Inhibition of RUNX1 promotes cisplatin-induced apoptosis in ovarian cancer cells

Runt-related transcription factor 1 (RUNX1), one subunit of core-binding factors in hematopoiesis and leukemia, was highly expressed in ovarian cancer (OC), but the role of RUNX1 in OC is largely unknown. Since we found that high expression of RUNX1 is correlated with poor survival in patients with OC through bioinformatic analysis of TCGA database, we developed RUNX1-knockout clones by CRISPR/Cas9 technique and discovered that RUNX1 depletion could promote cisplatin-induced apoptosis in OC cells, which was further confirmed by RUNX1 knockdown and overexpression. We also proved that RUNX1 could elevate the expression of BCL2. We then examined a total of 32 candidate miRNAs that might mediate the regulation between RUNX1 and BCL2, of which three miRNAs from the miR-17 similar to 92 cluster were found to be negatively regulated by RUNX1. Consistently, our analysis of data from TCGA database revealed the negative correlation between RUNX1 and the cluster. We further confirmed that miR-17 similar to 92 cluster could enhance cisplatin-induced apoptosis by directly targeting BCL2 3'UTR. Since rescue experiments proved that RUNX1 could repress cisplatin-induced apoptosis by up-regulating BCL2 via miR-17 similar to 92 cluster, combining RUNX1 inhibitor Ro5-3335 and cisplatin showed synergic effect in triggering OC cell apoptosis. Collectively, these findings show for the first time that combinational treatment of cisplatin and RUNX1 inhibitor could be used to potentiate apoptosis of ovarian cancer cells, and reveal the potential of targeting RUNX1 in ovarian cancer chemotherapy.