Catfish egg lectin affects influx and efflux rates of sunitinib in human cervical carcinoma HeLa cells.

New treatment protocols are aiming to reduce the dose of the multitargeted tyrosine kinase inhibitor sunitinib, as sunitinib elicits many adverse effects depending on its dosage. Silurus asotus egg lectin (SAL) has been reported to enhance the incorporation of propidium iodide as well as doxorubicin into Burkitt's lymphoma Raji cells through binding to globotriaosylceramide (Gb3) on the cell surface. The objective of this study was to examine whether SAL enhances the cytotoxic effect of sunitinib in Gb3-expressing HeLa cells. Although the treatment with SAL delayed the cell growth and enhanced the propidium iodide uptake, cell death accompanied by membrane collapse was not observed. The viability of sunitinib-treated HeLa cells was significantly reduced when the treatment occurred in combination with SAL compared to their separate usage. Sunitinib uptake significantly increased for 30 min in SAL-treated cells, and this increment was almost completely abolished by the addition of L-rhamnose, a hapten sugar of SAL, but not by D-glucose. After removal of SU from the medium, the intracellular sunitinib level in SAL-treated cells was higher than in untreated cells for 24 h, which was not observed in Gb3-deficient HeLa cells. Furthermore, we observed that SAL promoted the formation of lysosome-like structures, which are LAMP1 positive but not acidic in HeLa cells, which can trap sunitinib. Interestingly, SAL-induced vacuolation in HeLa cells was not observed in another Gb3 positive Raji cells. Our findings suggest that SAL/Gb3 interaction promoted sunitinib uptake and suppressed sunitinib excretion and that sunitinib efficiently exerted cytotoxicity against HeLa cells.

Sialic Acid-Binding Lectin from Bullfrog Eggs Exhibits an Anti-Tumor Effect Against Breast Cancer Cells Including Triple-Negative Phenotype Cells.

Sialic acid-binding lectin from Rana catesbeiana eggs (cSBL) is a multifunctional protein that has lectin and ribonuclease activity. In this study, the anti-tumor activities of cSBL were assessed using a panel of breast cancer cell lines. cSBL suppressed the cell growth of all cancer cell lines tested here at a concentration that is less toxic, or not toxic at all, to normal cells. The growth suppressive effect was attributed to the cancer-selective induction of apoptosis. We assessed the expressions of several key molecules associated with the breast cancer phenotype after cSBL treatment by western blotting. cSBL decreased the expression level of estrogen receptor (ER) α, while it increased the phosphorylation level of p38 mitogen-activated protein kinase (MAPK). cSBL also suppressed the expression of the progesterone receptor (PgR) and human epidermal growth factor receptor type 2 (HER2). Furthermore, it was revealed that cSBL decreases the expression of the epidermal growth factor receptor (EGFR/HER1) in triple-negative breast cancer cells. These results indicate that cSBL induces apoptosis with decreasing ErbB family proteins and may have great potential for breast cancer chemotherapy, particularly in triple-negative phenotype cells.

Catfish rhamnose-binding lectin induces G0/1 cell cycle arrest in Burkitt's lymphoma cells via membrane surface Gb3.

Silurus asotus egg lectin (SAL), an α-galactoside-binding protein isolated from the eggs of catfish, is a member of the rhamnose-binding lectin family that binds to Gb3 glycan (Galα1-4Galß1-4Glc). We have previously demonstrated that SAL reduces the proliferation of Gb3-expressing Burkitt's lymphoma Raji cells and confirm here that it does not reduce their viability, indicating that unlike other lectins, it is not cytotoxic. The aim of this study was to determine the signal transduction mechanism(s) underlying this novel SAL/Gb3 binding-mediated effect profile. SAL/Gb3 interaction arrested the cell cycle through increasing the G0/1 phase population of Raji cells. SAL suppressed the transcription of cell cycle-related factors such as c-MYC, cyclin D3, and cyclin-dependent protein kinase (CDK)-4. Conversely, the CDK inhibitors p21 and p27 were elevated by treatment with SAL. In particular, the production of p27 in response to SAL treatment increased steadily, whereas p21 production was maximal at 12 h and lower at 24 h. Activation of Ras-MEK-ERK pathway led to an increase in expression of p21. Notably, treatment of Raji cells with anti-Gb3 mAb alone did not produce the above effects. Taken together, our findings suggest that Gb3 on the Raji cell surface interacts with SAL to trigger sequential GDP-Ras phosphorylation, Ras-MEK-ERK pathway activation, p21 production, and cell cycle arrest at the G0/1 phase.

