Dissection of Mechanisms of Realgar Intervening Telomere Protein POT1, TRF1, TRF2 Expression to Regulate Telomere Dynamics in THP-1 Cells

Objective: To observe the mechanisms of realgar intervening telomere protein POT1, TRF1, TRF2 expression to regulate telomere dynamics in THP-1 cells, and elucidate the experimental and theoretical basis for realgar targeted threapy of AML.

Methods: 1.In vitro: (1)Cultured human acute myeloid leukemia THP-1 cells. (2), The cells were incubated in absence or presence of increasing concentration of realgar for 24/48 h, from which determined the IC50. Cell viability was tested by CCK-8 assay. (3)Apoptotic rate and cell cycle distribution were tested by FCM. (4)Each group of POT1, TRF1, TRF2 protein levels were tested by western-blot analysis. (5)Each group of POT1,TRF1,TRF2 mRNA levels were tested by RT-qPCR analysis. 2.In vivo: (1)Established THP-1 model in NOD/SCID mice, and the mouse were treated by realgar. (2)All the mouse were killed by institutionally approved method after 3 weeks. The apoptotic rate and cell cycle distribution of mice spleen cells were examined by FCM. (3)The changes of POT1, TRF1, TRF2 protein levels in organic tissue were detected by IHC.

Results: 1.In vitro: (1)CCK-8 assay showed that after treated by realgar, THP-1 cells growth were inhibited and the cell viability decreased in a dose- and time- dependent manner, IC50 was 0.023μg/mL. Therefore, we choose a medium concentration was 0.015μg/mL (lower than IC50) at 48h. (2)Our study demonstrated that after treatment for 48h, the apoptotic rate and the G1 arrest of these THP-1 cell increased, compared with control group. (3)As shown by western blot analysis, compared with controls, realgar group POT1, TRF1 protein levels significantly increaesed and TRF2 decreased(P<0.01). (4) As shown by by RT-qPCR analysis, POT1, TRF1, TRF2 mRNA levels were consistent with their protein levels. 2.In vivo: (1) The THP-1/NOD-SCID model was established, and survival curve showed that compared with controls, realgar group mouse had longer life span(P<0.01). (2) The results of FCM showed that after treatment of realgar, the rate of THP-1 cell apoptosis and G1 arrest significantly increased(P<0.01). (3) The results of IHC showed that compared with controls, POT1, TRF1 protein levels significantly increased and TRF2 decreased in realgar group mouse(P<0.01).

Conclusion: In vitro and in vivo studies results indicated that realgar could significantly prolong the life span of the THP-1/NOD-SCID mice, inhibit proliferation and induce apoptosis of THP-1 cell, and regulate telomere dynamics through intervening THP-1 cell telomere protein POT1, TRF1, TRF2 expression. Our studies results provided experimental and theoretical basis for realgar targeted threapy of AML.