Recognizing and stabilizing miR-21 by chiral ruthenium(II) complexes

Comparative studies on in vitro antitumor activities and apoptosis-inducing effects of enantiomeric ruthenium(II) complexes

On the basis of our previous comparative studies on the DNA binding of a pair of ruthenium(II) complex enantiomers, Δ-[Ru(bpy)2PBIP]2+ and Λ-[Ru(bpy)2PBIP]2+ {bpy = 2,2'-bipyridine, PBIP = 2-(4-bromophenyl)imidazo[4,5-f]1,10-phenanthroline}, in this study, their antitumor activities and mechanisms were further investigated comparatively. The cytotoxicity assay demonstrated that both the enantiomers exerted selective antiproliferative effects on cancer cell lines A2780 and PC3. Fluorescence localization experiments suggested that both the enantiomers effectively permeated the nucleus of HeLa cells and co-localized with DNA, resulting in their DNA damage and apoptosis. Flow cytometry experiments showed that the apoptosis was enhanced by increasing the concentration of each enantiomer. Western blotting analyses indicated that both extrinsic and intrinsic apoptosis pathways were activated by the two enantiomers. miRNA microarray analyses displayed that both the enantiomers up- and downregulated multiple miRNAs, some of which were predicted to be associated with carcinogenesis. The above experimental results also showed that the Δ-enantiomer exerted a more potent antitumor activity, a higher efficiency of entering cancer cells and a stronger apoptosis-inducing effect compared with the Λ-enantiomer. Combined with the previously published research results, experimental results from this study implied that the antitumor activity of a metal complex might have originated from the conformation change of DNA in tumor cells caused by the intercalation of the complex, that the antitumor mechanism of a metal complex could be related to its DNA-binding mode, and that the antitumor efficiency of a metal complex could result from its DNA-binding strength.

miR-21 inhibition reverses doxorubicin-resistance and inhibits PC3 human prostate cancer cells proliferation

Many approaches have been examined to reversing multidrug resistance (MDR), but sub-optimal target-based strategies have limited their efficacy. Herein, we investigate microRNA (miR-21) suppression on the doxorubicin (DOX)-sensitisation of the DOX-resistant (PC3/DOX) cell line in prostate cancer (PCa). Expression levels of miR-21, P-glycoprotein (P-gp), MDR-1 and PTEN evaluated in PC3/DOX cancer cells by qRT-PCR and western blot analyses. The cytotoxic effects of transfected of miR-21 were assessed by MTT assay for 72 hr. Rhodamine123 (Rh123) assay was employed to define the activity of P-gp. Apoptosis was detected by Flow cytometry. As expected, miR-21 was expressed highly in PC3/DOX cells (p < 0.05). It was shown that miRNA-21 suppression considerably hindered PC3/DOX cell viability. miR-21 suppression dramatically downregulated P-gp expression and activity in DOX-resistance cells and abolished MDR by an increment of intracellular accumulation of DOX in PC3/DOX cells (p < 0.05). PTEN is a key modulator of the PI3K/Akt/P-gp cascade, which miR-21 suppression led to the upregulation of PTEN and sequentially lower-expression of P-gp that reversed MDR. Also, miR-21 repression enhanced the apoptosis rate of PC3/DOX cells. The findings of this paper contribute to the current understanding of the functions of miR-21 in MDR-reversing in PCa.