MytiLec, a Mussel R-Type Lectin, Interacts with Surface Glycan Gb3 on Burkitt's Lymphoma Cells to Trigger Apoptosis through Multiple Pathways.

MytiLec; a novel lectin isolated from the Mediterranean mussel (Mytilus galloprovincialis); shows strong binding affinity to globotriose (Gb3: Galα1-4Galß1-4Glc). MytiLec revealed ß-trefoil folding as also found in the ricin B-subunit type (R-type) lectin family, although the amino acid sequences were quite different. Classification of R-type lectin family members therefore needs to be based on conformation as well as on primary structure. MytiLec specifically killed Burkitt's lymphoma Ramos cells, which express Gb3. Fluorescein-labeling assay revealed that MytiLec was incorporated inside the cells. MytiLec treatment of Ramos cells resulted in activation of both classical MAPK/ extracellular signal-regulated kinase and extracellular signal-regulated kinase (MEK-ERK) and stress-activated (p38 kinase and JNK) Mitogen-activated protein kinases (MAPK) pathways. In the cells, MytiLec treatment triggered expression of tumor necrosis factor (TNF)-α (a ligand of death receptor-dependent apoptosis) and activation of mitochondria-controlling caspase-9 (initiator caspase) and caspase-3 (activator caspase). Experiments using the specific MEK inhibitor U0126 showed that MytiLec-induced phosphorylation of the MEK-ERK pathway up-regulated expression of the cyclin-dependent kinase inhibitor p21, leading to cell cycle arrest and TNF-α production. Activation of caspase-3 by MytiLec appeared to be regulated by multiple different pathways. Our findings, taken together, indicate that the novel R-type lectin MytiLec initiates programmed cell death of Burkitt's lymphoma cells through multiple pathways (MAPK cascade, death receptor signaling; caspase activation) based on interaction of the lectin with Gb3-containing glycosphingolipid-enriched microdomains on the cell surface.

A galactose-binding lectin isolated from Aplysia kurodai (sea hare) eggs inhibits streptolysin-induced hemolysis.

A specific galactose-binding lectin was shown to inhibit the hemolytic effect of streptolysin O (SLO), an exotoxin produced by Streptococcus pyogenes. Commercially available lectins that recognize N-acetyllactosamine (ECA), T-antigen (PNA), and Tn-antigen (ABA) agglutinated rabbit erythrocytes, but had no effect on SLO-induced hemolysis. In contrast, SLO-induced hemolysis was inhibited by AKL, a lectin purified from sea hare (Aplysia kurodai) eggs that recognizes α-galactoside oligosaccharides. This inhibitory effect was blocked by the co-presence of d-galactose, which binds to AKL. A possible explanation for these findings is that cholesterol-enriched microdomains containing glycosphingolipids in the erythrocyte membrane become occupied by tightly stacked lectin molecules, blocking the interaction between cholesterol and SLO that would otherwise result in penetration of the membrane. Growth of S. pyogenes was inhibited by lectins from a marine invertebrate (AKL) and a mushroom (ABA), but was promoted by a plant lectin (ECA). Both these inhibitory and promoting effects were blocked by co-presence of galactose in the culture medium. Our findings demonstrate the importance of glycans and lectins in regulating mechanisms of toxicity, creation of pores in the target cell membrane, and bacterial growth.

Binding profiles and cytokine-inducing effects of fish rhamnose-binding lectins on Burkitt's lymphoma Raji cells.

