PCK2 and lung cancer: Because recent studies showed that lung cancer cells can become independent of glucose by upregulation of mitochondrial phosphoenolpyruvate carboxykinase (PCK2), which generates phosphoenolpyruvate from glutamine to generate ribose for nucleic acid synthesis18, 19, we set out to determine whether PCK2 was upregulated in the HCT116 and DLD1 cell lines when deprived of glucose.