miR-1271 enhances the sensitivity of colorectal cancer cells to cisplatin

Abstract

The high mortality of colorectal cancer (CRC) is likely caused by early invasion and metastasis. The chemoresistance of tumor cells is the critical reason for treatment failure. The present study aimed to develop targeted solutions to overcome chemotherapy drug resistance in CRC. CCK-8 assay was used to examine SW480 cell viability. SW480 cell apoptosis was examined using flow cytometry. The present study demonstrated that the expression of miR-1271 was significantly decreased in CRC tumors and cell lines compared with control tissues. Furthermore, the expression of microRNA (miR)-1271 was increased and decreased following the transfection of miR-1271 mimics and an inhibitor, respectively. Furthermore, miR-1271 regulated mammalian target of rapamycin (mTOR) expression by directly binding to the mTOR 3'-untranslated region and the relative luciferase activity of mTOR was decreased following miR-1271 overexpression. The results of the present study indicate that miR-1271 may be a potential target for anti-CRC therapy, particularly in the sensitivity of chemotherapeutic drugs. miR-1271 may therefore enhance the sensitivity of CRC cells to chemotherapy drugs and provide a novel approach for the gene therapy of CRC.

Keywords: colorectal cancer; mechanistic target of rapamycin; microRNA; microRNA-1271.

Figure 1.

miR-1271 expression in CRC tissues. Reverse transcription-quantitative polymerase chain reaction confirmed that miR-1271 was downregulated in CRC tissues compared with adjacent normal tissues (control). **P<0.01 vs. Control. miR, microRNA; CRC, colorectal cancer.

Figure 2.

miR-1271 expression in CRC cell line. (A) SW480 cells were transfected with miR-1271 mimics or a miR-NC inhibitor. No significance was observed between the NC and control group. Compared with NC group, the expression of miR-1271 was significantly upregulated. **P<0.01 vs. miR-NC mimics. (B) Following transfection with a miR-1271 inhibitor, the expression of miR-1271 was significantly decreased compared with the miR-NC inhibitor. **P<0.01 vs. miR-NC inhibitor. miR, microRNA; CRC, colorectal cancer; NC, negative control.

Figure 3.

miR-1271 upregulation inhibits SW480 cell viability. Cell proliferation was examined was assessed in the cisplatin, cisplatin+mimics, cisplatin+inhibitor and the control group via a cell counting kit-8 assay. **P<0.01 vs. Cisplatin group. miR, microRNA.

Figure 4.

miR-1271 upregulation promotes SW480 cell apoptosis. (A) SW480 cell apoptosis was assessed in the cisplatin, cisplatin+mimics, cisplatin+inhibitor and the control group via flow cytometric analysis. (B) Quantitative analysis of A. **P<0.01 vs. Cisplatin group. miR, microRNA; PI, propidium iodide; FITC, fluorescein isothiocyanate.

Figure 5.

mTOR is a direct a target of miR-1271. (A) mTOR 3′-UTR contains two putative miR-1271 binding sites. A luciferase assay was performed to measure relative luciferase activity of mTOR following treatment with (B) miR-1271 mimics and (C) a miR-1271 inhibitor. **P<0.01 vs. miR-NC mimics or miR-NC inhibitor. mTOR, mammalian target of rapamycin; UTR, untranslated region; miR, microRNA; WT, wild-type; NC, negative control.

Figure 6.

mTOR is upregulated in CRC tissues. (A) Reverse transcription-quantitative polymerase chain reaction, (B) western blotting and (C) densitometry were performed to confirm that mTOR was overexpressed in CRC tissues. **P<0.01 vs. Control. mTOR, mammalian target of rapamycin; CRC, colorectal cancer.

Figure 7.

miR-1271 regulates Bax, Bcl-2, caspase-3 and mTOR expression. Reverse transcription-quantitative polymerase chain reaction was performed to detect the transfection efficiency of control, cisplatin, cisplatin+mimics and cisplatin+inhibitor in SW480 cells. (A) Bax, (B) Bcl-2, (C) caspase-3 and (D) mTOR expression. (E) Western blotting and (F) densitometry were performed to assess the protein levels of Bax, Bcl-2, caspase-3 and mTOR. *P<0.05 vs. Cisplatin group; **P<0.01 vs. Cisplatin group. miR, microRNA; Bax, Bcl-2-associated X; Bcl-2, B cell lymphoma-2; mTOR, mammalian target of rapamycin.