Abstract
Background: Mammary carcinogenesis, being ranked second in cancer-related mortality and the inadequacy of existing chemotherapy advocates the development of a novel treatment approach targeting its molecular signalling. Hyperactivation of mammalian target of rapamycin (mTOR) has a critical role in developing invasive mammary cancer and it can be a potential target.
Objective: This experiment was to explore the efficacy of mTOR-specific siRNA on therapeutic targeting of the mTOR gene, assess its proficiency in suppressing in vitro breast cancer and determine underlying molecular mechanisms.
Methods: Specific siRNA targeting mTOR was transfected into MDA-MB-231 cells and mTOR downregulation was validated through qRT-PCR and western blot analysis. Cell proliferation was analysed by MTT assay and confocal microscopy. Apoptosis was studied through flow cytometry and S6K, GSK-3β and caspase 3 expression were estimated. Further, the effect of mTOR blockade on cell cycle progression was determined.
Results: Following transfection of mTOR-siRNA into the MDA-MB-231 cells, cell viability and apoptosis were examined which indicates that clinically relevant concentration of mTOR-siRNA inhibited cell growth and proliferation and promote apoptosis, resulting from the suppression of mTOR. This leads to the downregulation of mTOR downstream S6K and upregulation of GSK-3β. An increased level of caspase 3 symbolises that the apoptotic activity is mediated through caspasedependent pathway. Further, mTOR downregulation causes cell cycle arrest in G0/G1 phase as observed in the flow cytometry study.
Conclusion: With these results, we can conclude that mTOR-siRNA exerts direct ‘anti-breast cancer’ activity propagated by the S6K-GSK-3β- caspase 3 mediated apoptosis and by inducing cell cycle arrest.
Graphical Abstract
[http://dx.doi.org/10.3322/caac.21583] [PMID: 31577379]
[http://dx.doi.org/10.1021/acs.molpharmaceut.1c00132] [PMID: 34134485]
[http://dx.doi.org/10.3322/caac.21590] [PMID: 31912902]
[http://dx.doi.org/10.1200/GO.20.00122] [PMID: 32673076]
[http://dx.doi.org/10.4103/0973-1482.154000] [PMID: 27072229]
[http://dx.doi.org/10.1016/j.jconrel.2016.04.015] [PMID: 27090165]
[http://dx.doi.org/10.1016/j.colsurfb.2016.02.046] [PMID: 26938323]
[http://dx.doi.org/10.1016/S0140-6736(98)03301-7] [PMID: 9752815]
[http://dx.doi.org/10.1038/nrc1362] [PMID: 15122205]
[http://dx.doi.org/10.1158/1078-0432.CCR-050008] [PMID: 15448035]
[http://dx.doi.org/10.1097/01.cco.0000143964.74936.d1] [PMID: 15627018]
[http://dx.doi.org/10.1016/j.cub.2004.06.054] [PMID: 15268862]
[http://dx.doi.org/10.1126/science.1106148] [PMID: 15718470]
[http://dx.doi.org/10.2174/1566523220999200731002408] [PMID: 32807051]
[http://dx.doi.org/10.1517/14728222.2012.677439] [PMID: 22494490]
[http://dx.doi.org/10.1016/j.yexcr.2006.05.001] [PMID: 16765945]
[http://dx.doi.org/10.1177/1010428317710825] [PMID: 28639903]
[http://dx.doi.org/10.1186/s13578-020-00396-1] [PMID: 32175074]
[http://dx.doi.org/10.1001/jamaoncol.2019.2525] [PMID: 31465107]
[http://dx.doi.org/10.1038/nature10912] [PMID: 22367541]
[http://dx.doi.org/10.1016/j.mam.2019.10.006] [PMID: 31676107]
[http://dx.doi.org/10.18632/oncotarget.7043] [PMID: 26824988]
[http://dx.doi.org/10.1172/JCI41680] [PMID: 20530877]
[http://dx.doi.org/10.1007/s10549-010-0986-9] [PMID: 20945086]
[http://dx.doi.org/10.1080/15384047.2014.1002693] [PMID: 25692408]
