In the present study, we found that the miR-491 expression was significantly decreased in SP cells compared with non-SP cells, which was significantly reversed by ASA. ASA dramatically enhanced the inhibitory effect of Doxo on SP cell viability inside a concentration-dependent manner (P<0.05). Compared with non-SP cells, the miR-491 manifestation was significantly decreased in SP cells, which was significantly reversed by ASA (P<0.05). miR-491 directly controlled the ABCG2 manifestation. In the presence of Doxo, miR-491 inhibitor reduced the inhibitory effect of ASA within the cell viability of SP cells, which was significantly reversed by knockdown of ABCG2 (P<0.05). Summary: ASA enhanced the level of sensitivity of SP cells to Doxo via regulating the miR-491/ABCG2 signaling pathway. Keywords: Aspirin (ASA), hepatocellular carcinoma (HCC), part populace (SP), doxorubicin (Doxo), miR-491, ATP-binding cassette sub-family G member 2 (ABCG2) Intro Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related deaths in the world [1]. Chemotherapeutic providers (including doxorubicin [Doxo]) are widely used in the medical treatment of HCC [2]. However, drug resistance always results in the failure and thus limited use of chemotherapeutic medicines in treating HCC individuals [3]. Therefore, enhancing the drug level of sensitivity of HCC cells is beneficial for the medical treatment of individuals with HCC. Part populace (SP) cell is definitely a special type of tumor stem cell that is present in many solid tumor cells, including human main HCC [4C8]. In HCC cell lines, earlier studies have also reported the living of unique SP cells with malignancy stem/stem cell properties [9C11]. Compared with non-SP cells, the SP cells showed much stronger anti-apoptotic and proliferative activities [12]. Besides, it was found that the resistance of SP cells to chemotherapy medicines was significantly higher than that of non-SP cells [13,14]. A common cause of drug resistance is that a large number of tumor cells communicate the ATP-binding cassette (ABC) pump, which causes tumors to have little response to standard chemotherapy [15C18]. ATP-binding cassette sub-family G member 2 (ABCG2) is the main transport protein that mediates SP phenotype [19,20]. ABCG2 promotes drug resistance, and is a potential malignancy stem cell (CSC) marker in HCC. The manifestation of ABCG2 is definitely closely related to the event, proliferation, drug resistance, and metastasis of tumor. As reported, the up-regulation of ABCG2 enhanced the proliferation, Doxo resistance, migration, and invasion of HCC, which were lowered from the down-regulation of ABCG2 [21]. Hu et al. [22] analyzed the expression pattern of ABCG2 in HCC, and proved that the manifestation CPI-360 of ABCG2 endowed HCC cells, especially Cdc14A2 SP cells, with the efflux capacity, which was modulated by Akt signaling. It has been reported that aspirin (ASA), a cyclooxygenase inhibitor, advertised growth inhibition and apoptosis of HCC [23]. The ligation of ASA to cisplatin can lead to chemotherapy sensitization, thereby defeating resistance [24]. Recently, the scholars shown that ASA inhibited the acquisition of chemoresistance in breast malignancy by disrupting the NFkBCIL6 signaling pathway that was responsible for the generation of CSCs [25]. However, there have been few studies about the underlying mechanism CPI-360 of how ASA suppresses the drug resistance of HCC SP cells. MiRNAs, a well-known class of small non-coding RNAs, participate in several pathophysiological processes [26]. Multiple miRNAs are related to HCC, CPI-360 including miR-491. miR-491 was reported to be related with the CSC-like properties of HCC [27]. Its manifestation was much lower in poorly differentiated HCC cells compared with well-differentiated HCC cells, and miR-491 was negatively associated with CSC-like properties in both cell collection and cells samples of HCC [27]. Bioinformatics analysis (microRNA.org) has shown the binding site of miR-491 in ABCG2. Consequently, in the present study, we investigated whether ASA enhances the level of sensitivity of HCC SP cells to Doxo via up-regulating miR-491 and down-regulating target gene ABCG2, providing theoretical basis for the medical software of ASA. Materials and methods Isolation of non-SP and SP cells from your HCC cell collection MHCC-97L The isolation of non-SP and SP cells from MHCC-97L cell collection was carried out as previously reported [22]. Briefly, the adherent cells were dissolved by trypsin and suspended in DMEM medium comprising 2% FBS and 10 mM?N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid (1 106 cells/ml). The cells were then stained by 5 g/ml Hoechst 33342 (Invitrogen) at 37C for 1.5 h in the absence or presence of 10 M fumitremorgin C (FTC). Afterward, the cells were centrifuged at 4C and resuspended in ice-cold PBS with 2 g/ml propidium iodide (PI). Then circulation cytometry analysis and fluorescence-activated cell sorting were performed to isolate non-SP and SP cells. Colony formation assay To determine the colony-formation ability of MHCC-97L cells with drug treatment, the SP and non-SP cells were sorted in the presence of Doxo (500 ng/ml). The sorted cells were planted in 96-well microplates in triplicate (20 cells/well) and cultured in DMEM medium with 10%.