Atomic Force Microscopy study of lipid rafts in MDA-MB-231 human breast cancer cells after DHA incorporation
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Data di Pubblicazione:
2011
Citazione:
Atomic Force Microscopy study of lipid rafts in MDA-MB-231 human breast cancer cells after DHA incorporation / P.A. Corsetto, A. Cremona, F. Orsini, P. Arosio, I.E. Jovenitti, S. Zava, G. Montorfano, A. M Rizzo. ((Intervento presentato al convegno Convegno annuale della sezione ligure-lombardo-piemontese della società italiana di biochimica e biologia molecolare tenutosi a Novara nel 2011.
Abstract:
INTRODUCTION: One of the major targets for breast cancer therapy is the epidermal growth
factor receptor (EGFR). EGFR is a transmembrane protein with intrinsic protein tyrosine kinase
activity that is activated by ligand binding, most important being EGF. EGFR over-expression
contributes to increased cell proliferation and migration in breast cancer (1).
Recent findings in membrane biology suggest that the plasma membrane is composed by
microdomains of saturated lipids that segregate together to form lipid “rafts”. Lipid rafts have been
operationally defined as cholesterol- and sphingolipid-enriched membrane microdomains resistant
to solubilization by nonionic detergents at low temperatures. Lipid rafts are enriched in several
signaling proteins, including EGFR (2).
(N-3) polyunsaturated fatty acids (PUFA), namely eicosapentaenoic acid (EPA) and
docosahexaenoic acid (DHA), decrease proliferation and induce apoptosis in EGFR over-expressing
MDA-MB-231 human breast cancer cells (3).
Here we report a biophysical approach to investigate lipid rafts fatty acid and protein composition
in MDA-MB-231 treated with DHA, applying spectroscopic and imaging tools, namely AFM and
FTIR microspectroscopy. Moreover, the biophysical approach is coupled to a detailed biochemical
analysis by means of biochemical assays (SDS-PAGE, Western Blotting and HPLC/GC).
RESULTS: Biochemical analyses show that DHA increases the unsaturated state of phospholipids
in lipid rafts of breast cancer cells, therefore, alters their physical-chemical properties. Many
acylated proteins directly interact with membrane lipid bilayers by their saturated acyl moieties.
Then we suggest that altered lipid composition of microdomains might determine the displacement
of proteins from lipid rafts in n-3 PUFA-treated cells with alteration of signal transduction, with
particular regards to EGFR.
In addition, morpho-dimensional changes in lipid rafts are visualized and analyzed by AFM
studying purified membrane samples both before and after the DHA incorporation. AFM technique
allows to obtain three-dimensional images of the surface topography of lipid microdomains at
nanometer resolution in a physiological-like environment thus providing structural/functional
insights that cannot be obtained with more conventional approaches. High resolution AFM imaging
shows on MDA-MB-231 lipid rafts, after DHA incorporation, features in agreement, for dimensions
and shape, with membrane proteins. A more accurate investigation using specific antibodies could
confirm, in the next future, the nature of the observed structures and allow their identification.
These preliminary results suggest that AFM could be an useful tool to characterize changes in the
membrane protein content induced by DHA treatment at single protein level.
1. Muller-Todow C et al. (2004) Clin. Cancer Res. 10, 1241-1249
2. Foster LJ et al. (2003) Proc. Natl. Acad. Sci USA 100, 5813-5818
3. Corsetto PA et al. (2010) Chem. Phys. Lip. S28, doi: 10.1016/j.chemphyslip.2010.05.08
Tipologia IRIS:
14 - Intervento a convegno non pubblicato
Keywords:
Omega-3 ; Cancer ; Lipid Rafts
Elenco autori:
P.A. Corsetto, A. Cremona, F. Orsini, P. Arosio, I.E. Jovenitti, S. Zava, G. Montorfano, A. M Rizzo
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