Friction Dynamics of Wood Coated with Vegetable Oil.

Surface treatment of wood surface is an effective method to improve the physical properties. The friction dynamics of wood coated with vegetable oil were evaluated and compared to wood treated with polyurethane and untreated wood. The kinetic friction coefficient, µ k , was 0.39±0.01, which was smaller than the values for polyurethane-treated wood and untreated oak. The effect of the surface treatment was also observed in the dependence of velocity on the friction coefficient. The friction profile of the wood surface treated with vegetable oil was similar to that of untreated wood, and the friction coefficient was nearly constant, except in the static friction region of sliding out. These results suggest that wood treated with vegetable oil is suitable for inducing a smooth feel.

Study on polyethylene glycol cross-linker in peptide-conjugated antibody on efficiency of cell capture and release.

Cell separation is important in cell therapy and disease diagnosis. Therefore, various cell separation methods have been studied, but cellular damage and the need for pretreatment remain substantial problems. Recently, in the diagnostic field, the detachment and recovery of antibody-captured cells was actively studied to obtain more detailed information on cancer cells. Previously, we have developed a highly efficient cell separation method using microfibers. In the present study, the efficiency of cell capture and release was examined by controlling the molecular mobility of an immobilized antibody to efficiently detect cells with low expression of a marker molecule. We found that improvement in molecular mobility of antibodies enhances cell capture efficiency but decreases the detachment effectiveness of the captured cells. Therefore, the molecular mobility of antibodies can be utilized to control cell capture and release according to the level of expression of the marker molecule.

Rapid and highly efficient capture and release of cancer cells using polymeric microfibers immobilized with enzyme-cleavable peptides.

Circulating tumor cells (CTCs) are tumor cells present in the blood. CTCs have attracted much attention as a new tumor marker, because their analysis provides useful information for monitoring cancer progress. In this study, we developed cell-capture and release methods using three-dimensional (3D) microfiber fabrics without damaging the cells. Using functional peptides containing sequences from a polystyrene-binding site and a cleavable site for collagenase type IV, immobilized antibodies on the peptides were able to specifically capture MCF-7 cells in a few minutes and release the captured cells from 3D microfiber fabrics incorporating a vacuum system. The efficiency of cell capture was around 80% and that of the cell release was over 90%. The released cells proliferated normally in culture medium, suggesting that our system will be applicable for the culture and analysis of CTCs. STATEMENT OF SIGNIFICANCE: In this paper, we report cell-capture and release methods using enzyme-cleavable peptides immobilized on microfiber fabrics which has microporous polymeric three-dimensional structures. Detachment and collection of the selectively captured cancer cells are required for ex vivo culture and their further analysis, whereas the cell detachment methods developed so far might cause cell damage, even if cell viability is high enough. Therefore, specific attachment and gentle detachment from the device are required for the accurate analysis of cells. In this study, for capture and release of cancer cells we designed the peptide cleavable by collagenase type IV, which has no target molecule in cells. Our system will be useful for further CTC analysis and might lead to more accurate cancer diagnosis.

DNA double-strand break repair pathway regulates PD-L1 expression in cancer cells.

Accumulating evidence suggests that exogenous cellular stress induces PD-L1 upregulation in cancer. A DNA double-strand break (DSB) is the most critical type of genotoxic stress, but the involvement of DSB repair in PD-L1 expression has not been investigated. Here we show that PD-L1 expression in cancer cells is upregulated in response to DSBs. This upregulation requires ATM/ATR/Chk1 kinases. Using an siRNA library targeting DSB repair genes, we discover that BRCA2 depletion enhances Chk1-dependent PD-L1 upregulation after X-rays or PARP inhibition. In addition, we show that Ku70/80 depletion substantially enhances PD-L1 upregulation after X-rays. The upregulation by Ku80 depletion requires Chk1 activation following DNA end-resection by Exonuclease 1. DSBs activate STAT1 and STAT3 signalling, and IRF1 is required for DSB-dependent PD-L1 upregulation. Thus, our findings reveal the involvement of DSB repair in PD-L1 expression and provide mechanistic insight into how PD-L1 expression is regulated after DSBs.

BRCA1 Directs the Repair Pathway to Homologous Recombination by Promoting 53BP1 Dephosphorylation.

