Evaluation of an EZH2 inhibitor in patient-derived orthotopic xenograft models of pediatric brain tumors alone and in combination with chemo- and radiation therapies.

Brain tumors are the leading cause of cancer-related death in children. Tazemetostat is an FDA-approved enhancer of zeste homolog (EZH2) inhibitor. To determine its role in difficult-to-treat pediatric brain tumors, we examined EZH2 levels in a panel of 22 PDOX models and confirmed EZH2 mRNA over-expression in 9 GBM (34.6 ± 12.7-fold) and 11 medulloblastoma models (6.2 ± 1.7 in group 3, 6.0 ± 2.4 in group 4) accompanied by elevated H3K27me3 expression. Therapeutic efficacy was evaluated in 4 models (1 GBM, 2 medulloblastomas and 1 ATRT) via systematically administered tazemetostat (250 and 400 mg/kg, gavaged, twice daily) alone and in combination with cisplatin (5 mg/kg, i.p., twice) and/or radiation (2 Gy/day × 5 days). Compared with the untreated controls, tazemetostat significantly (Pcorrected < 0.05) prolonged survival times in IC-L1115ATRT (101% at 400 mg/kg) and IC-2305GBM (32% at 250 mg/kg, 45% at 400 mg/kg) in a dose-dependent manner. The addition of tazemetostat with radiation was evaluated in 3 models, with only one [IC-1078MB (group 4)] showing a substantial, though not statistically significant, prolongation in survival compared to radiation treatment alone. Combining tazemetostat (250 mg/kg) with cisplatin was not superior to cisplatin alone in any model. Analysis of in vivo drug resistance detected predominance of EZH2-negative cells in the remnant PDOX tumors accompanied by decreased H3K27me2 and H3K27me3 expressions. These data supported the use of tazemetostat in a subset of pediatric brain tumors and suggests that EZH2-negative tumor cells may have caused therapy resistance and should be prioritized for the search of new therapeutic targets.

Avaliação da alteração de cor da resina composta após imersão em diferentes soluções / Evaluation of color change of the composite resin after immersion in different solutions

Resinas compostas são materiais capazes de reproduzir as características ópticas próximas às do elemento dentário, além de possuírem propriedades mecânicas satisfatórias. Entretanto, elas apresentam instabilidade de cor em exposição prolongada a agentes corantes, tornando- -se um fator limitante, principalmente em áreas estéticas. O objetivo do presente trabalho foi avaliar a estabilidade de cor de duas resinas compostas, com partículas de carga diferentes, quando imersas em substâncias com potencial de manchamento. Foram confeccionadas 30 amostras da resina composta nano-particulada (Filtek Z350 XT, 3M ESPE, EUA) e 30 da resina micro-híbrida (Filtek Z250 XT, 3M ESPE, EUA). As amostras de cada resina foram divididas em 3 grupos (n=10) de acordo com as soluções utilizadas como meio de imersão: água destilada (controle), Cola-Cola® e café. A alteração de cor (ΔE) das amostras foram avaliadas através da diferença das tomadas de cor inicial e final (após 07 dias de imersão) por meio do espectrofotômetro. Os resultados mostraram que o meio de imersão influenciou significativamente no manchamento das resinas. A solução de café proporcionou os maiores valores de ΔE para ambas resinas testadas (nano-particulada = 20,07 +/- 0,67 e micro-híbrida = 17,24 +/- 0,53), e independente do meio de imersão, os maiores valores de ΔE foram encontrados na resina nano-particulada (p<0,05). Os resultados obtidos mostraram que o café é uma solução capaz de causar uma elevada alteração de cor nos compósitos e a resina nano-particulada Filtek Z350 XT é mais susceptível à alteração de cor do que a resina micro-híbrida Filtek Z250 XT (AU).

Composite resins are materials capable of reproducing optical characteristics close to the tooth and in addition have satisfactory mechanical properties. However, they present color instability in prolonged exposure to coloring agents, which becomes a limiting factor, mainly in aesthetic areas. The objective of this study was to evaluate the color stability of two composite resins with different charge particles when immersed in substances with staining potential. Thirty samples of nanoparticulated composite resin (Filtek Z350 XT, 3M ESPE, USA) and 30 of the micro-hybrid resin (Filtek Z250 XT, 3M ESPE, USA) were made. The samples of each resin were divided into 3 groups (n = 10) according to the solutions used as immersion medium: distilled water (control), Cola-Cola® and coffee. The color change (ΔE) of samples was evaluated using the difference of the initial and final color taken (after 07 days of immersion) through the spectrophotometer. The results showed that the immersion medium significantly influenced resin staining. The coffee solution provided the highest values of ΔE for both resins tested (nanoparticulated = 20,07 +/- 0,67 and micro-hybrid = 17,24 +/- 0,53), and independent of the immersion medium, higher values of ΔE were found in the nanoparticulated resin (p <0.05). The results showed that coffee is the solution capable of causing higher color change in the composites and Filtek Z350 XT nanoparticulated resin is more susceptible to color change than the Filtek Z250 XT micro-hybrid resin (AU).

Selective activators of protein phosphatase 5 target the auto-inhibitory mechanism.

Protein phosphatase 5 (PP5) is an evolutionary conserved serine/threonine phosphatase. Its dephosphorylation activity modulates a diverse set of cellular factors including protein kinases and the microtubule-associated tau protein involved in neurodegenerative disorders. It is auto-regulated by its heat-shock protein (Hsp90)-interacting tetratricopeptide repeat (TPR) domain and its C-terminal α-helix. In the present study, we report the identification of five specific PP5 activators [PP5 small-molecule activators (P5SAs)] that enhance the phosphatase activity up to 8-fold. The compounds are allosteric modulators accelerating efficiently the turnover rate of PP5, but do barely affect substrate binding or the interaction between PP5 and the chaperone Hsp90. Enzymatic studies imply that the compounds bind to the phosphatase domain of PP5. For the most promising compound crystallographic comparisons of the apo PP5 and the PP5-P5SA-2 complex indicate a relaxation of the auto-inhibited state of PP5. Residual electron density and mutation analyses in PP5 suggest activator binding to a pocket in the phosphatase/TPR domain interface, which may exert regulatory functions. These compounds thus may expose regulatory mechanisms in the PP5 enzyme and serve to develop optimized activators based on these scaffolds.