Rhamnose-binding lectin (RBL) is one of the animal lectin categories which take part in the innate immune responses of fish. Osmerus lanceolatus lectin (OLL) from shishamo smelt eggs is an RBL composed of two tandem-repeated domains, both of which are considered to be a carbohydrate-recognition domain. SAL, catfish (Silurus asotus) egg RBL composed of three domains, binds to Burkitt's lymphoma Raji cells through globotriaosylceramide (Gb3) carbohydrate chain and to reduce cell size and growth by altering membrane composition without causing cell death. In this experiment, we tried to compare the binding effects of these two RBLs on Raji cells. Flow cytometric and fluorescence microscopic analyses revealed that OLL also directly bound to and shrunk Raji cells with ten times less reactivity than SAL but reduced cell growth with decreasing cell viability. Anti-Gb3 antibody completely blocked the binding of SAL to Raji cells but not that of OLL. In addition, the direct bindings of OLL and SAL to Raji cells were comparably inhibited by melibiose, but lactose was more effective inhibitor for the binding of OLL than that of SAL. These results suggest that OLL has slightly different cell-binding property compared with SAL and binds not only to Gb3 but also to the other carbohydrate receptor-bearing ß-galactoside chains. The quantitative RT-PCR analysis revealed that SAL induced the expression of TNF-α but not of IFN-γ, IL-1ß, and IL-10. Thus, SAL-induced cytostatic effect on Raji cells might be partially caused by TNF-α-mediated signaling pathway.

Sialidase NEU3 Contributes to the Invasiveness of Bladder Cancer.

Bladder cancer is the 10th most commonly diagnosed cancer worldwide. The current standard treatment for advanced bladder cancer is neoadjuvant cisplatin (NAC)-based chemotherapy followed by cystectomy. However, the response rate to chemotherapy is only 50%, owing to cisplatin resistance, and there is a need for novel therapies. Because the invasiveness of bladder cancer greatly influences patient prognosis, a mechanistic analysis of the invasive function can lead to therapeutic targets. Sialidases, which remove sialic acid residues from the nonreducing ends of sugar chains and catalyze the initial reaction in the degradation of sugar chains, are predicted to be involved in cell invasion and motility. However, the involvement of sialidases in bladder cancer, especially their relationship with the invasive ability, remains unclear. Here, using patient tissues and multiple bladder cancer cell lines, we show that the sialidase NEU3 is highly expressed in bladder cancer. Analysis of NEU3's function using its siRNA-mediated knockdown revealed that NEU3 contributes to bladder cancer invasiveness. Mechanistic analysis showed that NEU3 activates ERK and PI3K signaling. Our results show that NEU3 is involved in the malignancy of bladder cancer, and its suppression may lead to novel treatments for bladder cancer.

A lectin from the mussel Mytilus galloprovincialis has a highly novel primary structure and induces glycan-mediated cytotoxicity of globotriaosylceramide-expressing lymphoma cells.

A novel lectin structure was found for a 17-kDa α-D-galactose-binding lectin (termed "MytiLec") isolated from the Mediterranean mussel, Mytilus galloprovincialis. The complete primary structure of the lectin was determined by Edman degradation and mass spectrometric analysis. MytiLec was found to consist of 149 amino acids with a total molecular mass of 16,812.59 Da by Fourier transform-ion cyclotron resonance mass spectrometry, in good agreement with the calculated value of 16,823.22 Da. MytiLec had an N terminus of acetylthreonine and a primary structure that was highly novel in comparison with those of all known lectins in the structure database. The polypeptide structure consisted of three tandem-repeat domains of ∼50 amino acids each having 45-52% homology with each other. Frontal affinity chromatography technology indicated that MytiLec bound specifically to globotriose (Gb3; Galα1-4Galß1-4Glc), the epitope of globotriaosylceramide. MytiLec showed a dose-dependent cytotoxic effect on human Burkitt lymphoma Raji cells (which have high surface expression of Gb3) but had no such effect on erythroleukemia K562 cells (which do not express Gb3). The cytotoxic effect of MytiLec was specifically blocked by the co-presence of an α-galactoside. MytiLec treatment of Raji cells caused increased binding of anti-annexin V antibody and incorporation of propidium iodide, which are indicators of cell membrane inversion and perforation. MytiLec is the first reported lectin having a primary structure with the highly novel triple tandem-repeat domain and showing transduction of apoptotic signaling against Burkitt lymphoma cells by interaction with a glycosphingolipid-enriched microdomain containing Gb3.

Domain composition of rhamnose-binding lectin from shishamo smelt eggs and its carbohydrate-binding profiles.