BRCA1 promotes homologous recombination (HR) by activating DNA-end resection. By contrast, 53BP1 forms a barrier that inhibits DNA-end resection. Here, we show that BRCA1 promotes DNA-end resection by relieving the 53BP1-dependent barrier. We show that 53BP1 is phosphorylated by ATM in S/G2 phase, promoting RIF1 recruitment, which inhibits resection. 53BP1 is promptly dephosphorylated and RIF1 released, despite remaining unrepaired DNA double-strand breaks (DSBs). When resection is impaired by CtIP/MRE11 endonuclease inhibition, 53BP1 phosphorylation and RIF1 are sustained due to ongoing ATM signaling. BRCA1 depletion also sustains 53BP1 phosphorylation and RIF1 recruitment. We identify the phosphatase PP4C as having a major role in 53BP1 dephosphorylation and RIF1 release. BRCA1 or PP4C depletion impairs 53BP1 repositioning, EXO1 recruitment, and HR progression. 53BP1 or RIF1 depletion restores resection, RAD51 loading, and HR in PP4C-depleted cells. Our findings suggest that BRCA1 promotes PP4C-dependent 53BP1 dephosphorylation and RIF1 release, directing repair toward HR.

Identification of DNA double strand breaks at chromosome boundaries along the track of particle irradiation.

Chromosomal translocations arise from misrejoining of DNA double strand breaks (DSBs) between loci located on two chromosomes. One current model suggests that spatial proximity of potential chromosomal translocation partners influences translocation probability. Ionizing radiation (IR) is a potent inducer of translocations. Accumulating evidence demonstrates that particle irradiation more frequently causes translocations compared with X-ray irradiation. This observation has led to the hypothesis that the high frequency of translocations after particle irradiation may be due to the formation of DSBs at chromosome boundaries along the particle track, because such DSBs can be misrejoined between distinct chromosomes. In this study, we simultaneously visualized the site of IR-induced DSBs and chromosome position by combining Immunofluorescence and fluorescence in situ hybridization. Importantly, the frequency of γH2AX foci at the chromosome boundary of chromosome 1 after carbon-ion irradiation was >4-fold higher than that after X-ray irradiation. This observation is consistent with the idea that particle irradiation generates DSBs at the boundaries of two chromosomes along the track. Further, we showed that resolution of γH2AX foci at chromosome boundaries is prevented by inhibition of DNA-PKcs activity, indicating that the DSB repair is NHEJ-dependent. Finally, we found that γH2AX foci at chromosome boundaries after carbon-ion irradiation contain DSBs undergoing DNA-end resection, which promotes repair utilizing microhomology mediated end-joining during translocation. Taken together, our study suggests that the frequency of DSB formation at chromosome boundaries is associated with the incidence of chromosomal translocations, supporting the notion that the spatial proximity between breaks is an important factor in translocation formation. © 2016 Wiley Periodicals, Inc.

Carbon-ion beam irradiation kills X-ray-resistant p53-null cancer cells by inducing mitotic catastrophe.

BACKGROUND AND PURPOSE: To understand the mechanisms involved in the strong killing effect of carbon-ion beam irradiation on cancer cells with TP53 tumor suppressor gene deficiencies. MATERIALS AND METHODS: DNA damage responses after carbon-ion beam or X-ray irradiation in isogenic HCT116 colorectal cancer cell lines with and without TP53 (p53+/+ and p53-/-, respectively) were analyzed as follows: cell survival by clonogenic assay, cell death modes by morphologic observation of DAPI-stained nuclei, DNA double-strand breaks (DSBs) by immunostaining of phosphorylated H2AX (γH2AX), and cell cycle by flow cytometry and immunostaining of Ser10-phosphorylated histone H3. RESULTS: The p53-/- cells were more resistant than the p53+/+ cells to X-ray irradiation, while the sensitivities of the p53+/+ and p53-/- cells to carbon-ion beam irradiation were comparable. X-ray and carbon-ion beam irradiations predominantly induced apoptosis of the p53+/+ cells but not the p53-/- cells. In the p53-/- cells, carbon-ion beam irradiation, but not X-ray irradiation, markedly induced mitotic catastrophe that was associated with premature mitotic entry with harboring long-retained DSBs at 24 h post-irradiation. CONCLUSIONS: Efficient induction of mitotic catastrophe in apoptosis-resistant p53-deficient cells implies a strong cancer cell-killing effect of carbon-ion beam irradiation that is independent of the p53 status, suggesting its biological advantage over X-ray treatment.