Inhibiting Inducible MiR-223 Enhances Anti-proliferative Effects Of Celastrol On Human Cancer Cell Lines MCF-7 And PC3

Purpose:Celastrol is a novel anti-tumor agent. Further understanding the mechanisms and enhancement of this effect of celastrol has attracted much research attention.Methods:The expression level of mi R-223 and protein in MCF-7 and PC3 cells were determined by q RT-PCR and Western blot.The proliferation of cancer cells were detected by flow cytometry assay.Results: Here we report the interaction between mi R-223, m TOR activation and HSP70 elevation in celastrol-treated cancer cells and the effects of these events on celastrol’s anti-proliferation. We found that after 6 h celastrol treatment human breast cancer cell line MCF-7 and prostate cancer cell line PC3 showed elevated mi R-223. Down-regulating or over-expressing mi R-223 could enhance or reduce celastrol’s anti-proliferation effects, respectively. In addition, celastrol could cause early activation and later inhibition of m TOR, as well as raise HSP70(preceded by HSF-1 activation). Interestingly, these three events, i.e., m TOR activation, HSF-1-related HSP70 elevation and mi R-223 induction showed mutually dependent relations, each action promoting the other two. Moreover, inhibiting m TOR or down-regulating HSP70 could reduce cell proliferation in both celastrol-treated and untreated cells, indicating m TOR activation and HSP70 elevation are also important to cell proliferation.Conclusions: For the first time, we disclose that in presence of toxic celastrol, cells used at least three inter-promoting anti-toxic weapons in struggling to survive and proliferate, and that down-regulating mi R-223 or inhibiting m TOR, in addition to blocking heat shock response, are novel ways to enhance celastrol’s anti-cancer effects.