Involvement of Bim in Photofrin-mediated photodynamically induced apoptosis

Background/aims: Photodynamic therapy (PDT) is a promising noninvasive technique, which has been successfully applied to the treatment of human cancers. Studies have shown that the Bcl-2 Family proteins play important roles in PDT-induced Apoptosis. However, whether Bcl-2-interacting mediator of cell death (Bim) is involved in photodynamic treatment remains unknown. In this study, we attempt to determine the effect of Bim on Photofrin photodynamic treatment (PPT)-induced Apoptosis in human lung adenocarcinoma ASTC-a-1 cells.

Methods: The translocation of Bim/Bax of the cells were monitored by laser confocal scanning microscope. The levels of Bim protein and activated Caspase-3 in cells were detected by western blot assay. Caspase-3 activities were measured by Caspase-3 Fluorogenic Substrate (Ac-DEVD-AFC) analysis. The induction of Apoptosis was detected by Hoechst 33258 and PI staining as well as flow cytometry analysis. The effect of Bim on PPT-induced Apoptosis was determined by RNAi.

Results: BimL translocated to mitochondria in response to PPT, similar to the downstream pro-apoptotic protein Bax activation. PPT increased the level of Bim and activated Caspase-3 in cells and that knockdown of Bim by RNAi significantly protected against Caspase-3 activity. PPT-induced Apoptosis were suppressed in cells transfected with shRNA-Bim.

Conclusion: We demonstrated the involvement of Bim in PPT-induced Apoptosis in human ASTC-a-1 lung adenocarcinoma cells and suggested that enhancing Bim activity might be a potential strategy for treating human cancers.