Abstract

Objective: Increasing evidence suggests that microRNA (miRNA) participates in regulating tumor cell apoptosis. We aimed to observe the effect of hsa-miR-33-5p on the apoptosis of breast cancer cells and to explore its regulatory relationship with selenoprotein T (SelT).Methods: RT-qPCR was used to examine the expression of hsa-miR-33-5p and SelT both in breast cancer tissues and cells. MCF-7 and MDA-MB-231 cells were transfected with hsa-miR-33-5p mimics or si-SelT. Then, a flow cytometry assay was carried out to examine the apoptosis of cells. Furthermore, SelT and apoptosis-related proteins including caspase-3, caspase-8, caspase-9, Bax, and Bcl-2 were detected via RT-qPCR and western blot. A luciferase reporter assay was utilized for assessing whether SelT was targeted by hsa-miR-33-5p.Results: Downregulated hsa-miR-33-5p was found both in breast cancer tissues and cells. After its overexpression, MCF-7 cell apoptosis was significantly promoted. Furthermore, our data showed that miR-33-5p elevated apoptosis-related protein expression in MCF-7 cells. Contrary to hsa-miR-33-5p, SelT was upregulated both in breast cancer tissues and cells. SelT expression was significantly inhibited by hsa-miR-33-5p overexpression. The luciferase reporter assay confirmed that SelT was a direct target of hsa-miR-33-5p. SelT overexpression could ameliorate the increase in apoptosis induced by hsa-miR-33-5p mimics.Conclusion: Our findings revealed that hsa-miR-33-5p, as a potential therapeutic target, could accelerate breast cancer cell apoptosis.

Highlights

  • Breast cancer is a commonly diagnosed malignancy worldwide [1]

  • We found that H2O2 significantly elevated hsamiR-33-5p expression in MCF-7 cells (Figure 1C; p < 0.0001). hsa-miR-33-5p expression was significantly higher in MCF-7 cells following transfection by hsa-miR-33-5p overexpression than H2O2 treatment (Figure 1C; p < 0.05)

  • We further investigated whether selenoprotein T (SelT) could promote the apoptosis of breast cancer cells

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Summary

Introduction

Despite considerable progress in early detection and diagnosis, breast cancer patients’ prognosis has been only slightly improved [2, 3]. There is ample evidence that aberrantly expressed miRNAs could be associated with breast cancer progression [13,14,15]. MiRNAs have become promising markers for breast cancer due to the fact that they can be detected in tumor biopsies or body fluids [16]. Dysregulated miRNAs have been recognized as early indicators and pathogenic factors of breast cancer [7, 17, 18]. MiRNA expression can predict the prognosis and progression of breast cancer [19,20,21]. A deeper understanding of miRNAs may provide opportunities for novel treatment strategies for breast cancer

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