Abstract 2678: Antitumor effect against 67 kDa laminin receptor expressed on high-grade tumor cells
Authors: Sugiyama Ikumi , Sadzuka Yasuyuki 
Published: August 2018

[Purpose] In chemotherapy for cancer, liposomes as drug delivery system (DDS) carriers are expected to have a useful effect. The aim of this study was, therefore to evaluate the antitumor effects of, and elucidate the mechanisms underlying, (-)-epigallocatechin-3-O-gallate (EGCG) and polyethyleneglycol (PEG)-modified liposomes. EGCG functions as a target ligand of the 67 kDa laminin receptor (67LR), which is expressed on high-grade tumor cells. An EGCG derivative was synthesized for binding to the end site of PEG structure. In this study, the antitumor effects of EGCG-modified liposomes as active-targeting liposome were evaluated.

[Methods] Liposome was loaded with doxorubicin (DOX) as an antitumor agent. C57BL/6 mice were subcutaneously inoculated with B16F10 mouse melanoma cells (5x105 cells/animal). Each sample was administered intravenously with 2.5 mg/kg DOX. EGCG solution (EGCG sol.) was also administered intravenously at 11.3 mg/kg, based on the amount of EGCG modification in DOX-loaded EGCG-PEG-modified liposomes (EPL). Caspase-3 was evaluated as 7-amino-4-trifluoromethyl coumarin (Ex: 400 nm, Em: 505 nm), following a reaction with the fluorescent substrate DEVD-AFC. Caspase-8 was determined reacted with DEVD-pNA and detected as chromophore p-nitroanilin (λ: 400nm).

[Results and Discussion] EPL significantly decreased tumor size against B16F10 mouse melanoma cells, in mice bearing 67LR-high-expression tumors. The tumor weight of the EPL group was significantly lower than that of the control (p&lt;0.01). Typical passive-targeting liposomes (PL) accumulated into the tumors due to improved blood circulation and an enhanced permeability and retention (EPR) effect, and decreased tumor weight. On the other hand, EPL disappeared from the blood immediately, compared with PL or PL + EGCG sol. DOX concentration of liver and spleen in EPL group did not increase, indicating that the rapid disappearance of EPL from the blood was not due to reticuloendothelial system (RES) trapping. Caspase-3 activity, which indicates apoptosis induction, was also elevated only in the EPL group, and the caspase-3 activity of the PL + EGCG sol. group was the same as that of the PL group. Hence, it was important that EGCG was included to modify the liposomes via PEG, as soluble EGCG did not accumulate at a high enough concentration to exert an apoptotic effect. Moreover, EPL significantly increased caspase-8 activity. It was suggested that EPL-induced apoptosis occurred due to caspase-8 activity induced following the binding of EGCG to 67LR as a cell-death ligand. In conclusion, it was suggested that EPL was a superior antitumor agent in high 67LR-expressing tumor cells as the liposomes had dual effects, namely antitumor effects due to the loaded DOX and apoptosis induced by the bound EGCG.

Citation Format: Ikumi Sugiyama, Yasuyuki Sadzuka. Antitumor effect against 67 kDa laminin receptor expressed on high-grade tumor cells [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 2678.