The miR-21/PTEN/Akt signaling pathway is involved in the anti-tumoral effects of zoledronic acid in human breast cancer cell lines

Abstract

Preclinical data indicate a direct anti-tumor effect of zoledronic acid (ZA) outside the skeleton, but its molecular mechanism is still not completely clarified. The aim of this study was to investigate the anti-cancer effects of ZA in human breast cancer cell lines, suggesting that they may in part be mediated via the miR-21/PTEN/Akt signaling pathway. The effect of ZA on cell viability was measured by MTT assay, and cell death induction was analyzed using either a double AO/EtBr staining and M30 ELISA assay. A Proteome Profiler Human Apoptosis Array was executed to evaluate the molecular basis of ZA-induced apoptosis. Cell cycle analysis was executed by flow cytometry. The effect of ZA on miR-21 expression was quantified by qRT-PCR, and the amount of PTEN protein and its targets were analyzed by Western blot. ZA inhibited cell growth in a concentration- and time-dependent manner, through the activation of cell death pathways and arrest of cell cycle progression. ZA downregulated the expression of miR-21, resulting in dephosphorilation of Akt and Bad and in a significant increase of p21 and p27 proteins expression. These results were observed also in MDA-MB-231 cells, commonly used as an experimental model of bone metastasis of breast cancer. This study revealed, for the first time, an involvement of the miR-21/PTEN/Akt signaling pathway in the mechanism of ZA anti-cancer actions in breast cancer cells. We would like to underline that this pathway is present both in the hormone responsive BC cell line (MCF-7) as well as in a triple negative cell line (MDA-MB-231). Taken together these results reinforce the use of ZA in clinical practice, suggesting the role of miR-21 as a possible mediator of its therapeutic efficacy.

Carbon-Ion Beam Irradiation Alone or in Combination with Zoledronic acid Effectively Kills Osteosarcoma Cells

“…Interestingly, in this study, we found that treatment with ZOL effectively inhibited the Pi3K/Akt and MAPK signaling pathways, and significantly increased miR-29b expression in OSA cells. This is partially consistent with previous studies that ZOL suppresses Erk1/2 and PI3K/Akt pathway in cervical cancer [45] and upregulates PTEN via the downregulation of Akt in breast cancer [46]. Since PTEN is positively correlated with the upregulation of miR-29b in lung cancer and tongue squamous cancer [38,40], we speculate that ZOL-enhanced PTEN levels might subsequently result in the upregulation of miR-29b.…”

Pharmacology of bisphosphonates

“…In preclinical models zoledronate was shown to inhibit cell migration, invasion and metastasis and several clinical studies have shown a beneficial effect for adjuvant use of the drug in elderly postmenopausal women in addition to a role in preventing bone metastases (see also papers in this Themed Issue by Dionisio et al and Chukir et al). Zoledronate might exert its anti‐tumour effects through the miR‐21/PTEN/Akt signalling and Activin signalling pathways …”

Emerging Role of MicroRNAs in mTOR Signaling

“…In particular, miR-21 targets multiple genes in mTOR pathway, including PTEN, p85α and PDCD4. Besides promoting malignant growth, the miR-21/PTEN/PI3K/AKT/mTOR axis has been shown to influence anti-cancer effects of zoledronic acid [80] , triptolide [81] , Metformin [82] , Matrine [83] and curcumin [84] , and modulate radiosensitivity [85, 86] and chemosensitivity to tamoxifen, fulvestrant [87] , sorafenib [88] , cisplatin [89, 90] , imatinib [91] , gefitinib [92] , doxorubicin [93] , daunorubicin [94] , anti-EGFR tyrosine kinase inhibitors (TKI) [95] and the CHOP chemotherapy regimen [96] . miR-21 also influences PI3K/AKT/mTOR signaling via PIK3R1 that negatively regulates p110 subunit under certain circumstances.…”