Tatsuya Asai

The use of nanoimprinted scaffolds as 3D culture models to facilitate spontaneous tumor cell migration and well-regulated spheroid formation.

Two-dimensional (2D) cell cultures are essential for drug development and tumor research. However, the limitations of 2D cultures are widely recognized, and a better technique is needed. Recent studies have indicated that a strong physical contact between cells and 2D substrates induces cellular characteristics that differ from those of tumors growing in vivo. 3D cell cultures using various substrates are then developing; nevertheless, conventional approaches have failed in maintenance of cellular proliferation and viability, uniformity, reproducibility, and/or simplicity of these assays. Here, we developed a 3D culture system with inorganic nanoscale scaffolding using nanoimprinting technology (nano-culture plates), which reproduced the characteristics of tumor cells growing in vivo. Diminished cell-to-substrate physical contact facilitated spontaneous tumor cell migration, intercellular adhesion, and multi-cellular 3D-spheroid formation while maintaining cellular proliferation and viability. The resulting multi-cellular spheroids formed hypoxic core regions similar to tumors growing in vivo. This technology allows creating uniform and highly-reproducible 3D cultures, which is easily applicable for microscopic and spectrophotometric assays, which can be used for high-throughput/high-content screening of anticancer drugs and should accelerate discovery of more effective anticancer therapies.

Hemispheric Asymmetry of Frequency-Dependent Suppression in the Ipsilateral Primary Motor Cortex During Finger Movement: A Functional Magnetic Resonance Imaging Study

Electrophysiological studies have suggested that the activity of the primary motor cortex (M1) during ipsilateral hand movement reflects both the ipsilateral innervation and the transcallosal inhibitory control from its counterpart in the opposite hemisphere, and that their asymmetry might cause hand dominancy. To examine the asymmetry of the involvement of the ipsilateral motor cortex during a unimanual motor task under frequency stress, we conducted block-design functional magnetic resonance imaging with 22 normal right-handed subjects. The task involved visually cued unimanual opponent finger movement at various rates. The contralateral M1 showed symmetric frequency-dependent activation. The ipsilateral M1 showed task-related deactivation at low frequencies without laterality. As the frequency of the left-hand movement increased, the left M1 showed a gradual decrease in the deactivation. This data suggests a frequency-dependent increased involvement of the left M1 in ipsilateral hand control. By contrast, the right M1 showed more prominent deactivation as the frequency of the right-hand movement increased. This suggests that there is an increased transcallosal inhibition from the left M1 to the right M1, which overwhelms the right M1 activation during ipsilateral hand movement. These results demonstrate the dominance of the left M1 in both ipsilateral innervation and transcallosal inhibition in right-handed individuals.

Optical responses evoked by single-pulse stimulation to the dorsal root in the rat spinal dorsal horn in slice.

Neuronal excitation evoked after dorsal-root (DR) stimulation in the spinal dorsal horn (DH) of rats was visualized with a high-resolution optical-imaging method, and the propagation mechanism was studied. Transverse slices of the spinal cord were obtained from 2-4 week-old rats and stained with the voltage-sensitive dye RH-482. Single-pulse stimulation to the primary-afferent A fibers in the DR attached to the slice evoked a weak, brief (<10 ms) excitatory optical response in the laminae I and III-V. When the stimulus intensity and duration were increased to activate both A and C fibers, an additional, much greater, and longer-lasting (>100 ms) excitatory response was generated in the laminae I-III, most intensely in the lamina II. A treatment with excitatory amino acid (EAA) antagonists, dl-2-amino-5-phosphonovaleric acid and 6-cyano-7-nitroquinoxaline-2, 3-dione, significantly reduced the amplitude and duration of the response in the lamina II. The optical response in the antagonists-containing solution was quite similar to that recorded in a Ca2+-free solution that blocked afferent synaptic transmission. The late component (>10 ms) was, however, slightly greater than that in the Ca2+-free solution. Treatment with the ATP-receptor antagonist, suramin, had a minimal effect on the response in the presence of EAA antagonists. These results suggested that the propagation of the DR-stimulus-elicited excitation was contributed largely by EAA receptors, but also by other receptors to a much lesser extent.

