Sphingolipid Metabolism Enzymes as Targets for Anti-Cancer Therapy

J.   W.   Kok; H.      Sietsma

Abstract

Treatment with anti-cancer agents in most cases ultimately results in apoptotic cell death of the target tumor cells. Unfortunately, tumor cells can develop multidrug resistance, e.g., by a reduced propensity to engage in apoptosis by which they become insensitive to multiple chemotherapeutics. Ceramide, the central molecule in cellular sphingolipid metabolism, has been recognized as an important mediator of apoptosis. Moreover, an increased cellular capacity for ceramide glycosylation has been identified as a novel multidrug resistance mechanism. Indeed, virtually all multidrug resistant cell types exhibit a deviating sphingolipid composition, most typically an increased level of glucosylceramide. Thus, the enzyme glucosylceramide synthase, which converts ceramide into glucosylceramide, has emerged as a potential target to increase apoptosis and decrease drug resistance of tumor cells. In addition, several other steps in the pathways of sphingolipid metabolism are altered in multidrug resistant cells, opening a perspective on additional sphingolipid metabolism enzymes as targets for anti-cancer therapy. In this article, we present an overview of the current understanding concerning drug resistance-related changes in sphingolipid metabolism and how interference with this metabolism can be exploited to over come multidrug resistance.

Keywords: sphingolipid, ceramide, glucosylceramide, glucosylceramide synthase, lactosylceramide, gangliosides, multidrug resistance, p-glycoprotein