[http://dx.doi.org/10.1038/nrd2062] [PMID: 16883305]
[http://dx.doi.org/10.3390/ijms13021886] [PMID: 22408430]
[http://dx.doi.org/10.3892/or.12.4.701] [PMID: 15375488]
[PMID: 10969801]
[http://dx.doi.org/10.7150/jca.18457] [PMID: 29158785]
[http://dx.doi.org/10.1023/A:1023366117157] [PMID: 12779083]
[http://dx.doi.org/10.3233/BD-2010-0307] [PMID: 21778573]
[http://dx.doi.org/10.4103/pm.pm_223_20]
[http://dx.doi.org/10.1039/D0RA05793B] [PMID: 35518142]
[http://dx.doi.org/10.1016/j.drudis.2019.09.001] [PMID: 31520748]
[http://dx.doi.org/10.1038/s41598-017-14159-5] [PMID: 28127051]
[PMID: 26753650]
[PMID: 23071863]
[http://dx.doi.org/10.1016/j.breast.2011.09.008] [PMID: 21963359]
[http://dx.doi.org/10.7497/j.issn.2095-3941.2015.0089] [PMID: 26779371]
[http://dx.doi.org/10.4149/BLL_2020_049] [PMID: 32356448]
[http://dx.doi.org/10.1038/s41416-022-02011-1] [PMID: 36261586]
[http://dx.doi.org/10.1371/journal.pone.0092099] [PMID: 24637915]
[http://dx.doi.org/10.1038/s41419-019-1855-z] [PMID: 31406104]
[http://dx.doi.org/10.1038/418038a] [PMID: 12097900]
[http://dx.doi.org/10.1128/MMBR.67.4.657-685.2003] [PMID: 14665679]
[http://dx.doi.org/10.2147/IJN.S121141] [PMID: 27920526]
[http://dx.doi.org/10.1016/j.cell.2009.01.035] [PMID: 19239886]
[http://dx.doi.org/10.1109/TNB.2016.2621730] [PMID: 28092499]
[http://dx.doi.org/10.1016/j.ymthe.2021.01.015] [PMID: 33472033]
[http://dx.doi.org/10.1080/17425255.2022.2039118] [PMID: 35129006]
[http://dx.doi.org/10.1038/mtna.2013.45] [PMID: 24022053]
[http://dx.doi.org/10.1016/j.biopha.2018.05.114] [PMID: 29843042]
[http://dx.doi.org/10.1111/1440-1681.12608] [PMID: 27297262]
[http://dx.doi.org/10.1016/j.jep.2020.113758] [PMID: 33359860]
[http://dx.doi.org/10.1186/s12929-016-0257-0] [PMID: 27084510]
[http://dx.doi.org/10.1017/S1751731116000380] [PMID: 26956906]
[http://dx.doi.org/10.1016/j.ejphar.2021.174337] [PMID: 34265292]
[http://dx.doi.org/10.1155/2020/1215395] [PMID: 33082906]
[http://dx.doi.org/10.1038/srep26277] [PMID: 27195613]
[PMID: 28560197]
[http://dx.doi.org/10.1245/s10434-009-0555-9] [PMID: 19517193]
[http://dx.doi.org/10.1007/s11095-018-2460-z] [PMID: 30105526]
[http://dx.doi.org/10.1007/s10585-013-9607-4] [PMID: 23975155]
[http://dx.doi.org/10.1016/j.molonc.2007.02.004] [PMID: 18516279]
[http://dx.doi.org/10.3816/CBC.2003.n.018] [PMID: 12864941]
[http://dx.doi.org/10.1016/j.semcancer.2019.08.005] [PMID: 31408722]
[http://dx.doi.org/10.3390/ijms22020817] [PMID: 33467535]
[http://dx.doi.org/10.1038/sj.emboj.7600193] [PMID: 15071500]
[http://dx.doi.org/10.1093/emboj/20.16.4370] [PMID: 11500364]
[http://dx.doi.org/10.1126/science.1130276] [PMID: 17053147]
[http://dx.doi.org/10.1073/pnas.171301998] [PMID: 11493700]
[http://dx.doi.org/10.1038/emboj.2010.166] [PMID: 20657550]
[http://dx.doi.org/10.1016/j.bbamcr.2019.118635] [PMID: 31884070]
[http://dx.doi.org/10.1002/pros.23836] [PMID: 31104320]
[http://dx.doi.org/10.1038/cdd.2011.30] [PMID: 21455218]
[http://dx.doi.org/10.1038/bjc.1972.33] [PMID: 4561027]
[http://dx.doi.org/10.1038/s41598-018-29308-7] [PMID: 30050147]
[http://dx.doi.org/10.3390/ijms22010173] [PMID: 33375317]
[http://dx.doi.org/10.1038/sj.onc.1206044] [PMID: 12483536]
[http://dx.doi.org/10.1186/1756-9966-30-87] [PMID: 21943236]
[http://dx.doi.org/10.3322/canjclin.55.3.178] [PMID: 15890640]
[http://dx.doi.org/10.1177/1947601910392989] [PMID: 21779436]