Secondly, potential dynamic metabolic flux differences between breast cancer cell lines were studied by stable-isotope dynamic labeling for key targets, such as pyruvate, based on preferential pyruvate dehydrogenase (PDH) or pyruvate carboxylase (PC) activities to quantitatively analyze the degree of TCA reliance, and other central pathways as glutamine/glutamate metabolism preferences based on anaplerotic input to TCA or their preferential use by reductive carboxylation. The gene discussed is PC; the disease is breast cancer.