Abstract
BackgroundThe emergence of drug resistance in cancer patients limits the success rate of clinical chemotherapy. MicroRNAs (miRNAs) may play a role in chemoresistance and may be involved in modulating of some drug resistance-related pathways in cancer cells. In this study, the involvement of microRNA-148b (miR-148b) and its roles in the development of chemoresistance in lung cancer are determined.MethodsThis study was performed in two lung cancer cell lines (A549 and SPC-A1). The levels of miR-148b and DNMT1 mRNA expression were determined by using Quantitative Real-Time PCR. Proteins of DNMTs are represented by western blot assay. Cell viability was assessed by MTT assay. Cell apoptosis was evaluated using flow cytometry.ResultsThe data showed a down-regulated of miR-148b expression and evaluated methyltransferases (DNMTs) expression in cisplatin-resisted human non-small cell lung cancer (NSCLC) cell line-A549/DDP and SPC-A1/DDP compared with their parental A549 and SPC-A1 cell line. In transfection experiments, miR-148b mimics reduced the DNMT1 expression, as well as enhanced the sensitivity of cells to cisplatin and cisplatin-induced apoptosis in A549/DDP or SPC-A1/DDP cells. While miR-148b inhibitor increased DNMT1 expression, as well as attenuated the sensitivity of cells to cisplatin in A549 and SPC-A1 cells. miR-148b was showed to exert negative effect on DNMT1 expression by targeting its 3′UTR in A549/DDP and A549 cells. Importantly, silenced DNMT1 increases cisplatin sensitivity of A549/DDP cells and over-expressed DNMT1 reverses pro-apoptosis effect of miR-148b mimic.ConclusionsmiR-148b reverses cisplatin-resistance in non-small cell cancer cells via negatively regulating DNMT1 expression.
Highlights
The emergence of drug resistance in cancer patients limits the success rate of clinical chemotherapy
Differential expression of miR-148b and DNA methyltransferases (DNMTs) in both A549/DPP and SPC-A1/DPP cells compared with their parental cell lines We detected the expression levels of miR-148b and DNMTs protein in A549/DPP and SPC-A1/DPP as well as their parental cell lines using Q-RT-PCR and Western blot, respectively
The results showed that miR-148b had an average of 2-fold lower expression level in A549/DPP cells and an average of 2.5-fold lower expression level in SPC-A1/DPP cells than that in A549 cells and SPC-A1 cell, respectively (P < 0.05, Figure 2A)
Summary
The emergence of drug resistance in cancer patients limits the success rate of clinical chemotherapy. Chemotherapy is well known as the main method to treat lung cancer in earlier stages of treatment, especially as adjuvant chemotherapy microRNAs are small non-coding RNA molecules consisting of 20–24 nucleotides and function as the suppressor for gene expression by interacting with the 3′untranslated regions (3′UTRs) of target mRNAs at 5–7 nucleotides. These interactions may lead to either obstruction of translation or degradation of the targeted mRNAs [4]. Accumulated studies have shown that miRNAs may play a role in chemoresistance of cancer treatment and may be involved in the modulation of some drug resistance-related pathways in some cancer cells
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