Down-regulation of cellular FLICE-inhibitory protein (Long Form) contributes to apoptosis induced by Hsp90 inhibition in human lung cancer cells

Cancer Cell International

Xiangguo Liu³  Ling Su⁴  Tianliang Li⁴  Xuexi Hao¹  Wendong Sun¹  Qilin Wang² 

[1] The Second Hospital, Shandong University, Jinan, China;Liaocheng University School of Life Sciences, Liaocheng, China;Shandong University School of Life Sciences, Room103, South Building, 27 Shandananlu Road, Jinan, 250100, China;Key Laboratory for Experimental Teratology of the Ministry of Education and School of Life Sciences, Shandong University, Jinan, China

关键词: Hsp90;    CHIP;    Apoptosis;    c-FLIP_L;   

Others  :  794565
DOI  :  10.1186/1475-2867-12-54

 received in 2012-11-26, accepted in 2012-12-20,  发布年份 2012

【 摘 要 】

Background

Cellular FLICE-Inhibitory Protein (long form, c-FLIP_L) is a critical negative regulator of death receptor-mediated apoptosis. Overexpression of c-FLIP_L has been reported in many cancer cell lines and is associated with chemoresistance. In contrast, down-regulation of c-FLIP may drive cancer cells into cellular apoptosis. This study aims to demonstrate that inhibition of the heat shock protein 90 (Hsp90) either by inhibitors geldanamycin/17-N-Allylamino-17-demethoxygeldanamycin (GA/17-AAG) or siRNA technique in human lung cancer cells induces c-FLIP_L degradation and cellular apoptosis through C-terminus of Hsp70-interacting protein (CHIP)-mediated mechanisms.

Methods

Calu-1 and H157 cell lines (including H157-c-FLIP_L overexpressing c-FLIP_L and control cell H157-lacZ) were treated with 17-AAG and the cell lysates were prepared to detect the given proteins by Western Blot and the cell survival was assayed by SRB assay. CHIP and Hsp90 α/β proteins were knocked down by siRNA technique. CHIP and c-FLIP_L plasmids were transfected into cells and immunoprecipitation experiments were performed to testify the interactions between c-FLIP_L, CHIP and Hsp90.

Results

c-FLIP_L down-regulation induced by 17-AAG can be reversed with the proteasome inhibitor MG132, which suggested that c-FLIP_L degradation is mediated by a ubiquitin-proteasome system. Inhibition of Hsp90α/β reduced c-FLIP_L level, whereas knocking down CHIP expression with siRNA technique inhibited c-FLIP_L degradation. Furthermore, c-FLIP_L and CHIP were co-precipitated in the IP complexes. In addition, overexpression of c-FLIP_L can rescue cancer cells from apoptosis. When 17-AAG was combined with an anti-cancer agent celecoxib(CCB), c-FLIP_L level declined further and there was a higher degree of caspase activation.

Conclusion

We have elucidated c-FLIP_L degradation contributes to apoptosis induced by Hsp90 inhibition, suggesting c-FLIP and Hsp90 may be the promising combined targets in human lung cancer treatment.

【 授权许可】

   
2012 Wang et al.; licensee BioMed Central Ltd.

【 图 表 】

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