Studies in P-gp-expressing leukemia cells demonstrated that the GCS inhibitor PDMP elicited sensitization to daunorubicin via (i) efflux blockade, (ii) ceramide accumulation, and (iii) reduction in GlcCer levels [167], a clear example of the duplicitous role exerted by agents like PDMP. This evidence concerns the gene UGCG and leukemia.