Doxorubicin is an anthracycline antibiotic that acts as a DNA intercalating agent, inhibiting the topoisomerase II and inducing the apoptotic cell death, mainly due to the accumulation of double-strand DNA breaks (DSB). This research aims to identify in what way the abnormalities in microRNA (miRNA) expression profile in cancer cells can confer them the resistance to doxorubicin.
MiRNA targets within gene transcripts were predicted in silico using the TargetScan software.
Binding sites for miRNAs miR-21, miR-96, miR-183 and miR-365, which are usually upregulated in cancer cells, were revealed in transcript of TOP2A gene encoding topoisomerase II-alpha. Transcripts of proapoptotic genes BID, BCL2L11 (BIM), BMF, BAX, BAK1, PMAIP1 (NOXA), and BBC3 (PUMA) as well as transcripts of tumor suppressor genes TP53 and PTEN carry targets for at least one of hyperexpressed miRNAs miR-19, miR-21, miR-23, miR-27, miR-29, miR-155, miR-181, miR-221/222 and miR-375. Downregulation of anti-onco-miRNAs let-7, miR-22, miR-34, miR-101, miR-125, miR-140, miR-143, miR-199, miR-200, miR-203, miR-204 and miR-205 allows overexpression of antiapoptotic genes BCL2, BCL2L1 (Bcl-XL), MCL1 and AKT1. In the same way, downregulation of the anti-onco-miRNAs can lead to overexpression of ABCA1/4/12, ABCB1 (MDR1), ABCB6, ABCC1 (MRP1) and ABCC3/5/8/11 genes encoding the ATP binding cassette (ABC) transporters. Moreover, multiple targets for the both up- and downregulated miRNAs were found in transcripts of XRCC5/6, PRKDC, LIG4, DCLRE1C, NHEJ1 (XLF), RAD50/51/51B/51D/52/54B/54L, MRE11A, NBN (NBS1), GEN1, ATM and ATR genes encoding the key elements of non-homologous end joining and homologous recombination pathways.
Obviously, in case of doxorubicin administration, strategy of early tumors consists in strengthening of miR-21 expression with the purpose to silence TOP2A gene and escape from immediate apoptotic death. Advanced tumors with more profound abnormalities in miRNA signature overexpress antiapoptotic genes as well as genes responsible for DSB repair and drug efflux and, therefore, can do without the TOP2A silencing.
Palladin Institute of Biochemistry of the National Academy of Sciences of Ukraine.
Has not received any funding.
All authors have declared no conflicts of interest.