Carbon and nitrogen are essential elements for life. Glucose as a carbon source and glutamine as a nitrogen source are important nutrients for cell proliferation. About 100 years ago, it was discovered that cancer cells that have acquired unlimited proliferative capacity and undergone malignant evolution in their host manifest a cancer‐specific remodeling of glucose metabolism (the Warburg effect). Only recently, however, was it shown that the metabolism of glutamine‐derived nitrogen is substantially shifted from glutaminolysis to nucleotide biosynthesis during malignant progression (...) of cancer—which might be referred to as a “second” Warburg effect. In this review, address the mechanism and relevance of this metabolic shift of glutamine‐derived nitrogen in human cancer. We also examine the clinical potential of anticancer therapies that modulate the metabolic pathways of glutamine‐derived nitrogen. This shift may be as important as the shift in carbon metabolism, which has long been known as the Warburg effect. (shrink)