Cell type-specific transcriptomes are enabled by the action of multiple regulators, which are frequently expressed within restricted tissue regions. In the present study, we identify one such ...regulator, Quaking 5 (Qki5), as an RNA-binding protein (RNABP) that is expressed in early embryonic neural stem cells and subsequently down-regulated during neurogenesis. mRNA sequencing analysis in neural stem cell culture indicates that Qki proteins play supporting roles in the neural stem cell transcriptome and various forms of mRNA processing that may result from regionally restricted expression and subcellular localization. Also, our in utero electroporation gain-of-function study suggests that the nuclear-type Qki isoform Qki5 supports the neural stem cell state. We next performed in vivo transcriptome-wide protein-RNA interaction mapping to search for direct targets of Qki5 and elucidate how Qki5 regulates neural stem cell function. Combined with our transcriptome analysis, this mapping analysis yielded a bona fide map of Qki5-RNA interaction at single-nucleotide resolution, the identification of 892 Qki5 direct target genes, and an accurate Qki5-dependent alternative splicing rule in the developing brain. Last, our target gene list provides the first compelling evidence that Qki5 is associated with specific biological events; namely, cell-cell adhesion. This prediction was confirmed by histological analysis of mice in which Qki proteins were genetically ablated, which revealed disruption of the apical surface of the lateral wall in the developing brain. These data collectively indicate that Qki5 regulates communication between neural stem cells by mediating numerous RNA processing events and suggest new links between splicing regulation and neural stem cell states.
Understanding tumor‐specific metabolism under hypoxia is important to find novel targets for antitumor drug design. Here we found that tumor cells expressed higher levels of cytosolic acetyl‐CoA ...synthetase (ACSS2) under hypoxia than normoxia. Knockdown of ACSS2 by RNA interference (RNAi) in tumor cells enhanced tumor cell death under long‐term hypoxia in vitro. Our data also demonstrated that the ACSS2 suppression slowed tumor growth in vivo. These findings showed that ACSS2 plays a significant role in tumor cell survival under hypoxia and that ACSS2 would be a potential target for tumor treatment. Furthermore, we found that tumor cells excreted acetate and the quantity increased under hypoxia: the pattern of acetate excretion followed the expression pattern of ACSS2. Additionally, the ACSS2 knockdown led to a corresponding reduction in the acetate excretion in tumor cells. These results mean that ACSS2 can conduct the reverse reaction from acetyl‐CoA to acetate in tumor cells, which indicates that ACSS2 is a bi‐directional enzyme in tumor cells and that ACSS2 might play a buffering role in tumor acetyl‐CoA/acetate metabolism. (Cancer Sci 2009; 100: 821–827)
The accurate prediction of hepatic (Fh) and intestinal availability (Fg) is vital for determining human pharmacokinetics. To predict these PK parameters for cytochrome P450 (P450) metabolism, ...in vitro–in vivo extrapolation (IVIVE) using hepatic microsomes, hepatocytes, and intestinal microsomes has been actively investigated. However, IVIVE has not been sufficiently evaluated for non-P450 enzymes. UDP-glucuronosyltransferase (UGT) is a non-P450 enzyme that catalyzes glucuronidation, a major pathway for drugs possessing carboxylic acid, hydroxyl, and amine moieties. In drug metabolism, UGT is the most important enzyme after P450, and prediction of Fh for UGT substrates has mainly been attempted using hepatic models based on the clearance concepts. While various approaches for achieving improved prediction of clearance have been investigated—such as the addition of bovine serum albumin to microsomal incubation mixtures—optimized in vitro methods that utilize both hepatic microsomes and hepatocytes for more accurate prediction are still required. Although application of the simplified intestinal availability (SIA) model is effective in predicting the Fg of UGT substrates, this model is limited to compounds with high oral absorption. In this review, we discuss the current state, issues, and future directions of predicting Fh and Fg for glucuronidation.
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Gold nanoparticles (AuNPs) are candidate radiosensitizers for medium-energy photon treatment, such as γ-ray radiation in high-dose-rate (HDR) brachytherapy. However, high AuNP concentrations are ...required for sufficient dose enhancement for clinical applications. Here, we investigated the effect of positively (+) charged AuNP radiosensitization of plasmid DNA damage induced by 192Ir γ-rays, and compared it with that of negatively (-) charged AuNPs.
