Effect Of 27-Hydroxycholesterol-Activated LXR Signaling Pathway On Proliferation/Apoptosis Of Lung Cancer Cells And Its Mechanism

Aim: To investigate the impact of cholesterol metabolite 27-hydroxycholesterol(27-OHC) on lung cancer cell proliferation/apoptosis,and further explore its mechanism.Methods:Based on the literature review and preliminary experiments.Human lung adenocarcinoma cell line A549 and human large cell lung cancer cell H460 were treated with 0-10 ?M 27-OHC for 24-48 hours,the cell viability was then assessed using the Cell Counting Kit CCK-8,under the condition of 0-5 ?M 27-OHC treatment,the cell cycle and apoptosis of A549 cells were detected with flow cytometry,and the apoptosis was detected with TUNEL assay.The proliferation of A549 cells were detected with EdU proliferation assay.The total cholesterol level of A549 cells was detected by tissue total cholesterol test kit.ATP-binding cassette transporter A1(ABCA1),3-hydroxy-3-methylglutaryl-CoA reductase(HMG-CR)and low density lipoprotein receptor(LDLR)gene/protein expression in A549 cells were detected with real-time PCR and Western blotting.A549 cellswere treated again with 5 ?M liver X receptor(LXRs)pathway inhibitor GSK2033,the cell viability was then assessed using CCK-8.RESULTS: We demonstrated that 27-OHC decreased the A549 cell viability in a dose-dependent manner(P < 0.01)and inhibited the cell proliferation(P<0.05).The expression of typical LXRs downstream target proteins/gene including ABCA1,HMG-CR and LDLR were modulated,which promoted the efflux of intracellular cholesterol,reduced cholesterol de novo synthesis and influx,resulting in the decreased intracellular cholesterol levels and the cell viability.Furthermore,the inhibition role of27-OHC on A549 cell viability was significantly attenuated after the LXRs pathway was partially blocked by 5 ?M GSK2033 treatment(P < 0.05).However,no significant effect of 27-OHC on apoptosis of A549 cells was observed by flow cytometry and TUNEL assay.CONCLUSION: 27-OHC inhibit A549 cell proliferation via activation of LXR pathway.