PURPOSE: We compared the metabolic profiles and the association between LDH-A expression and Lactate production in two isogenic murinebreast cancer cell lines and tumors (67NR and 4T1). These cell lines were derived from a single mammary tumor and have different growth and metabolic phenotypes. EXPERIMENTAL DESIGN: LDH-A expression, Lactate concentration, glucose utilization, and oxygen consumption were measured in cells, and the potential relationship between tumorLactate levels [measured by magnetic resonance spectroscopic imaging (MRSI)] and tumorglucose utilization [measured by [(18)F]2-deoxy-2-fluoro-D-glucose positron emission tomography ([(18)F]FDG-PET)] was assessed in orthotopic breast tumors derived from these cell lines. RESULTS: We show a substantial difference in LDH-A expression between 67NR and 4T1 cells under normoxia and hypoxia. We also show that small orthotopic 4T1tumors generate 10-fold more Lactate than corresponding 67NRtumors. The high Lactate levels in small primary 4T1tumors are associated with intense pimonidazole staining (a hypoxia indicator). Less-intense hypoxia staining was observed in the larger 67NRtumors and is consistent with the gradual increase and plateau of Lactate concentration in enlarging 67NRtumors. CONCLUSIONS: Lactate-MRSI has a greater dynamic range than [(18)F]FDG-PET and may be a more sensitive measure with which to evaluate the aggressive and metastatic potential of primary breast tumors.
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