Blood cholesterol and sphingomyelin in patients with cancer

Background: It is generally believed that high levels of blood cholesterol are harmful to health, whereas low levels seem to be positive and therefore are often neglected. Unfortunately this assumption is far from true, since severe hypocholesterolemia can be indicative of cancer. Cancer cells avidly incorporate serum cholesterol, favouring the expression of proteins involved in cell proliferation such as RNA polymerase II, STAT3, PKCz and cyclin D1 (Pugliese et Al. Eur. J. Cancer 46:1735). Numerous studies have shown that a strong interaction exists between unesterified cholesterol and saturated fatty acid sphingomyelin, which arises from the Van der Waals interaction. Since sphingomyelin and cholesterol association is responsible for formation of membrane lipid rafts involved in cell signalling we have studied the possible hyposphingomyelinemia associated to hypocholesterolemia in patients with cancer. Methods: The blood of 25 patients with monoclonal gammopathy were analyzed for their proteins and lipids content. Results: The results demonstrated that the patients with high level of gamma proteins present a strong decrease of both cholesterol and sphingomyelin content in blood. Conclusions: The results suggested the possible incorporation of cholesterol-sphingomyelin nano-sized vesicles that could change the structure/function of cell membrane or intracellular virtosomes. To investigate the reason for increased lipid incorporation by tumor cells, we performed lipidomicic study on the serum of the same patients. Initial results show a lipid profile different from that of healthy subjects.