Osmerus (Spirinchus) lanceolatus egg lectin (OLL) is a member of the rhamnose-binding lectin (RBL) family which is mainly found in aqueous beings. cDNA of OLL was cloned, and its genomic architecture was revealed. The deduced amino acid (aa) sequence indicated that OLL was composed of 213 aa including 95 aa of domain N and 97 aa of domain C. N and C showed 73 % sequence identity and contained both -ANYGR- and -DPC-KYL-peptide motifs which are conserved in most of the RBL carbohydrate recognition domains. The calculated molecular mass of mature OLL was 20,852, consistent with the result, and 20,677.716, from mass spectrometry. OLL was encoded by eight exons: exons 1 and 2 for a signal peptide; exons 3-5 and 6-8 for N- and C-domains, respectively. Surface plasmon resonance spectrometric analyses revealed that OLL showed comparable affinity for Galα- and ß-linkages, whereas Silurus asotus lectin (SAL), a catfish RBL, bound preferentially to α-linkages of neoglycoproteins. The Kd values of OLL and SAL against globotriaosylceramide (Gb3) were 1.69 × 10⁻5 M for and 2.81 × 10⁻6 M, respectively. Thus, the carbohydrate recognition property of OLL is slightly different from that of SAL. On the other hand, frontal affinity chromatography revealed that both OLL and SAL interacted with only glycolipid-type oligosaccharides such as Gb3 trisaccharides, not with N-linked oligosaccharides. The domain composition of these RBLs and an analytical environment such as the "cluster effect" of a ligand might influence the binding between RBL and sugar chains.

Catfish Egg Lectin Enhances the Cytotoxicity of Sunitinib on Gb3-Expressing Renal Cancer Cells.

Metastatic renal cell carcinoma (RCC) is not sufficiently responsive to anticancer drugs, and thus, developing new drugs for advanced RCC remains vital. We previously reported that the treatment of globotriaosylceramide (Gb3)-expressing cells with catfish (Silurus asotus) egg lectin (SAL) increased the intracellular uptake of propidium iodide (PI) and sunitinib (SU). Herein, we investigated whether SAL pretreatment affects the intracellular uptake and cytotoxic effects of molecular-targeted drugs in RCC cells. We analyzed Gb3 expression in TOS1, TOS3, TOS3LN, and ACHN human RCC cells. Surface Gb3 expression was higher in TOS1 and TOS3 cells than in TOS3LN and ACHN cells. In the PI uptake assay, 41.5% of TOS1 cells and 21.1% of TOS3 cells treated with SAL were positive for PI. TOS1 cell viability decreased to 70% after treatment with 25 µM SU alone and to 48% after pretreatment with SAL (50 µg/mL). Time-series measurements of the intracellular fluorescence of SU revealed significantly enhanced SU uptake in SAL-treated TOS1 cells compared to control cells. SAL treatment did not increase PI uptake in normal renal cells. Our findings suggest that adequate cytotoxic activity may be achieved even when SU is administered at a sufficiently low dose not to cause side effects in combination with SAL.

Relationship between structure and P-glycoprotein inhibitory activity of dimeric peptides related to the Dmt-Tic pharmacophore.

To develop novel inhibitors of P-glycoprotein (P-gp), dimeric peptides related to an opioid peptide containing the Dmt-Tic pharmacophore were synthesized and their P-gp inhibitory activities were analyzed. Of the 30 analogs synthesized, N(α),N(ε)-[(CH(3))(2)Mle-Tic](2)Lys-NH(2) and its D-Lys analog were found to exhibit potent P-gp inhibitory activity, twice that of verapamil, in doxorubicin-resistant K562 cells. Structure-activity studies indicated that the correct hydrophobicity and spacer length between two aromatic rings are important structural elements in this series of analogs for inhibition of P-gp.

Transcriptomic alterations in malignant pleural mesothelioma cells in response to long­term treatment with bullfrog sialic acid­binding lectin.

