LAUSR

Background: The exposure of phosphatidylserine (PS) is one of the first steps of programmed cell death. Phagocytosis on cancer microenvironment is well described in tumors and is associated with malignancy and poor prognosis. Tumor associated macrophages (TAMs) act suppressing the anticancer immune response. The tumor parenchymal cells are also capable of phagocytosis cells in apoptosis. In a previous study we observed that 7-ketocholesterol is capable of inducing autophagy on melanoma cell. Aims: Evaluate the activities of a 7-ketocholesterol loaded-phosphatidylserine liposome on autophagy and phagocytosis of tumor microenvironment. Methods: Liposomes were constituted by 20 mg commercial Phosphatidylserine (PS) and PS associated with 5 mg of 7-ketocholesterol extracted with chloroform/methanol (10: 1), dried, resuspended in 10 mL phosphate buffer, homogenized and sonicated for 6 minutes. The size and Zeta Pontencial (ZP) of liposomes were evaluated. Antiinflammatory activity of liposomes was evaluated by paw edema induced by carrageenan. A dependent-dose effect of liposomes on J774 macrophages, B16F10 melanoma cells, and 4T1 breast cancer cells was assessed by MTT. Cell death evaluations, for the same cells, were performed by flow cytometry with propidium iodide (PI) staining. The presence of acid vacuoles related to autophagy was evaluated by flow cytomery by acridine orange staining. The effects of the liposomes in vivo were evaluated by B16F10 melanoma-bearing C57/bl6 mice and 4T1 breast cancer-bearing Balb c mice. Endocytosis efficiency of the liposomes was observed by labeling it with PKH26 fluorescent staining and evaluated in 4T1 cells after 12 h. Liposomes were radiolabeled by adding 1 to 30 mCi of 99mTc radiopharmaceuticals (99mTcO4-, 99mTc-dextran-70, 99mTc-MIBI, 99mTc-DISIDA) and 18FDG; the solution was homogenized and sonicated for 6 minutes. The samples were centrifuged and part of the supernatant was added to an Amicon® filter (10kD) and concentrated, the concentrated was diluted with 400 uL of PBS and concentrated again. Liposome incorporation was determined by quotient of the radioactivity in the Amicon® by sum of Amicon® and filtrated solutions. Furthermore, lipophilicity (L), hydrophilicity (H), and charge (-/0/+) of the radioactive material were considered in the final analysis. Results: PS liposomes presented 141,9nm + 9,101 size with a -25,2 ZP; PS-7-ketocholesterol (PS/7KC) liposomes presented 153,9 nm + 10,35 size with a -29,1 ZP. The paw edema was inhibited by both liposomes after 240 min of the carrageenan induction. The concentration of 26 uM/mL of PS and PS/7KC liposomes stimulated cell proliferation. PS/7KC at the concentrations above 84 uM/mL inhibited the cell proliferation. PS/7KC showed intense antiproliferative activity in melanoma cells and breast adenocarcinoma cells, assessed by the MTT method and by flow cytometry with PI. It was observed 10% more autophagic vacuoles on melanoma cells treated with PS/7KC than the control groups. Both in vivo tumor models had the same antiproliferative effect of the PS/7KC liposomes with daily doses. Daily doses of PS liposomes induced a high size of tumors. 99mTc-MIBI was efficiently and strongly incorporated to liposomes than the other proposed formulations. Conclusion: PS liposomes have effects in vivo and in vitro and must be related to phagocyte and autophagy activities. PS/7KC impairs J774 macrophage, B16F10 melanoma, and 4T1 breast adenocarcinoma cell growth. PS/7KC induces the presence of acid vacuoles corresponding to autophagy. The liposomes had a high endocytosis evaluated by PKH 26 labelled particles. PS keeps the tumor proliferation and PS/7KC inhibits tumor growth after ten days of daily doses. Supported by CNPq and Fundacao Araucaria. Citation Format: Giovani Marino Favero, Tharcisio Citrangulo Tortelli, Jr., Daniel Fernandes, Ana Paula Prestes, Louise N.B. Kmetiuk, Andreia Hanada Otake, Luciana N.S. Andrade, Daniele de Paula Faria, Camila de Godoi Carneiro, Alexandre Teles Garcez, Fabio L.N. Marques, Roger Chammas. 7-Ketocholesterol loaded-phosphatidylserine liposome induces cell death, autophagy, and growth inhibition of melanoma and breast adenocarcinoma [abstract]. In: Proceedings of the AACR International Conference held in cooperation with the Latin American Cooperative Oncology Group (LACOG) on Translational Cancer Medicine; May 4-6, 2017; Sao Paulo, Brazil. Philadelphia (PA): AACR; Clin Cancer Res 2018;24(1_Suppl):Abstract nr A50.