Molecular Basis for Anticancer Activity of Host Defense Peptides

• DOI: 10.1016/j.bpj.2010.12.2030
• Publication Date: 2011-02-10T05:45:27Z
• Authors: Andrey Ivankin; Paul A. Adamczyk; Binill H. Shah; David Gidalevitz
• Keywords: Biophysics; 3. Good health

The high toxicity of most anticancer chemotherapeutic drugs and their deactivation by multidrug resistant phenotypes motivated an extensive search for drugs with new modes of action. Host defense peptides (HDPs) represent a promising class of natural-source drugs with a distinct mode of action, decreased likelihood of resistance development, and low intrinsic cytotoxicity. However, the development of antitumoral HDP-based compounds has been hindered by poor understanding of the molecular mechanisms of the HDPs’ selective killing of cancer cells. Accumulating evidence indicates that the outer leaflet of tumor cell plasma membranes is enriched in anionic lipids such as phosphatidylserine (PS) and various gangliosides that may render the cancer cells susceptible to cationic HDPs. Here we report results of a combined AFM-X-ray study aimed at the understanding an impact of elevated levels of PS and gangliosides GM3 and GD3 in cell membranes on the cytotoxic activity of HDPs. Lipid monolayers at the air-liquid interface and supported lipid bilayers composed of DPPC and GD3, GM3, or DPPS at different ratios were used to model plasma membrane of cancer cells. The electron density profiles across the films, derived from X-ray reflectivity data, demonstrate that HDPs penetrate into all DPPC/anionic lipid monolayers, however with a different propensity. The HDPs’ membrane-insertion propensity rises with increase in concentration of anionic lipids in the films and is the highest for GD3 and the lowest for DPPS. Grazing incidence X-ray diffraction data together with AFM indicate that HDPs can degrade effectively ordering of anionic lipids in the membranes. Our results suggest that the molecular mechanisms underlying the antibacterial and anticancer activities of HDPs may be the same.