Effect of liposome-encapsulated alpha- or beta-interferon on breast cancer cell lines

Experimental evidence and clinical studies have indicated that interferons (IFN) inhibit proliferation in a wide panel of neoplasms, including breast cancer. However, the antitumor activity of IFN requires the continuous presence of high concentrations of the drug and is associated with side effects. To explore the potential of liposomes as an IFN delivery system, we compared the effect of free or liposome-encapsulated alpha-IFN and beta-IFN on the growth of two breast cancer cell lines (MCF7 and MDA-MB231). Cells were cultured in the presence of IFN at different concentrations (500, 1000, 2000 IU/ml) or in the presence of multilamellar liposomes (phosphatidylcholine-phosphatidylserine at a molar ratio of 7:3) containing saline buffer, alpha-IFN or beta-IFN. Additional control groups consisted of cells cultured with alpha-IFN or beta-IFN plus empty liposomes. Empty liposomes were not cytotoxic and did not interfere with IFN activity. In both cell lines liposomes encapsulating alpha-IFN (at the highest lipid:drug ratio) inhibited cell growth in a manner similar to that of free alpha-IFN, whereas liposomes encapsulating beta-IFN showed slightly, lower inhibition than free beta-IFN, this was more evident in MCF7 cells. The present results indicate that liposomes encapsulating alpha-IFN or beta-IFN were effective on the growth of both breast cancer cell lines, which are characterized by a different estrogen responsiveness, and that they might be a useful carrier system for the delivery of high doses of IFN.