Membrane lipids modifications in human gliomas of different degree of malignancy

A great deal of experimental evidence shows that the growth of tumors is accompanied by significant changes at the expense of the cell surface. For the present paper, we set out to analyse the composition of membrane lipids (cholesterol, phospholipids, neutral and acidic glycosphingolipids, sulphatides) in human cerebral astrocytomas, which is a group of tumors that offer a valid model for the study of the various grades of cellular transformations in vivo. The results obtained in the present study permit us to draw a series of conclusions in relation to the malignancy grade of glial human tumors. In particular, an increase in the malignancy is accompanied by: 1) a reduction of the total lipids, a reduction that involves all the principal classes of lipids of the plasma membrane, for which it has been possible to demonstrate a correlation of an exponential nature, which is significant with the increasing of the histological grading; 2) a gradual accumulation, in the area of glycosphingolipids, of lattosylceramide and GD3, molecules that can constitute a valid marker of the malignancy grade; moreover, the glycolipid composition of astrocytomas of high degree differs from that of tumors of a low grade because of the presence of more complex glycolipids (trihexosylceramide and tetraosylceramide); 3) a gradual increase, in the area of phospholipids, of PC/PE and PC/SM ratios, indices of the microviscosity of the membrane. The data obtained suggest that the profound modifications of membrane lipids, which are gradually accompanied by a progressive increase in the malignancy of the tumor, can, on the one hand, be responsible for functional variations connected with neoplastic growth, and, on the other hand, constitute valuable biochemical parameters which are useful, together with histological studies, in the diagnosis of these tumors.