| Background Since 1980's, domestic scholars have found all-trans retinoic acid (ATRA) and arsenic trioxide (As2o3) could induce differentiation and apoptosis of promyelocytes in acute promyelocytic leukemia(APL)successively. It improves complete remission (CR) rate of APL. But relapse and drug resistance often happened in the patients only receiving ATRA as maintained therapy after getting CR. So it is necessary to make clear the mechanism of drug resistance and study on how to reverse drug resistance, and then to exploit a novel inducer. Tanshinone IIA ( Tan II A) is an extractive of Salvia miltiorrhiza Bge which is one kind of traditional Chinese medicine. It has been reported that Tan IIA could induce differentiation and apoptosis of mature/ATRA resistant human APL cell line, MR-2. But the mechanism was unknown.Objective To study the differentiation and apoptosis of mature/ATRA resistant human APL cell line MR-2 induced by Tan II A and explore the potential mechanism of it.Methods Human acute myeloid leukemia cell line NB4 treated with 0.5 u g/ml Tan IIA was regarded as positive control. Growth status, morphology and nitroblue tetrazolium (NBT) reduction were observed after MR-2 cells were treated with 1.On g/ml TanIIA for 4 days. Cell-surface antigens (CD33,CDnb) , cell cycle and oncoprotein (P53 . c-Fos. Bcl-2. c-Myc) were also analysed by flow cytometry (FCM).Results The growth of MR-2 and NB4 cells was inhibited after Tan IIA3treatment, the inhibition rate were 73.5% and 67.7% respectively (P.01, P.01) which had no significant difference. After Tan II A treatment, MR-2 and NB4 cells were induced morphological differentiation, which exhibited small cell bulk and decreased nucleus/cytoplasm proportion, rough chromatin, disappeared nucleolus and azurophil granules, and anomalous nucleus. MR-2 cells could be induced to metamyelocyte while NB4 could be induced to granulocyte rod. NET reduction of MR-2 and NB4 treated with Tan II A showed that positive cells account for 95.3% ?.76% and 93. 2% ?.04% respectively, which had no significant difference; but the positive rate of either group of the treated positive cells was significant higher than that of those untreated, which were 3. 5% ?.32% and 2.8% ?.29% respectively (PO.01). FCM showed that the expression rate of CD33 was reduced and that of CDnbwas increased. The quantity of treated cells in Go/G| phase increased and that in S phase decreased. The proliferous index (PI) was also decreased. But Tan II A had no effect on GiM and apoptosis cells. After treated with Tan II A, the expressions of anti-oncogene p53 and c-fos were up-regulated while those of oncogene bcl-2 and c-myc were down-regulatedConclusion 1 . 1 .0 u g/ml Tan II A could inhibit proliferation of MR-2 cells and induce differentiation of MR-2 cells into mature granulocyte, the effectivity was as same as 0.5 n g/ml Tan II A treated NB4 cells.2. Tan II A could make MR-2 cells Go/Gi arrest, reduce S phase cells and DNA synthesis and then inhibit proliferation and induce differentiation, which were probably through regulating genes involved in cell proliferation and differentiation.3 . That the concentration of Tan II A needed to induce MR-2 differentiation was higher than that of NB4 (1. On g/ml vs 0.5 u g/ml) probably implied MR-2 cell differentiation was dependent on the concentration of Tan II A.4. That Tan IIA could induce drug resistant cell line MR-2 differentiation probably implied Tan IIA could reverse drug resistance through some mechanism.5. Tan IIA probably can be applied to treat the patients with APL, particularly to the relapsed and drug resistant patients, which implied broad prospect. |
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