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This Week in PNAS: Dec 13, 2016

In the early, online edition of the Proceedings of the Academy of Sciences, researchers from Stanford University demonstrate the feasibility of using circulating tumor cell analysis to track advanced lung cancer in individuals with non-small cell lung cancer. Using an integrated nanoplatform method and single-cell multigene RT-PCR, the team isolated circulating tumor cells from 35 individuals with stage IV non-small cell lung cancer and 20 healthy controls, assessing multigene expression and mutations in the process. From their results so far, the authors propose that their nanoplatform may be "a compelling research tool to investigate the dynamics of cancer disease processes, as well as a viable clinical platform for minimally invasive yet comprehensive cancer assessment."

 A team from the University of York and the University of Reading report on an analysis of production of the malaria-combating compound artemisinin by the sweet wormwood plant Artemisia annua. Using mass spectroscopy, labeled carbon assays, and other approaches, the researchers profiled the metabolites present during leaf development and maturation in an A. annua mutant that alters the activity of an oxidase enzyme involved in artemisinin biosynthesis. Their results suggest that sesquiterpene metabolism that would normally lead to artemisinin production gets swapped over to sesquiterpene epoxide formation in the A. annua glandular trichome tissues when a CYP71AV1 enzyme is missing — a non-enzymatic conversion leading to an alternative secondary compound.

Finally, an international team investigates genome-wide methylation patterns in Arabidopsis and rice cells in an effort to understand the process of demethylation in endosperm seed tissue during sexual reproduction in these and other flowering plants. After isolating cells from wild type or mutant Arabidopsis and rice tissues, the researchers used modified bisulfite sequencing method to follow DNA methylation and demethylation in the plants. From these and other experiments, they conclude that maternal chromosome methylation drops in the endosperm due to locus-specific demethylation originating in so-called central cells in both plant species.