Autophagy enhanced antitumor effect in K562 and K562/ADM cells using realgar transforming solution.

Realgar transforming solution (RTS) can be produced from a biotransformation process by using microorganisms cultured with realgar in our lab. RTS has been demonstrated as a novel arsenic anti-leukemia agent in K562 and K562/ADM. However, its underlying mechanism is unclear. In this study, we showed that RTS could strongly induce apoptosis in K562 and K562/ADM cells. After the cells were treated by RTS, apoptotic population were increased compared to control and clearly distinguishable by DAPI nuclei staining. With increasing the dose of RTS, more cells arrested in S phase and G2/M phase. Secondly, we also showed that RTS could induce autophagy via up-regulation of LC3, p62/SQSTM1 and inhibition of mTOR in a much lower arsenic dosage in contrast to ATO and realgar. In addition, autophagy induced by RTS partially due to the degradation of fusion oncoprotein Bcr-Abl, which is associated with multidrug resistant in (MDR)-CML. Our results also showed that the apoptotic rate decreased when autophagic flux was attenuated by CQ via inhibiting cleaved-caspase-3 and alleviating Bcl-2 level. These suggested that RTS triggered autophagy is a pro-death process in CML and MDR-CML cells. In conclusion, our findings demonstrated that RTS could serve as a promising arsenic candidate for anti-CML/MDR-CML by inducing apoptosis and autophagy and is more potent than ATO and realgar.