这篇论文描述了向癌细胞供应养分的一个以前没有被识别出来的通道。致癌的Ras蛋白已知促进“巨胞饮”（macropinocytosis）。这是一个“内吞”过程，在其中，细胞外流体及其成分通过名为“巨胞饮小体”（macropinosome）的小泡被内化到细胞中。
现在，Dafna Bar-Sagi及其同事发现，被Ras改变的细胞可利用这一过程来“吃”细胞外蛋白。被“巨胞饮”的蛋白发生降解，产生支持肿瘤生长所必需的自由氨基酸。这一发现表明，“巨胞饮”的抑制对于治疗一个亚组的癌症可能会有效。（生物谷Bioon.com）
生物谷推荐英文摘要：
Nature doi:10.1038/nature12138
Macropinocytosis of protein is an amino acid supply route in Ras-transformed cells
Cosimo Commisso, Shawn M. Davidson, Rengin G. Soydaner-Azeloglu, Seth J. Parker, Jurre J. Kamphorst, Sean Hackett, Elda Grabocka, Michel Nofal, Jeffrey A. Drebin, Craig B. Thompson, Joshua D. Rabinowitz, Christian M. Metallo, Matthew G. Vander Heiden & Dafna Bar-Sagi
Macropinocytosis is a highly conserved endocytic process by which extracellular fluid and its contents are internalized into cells through large, heterogeneous vesicles known as macropinosomes. Oncogenic Ras proteins have been shown to stimulate macropinocytosis but the functional contribution of this uptake mechanism to the transformed phenotype remains unknown. Here we show that Ras-transformed cells use macropinocytosis to transport extracellular protein into the cell. The internalized protein undergoes proteolytic degradation, yielding amino acids including glutamine that can enter central carbon metabolism. Accordingly, the dependence of Ras-transformed cells on free extracellular glutamine for growth can be suppressed by the macropinocytic uptake of protein. Consistent with macropinocytosis representing an important route of nutrient uptake in tumours, its pharmacological inhibition compromises the growth of Ras-transformed pancreatic tumour xenografts. These results identify macropinocytosis as a mechanism by which cancer cells support their unique metabolic needs and point to the possible exploitation of this process in the design of anticancer therapies.