We observed DNA breaks and reactive oxygen species (ROS) generation in the presence of AuNPs at low concentrations. pBR322 plasmid DNA exposed to 64 ng/mL AuNPs was irradiated with 192Ir γ-rays via HDR brachytherapy. DNA breaks were detected by observing the changes in the form of the plasmid and quantified by agarose gel electrophoresis. The ROS generated by the AuNPs were measured with the fluorescent probe sensitive to ROS. The effects of positively (+) and negatively (-) charged AuNPs were compared to study the effect of surface charge on dose enhancement.
+AuNPs at lower concentrations promoted a comparable level of radiosensitization by producing both single-stranded breaks (SSBs) and double-stranded breaks (DSBs) than those used in cell assays and Monte Carlo simulation experiments. The dose enhancement factor (DEF) for +AuNPs was 1.3 ± 0.2 for SSBs and 1.5 ± 0.4 for DSBs. The ability of +AuNPs to augment plasmid DNA damage is due to enhanced ROS generation. While -AuNPs generated similar ROS levels, they did not cause significant DNA damage. Thus, dose enhancement using low concentrations of +AuNPs presumably occurred via DNA binding or increasing local +AuNP concentration around the DNA.
+AuNPs at low concentrations displayed stronger radiosensitization compared to -AuNPs. Combining +AuNPs with 192Ir γ-rays in HDR brachytherapy is a candidate method for improving clinical outcomes. Future development of cancer cell-specific +AuNPs would allow their wider application for HDR brachytherapy.
Abstract 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.
Imaging of
14
C outside of the subject is considered to be difficult because it is a radionuclide that emits only low-energy beta particles. However, we found that bremsstrahlung X-rays form
14
C ...could be imaged from outside of subjects and is thus applicable to in vivo small animal imaging. We developed a high-resolution low-energy X-ray imaging system using a (Gd, La)
2
Si2O
7
:Ce(La-GPS) plate combined with a flat panel photomultiplier tube (FP-PMT) for in vivo imaging of a mouse to detect the X-rays from a
14
C solution administered. Without using a parallel hole collimator, accumulated
14
C in the mouse's abdomen was imaged in 1 min and dynamic in vivo imaging was possible although the spatial resolution was moderate. With a parallel hole collimator,
14
C in the abdomen was obtained with a higher spatial resolution with a 60-min acquisition time. We conclude that in vivo imaging of
14
C is possible by using the developed high-resolution La-GPS imaging system and may be promising for molecular imaging research.
Fused in sarcoma/translated in liposarcoma (FUS) is an RNA-binding protein, and its mutations are associated with neurodegenerative diseases, including amyotrophic lateral sclerosis (ALS), through ...the DNA damage stress response, aberrant stress granule (SG) formation, etc. We previously reported that translocation of endogenous FUS into SGs was achieved by cotreatment with a DNA double-strand break inducer and an inhibitor of DNA-PK activity. In the present study, we investigated cytoplasmic SG formation using various fluorescent protein-tagged mutant FUS proteins in a human astrocytoma cell (U251) model. While the synergistic enhancement of the migration of fluorescent protein-tagged wild-type FUS to cytoplasmic SGs upon DNA damage induction was observed when DNA-PK activity was suppressed, the fluorescent protein-tagged FUS
mutant showed cytoplasmic localization. It migrated to cytoplasmic SGs upon DNA damage induction alone, and DNA-PK inhibition also showed a synergistic effect. Furthermore, analysis of 12 sites of DNA-PK-regulated phosphorylation in the N-terminal LC region of FUS revealed that hyperphosphorylation of FUS mitigated the mislocalization of FUS into cytoplasmic SGs. By using this cell model, we performed screening of a compound library to identify compounds that inhibit the migration of FUS to cytoplasmic SGs but do not affect the localization of the SG marker molecule G3BP1 to cytoplasmic SGs. Finally, we successfully identified 23 compounds that inhibit FUS-containing SG formation without changing normal SG formation.
Characterization of DNA-PK-dependent FUS stress granule localization.A compound library was screened to identify compounds that inhibit the formation of FUS-containing stress granules.
