To summarize, the presumption that P-gp plays a role in ceramide glycosylation is substantiated by (i) work implicating GlcCer in the biochemistry of multidrug resistance [9], (ii) studies showing that elevated levels of GlcCer in cancer cells correlate with overexpression of P-gp [101], (iii) the finding that commonly employed P-gp antagonists suppress ceramide glycosylation in drug-resistant cancer cells [104], and (iv) insightful research showing that Golgi-resident P-gp can function as a sphingomyelin and GlcCer transmembrane flippase [149,154]. Here, PGP is linked to cancer.