Copper-64-diacetyl-bis (N4-methylthiosemicarbazone) accumulates in rich regions of CD133+ highly tumorigenic cells in mouse colon carcinoma

INTRODUCTION (64)Cu-diacetyl-bis (N(4)-methylthiosemicarbazone) ((64)Cu-ATSM) is a potential imaging agent of hypoxic tumor for use with PET. Recent literature demonstrated that cancer cells expressing CD133, which is a frequently used marker for so-called cancer stem cells or cancer stem cell-like cells (collectively referred to here as CSCs), contribute to tumors therapeutic resistance and metastasis ability. Culturing under hypoxia is also reported to enlarge the proportion of CD133(+) cells, which would indicate survival advantage of CD133(+) cells under hypoxia. Here, we investigated the relationships between (64)Cu-ATSM accumulation and existence of CD133(+) cells using mouse colon carcinoma (colon-26) tumor. METHODS Intratumor distribution of (64)Cu-ATSM and (18)F-fluorodeoxyglucose ((18)FDG) was compared with immunohistochemical staining for CD133 with a colon-26 model. In vitro characterization of CD133(+) colon-26 cells was also performed. RESULTS In colon-26 tumors, (64)Cu-ATSM localized preferentially in regions with a high density of CD133(+) cells. The percentage of CD133(+) cells was 11-fold higher in (64)Cu-ATSM high-uptake regions compared with (18)FDG high- (but (64)Cu-ATSM low-) uptake regions. CD133(+) colon-26 cells showed characteristics previously linked with CSCs in other cancer cell lines, such as high colony-forming ability, high tumor-initiating ability and enrichment under hypoxic cultivation. The proportion of CD133(+) cells was enlarged by culturing under glucose starvation as well as hypoxia, and (64)Cu-ATSM uptake was increased under such conditions. CONCLUSIONS Our findings showed that, in colon-26 tumors, (64)Cu-ATSM accumulates in rich regions of CD133(+) cells with characteristics of CSCs. Therefore (64)Cu-ATSM could be a potential imaging agent for rich regions of CD133(+) cells, associated with CSCs, within tumors.

Internal radiotherapy with copper-64-diacetyl-bis (N4-methylthiosemicarbazone) reduces CD133+ highly tumorigenic cells and metastatic ability of mouse colon carcinoma.

INTRODUCTION (64)Cu-diacetyl-bis (N(4)-methylthiosemicarbazone) ((64)Cu-ATSM) is an imaging agent for positron emission tomography (PET) that targets hypoxic tumors. (64)Cu-ATSM is also reported to be a potential agent for internal radiotherapy. In a mouse colon carcinoma (Colon-26) model, we have shown that (64)Cu-ATSM preferentially localizes in intratumoral regions with a high density of CD133(+) cells, which show characteristics of cancer stem cells or cancer stem cell-like cells (collectively referred here as CSCs). In this study, we evaluated the therapeutic effect of (64)Cu-ATSM in relation to CD133 expression using this model. METHODS Systemic administration of 37 MBq (64)Cu-ATSM or saline was conducted twice within a 1-week interval to mice bearing 1-week-old Colon-26 tumors (days 0-7). At day 19, tumor size measurement, flow cytometry analysis and experimental lung metastatic assay were performed. The therapeutic effect of (64)Cu-ATSM on sorted CD133(+) and CD133(-) Colon-26 cells was also examined in vitro. RESULTS In vivo studies showed that (64)Cu-ATSM treatment inhibited tumor growth. The percentage of CD133(+) cells and metastatic ability in (64)Cu-ATSM treated tumors was decreased compared with that in control animals. In vitro studies demonstrated that (64)Cu-ATSM accumulated in cells under hypoxic conditions and incorporation of (64)Cu-ATSM under hypoxia caused cell death in both CD133(+) and CD133(-) cells in a similar extent. CONCLUSIONS (64)Cu-ATSM administration reduced tumor volume as well as the percentage of CD133(+) cells and the metastatic ability of Colon-26 tumors. Together with our data, it is suggested that (64)Cu-ATSM accumulates in regions high in CD133(+) highly tumorigenic cells and kills such regions by radiation, resulting in a decrease of the percentage of CD133(+) cells.

