Let-7 MicroRNA Family Is Selectively Secreted into the Extracellular Environment via Exosomes in a Metastatic Gastric Cancer Cell Line http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0013247胃癌転移細胞株AZ-P7aは特異的に…