Phytosterol-β-
sitosterol promotes apoptosis in various
cancer cells and inhibits their growth. Supplementation of
cancer cells with this compound causes modifications in membrane composition, namely, substitution of
cholesterol (Chol), decrease of
sphingomyelin (SM) content and increase of
ceramide (Cer) level. The aim of this work was to investigate the influence of partial replacement of
cholesterol by
plant sterol, substitution of
sphingomyelin by
ceramide and both these factors simultaneously on the properties of the monolayers composed of major
lipids identified in
breast cancer membranes, namely Chol/SM/GM3 mixtures. Brewster Angle Microcopy experiments and the analysis of the isotherms recorded during films compression and resulting parameters evidenced that β-
sitosterol weakens the interactions between molecules, decreases films stability and condensation. The influence of
ceramide on
sterol/SM/GM3 films was reflected in strong modifications of their texture, however, the morphology of monolayer was determined by the structure of
sterol present in the system. It was also found, that simultaneous replacement of 50mol% of Chol and SM by
phytosterol and Cer, respectively, induces
lipids segregation, which is manifested in large diversity of phases observed in BAM images. To facilitate the analysis of the data collected for multicomponent monolayers, the properties of selected
sterol/GM3,
sterol/Cer, SM/GM3, Cer/GM3 binary films were also investigated. The obtained results evidenced that the studied herein modifications in the composition of Chol/SM/GM3 monolayer, reflecting compositional alterations induced by
phytosterol in
cancer membranes, strongly affect the organization of model system, therefore they should be considered in the studies on anticancer mechanism of β-
sitosterol.