Photo-excitation of carotenoids causes cytotoxicity via singlet oxygen production

Carotenoids, natural pigments widely distributed in algae and plants, have a conjugated double bond system. Their excitation energies are correlated with conjugation length. We hypothesized that carotenoids whose energy states are above the singlet excited state of oxygen (singlet oxygen) would possess photosensitizing properties. Here, we demonstrated that human skin melanoma (A375) cells are damaged through the photo-excitation of several carotenoids (neoxanthin, fucoxanthin and siphonaxanthin). In contrast, photo-excitation of carotenoids that possess energy states below that of singlet oxygen, such as β-carotene, lutein, loroxanthin and violaxanthin, did not enhance cell death. Production of reactive oxygen species (ROS) by photo-excited fucoxanthin or neoxanthin was confirmed using a reporter assay for ROS production with HeLa Hyper cells, which express a fluorescent indicator protein for intracellular ROS. Fucoxanthin and neoxanthin also showed high cellular penetration and retention. Electron spin resonance spectra using 2,2,6,6-tetramethil-4-piperidone as a singlet oxygen trapping agent demonstrated that singlet oxygen was produced via energy transfer from photo-excited fucoxanthin to oxygen molecules. These results suggest that carotenoids such as fucoxanthin, which are capable of singlet oxygen production through photo-excitation and show good penetration and retention in target cells, are useful as photosensitizers in photodynamic therapy for skin disease.

Timing of Metabolic Response Monitoring During Erlotinib Treatment in Non–Small Cell Lung Cancer

The purpose of this study was to prospectively evaluate the timing of metabolic response monitoring with 18F-FDG PET of (neoadjuvant) erlotinib treatment in patients with early-stage non–small cell lung cancer. Methods: This study was designed as an open-label phase II trial performed in 4 hospitals in The Netherlands. Patients received preoperative erlotinib (150 mg) once daily for 3 wk. Response evaluation was performed after 4–7 d and at 3 wk with 18F-FDG PET/CT scans. Tumor 18F-FDG uptake and changes were measured as standardized uptake values (SUVs). The metabolic response was classified on the basis of European Organization for Research and Treatment of Cancer criteria (>25% decrease in the maximum SUV) and was compared with histopathologic regression as observed in the resection specimen. Results: From December 2006 to November 2010, 60 patients with non–small cell lung cancer eligible for surgical resection were enrolled in this study. For 43 patients (18 men and 25 women), baseline 18F-FDG PET/CT scans as well as both monitoring scans and histopathologic response monitoring were available. A partial metabolic response on 18F-FDG PET/CT scans was observed for 10 patients (23%) after 1 wk and for 14 patients (33%) after 3 wk. Histopathologic examination revealed regression (necrosis of >50%) in 11 patients (26%). In these patients, the maximum SUV decreased by a mean of 17% within 1 wk and a mean of 31% at 3 wk. Seven patients were identified as responders within 1 wk. Conclusion: Response monitoring with 18F-FDG PET/CT within 1 wk after the start of erlotinib treatment identified approximately 64% of histopathologic responders on the basis of European Organization for Research and Treatment of Cancer criteria.

354 Possible conduction block by mu opioid in primary afferent fibers in the spinal dorsal horn

Murase, Kazuyuki, Asai, Tatsuya, Ikeda, Hiroshi Presynaptic inhibition by mu opioids in fine afferent fibers is known to be important in the production of antinociception within the superficial spinal dorsal horn. However, little is know about the mechanism by which transmitter release is inhibited by mu opioids at the terminals. We applied a high-resolution (128x 128 pixels) optical imaging method to rat spinal cord slices, and presynaptic excitation was directly visualized. A mu-opioid receptor agonist, [d-AlaZ,N-Me-Phe4, GlyS-ol]-enkephalin, reversibly reduced the presynaptic excitation in lamina II which was evoked by dorsal root stimulation. Spatial analysis of the optical response revealed that the degree of inhibition at each pixel measuring 4.3-6.5 micrometer-squared area varied from 0 to 100% and that the variability occurred even among the neighbouring pixels. We propose that m opioids suppress transmitter release by blocking the spread of excitation along the axonal arbors and/or into the terminals.

