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This Week in Science: Aug 4, 2017

In this week's Science, an international research team uses genomic data to show that the agricultural use of maize throughout the highlands of the US likely occurred due to propagation of varieties with earlier flowering times. Although maize became a staple crop in the southern lowlands of the US when it was introduced from Mexico about 4,000 years ago, it took about 2,000 more years until it was widely grown at higher elevations. By reconstructing and analyzing the genomes of 15 ancient samples of maize and comparing the data to a global collection of more than 2,500 modern lines, the investigators noticed that higher-elevation varieties with earlier flowering times — a trait useful in Northern locales — did not appear to come from modern-day Mexico. Rather, this trait appears to have been selected for by higher-altitude farmers over thousands of years.

And in Science Translational Medicine, researchers from Purdue University and Ohio State University describe a new approach that allows an investigational gene-silencing cancer treatment to go directly to tumor cells without the need for often-toxic delivery vehicles. Many tumors overexpress the receptor for folate on their surfaces, so by linking therapeutic microRNAs to folate, the researchers were able to cause cancer cells to selectively take up the molecules. In mouse models of triple-negative breast cancer and non-small cell lung cancer, single intravenous administrations of folate-linked miRNAs accumulated at high levels inside malignant masses — but not in normal tissue — within 24 hours. The miRNAs downregulated their targets and suppressed tumor growth without any evidence of whole-organ toxicity.