Nutlin3 enhances JQ1-triggered apoptosis in osteosarcoma cancer cells

Objective To explore whether Nutlin3 and JQ1 have a synergistic anti-osteosarcoma effect in osteosarcoma cells. Methods Osteosarcoma cells were treated with 1.0 μmol/L Nutlin3 alone, 0.5 μmol/L JQ1 alone or their combination. By counting kit-8 (CCK-8) assay, synergistic effect analysis, flow cytometry and Western blotting, synergistic anti-osteosarcoma effects of Nutlin3 and JQ1 and their molecular mechanisms were studied. Results The results of CCK-8 assay showed that both Nutlin3 and JQ1 could inhibit osteosarcoma cell activity in SJSA-1 cell line with half maximal inhibitory concentration (IC50) values of 3.7 μmol/L and 1.0 μmol/L, respectively. The effect was significantly improved with the IC50 value being reduced to 0.12 μmol/L. A combined effect index study showed a CI of 0.18 in SJSA-1 osteosarcoma cells harboring wild-type p53, and a CI of 0.94 in Saos-2 osteosarcoma cells that were deficient in p53, indicating that the two anticancer agents had a high degree of synergic effects, and that the synergic effects of the two novel anticancer agents depended on the activity of p53. Apoptosis detected by flow cytometry showed that 1 μmol/L of Nutlin3 and 0.5 μmol/L of JQ1 induced apoptosis in 15% and 37% of cells, respectively. The combination of them could induce apoptosis in 80% of cells, which was significantly higher than that of Nutlin3 and JQ1 used alone (P=0.001), indicating that the combination of the two drugs could induce apoptosis of a large number of osteosarcoma cells. Western blotting results showed that combination of Nutlin3 and JQ1 could stimulate the high activation of cysteinyl aspartate-specific protease (Caspase)-3, resulting in the majority of PARP cleavage and promoting the activation of apoptosis signals; meanwhile, the combination of Nutlin3 and JQ1 could also promote the expression of p53. Conclusion The novel anticancer agents Nutlin3 and JQ1 have a significantly synergistic anti-osteosarcoma effect, and this synergistic effect is p53 dependent. Key words: Osteosarcoma; Nutlin3; JQ1; p53; Apoptosis