytotoxicity (ADCC) or photodynamic therapy (PDT), respectively. Our results show that death promoted by using the designed synthetic glycoconjugates coupled with ADCC or PDT takes place selectively in pathogenic bacteria expressing lectins on their surfaces.

Mitochondrial Cl--Selective Fluorescent Probe for Biological Applications

Herein we describe the development of the first mitochondrial Cl^--selective fluorescent probe, Mito-MQAE, and its applications in biological systems. Fluorescence of Mito-MQAE is insensitive to pH over the physiological pH range and is quenched by Cl^- with a Stern-Volmer quenching constant of 201 M^-1 at pH 7.0. The results of cell studies using Mito-MQAE show that substances with the ability to disrupt mitochondrial membranes cause increases in the mitochondrial Cl^- concentration.

O-GlcNAcylation of Mef2c regulates myoblast differentiation

Unlike other types of glycosylation, O-GlcNAcylation is a single glycosylation which occurs exclusively in the nucleus and cytosol. O-GlcNAcylation underlie metabolic diseases, including diabetes and obesity. Furthermore, O-GlcNAcylation affects different oncogenic processes such as osteoblast differentiation, adipogenesis and hematopoiesis. Emerging evidence suggests that skeletal muscle differentiation is also regulated by O-GlcNAcylation, but the detailed molecular mechanism has not been fully elucidated. In this study, we showed that hyper-O-GlcNAcylation reduced the expression of myogenin, a transcription factor critical for terminal muscle development, in C2C12 myoblasts differentiation by O-GlcNAcylation on Thr9 of myocyte-specific enhancer factor 2c. Furthermore, we showed that O-GlcNAcylation on Mef2c inhibited its DNA binding affinity to myogenin promoter. Taken together, we demonstrated that hyper-O-GlcNAcylation attenuates skeletal muscle differentiation by increased O-GlcNAcylation on Mef2c, which downregulates its DNA binding affinity.

Synthetic ratiometric fluorescent probes for detection of ions

Metal cations and anions are essential for versatile physiological processes. Dysregulation of specific ion levels in living organisms is known to have an adverse effect on normal biological events. Owing to the pathophysiological significance of ions, sensitive and selective methods to detect these species in biological systems are in high demand. Because they can be used in methods for precise and quantitative analysis of ions, organic dye-based ratiometric fluorescent probes have been extensively explored in recent years. In this review, recent advances (2015-2019) made in the development and biological applications of synthetic ratiometric fluorescent probes are described. Particular emphasis is given to organic dye-based ratiometric fluorescent probes that are designed to detect biologically important and relevant ions in cells and living organisms. Also, the fundamental principles associated with the design of ratiometric fluorescent probes and perspectives about how to expand their biological applications are discussed.

An Inhibitor of the Interaction of Survivin with Smac in Mitochondria Promotes Apoptosis

Herein we report the first small molecule that disrupts the survivin-Smac interaction taking place in mitochondria. The inhibitor, PZ-6-QN, was identified by initially screening a phenothiazine library using a fluorescence anisotropy assay and then conducting a structure-activity relationship study. Mutagenesis and molecular docking studies suggest that PZ-6-QN binds to survivin similarly to the known Smac peptide, AVPI. The results of the effort also show that PZ-6-QN exhibits good anticancer activity against various cancer cells. Moreover, cell-based mechanistic studies provide evidence for the proposal that PZ-6-QN enters mitochondria to inhibit the survivin-Smac interaction and promotes release of Smac and cytochrome c from mitochondria into the cytosol, a process that induces apoptosis in cancer cells. Overall, the present study suggests that PZ-6-QN can serve as a novel chemical probe for study of processes associated with the mitochondrial survivin-Smac interaction and it will aid the discovery of novel anticancer agents.

Raman-Based in Situ Monitoring of Changes in Molecular Signatures during Mitochondrially Mediated Apoptosis

Obtaining molecular information from inside cells is an important topic to understand the outcome of molecular interactions between potential drug molecules and biomolecules inside cells. To envision this goal, we investigated the surface-enhanced Raman scattering-based single-cell spectroscopic method to monitor changes in intracellular molecular signatures during mitochondrially mediated apoptosis in real time. Triphenylphosphine-modified gold nanoparticles were localized successfully to the mitochondria and greatly enhanced to obtain the intrinsic Raman scattering spectrum of mitochondria and cytochrome c in the live cell. Photothermally induced apoptosis showed a moderate decrease in the disulfide bond and a sharp increase in β-sheet structures depending on the input-laser power, along with morphological changes. However, chemical drug induced-apoptosis showed more subtle changes in the disulfide bond, as well as changes in Raman peaks corresponding to cytochrome c, and the appearance of a new peak at 1420 cm-1, which enabled us to study the molecular interactions within the mitochondria in real time from a single cell, following treatment with a novel pyruvate dehydrogenase kinase inhibitor.

