While upregulation of miRNA-34a in both these breast cancer cell lines increased the activity of caspase-3 via downregulation of stem cell-associated transcription factors, E2F1 and E2F3. MiRNA-34a mimic was determined to inhibit the proliferation and colony formation of SKOV3 and OVCA433 ovarian cancer cells and enhanced cisplatin sensitivity of cisplatin-resistant SKOV3 ovarian cells via direct suppressing of HDAC1 [44]. The gene discussed is HDAC1; the disease is ovarian cancer.