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  • br E ects of doxorubicin and cisplatin br The


    3.5. Effects of doxorubicin and cisplatin
    The 3D survivin promoter assay was used to evaluate two antitumor agents (doxorubicin and cisplatin) for their potential anti-survivin
    Fig. 3. Fluorescence microcopy test to evaluate the effect of YM155 on EGFP expression in MCF-7-SP-EGFP and MCF-7-CMV-EGFP cells. A: Fluorescence images of
    cells at 0 h and 120 h of YM155 treatment (10 nM). (Green: EGFP, Blue: Dapi), scale bar: 20 μm. B: EGFP expression in Ruxolitinib (INCB018424) treated with YM155 as compared to the initial (0 h). Fluorescence intensities in the images were analyzed by using NIS element software (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article).
    effects. Both agents are widely applied for treating various cancers, including breast cancer, for their ability to induce DNA damage and apoptosis in tumor cells (Moraes et al., 2013; Thorn et al., 2011; Dasari et al., 2010). As can be seen in Fig. 6, doxorubicin at > 100 nM was highly toxic to MCF-7 cells and at 100 nM significantly down-regulated survivin promoter. This finding is consistent with a previous study showing that doxorubicin at 5 μM inhibited survivin mRNA and protein levels in MCF-7 cells by more than 80% after 72 h (Moraes et al., 2013). Similar results were also reported in the study of CDK4 inhibitor/dox-orubicin combination therapy for breast cancer treatment (Tarasewicz et al., 2014). It was thus clear that the down-regulation effect of dox-orubicin on survivin was at least partially attributed to the inhibition of its transcription.
    In contrast, cisplatin was not as toxic to MCF-7 cells, had a relatively high IC50 of 10 μM, and showed no effect on survivin down-regulation (Fig. 7). An earlier study showed that cisplatin might slightly increase survivin mRNA level in small cell lung cancer (SCLC) cells (Belyanskaya et al., 2005). Thus, the result from our survivin assay should be reliable, although further investigations may be warranted. 
    4. Discussion
    Due to its overexpression in a variety of cancer tissues and the key role in cancer progression, survivin is increasingly attracting attentions as a novel molecular target for developing emerging antitumor therapy (Altieri, 2008; Garg et al., 2016). A number of studies have proven that the down-regulation of survivin expression could reverse drug re-sistance and induce synergistic effects with antitumor agents. For ex-ample, the co-delivery of paclitaxel and anti-survivin siRNA resulted in lower viability and higher apoptotic rate of breast cancer cells as compared to mono-drug treatment (Chen et al., 2017). Various small-molecule survivin inhibitors were thus developed in recent years, with distinct mechanisms of action targeting: i) survivin gene transcription like YM155 and FL118 (Nakahara et al., 2007; Ling et al., 2012); ii) survivin phosphorylation like flavopiridol (Wall et al., 2003) and iii) interaction between survivin and Hsp90 like 5-aminoimidazole-4-car-boxamide-1-β-D-ribofuranoside (AICAR) (Xiao and Li, 2015). However, the number of existing survivin inhibitors is still small and their cor-responding antitumor efficacy in clinical trials appears to be limited
    Fig. 4. Cytotoxicity assay of YM155 in 40-MBR. A: Fluorescence kinetics of MCF-7-CMV-EGFP cells under different concentrations of YM155. Each data point was normalized by the initial fluorescence intensity (0 h). Drug was added at 48 h. B: Specific growth rates of MCF-7-CMV-EGFP cells at different con-centrations of YM155. Each data point represents the average from triplicate samples with the error bar indicating the standard deviation.
    (Wang et al., 2016; Xiao and Li, 2015). More drug discovery efforts for survivin-targeted cancer therapy are thus needed, which can be fa-cilitated by the development of a robust, high throughput, survivin-specific assay (Xiao and Li, 2015).