Miranda Y. Fong, Weiying Zhou, Liang Liu et al.
The authors find that many breast cancer cell lines secrete the microRNA miR-122, in vesicles composed of both protein and microRNA. They show that this factor suppresses glucose metabolism by suppressing pyruvate kinase: the last step in glycolysis which generates pyruvate, which is the substrate for the citric acid cycle. The authors show that these vesicles are easily taken up by untransformed cells, and that glucose metabolism is then inhibited as a result. In vivo models show that mice receiving high levels of miR-122 developed significant metastatic colonisation, despite reduced primary tumour formation. The authors suggest that miR-122 is involved in preparing the pre-metastatic niche for tumour cell arrival, by suppressing nutrient uptake of other cells, to favour themselves.