Malignant pleural mesothelioma (MPM) is a universally lethal type of cancer that is increasing in incidence worldwide; therefore, the development of new drugs for MPM is an urgent task. Bullfrog sialic acid­binding lectin (cSBL) is a multifunctional protein that has carbohydrate­binding and ribonuclease activities. cSBL exerts marked antitumor activity against numerous types of cancer cells, with low toxicity to normal cells. Although in vitro and in vivo studies revealed that cSBL was effective against MPM, the mechanism by which cSBL exerts antitumor effects is not fully understood. To further understand the mechanism of action of cSBL, the present study aimed to identify the key molecules whose expression was affected by cSBL. The present study established cSBL­resistant MPM cells. Microarray analyses revealed that there were significant pleiotropic changes in the expression profiles of several genes, including multiple genes involved in metabolic pathways in cSBL­resistant cells. Furthermore, the expression of some members of the aldo­keto reductase family was revealed to be markedly downregulated in these cells. Among these, it was particularly interesting that cSBL action reduced the level of AKR1B10, which has been reported as a biomarker candidate for MPM prognosis. These findings revealed novel aspects of the effect of cSBL, which may contribute to the development of new therapeutic strategies for MPM.

Binding of Silurus asotus lectin to Gb3 on Raji cells causes disappearance of membrane-bound form of HSP70.

Heat shock proteins (HSPs) are divided into stress-inducible and constitutive types. Generally, HSP70 (stress inducible) and HSC70 (constitutive) are representative of their types, respectively. From the results of immunocytochemical analysis, both HSP70 and HSC70 were constitutively expressed in globotriaosylceramide (Gb3)-expressing Raji cells as well as Gb3-negative K562 cells. Furthermore, the membrane-bound form of HSP70 was present on the surfaces of two cell lines as patch and cap-like structures, and was recovered in the cholesterol rich microdomains (CRM) prepared from them. On the other hand, HSP70 was partially co-localized with Gb3 on the surface of Raji cells. This result suggested that HSP70 was not associated with all of Gb3 molecules but with Gb3 specifically located in the particular environment. The effect of Silurus asotus lectin (SAL), which is one of the rhamnose-binding lectins and specifically binds to Gb3, on the disappearance of membrane-bound HSP70 was dependent on whether Gb3 was present or not. These results suggested that the disappearance of membrane-bound HSP70 was caused by SAL binding to Gb3, that the reduction of membrane-bound HSP70 might result in the decrease in cell volume observed, and that the mechanism of SAL-induced HSP70 expression may differ from that of heat shock in Raji cells.

Whole-brain perfusion measurement using 320-detector row computed tomography in patients with cerebrovascular steno-occlusive disease: comparison with 15O-positron emission tomography.

OBJECTIVE: The 320-detector row computed tomography (CT) can provide whole-brain CT perfusion (CTP) maps with continuous angiographic images by performing a single dynamic scan. We investigated the reliability of CTP cerebral blood flow (CTP-CBF) with 320-detector row CT by comparing findings with O-positron emission tomography (PET-CBF). METHODS: Whole-brain CTP and PET were performed in 10 patients with chronic unilateral steno-occlusive disease. We compared absolute and relative CBF values of bilateral middle cerebral artery territories between CTP and PET. RESULTS: Although mean CTP-CBF values were approximately 30% lower than mean PET-CBF values, the mean ischemic-to-nonischemic CBF ratios of CTP and PET were almost identical (P = 0.804). Regression analysis showed a significant correlation between CTP-CBF and PET-CBF values for each patient (r = 0.52-0.85, P < 0.001). CONCLUSIONS: Whole-brain CTP using 320-detector row CT is useful for evaluating the degree of ischemia for the entire brain with chronic cerebrovascular disease.

Bacterial Expression of Rhamnose-Binding Lectin from Catfish Eggs.

SUEL-like lectins, also termed rhamnose-binding lectins (RBL), are unique in animal lectin families because of their tandemly repeated structure that is characteristic of carbohydrate-recognition domains, as well as their α-galactoside-binding capacity. RBLs are known to be expressed in inclusion bodies in Escherichia coli. Here, we describe the methods for the expression and refolding of Silurus asotus lectin (SAL) using E. coli KRX as the host strain. From our results, highly basic and reduced conditions due to arginine and dithiothreitol, respectively, tend to keep SAL recombinants soluble.

A GM1b/asialo-GM1 oligosaccharide-binding R-type lectin from purplish bifurcate mussels Mytilisepta virgata and its effect on MAP kinases.

