Despite recent advances in treatment medulloblastoma continues to remain a vexing problem. Recently increased expression of cyclin dependent kinase 6 (CDK6) was identified as an adverse prognostic marker in medulloblastoma. Genomic amplification accounts for some, but not all of the CDK6 over-expression. We hypothesized that CDK6 expression is also regulated by microRNAs in medulloblastoma. We identified putative miR sites in the CDK6 including microRNA 124a, a brain enriched microRNA. Expression of miR 124a was significantly decreased in medulloblastoma cells compared to normal adult cerebellum. Functional association between miR 124a and CDK6 in medulloblastoma was established using luciferase assays. Additionally, re-expression of miR 124a in medulloblastoma cells decreased expression of CDK6 protein. Transfection of miR 124 significantly decreases medulloblastoma cell growth but does not alter apoptosis. Furthermore, in patient samples expression of miR 124a is significantly decreased. Our data strongly indicate that CDK6 is regulated by microRNA 124 in medulloblastoma and that miR 124 modulates medulloblastoma cell growth.

BackgroundMicroRNAs (miRNAs) are a class of short non-coding RNAs that regulate cell homeostasis by inhibiting translation or degrading mRNA of target genes, and thereby can act as tumor suppressor genes or oncogenes. The role of microRNAs in medulloblastoma has only recently been addressed. We hypothesized that microRNAs differentially expressed during normal CNS development might be abnormally regulated in medulloblastoma and are functionally important for medulloblastoma cell growth.Methodology and Principal FindingsWe examined the expression of microRNAs in medulloblastoma and then investigated the functional role of one specific one, miR-128a, in regulating medulloblastoma cell growth. We found that many microRNAs associated with normal neuronal differentiation are significantly down regulated in medulloblastoma. One of these, miR-128a, inhibits growth of medulloblastoma cells by targeting the Bmi-1 oncogene. In addition, miR-128a alters the intracellular redox state of the tumor cells and promotes cellular senescence.Conclusions and SignificanceHere we report the novel regulation of reactive oxygen species (ROS) by microRNA 128a via the specific inhibition of the Bmi-1 oncogene. We demonstrate that miR-128a has growth suppressive activity in medulloblastoma and that this activity is partially mediated by targeting Bmi-1. This data has implications for the modulation of redox states in cancer stem cells, which are thought to be resistant to therapy due to their low ROS states.

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is well known as a critical component involving the nonhomologous end joining pathway of DNA double-strand breaks repair. Here, we showed another important role of DNA-PKcs in stabilizing spindle formation and preventing mitotic catastrophe in response to DNA damage. Inactivation of DNA-PKcs by small interfering RNA or specific inhibitor NU7026 resulted in an increased outcome of polyploidy after 2-Gy or 4-Gy irradiation. Simultaneously, a high incidence of multinucleated cells and multipolar spindles was detected in DNA-PKcs-deficient cells. Time-lapse video microscopy revealed that depression of DNA-PKcs results in mitotic catastrophe associated with mitotic progression failure in response to DNA damage. Moreover, DNA-PKcs inhibition led to a prolonged G 2 -M arrest and increased the outcome of aberrant spindles and mitotic catastrophe in Ataxia-telangiectasia mutated kinase (ATM)-deficient AT5BIVA cells. We have also revealed the localizations of phosphorylated DNA-PKcs/T2609 at the centrosomes, kinetochores, and midbody during mitosis. We have found that the association of DNA-PKcs and checkpoint kinase 2 (Chk2) is driven by Ku70/80 heterodimer. Inactivation of DNA-PKcs strikingly attenuated the ionizing radiation-induced phosphorylation of Chk2/T68 in both ATMefficient and ATM-deficient cells. Chk2/p-T68 was also shown to localize at the centrosomes and midbody. These results reveal an important role of DNA-PKcs on stabilizing spindle formation and preventing mitotic catastrophe in response to DNA damage and provide another prospect for understanding the mechanism coupling DNA repair and the regulation of mitotic progression. Cancer Res; 70(9); 3657-66. ©2010 AACR.

In response to the daily light-dark (LD) cycle, organisms on Earth have evolved with the approximately 24-h endogenous oscillations to coordinate behavioral and physiological processes, including feeding, sleep, and metabolism homeostasis. Circadian desynchrony triggered by an energy-dense diet rich in fats and fructose is intimately connected with a series of metabolic disorders. Previous studies revealed that (-)-Epigallocatechin-3-gallate (EGCG) could mitigate metabolic misalignment; however, only a few reports have focused on its potential effect on directly manipulating circadian rhythms to ameliorate metabolic syndrome. Our goal was to investigate the regulating effect of EGCG treatment on metabolic misalignment triggered by a high-fat and high-fructose diet (HFFD) associating with the circadian clock. Our results indicated that HFFD treatment partially exhibited poor circadian oscillations of the core clock gene and the clock-controlled gene in the liver and fat relative to the control group. EGCG administration may ameliorate the diet-dependent decline in circadian function by controlling the Sirt1-PGC1αloop, implying the existence of an EGCG-entrainable oscillator. Subsequently, reducing fatty acid synthesis and elevating β-oxidation in the liver coupled with the increasing brown adipose tissue (BAT) energy expenditure observed in the EGCG group of mice prevented the adipocyte hypertrophy and fat accumulations common to BAT and white adipose tissue (WAT) derived from the HFFD mice. This study is the first to provide compelling evidences that EGCG may ameliorate diet-induced metabolic misalignment by regulating the rhythmic expression of the circadian clock genes in the liver and fat.

