SLC22A2 and colon carcinoma: As for spermidine uptake by the carnitine transporter SLC22A16, the uptake activity in human colon carcinoma HCT116 cells (Vmax = 23.1 pmol/107 cells/h) seems to be lower compared to the spermidine uptake activity by hOCT2, although the Km value is very low (0.35 μM) [20].