A 15-kDa lectin, termed SeviL, was isolated from Mytilisepta virgata (purplish bifurcate mussel). SeviL forms a noncovalent dimer that binds strongly to ganglio-series GM1b oligosaccharide (Neu5Acɑ2-3Galß1-3GalNAcß1-4Galß1-4Glc) and its precursor, asialo-GM1 (Galß1-3GalNAcß1-4Galß1-4Glc). SeviL also interacts weakly with the glycan moiety of SSEA-4 hexaose (Neu5Acα2-3Galß1-3GalNAcß1-3Galα1-4Galß1-4Glc). A partial protein sequence of the lectin was determined by mass spectrometry, and the complete sequence was identified from transcriptomic analysis. SeviL, consisting of 129 amino acids, was classified as an R(icin B)-type lectin, based on the presence of the QxW motif characteristic of this fold. SeviL mRNA is highly expressed in gills and, in particular, mantle rim tissues. Orthologue sequences were identified in other species of the family Mytilidae, including Mytilus galloprovincialis, from which lectin MytiLec-1 was isolated and characterized in our previous studies. Thus, mytilid species contain lectins belonging to at least two distinct families (R-type lectins and mytilectins) that have a common ß-trefoil fold structure but differing glycan-binding specificities. SeviL displayed notable cytotoxic (apoptotic) effects against various cultured cell lines (human breast, ovarian, and colonic cancer; dog kidney) that possess asialo-GM1 oligosaccharide at the cell surface. This cytotoxic effect was inhibited by the presence of anti-asialo-GM1 oligosaccharide antibodies. With HeLa ovarian cancer cells, SeviL showed dose- and time-dependent activation of kinase MKK3/6, p38 MAPK, and caspase-3/9. The transduction pathways activated by SeviL via the glycosphingolipid oligosaccharide were triggered apoptosis. DATABASE: Nucleotide sequence data have been deposited in the GenBank database under accession numbers MK434191, MK434192, MK434193, MK434194, MK434195, MK434196, MK434197, MK434198, MK434199, MK434200, and MK434201.

Quantification of cerebral blood flow and oxygen metabolism with 3-dimensional PET and 15O: validation by comparison with 2-dimensional PET.

UNLABELLED: Quantitative PET with (15)O provides absolute values for cerebral blood flow (CBF), cerebral blood volume (CBV), cerebral metabolic rate of oxygen (CMRO(2)), and oxygen extraction fraction (OEF), which are used for assessment of brain pathophysiology. Absolute quantification relies on physically accurate measurement, which, thus far, has been achieved by 2-dimensional PET (2D PET), the current gold standard for measurement of CBF and oxygen metabolism. We investigated whether quantitative (15)O study with 3-dimensional PET (3D PET) shows the same degree of accuracy as 2D PET. METHODS: 2D PET and 3D PET measurements were obtained on the same day on 8 healthy men (age, 21-24 y). 2D PET was performed using a PET scanner with bismuth germanate (BGO) detectors and a 150-mm axial field of view (FOV). For 3D PET, a 3D-only tomograph with gadolinium oxyorthosilicate (GSO) detectors and a 156-mm axial FOV was used. A hybrid scatter-correction method based on acquisition in the dual-energy window (hybrid dual-energy window [HDE] method) was applied in the 3D PET study. Each PET study included 3 sequential PET scans for C(15)O, (15)O(2), and H(2)(15)O (3-step method). The inhaled (or injected) dose for 3D PET was approximately one fourth of that for 2D PET. RESULTS: In the 2D PET study, average gray matter values (mean +/- SD) of CBF, CBV, CMRO(2), and OEF were 53 +/- 12 (mL/100 mL/min), 3.6 +/- 0.3 (mL/100 mL), 3.5 +/- 0.5 (mL/100 mL/min), and 0.35 +/- 0.06, respectively. In the 3D PET study, scatter correction strongly affected the results. Without scatter correction, average values were 44 +/- 6 (mL/100 mL/min), 5.2 +/- 0.6 (mL/100 mL), 3.3 +/- 0.4 (mL/100 mL/min), and 0.39 +/- 0.05, respectively. With the exception of OEF, values differed between 2D PET and 3D PET. However, average gray matter values of scatter-corrected 3D PET were comparable to those of 2D PET: 55 +/- 11 (mL/100 mL/min), 3.7 +/- 0.5 (mL/100 mL), 3.8 +/- 0.7 (mL/100 mL/min), and 0.36 +/- 0.06, respectively. Even though the 2 PET scanners with different crystal materials, data acquisition systems, spatial resolution, and attenuation-correction methods were used, the agreement of the results between 2D PET and scatter-corrected 3D PET was excellent. CONCLUSION: Scatter coincidence is a problem in 3D PET for quantitative (15)O study. The combination of both the present PET/CT device and the HDE scatter correction permits quantitative 3D PET with the same degree of accuracy as 2D PET and with a lower radiation dose. The present scanner is also applicable to conventional steady-state (15)O gas inhalation if inhaled doses are adjusted appropriately.

