Abstract.To explore the mechanism of apoptosis induced by cisplatin, the expression of microRNAs (miRNAs) and regulating genes in K562 cells was analyzed using reverse transcription PCR, quantitative real-time PCR and enzymelinked immunosorbent assays. Our results showed that miR-16, miR-34a-c, miR-17-5p and miR-125 were upregulated, and their associated oncogenes (BCL2, E2F1 and E2F3, respectively) were down-regulated after cisplatin treatment. We also showed that miR-106 and miR-150 were down-regulated while their target genes (RB1 and P53, respectively) were up-regulated after cisplatin treatment. Moreover, miR-16, miR-34a-c and miR-17-5p proved to be upstream factors, regulating the expression of BCL2, E2F1 and E2F3, respectively. The oncogene E2F3 was downregulated when RB1 expression was increased after treatment with antisense oligonucleotides (ASO). Similarly, BCL2 and E2F3 were down-regulated when P53 expression was elevated by ASO treatment. The study demonstrated that cisplatin induces K562 cells to apoptosis by reducing miR-106 which up-regulates RB1 or by inhibiting miR-150 which increases P53 expression.
IntroductionCisplatin [cis-diamminedichloroplatinum (II), CDDP] has been used in numerous studies to induce the apoptosis of carcinoma cells. Cells, growth-arrested by cisplatin treatment, showed a higher spontaneous cell death rate than that of untreated proliferating cells. Cisplatin is an effective chemotherapeutic agent that elicits its antineoplastic activity by binding to DNA and disrupting template functions (1). Studies have shown that cisplatin strongly inhibits the decatenation activity of topoisomerase II (2), which is critical for relieving the torsional stress that occurs during replication and transcription and for daughter strand separation during mitosis. Cisplatin can also regulate the expression of oncogenes or tumor suppressor genes to induce tumor cell apoptosis. Likewise, these genes can predict the cisplatin sensitivity of cancer cell lines. Cisplatin was found to induce p53-dependent Fas-associated death domain-like interleukin-1ß-converting enzyme (FLICE)-like inhibitory protein (FLIP) degradation in chemosensitive ovarian cancer cells. A recent study demonstrated that cisplatin induces the PIDD (p53-induced protein with a death domain)-dependent activation of caspase-2. In turn, caspase-2 cleaves and activates Bid, resulting in the oligomerization of Bak and the release of cytochrome c, resulting in a synergistic induction of cisplatininduced cytotoxicity (3). Farnebo et al found that single nucleotide polymorphisms in the DNA repair genes XRCC3241 and XPD751 influence the intrinsic cisplatin sensitivity and that XRCC3241, XPD751, EGFR, Hsp70, Bax and Bcl-2 predict the cisplatin sensitivity of head and neck cancer cell lines (4).A family of 20-to 22-nucleotide (nt) noncoding RNAs termed microRNAs (miRNAs) has been identified in eukaryotic organisms ranging from nematodes to humans (5-7). After maturation, these small RNAs are incorporated into the RNA-induced silencing comp...