Metabolic screening of cancer cell metabolism

Objectives Characterize metabolic indices as potential biomarkers of chemoresistant cancer cells or cancer stem cells.

Methods 18F-FDG (FDG), 14C-acetate (ACE), and 3H-glutamine (GLN) or 14C-leucine (LEU) provide indices of glycolysis, fatty acid (FA), and amino acid (AA) metabolism. Radiotracer % uptake was optimized and measured in triplicate cell assays. To assess EGFR2 inhibition with lapatinib, EGFR2+ breast cancer cell lines included: parental control (BT474), short term treatment (tBT474=24hr lapatinib), resistant (rBT474=cultured >2 weeks in lapatinib), and Released resistant (RrBT474=cultured >2 weeks in lapatinib, followed by lapatinib withdrawl). Metabolic indices in similarly treated EGRF2+ skBr3 were also tested.

Results Baseline BT474 glycolytic index was modest (%uptake FDG<5%). Compared to baseline, % uptake FDG was inhibited with 24 hrs lapatinib tBT474 (p=0.0002), returned to baseline levels after chronic lapatinib exposure rBT474 (p=0.41), and increased over baseline after lapatinib withdrawl RrBT474 (p=0.002). FA index showed a high baseline ACE (13.9+2.2%). % uptake ACE decreased after treatment tBT474 (6.5+0.6; p=0.004), returned to baseline after chronic exposure rBT474 (10.5+2.4%; p=0.14), but remained at baseline after withdrawl RrBT474 (13.4+1.7%; p=0.75). The AA index LEU showed the highest baseline % uptake BT474 (37.9+2.3). LEU decreased with treatment tBT474 (21.9+1.8; p=0.0007), returned to baseline after chronic exposure rBT474 (41.9+3.1%; p=0.15), and significantly increased after withdrawl RrBT474 (46.5+2.7%; p=0.01). The AA index GLN showed results similar to those for BT474.

Conclusions All metabolic indices demonstrate significant changes with drug exposure. AA indices showed the highest overall baseline uptake, and are promising alternative metabolic substrates to detect acute and chronic drug effects, including chemoresistant cancer and cancer stem cells.

Research Support DOD Award W81XWH-08-1-051