A lysosomal chloride ion-selective fluorescent probe for biological applications

Lysosomal pHs are maintained at low values by the cooperative action of a proton pump and a chloride channel to maintain electroneutrality. Owing to the biological significance of lysosomal chloride ions, measurements of their levels are of great importance to understand lysosome-associated biological events. However, appropriate probes to selectively detect Cl^- ions within acidic lysosomes have not been developed to date. In this study, we prepared MQAE-MP, a lysosomal Cl^--selective fluorescent probe, and applied it to gain information about biological processes associated with lysosomes. The fluorescence of MQAE-MP is pH-insensitive over physiological pH ranges and is quenched by Cl^- with a Stern-Volmer constant of 204 M^-1. Because MQAE-MP detects lysosomal Cl^- selectively, it was employed to assess the effects of eleven substances on lysosomal Cl^- concentrations. The results show that lysosomal Cl^- concentrations decrease in cells treated with substances that inhibit proteins responsible for lysosomal membrane stabilization, induce lysosomal membrane permeabilization, and transport lysosomal Cl^- to the cytosol. In addition, we investigated the effect of lysosomal chloride ions on the fusion of autophagosomes with lysosomes to generate autolysosomes during autophagy inhibition promoted by substances. It was found that changes in lysosomal Cl^- concentrations did not affect the fusion of autophagosomes with lysosomes but an increase in the cytosolic Ca²⁺ concentration blocked the fusion process. We demonstrate from the current study that MQAE-MP has great potential as a lysosomal Cl^--selective fluorescent probe for studies of biological events associated with lysosomes.

First SAR Study for Overriding NRAS Mutant Driven Acute Myeloid Leukemia

GNF-7, a multitargeted kinase inhibitor, served as a dual kinase inhibitor of ACK1 and GCK, which provided a novel therapeutic strategy for overriding AML expressing NRAS mutation. This SAR study with GNF-7 derivatives, designed to target NRAS mutant-driven AML, led to identification of the extremely potent inhibitors, 10d, 10g, and 11i, which possess single-digit nanomolar inhibitory activity against both ACK1 and GCK. These substances strongly suppress proliferation of mutant NRAS expressing AML cells via apoptosis and AKT/mTOR signaling blockade. Compound 11i is superior to GNF-7 in terms of kinase inhibitory activity, cellular activity, and differential cytotoxicity. Moreover, 10k possessing a favorable mouse pharmacokinetic profile prolonged life-span of Ba/F3-NRAS-G12D injected mice and significantly delayed tumor growth of OCI-AML3 xenograft model without causing the prominent level of toxicity found with GNF-7. Taken together, this study provides insight into the design of novel ACK1 and GCK dual inhibitors for overriding NRAS mutant-driven AML.

Analysis of binding properties of pathogens and toxins using multivalent glycan microarrays

Pathogens infect hosts often through initial binding of their cell surface lectins to glycans expressed on the exterior of host cells. Thus, methods to evaluate the glycan-binding properties of pathogens are of great importance. Because of the multivalent nature of interactions of pathogens with glycans, the ability to assess the glycan density-dependent binding of pathogens is particularly important. In this study, we developed a facile technique to construct multivalent carbohydrate microarrays through immobilization of unmodified glycans on multivalent hydrazide-derivatized glass surfaces. This immobilization strategy does not require the use of multivalent glycoconjugates, which are typically prepared by using multistep sequences. The results of analysis of microarray images, obtained after incubation of multivalent glycan microarrays with cholera toxin B and pathogens such as uropathogenic E. coli and H. pylori, show that the binding affinities of toxins and pathogens for glycans are highly glycan density-dependent. Specifically, toxins and pathogens bind to glycans more strongly as the valency of the glycans on the microarrays is increased from 1 to 4. It is anticipated that the newly developed immobilization method will be applicable to the preparation of multivalent carbohydrate microarrays that are employed to evaluate multivalent glycan binding properties of a variety of pathogens and toxins.

