Mutations of KRAS gene are found in various types of cancer, including colorectal cancer (CRC). Despite intense efforts, no pharmacological approaches are expected to be effective against KRAS-mutant cancers. Macropinocytosis is an evolutionarily conserved actin-dependent endocytic process that internalizes extracellular fluids into large vesicles called macropinosomes. Recent studies have revealed macropinocytosis's important role in metabolic adaptation to nutrient stress in cancer cells harboring KRAS mutations. Here we showed that KRAS-mutant CRC cells enhanced macropinocytosis for tumor growth under nutrient-depleted conditions. We also demonstrated that activation of Rac1 and phosphoinositide 3-kinase were involved in macropinocytosis of KRAS-mutant CRC cells. Furthermore, we found that macropinocytosis was closely correlated with asparagine metabolism. In KRAS-mutant CRC cells engineered with knockdown of asparagine synthetase, macropinocytosis was accelerated under glutamine-depleted condition, and albumin addition could restore the glutamine depletion-induced growth suppression by recovering the intracellular asparagine level. Finally, we discovered that the combination of macropinocytosis inhibition and asparagine depletion dramatically suppressed the tumor growth of KRAS-mutant CRC cells in vivo. These results indicate that dual blockade of macropinocytosis and asparagine bioavailability could be a novel therapeutic strategy for KRAS-mutant cancers.

KRAS基因的突变存在于各种类型的癌症中，包括结肠直肠癌 (CRC)。尽管付出了巨大的努力，但预计没有药理学方法对KRAS突变癌症有效。巨胞饮作用是一种进化上保守的肌动蛋白依赖性内吞过程，它将细胞外液内化成称为巨胞饮体的大囊泡。最近的研究揭示了巨胞饮作用在具有KRAS突变的癌细胞中代谢适应营养应激的重要作用。在这里，我们展示了KRAS在营养耗尽的条件下，突变的 CRC 细胞增强了肿瘤生长的巨胞饮作用。我们还证明了 Rac1 和磷酸肌醇 3-激酶的激活参与了KRAS突变 CRC 细胞的巨胞饮作用。此外，我们发现巨胞饮作用与天冬酰胺代谢密切相关。在用敲低天冬酰胺合成酶工程改造的KRAS突变 CRC 细胞中，在谷氨酰胺耗尽的条件下，巨胞饮作用加速，白蛋白添加可以通过恢复细胞内天冬酰胺水平来恢复谷氨酰胺耗尽诱导的生长抑制。最后，我们发现巨胞饮抑制和天冬酰胺耗竭的组合显着抑制了KRAS的肿瘤生长体内的突变CRC细胞。这些结果表明，巨胞饮作用和天冬酰胺生物利用度的双重阻断可能是KRAS突变癌症的新治疗策略。