Proteome Analysis of Apoptotic MR2 Cells, Acute Promyelocytic Leukemia Cell Line with All-Trans Retinoic Acid Resistance, Induced by Arsenic Trioxide

Although all-trans retinoic acid(ATRA) provides complete remission in 90% patients with untreated acute promyelocytic leukemia(APL), it becomes ineffective to quite a few APL patients who have received ATRA before when their disease relapsed and used ATRA again. Arsenic trioxide(ATO) can make APL patients with ATRA-resistance obtain complete remission again by inducing APL cells apoptosis. However, the molecular mechanisms of apoptosis in ATRA-resistance APL cells induced by ATO remain unclear. For this reason, we take the apoptotic MR2 cells (APL cell line with ATRA-resistance) induced by ATO as a model, to screen and identify the proteins related with ATO-induced apoptosis by comparative proteomics. After MR2 cells were dyed with annexin V and PI staining, the percentage of the apoptotic MR2 cells induced by 1.0μmol/L ATO for 0h, 6h, 12h, 24h and 48h respectively was detected by Flow cytometry. The results showed that the majority of the apoptotic cells were in the earlier and later stage of apoptosis respectively, when MR2 cells were treated with ATO for 24 and 48 hours in sequence. The total proteins of MR2 cells of the control group, the earlier stages apoptosis group and the later stages apoptosis group were separated by two-dimensional electrophoresis(2-DE) respectively. Then, the differences in proteome profile among three groups were analyzed by ImageMaster^™ 2D Platinum software. 14 protein pots were selected to be identified by Matrix-assisted laser desorption/ionization time of flight-mass spectrometry(MALDI-TOF-MS), in which the quantity of the protein differentially expressed was more than two times(≥2 or ≤0.5) among MR2-0h, MR2-24h and MR2-48h cells’ 2-DE map. However, only 11 proteins were successfully identified and their definite information was obtained. Among them, there were 8 proteins that were all probably involved in the mechanisms of apoptosis in MR2 cells and they were Calreticulin(CRT), Heat shock 70 kDa protein(HSP70), High mobility group protein B1(HMGB1), Ran-specific GTPase-activating protein(RanGAP1), Elongation factor 1-beta(EF-1β), Beta-tubulin, Cofilin-1, and Prolyl 4-hydroxylase(P4H) respectively. CRT was probably related with the early stage of apoptosis in MR2 cells, while RanGAP1 and HSP70 might related with the late stage of apoptosis in MR2 cells. Moreover, so far there was no related report on the roles of CRT, HMGB1, RanGAP1, cofilin-1 and beta-tubulin in the mechanisms of APL cells apoptosis. These differential proteins identified provide the new clues for further researching the molecular mechanisms of apoptosis in the ATRA-resistance APL cells induced by ATO.