To perform a functional analysis of whether Slc15A2 activity was in fact implicated in the observed dipeptide accumulation, we first incubated CML-KLS+ cells in vitro with [3H]-labelled glycylsarcosine (GlySar)21, 22, which is a dipeptide analogue that cannot be metabolized and acts as a substrate of Slc15A family transporters. The gene discussed is RPS6KB2; the disease is chronic myelogenous leukemia, BCR-ABL1 positive.