Research on different compound combinations of Realgar-Indigo naturalis formula to reverse acute promyelocytic leukemia arsenic resistance by regulating autophagy through mTOR pathway

Ethnopharmacological relevance: In China, the Chinese patent drug Realgar-Indigo naturalis Formula (RIF) is utilized for the therapy of acute promyelocytic leukemia (APL). Comprising four traditional Chinese herb-Realgar, Indigo naturalis, Salvia miltiorrhiza, and Pseudostellaria heterophylla-it notably includes tetra-arsenic tetra-sulfide, indirubin, tanshinone IIa, and total saponins of Radix Pseudostellariae as its primary active components. Due to its arsenic content, RIF distinctly contributes to the therapy for APL. However, the challenge of arsenic resistance in APL patients complicates the clinical use of arsenic agents. Interestingly, RIF demonstrates a high remission rate in APL patients, suggesting that its efficacy is not significantly compromised by arsenic resistance. Yet, the current state of research on RIF's ability to reverse arsenic resistance remains unclear.

Aim of the study: To investigate the mechanism of different combinations of the compound of RIF in reversing arsenic resistance in APL.

Materials and methods: The present study utilized the arsenic-resistant HL60-PML^A216V-RARα cell line to investigate the effects of various RIF compounds, namely tetra-arsenic tetra-sulfide (A), indirubin (I), tanshinone IIa (T), and total saponins of Radix Pseudostellariae (S). The assessment of cell viability, observation of cell morphology, and evaluation of cell Apoptosis were performed. Furthermore, the mitochondrial membrane potential, changes in the levels of PML^A216V-RARα, apoptosis-related factors, and the PI3K/Akt/mTOR pathway were examined, along with Autophagy in all experimental groups. Meanwhile, we observed the changes about Autophagy after blocking the PI3K or mTOR pathway.

Results: Tanshinone IIa, indirubin and total saponins of Radix Pseudostellariae could enhance the effect of tetra-arsenic tetra-sulfide down-regulating PML^A216V-RARα, and the mechanism was suggested to be related to inhibiting mTOR pathway to activate Autophagy.

Conclusions: We illustrated that the synergistic effect of different compound combinations of RIF can regulate Autophagy through the mTOR pathway, enhance cell Apoptosis, and degrade arsenic-resistant PML^A216V-RARα.

Acute promyelocytic leukemia; Realgar-Indigo naturalis formula; arsenic resistance; autophagy; mTOR.