Neuroprotective effect of ketone bodies against hypoxia and ischemia in rat brain slices: A study using the glucose metabolic rate measured with dynamic positron autoradiography

By the use of a transient 90-min middle cerebral artery occlusion (MCAO) model of rats, we have shown that highly proliferative macrophage-like cells derived from bone marrow, started to accumulate in 2 days post reperfusion (2 dpr), and their number peaked at 7 dpr. Such macrophage-like cells expressed Iba1 and NG2 proteoglycan, therefore they were termed BINCs (Brain Iba1+/NG2+ Cells). Since the cells elicited ameliorative effects on the ischemic brains, some methods that enhance the accumulation of BINCs in ischemic lesions may become an effective treatment. However, it is an open question what kinds of factors are responsible for the recruitment of BINCs or their progenitors from the bone marrow to the ischemic brain lesions. In this study, we focused on fractalkine and MCP-1 as candidate factors responsible for the recruitment. BINCs were isolated from the cerebral ischemic lesion at 7 dpr, and mRNAs encoding MCP-1 and fractalkine as well as their receptors CCR2 and CX3CR1 were quantified using real-time RT-PCR. The expression levels of mRNAs by BINCs were compared with those by primary astrocytes and microglia. BINCs expressed CCR2 and CX3CR1 at the highest levels among the three types of cells, whereas astrocytes their ligands fractalkine and MCP-1 at the highest levels. Kinetic study using in vivo samples revealed that ischemic brain tissue contained significant level of mRNAs of both chemokines by 2 dpr, but the expressed level of the mRNAs decreased in time by 5dpr. The chemokines induced directed chemotaxis of BINCs, as revealed by migration assay using Boyden chambers. Taken together the present data and our previous study showing that BINCs or BINC progenitors may invade into ischemic brain tissue by 2dpr, it is probable that the two chemokines are responsible for the recruitment of BINCs or BINC progenitor from bone marrow.

Measurement of glucose metabolism in rat spinal cord slices with dynamic positron autoradiography

We attempted to measure the regional metabolic rate of glucose (MRglc) in sliced spinal cords in vitro. The thoracic spinal cord of a mature Wister rat was cut into 400-mum slices in oxygenated and cooled (1-4 degrees C) Krebs-Ringer solution. After at least 60 min of preincubation, the spinal cord slices were transferred into double polystyrene chambers and incubated in Krebs-Ringer solution at 36 degrees C, bubbled with 5% O(2)/5% CO(2) gas. To measure MRglc, we used the dynamic positron autoradiography technique (dPAT) with F-18-2-fluoro-2-deoxy-d-glucose ([(18)F]FDG) and the net influx constant of [(18)F]FDG as an index. Uptake curves of [(18)F]FDG were well fitted by straight lines for more than 7 h after the slicing of the spinal cord (linear regression coefficient, r=0.99), indicating a constant uptake of glucose by the spinal cord tissue. The slope (K), which denotes MRglc, is affected by tetrodotoxin, and high K(+) (50 mM) or Ca(2+)-free, high Mg(2+) solution. After 10 min of hypoxia, the K value following reoxygenation was similar to the unloaded control value, but after 45 min of hypoxia, the K value was markedly lower than the unloaded control value, and after >90 min of reoxygenation it was nearly 0. Our results indicate that the living spinal cord slices used retained an activity-dependent metabolism to some extent. This technique may provide a new approach for measuring MRglc in sliced living spinal cord tissue in vitro and for quantifying the dynamic changes in MRglc in response to various interventions such as hypoxia.