[Application of Lectin from Catfish Eggs to Cancer Therapy: A Fundamental Study].

Silurus asotus egg lectin (SAL) is an α-galactoside-binding protein, isolated from the egg of catfish. It belongs to the rhamnose-binding lectin family that binds to Gb3 glycan (Galα1-4Galß1-4Glc). SAL has resulted in the induction of early apoptosis in the Raji cell line, which is a Burkitt's lymphoma cell line expressing Gb3. The apoptosis was characterized by i) increased externalization of phosphatidylserin via multidrug resistance 1 P-glycoprotein (MDR1 P-gp), and ii) reduced cell size through the activation of voltage-gated potassium channel Kv1.3. Although the incorporation of propidium iodide (PI) was observed, SAL did not cause apoptosis in Raji cells. This event may be due to an increased expression of membrane-anchored tumor necrosis factor α (TNFα) and TNF receptor 1 (TNFR1) after the binding of SAL to Gb3. Moreover, SAL arrested the cell cycle at the G0/1 phase, thus inhibiting cell proliferation. The suppression of cell proliferation by SAL was likely due to the enhanced expression of p21 caused by the phosphorylation of ERK1/2 through the Ras-MEK-ERK1/2 pathway. Combination of SAL with anti-cancer drugs was also examined in this study. Interestingly, SAL increased the incorporation of doxorubicin (Dox) into Raji cells, consequently enhancing its cytotoxic effect. Similarly, the cytotoxic effects of vinblastine and irinotecan were also significantly increased in Raji cells treated with SAL. These studies demonstrate that SAL may be applied to cancer therapy.

Sialic acid-binding lectin from bullfrog eggs inhibits human malignant mesothelioma cell growth in vitro and in vivo.

Malignant mesothelioma is an aggressive cancer that results from exposure to asbestos. The therapeutic options for this type of cancer are limited; therefore, the development of novel therapeutic agents is urgently required. Sialic acid-binding lectin isolated from Rana catesbeiana oocytes (cSBL) is a novel therapeutic candidate for cancer, which exhibits antitumor activity mediated through RNA degradation. In the present study, we evaluated the effect of cSBL in vitro and in vivo. Xenograft-competent H2452 and MSTO human mesothelioma cell lines were treated with cSBL, and the pathway by which cSBL induces apoptosis was analyzed. In vivo studies were performed using nude mice inoculated with one of the two cell lines, and the effects of cSBL and pemetrexed were monitored simultaneously. Furthermore, the pharmacological interactions between the three agents (pemetrexed, cisplatin and cSBL) were statistically assessed. It was demonstrated that cSBL treatments caused morphological and biochemical apoptotic changes in both cell lines. Caspase cascade analysis revealed that an intrinsic pathway mediated cSBL-induced apoptosis. The administration of cSBL significantly inhibited tumor growth in two xenograft models, without any adverse effects. Furthermore, the combination index and dose reduction index values indicated that the cSBL + pemetrexed combination showed the highest synergism, and thus potential for reducing dosage of each drug, compared with the other combinations, including the existing pemetrexed + cisplatin regimen. cSBL exerted prominent antitumor effects on malignant mesothelioma cells in vitro and in vivo, and showed favorable effects when combined with pemetrexed. These results suggest that cSBL has potential as a novel drug for the treatment of malignant mesothelioma.