Abstract
BackgroundMicroRNAs are a class of small non-coding RNAs that are involved in many important physiological and pathological processes by regulating gene expression negatively. The purpose of this study was to investigate the effect of miR-32 on cell proliferation, migration and apoptosis and to determine the functional connection between miR-32 and FBXW7 in breast cancer.MethodsIn this study, quantitative RT-PCR was used to evaluate the expression levels of miR-32 in 27 breast cancer tissues, adjacent normal breast tissues and human breast cancer cell lines. The biological functions of miR-32 in MCF-7 breast cancer cells were determined by cell proliferation, apoptosis assays and wound-healing assays. In addition, the regulation of FBXW7 by miR-32 was assessed by qRT-PCR, Western blot and luciferase reporter assays.ResultsMiR-32 was frequently overexpressed in breast cancer tissue samples and cell lines as was demonstrated by qRT-PCR. Moreover, the up-regulation of miR-32 suppressed apoptosis and promoted proliferation and migration, whereas down-regulation of miR-32 showed an opposite effect. Dual-luciferase reporter assays showed that miR-32 binds to the 3′-untranslated region of FBXW7, suggesting that FBXW7 is a direct target of miR-32. Western blot analysis showed that over-expression of miR-32 reduced FBXW7 protein level. Furthermore, an inverse correlation was found between the expressions of miR-32 and FBXW7 mRNA levels in breast cancer tissues. Knockdown of FBXW7 promoted proliferation and motility and suppressed apoptosis in MCF-7 cells.ConclusionsTaken together, the present study suggests that miR-32 promotes proliferation and motility and suppresses apoptosis of breast cancer cells through targeting FBXW7.
Highlights
MicroRNAs are a class of small non-coding RNAs that are involved in many important physiological and pathological processes by regulating gene expression negatively
Expression of miR‐32 is greatly increased in breast cancer tissues and cell lines In order to evaluate the potential involvement of miR32 in breast cancer, the expression level of miR-32 was detected in 27 breast cancer tissues and corresponding adjacent non-tumor tissues by real-time PCR
We found an inverse correlation between the expression of miR-32 and the level of F-box and WD-40 domain protein 7 (FBXW7) mRNA (Fig. 1b, r = −0.431, P = 0.0248)
Summary
MicroRNAs are a class of small non-coding RNAs that are involved in many important physiological and pathological processes by regulating gene expression negatively. Molecular biology studies on breast cancer have shown that it is a complex process with multi-gene and MicroRNAs (miRNAs) are a class of evolutionarily conserved, endogenous, small, about 20–22 nt nucleotides in length, non-coding single-stranded RNAs that regulate gene expression by targeting the 3′ untranslated region (3′-UTR) of mRNAs [6, 7]. A growing number of studies have indicated that miRNA expression is associated with various tumors, including breast cancer [8,9,10]. MiR-32 has been identified as an important regulator in tumorigenesis and it may act as a tumor suppressor or an oncogene in different cancers [12,13,14].
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