Considering a strong link between GLUT5 activity and breast cancer [19], we have selected breast cancer cells for biochemical evaluation of probes I–IV: GLUT5-positive breast adenocarcinoma MCF7 cell line, GLUT5-positive human breast invasive ductal carcinoma MDA-MB-231 cell line, and GLUT5-negative normal breast 184B5 cells. The gene discussed is SLC2A5; the disease is invasive ductal breast carcinoma.