Genome-wide map of nuclear protein degradation shows NCoR1 turnover as a key to mitochondrial gene regulation.

Transcription factor activity and turnover are functionally linked, but the global patterns by which DNA-bound regulators are eliminated remain poorly understood. We established an assay to define the chromosomal location of DNA-associated proteins that are slated for degradation by the ubiquitin-proteasome system. The genome-wide map described here ties proteolysis in mammalian cells to active enhancers and to promoters of specific gene families. Nuclear-encoded mitochondrial genes in particular correlate with protein elimination, which positively affects their transcription. We show that the nuclear receptor corepressor NCoR1 is a key target of proteolysis and physically interacts with the transcription factor CREB. Proteasome inhibition stabilizes NCoR1 in a site-specific manner and restrains mitochondrial activity by repressing CREB-sensitive genes. In conclusion, this functional map of nuclear proteolysis links chromatin architecture with local protein stability and identifies proteolytic derepression as highly dynamic in regulating the transcription of genes involved in energy metabolism.

Effects of low-fat and high-fat meals on steady-state pharmacokinetics of lapatinib in patients with advanced solid tumours.

AIM: To quantify the effect of food on the systemic exposure of lapatinib at steady state when administered 1 h before and after meals, and to observe the safety and tolerability of lapatinib under these conditions in patients with advanced solid tumours. METHODS: This was a three-treatment, randomised, three-sequence cross-over study. Lapatinib was administered 1 h after a low- [B] or a high-fat [C] meal and systemic exposure was compared with that obtained following administration 1 h before a low-fat meal [A]. RESULTS: In total, 25 patients were included, of whom 12 were evaluable for the pharmacokinetic analysis. Both low-fat and high-fat meals affected lapatinib exposure. Lapatinib AUC0-24 increased following lapatinib administration 1 h after a low-fat meal by 1.80-fold (90 % CI: 1.37-2.37) and after a high-fat meal by 2.61-fold (90 % CI: 1.98-3.43). Lapatinib Cmax increased following lapatinib administration 1 h after a low-fat meal by 1.90-fold (90 % CI: 1.49-2.43) and after a high-fat meal by 2.66-fold (90 % CI: 2.08-3.41). The most commonly occurring treatment-related toxicity was diarrhoea (8/25, 32 % CTCAE grade 1 and 2/25, 8 % grade 2) and one treatment-related grade ≥ 3 event occurred (fatigue grade 3, 4 %). CONCLUSIONS: Both low-fat and high-fat food consumed 1 h before lapatinib administration increased lapatinib systemic exposure compared with lapatinib administration 1 h before a low-fat meal. In order to administer lapatinib in a fasted state, it is advised to administer the drug 1 h before a meal.

Deconstructing stem cell self-renewal: genetic insights into cell-cycle regulation.

The regulation of stem cell self-renewal must balance the regenerative needs of tissues that persist throughout life with the potential for cell overgrowth, transformation and cancer. Here, we attempt to deconstruct the relationship that exists between cell-cycle progression and the self-renewal versus commitment cell-fate decision in embryonic and adult stem cells. Recent genetic studies in mice have provided insights into the regulation of the cell cycle in stem cells, including its potential modulation by the stem cell niche. Although the dynamics of the embryonic and adult stem cell cycles are profoundly dissimilar, we suggest that shared principles underlie the governance of this important decision point in diverse stem cell types.

Trametinib, a first-in-class oral MEK inhibitor mass balance study with limited enrollment of two male subjects with advanced cancers.

1. This study assessed the mass balance, metabolism and disposition of [(14)C]trametinib, a first-in-class mitogen-activated extracellular signal-related kinase (MEK) inhibitor, as an open-label, single solution dose (2 mg, 2.9 MBq [79 µCi]) in two male subjects with advanced cancer. 2. Trametinib absorption was rapid. Excretion was primarily via feces (∼81% of excreted dose); minor route was urinary (∼19% of excreted dose). The primary metabolic elimination route was deacetylation alone or in combination with hydroxylation. Circulating drug-related component profiles (composed of parent with metabolites) were similar to those found in elimination together with N-glucuronide of deacetylation product. Metabolite analysis was only possible from <50% of administered dose; therefore, percent of excreted dose (defined as fraction of percent of administered dose recovery over total dose recovered in excreta) was used to assess the relative importance of excretion and metabolite routes. The long elimination half-life (∼10 days) favoring sustained targeted activity was important in permitting trametinib to be the first MEK inhibitor with clinical activity in late stage clinical studies. 3. This study exemplifies the challenges and adaptability needed to understand the metabolism and disposition of an anticancer agent, like trametinib, with both low exposure and a long elimination half-life.