Microarrays constructed by immobilizing free glycans on multivalent hydrazide-coated surfaces were applied to evaluate multivalent glycan binding properties of pathogens.

Structural Revision of Baulamycin A and Structure-Activity Relationships of Baulamycin A Derivatives

Total synthesis of the proposed structure of baulamycin A was performed. The spectral properties of the synthetic compound differ from those reported for the natural product. On the basis of comprehensive NMR study, we proposed two other possible structures for natural baulamycin A. Total syntheses of these two substances were performed, which enabled assignment of the correct structure of baulamycin A. Key features of the convergent and fully stereocontrolled route include Evans Aldol and Brown allylation reactions to construct the left fragment, a prolinol amide-derived alkylation/desymmetrization to install the methyl-substituted centers in the right fragment, and finally, a Carreira alkynylation to join both fragments. In addition, we have determined the inhibitory activities of novel baulamycin A derivatives against the enzyme SbnE. This SAR study provides useful insight into the design of novel SbnE inhibitors that overcome the drug resistance of pathogens, which cause life-threatening infections.

Helicobacter pylori infection and serum level of pepsinogen are associated with the risk of metachronous gastric neoplasm after endoscopic resection

BACKGROUND

Patients who have undergone endoscopic resection of early gastric cancers (EGCs) are at risk for metachronous gastric neoplasm.

AIM

To determine whether serum level of pepsinogen (PG), a marker of gastric atrophy, can determine which patients who have undergone endoscopic submucosal dissection for EGC are at risk for metachronous gastric neoplasm. We also investigated the effects of Helicobacter pylori eradication on metachronous gastric neoplasm incidence.

METHODS

We performed a retrospective study of 590 consecutive patients who underwent endoscopic submucosal dissection for EGC, from January 2008 to May 2013 at a tertiary centre in South Korea; serum levels of PG were measured at the time of endoscopic submucosal dissection and H. pylori infection status were recorded. In case of proven presence of current H. pylori infection, eradication treatment was provided. Patients underwent follow-up endoscopies at 3 months, 9 months, and each year after the procedure to detect neoplasms and were tested for H. pylori infection; serum levels of PG were measured at these time points from 442 of the patients. The main and sub-cohorts were assessed for baseline characteristics, H. pylori infection, serum level of PG, and metachronous gastric neoplasm lesions.

RESULTS

During a median follow-up period of 47.7 months, 64 patients developed metachronous gastric neoplasms. In multivariate analysis of the main cohort (n = 590), risk factors for metachronous gastric neoplasm included persistent H. pylori infection (hazard ratio [HR], 2.532; P = .022) and serum ratio of PGI:PGII of three or less at the time of endoscopic submucosal dissection (HR, 1.881; P = .018). Among patients with serum PG measurements, persistent H. pylori infection (odds ratio [OR], 4.404; P = .009) and persistent decrease in mean serum ratio of PGI:PGII to 3 or less were associated with increased risk of metachronous gastric neoplasm (OR, 2.141; P = .039).

CONCLUSIONS

In a retrospective analysis of patients who underwent endoscopic resection of EGCs, eradication of H. pylori infection reduced risk for metachronous gastric neoplasm. Serum ratio of PGI:PGII of 3 or less also increase risk of metachronous gastric neoplasm after endoscopic submucosal dissection. ClinicalTrials.gov. registry number, NCT02682446.

A synthetic ion transporter that disrupts autophagy and induces apoptosis by perturbing cellular chloride concentrations

Perturbations in cellular chloride concentrations can affect cellular pH and autophagy and lead to the onset of apoptosis. With this in mind, synthetic ion transporters have been used to disturb cellular ion homeostasis and thereby induce cell death; however, it is not clear whether synthetic ion transporters can also be used to disrupt autophagy. Here, we show that squaramide-based ion transporters enhance the transport of chloride anions in liposomal models and promote sodium chloride influx into the cytosol. Liposomal and cellular transport activity of the squaramides is shown to correlate with cell death activity, which is attributed to caspase-dependent apoptosis. One ion transporter was also shown to cause additional changes in lysosomal pH, which leads to impairment of lysosomal enzyme activity and disruption of autophagic processes. This disruption is independent of the initiation of apoptosis by the ion transporter. This study provides the first experimental evidence that synthetic ion transporters can disrupt both autophagy and induce apoptosis.