Fatty acid synthase (FASN) expression is elevated in several cancers, and this over-expression is associated with poor prognosis. Inhibitors of FASN, such as orlistat, reportedly show antitumor ...effects against cancers that over-express FASN, making FASN a promising therapeutic target. However, large variations in FASN expression levels in individual tumors have been observed, and methods to predict FASN-targeted therapy outcome before treatment are required to avoid unnecessary treatment. In addition, how FASN inhibition affects tumor progression remains unclear. Here, we showed the method to predict FASN-targeted therapy outcome using radiolabeled acetate uptake and presented mechanisms of FASN inhibition with human prostate cancer cell lines, to provide the treatment strategy of FASN-targeted therapy. We revealed that tumor uptake of radiolabeled acetate reflected the FASN expression levels and sensitivity to FASN-targeted therapy with orlistat in vitro and in vivo. FASN-targeted therapy was noticeably effective against tumors with high FASN expression, which was indicated by high acetate uptake. To examine mechanisms, we established FASN knockdown prostate cancer cells by transduction of short-hairpin RNA against FASN and investigated the characteristics by analyses on morphology and cell behavior and microarray-based gene expression profiling. FASN inhibition not only suppressed cell proliferation but prevented pseudopodia formation and suppressed cell adhesion, migration, and invasion. FASN inhibition also suppressed genes involved in production of intracellular second messenger arachidonic acid and androgen hormones, both of which promote tumor progression. Collectively, our data demonstrated that uptake of radiolabeled acetate is a useful predictor of FASN-targeted therapy outcome. This suggests that 1-(11)Cacetate positron emission tomography (PET) could be a powerful tool to accomplish personalized FASN-targeted therapy by non-invasive visualization of tumor acetate uptake and selection of responsive tumors. FASN-targeted therapy could be an effective treatment to suppress multiple steps related to tumor progression in prostate cancers selected by 1-(11)Cacetate PET.
Aquaglycero-aquaporins (agAQPs) are one of the water channel proteins located in the cell membrane that transport not only water but also some small solutes such as glycerol. Since agAQPs are ...involved in cancer proliferation and malignancy, it might be possible to utilize them as new targets for cancer molecular imaging. In this study, we investigated whether agAQPs can be specifically targeted by using 14C-labeled glycerol (14Cglycerol), which passes through agAQPs. In the in vitro experiments, comparing the cancer cell lines with different expression levels of AQP3 and AQP9, major agAQPs known to be expressed in cancers, and examining the effect of their inhibitors on these cells, the expression of AQP3 and AQP9 in cell lines was shown to be closely related to 14Cglycerol uptake. When 14Cglycerol was injected into tumor-bearing mice, Spearman’s rank coefficient analysis revealed that radioactivity levels in tumor and in plasma were mutually correlated only in tumors expressing agAQPs at a high level. These results indicate the possibility of using agAQPs as new targets to characterize cancer using radiolabeled glycerol as a molecular probe.
Copper-64 (64Cu)-labeled antibody fragments such as Fab are useful for molecular imaging (immuno-PET) and radioimmunotherapy. However, these fragments cause high and persistent localization of ...radioactivity in the kidneys after injection. To solve this problem, this study assessed the applicability of a molecular design to 64Cu, which reduces renal radioactivity levels by liberating a urinary excretory radiometabolite from antibody fragments at the renal brush border membrane (BBM). Since 1,4,7-triazacyclononane-1,4,7-triacetic acid (NOTA) forms a stable complex with Cu, NOTA-conjugated Met-Val-Lys-maleimide (NOTA-MVK-Mal), which is a radio-gallium labeling agent for antibody fragments, was evaluated for applicability to 64Cu. The MVK linkage was recognized by the BBM enzymes to liberate 64CuCu-NOTA-Met although the recognition of the MVK sequence for the 64CuCu-NOTA-MVK derivative was reduced compared with that of its 67GaGa-counterpart, probably due to the difference in the charge of the metal-NOTA complexes. When injected into mice, 64CuCu-NOTA-MVK-Fab resulted in similar renal radioactivity levels to the 67Ga-labeled counterpart. In addition, 64CuCu-NOTA-MVK-Fab resulted in lower renal radioactivity levels than those from 64Cu-labeled Fab using a conventional method, without a reduction in the tumor radioactivity levels. These findings indicate that our approach to reducing renal radioactivity levels by liberating a radiolabeled compound from antibody fragments at the renal BBM for urinary excretion is applicable to 64Cu-labeled antibody fragments and useful for immuno-PET and radioimmunotherapy.
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