Background: Fructose is an abundant source of carbon and energy for cells to use for metabolism, but only certain cell types use fructose to proliferate. Tumor cells that can metabolize fructose have a fitness advantage over their neighboring cells, but the proteins that mediate fructose metabolism in this context are unknown. Here, we investigated the determinants of fructose-mediated cell proliferation.
Methods: We quantified the ability of 14 cell lines to proliferate in fructose-containing media (i.e. the fructolytic ability) using live cell imaging and crystal violet assays. The expression and abundance of proteins related to fructose metabolism were assessed using RT-qPCR and western blot, respectively, for each cell line. Using a positive selection approach, we “trained” the non-fructolytic PC3 cell line to utilize fructose for proliferation. RNA-seq was then performed to identify key transcriptional changes associated with fructolytic ability. We overexpressed and deleted proteins associated with fructose metabolism, and performed metabolic profiling using the Seahorse Bioanalyzer and LC/MS-based metabolomics.
Results: We found that neither the tissue of origin nor expression level of any single gene related to fructose catabolism determine a cell’s fructolytic ability. Cells cultured chronically in fructose can develop fructolytic ability if SLC2A5, encoding the fructose transporter, GLUT5, gets upregulated. Overexpression of GLUT5 in non-fructolytic cells enables growth in fructose-containing media across cells of different origins. GLUT5 permitted fructose to flux through glycolysis using hexokinase (HK) and not ketohexokinase (KHK).
Conclusions: We show that GLUT5 is a robust and generalizable driver of fructose-dependent cell proliferation. This indicates that fructose uptake is a limiting factor for fructose-mediated cell proliferation. We further demonstrate that cancer cell proliferation with fructose is independent of KHK.