Thioredoxin reductase (TrxR) participates in the regulation of redox reactions in organisms. It works mainly via its substrate molecule, thioredoxin, to maintain the redox balance and regulate signal transduction, which controls cell proliferation, differentiation, death, and other important physiological processes. In recent years, increasing evidence has shown that the overactivation of TrxR is related to the development of tumors. The exploration of TrxR-targeted antitumor drugs has attracted wide attention and is expected to provide new therapies for cancer treatment. In this perspective, we highlight the specific relationship between TrxR and apoptotic signaling pathways. The cytoplasm and mitochondria both contain TrxR, resulting in the activation of apoptosis. TrxR activity influences reactive oxygen species (ROS) and further regulates the inflammatory signaling pathway. In addition, we discuss representative TrxR inhibitors with anticancer activity and analyze the challenges in developing TrxR inhibitors as anticancer drugs.

Obesity, which is caused by an energy imbalance between calorie intake and consumption, has become a major international health burden. Obesity increases the risk of insulin resistance and age-related cognitive decline, accompanied by peripheral inflammation. (-)-Epigallocatechin-3-gallate (EGCG), the major polyphenol in green tea, possesses antioxidant, anti-inflammatory, and cardioprotective activities; however, few reports have focused on its potential effect on cognitive disorders. In this study, our goal was to investigate the protective effects of EGCG treatment on insulin resistance and memory impairment induced by a high-fat and high-fructose diet (HFFD). We randomly assigned 3-mo-old C57BL/6J mice to 3 groups with different diets: control group, HFFD group, and HFFD plus EGCG group. Memory loss was assessed by using the Morris water maze test, during which EGCG was observed to prevent HFFD-elicited memory impairment and neuronal loss. Consistent with these results, EGCG attenuated HFFD-induced neuronal damage. Of note, EGCG significantly ameliorated insulin resistance and cognitive disorder by up-regulating the insulin receptor substrate-1 (IRS-1)/AKT and ERK/cAMP response element binding protein (CREB)/brain-derived neurotrophic factor (BDNF) signaling pathways. Long-term HFFD-triggered neuroinflammation was restored by EGCG supplementation by inhibiting the MAPK and NF-κB pathways, as well as the expression of inflammatory mediators, such as TNF-α. EGCG also reversed high glucose and glucosamine-induced insulin resistance in SH-SY5Y neuronal cells by improving the oxidized cellular status and mitochondrial function. To our knowledge, this study is the first to provide compelling evidence that the nutritional compound EGCG has the potential to ameliorate HFFD-triggered learning and memory loss.-Mi, Y., Qi, G., Fan, R., Qiao, Q., Sun, Y., Gao, Y., Liu, X. EGCG ameliorates high-fat- and high-fructose-induced cognitive defects by regulating the IRS/AKT and ERK/CREB/BDNF signaling pathways in the CNS.

Objective Urolithin A (UroA) is a major metabolite of ellagic acid produced following microbial catabolism in the gut. Emerging evidence has suggested that UroA modulates energy metabolism in various cells. However, UroA’s physiological functions related to obesity and insulin resistance remain unclear. Methods Male mice were intraperitoneally administrated either UroA or dimethyl sulfoxide (vehicle) along with a high‐fat diet for 12 weeks. Insulin sensitivity was evaluated via glucose and insulin tolerance tests and acute insulin signaling. The effects of UroA on hepatic triglyceride accumulation, adipocyte size, mitochondrial DNA content, and proinflammatory gene expressions were determined. The impact of UroA on macrophage polarization and mitochondrial respiration were assessed in bone marrow–derived macrophages. Results Administration of UroA (1) improved systemic insulin sensitivity, (2) attenuated triglyceride accumulation and elevated mitochondrial biogenesis in the liver, (3) reduced adipocyte hypertrophy and macrophage infiltration into the adipose tissue, and (4) altered M1/M2 polarization in peritoneal macrophages. In addition, UroA favored macrophage M2 polarization and mitochondrial respiration in bone marrow‐derived macrophages. Conclusions UroA plays a direct role in improving systemic insulin sensitivity independent of its parental compounds. This work supports UroA’s role in the metabolic benefits of ellagic acid–rich foods and highlights the significance of its microbial transformation in the gut.

These data indicate that inhibition of Aurora Kinase A inhibits cell growth in medulloblastoma through inhibition of pro-proliferative signaling pathways Wnt, Myc, and RB. Additionally, combining Aurora Kinase A inhibition with other chemotherapeutic agents significantly lowers their IC(50), which make it a promising small molecule target for medulloblastoma therapy.