Fluidity of Red Blood Cells’ Membranes in Cancer Patients − an Electronic Paramagnetic Resonance Study
Background: Hypocholesterolemia in cancer patients is a frequent and expected phenomenon. Higher fluidity of plasma membranes (as a result of lower concentration of cholesterol) is a characteristic of most cancer cells. Erythrocytes lack organelles and inner membranes and with that any possibility of endogenous synthesis of lipids. Changes in serum lipid concentration could be shown in the fluidity of erythrocyte cell membranes. Aim: To compare the fluidity of erythrocyte membranes in cancer patients and in healthy controls in relation to serum lipid concentration, type, stage of cancer and age. Hypothesis: Hypocholesterolemia in cancer patients is the cause that erythrocyte membranes have higher fluidity. Methods: In prospective study we included 49 cancer patients and 25 healthy controls. We studied the membrane fluidity of isolated erythrocytes by the electronic paramagnetic resonance method. In membranes incorporated spin label gives us information (spectrum) about fluidity in the neighborhood. We also added 0.5 M cholesterol to erythrocytes samples from healthy individuals and measured the change in membrane fluidity. Results: Cancer patients in comparison to healthy controls do not have higher erythrocytes membrane fluidity but they do have significantly lower serum lipid concentrations. Fluidity of erythrocyte membranes is higher in patients with higher total serum cholesterol, HDL and LDL. Addition of cholesterol (in vitro) to erythrocytes of healthy individuals significantly increases the concentration of cholesterol in cell membranes and their fluidity as well. Conclusions: The surprising result that hypocholesterolemia does not cause higher fluidity of erythrocyte membranes we explained with the existence of membrane domains and changes in metabolism in cancer patients. The EPR method is not clinically important; however it could be used for further basic science research for there is very good correlation between fluidity of erythrocytes membranes and serum lipid concentration. It would also be necessary to biochemically measure the real cholesterol concentration in erythrocytes membranes.