OBJECTIVE: To investigate retinoic acid-resistant acute promyelocytic leukemia (APL) cell differentiation induced by tanshinone IIA (Tan IIA) and its molecular mechanism. METHODS: NB4 cells treated with 0.5 mg/L Tan IIA was regarded as positive control. After in vitro incubation of MR-2 cells with Tan IIA at the concentration of 1.0 mg/L for 4 days, the cell differentiation was observed by growth status, cytomorphology, and nitroblue tetrazolium test. Cell cycle, membrane cluster differentiation (CD) antigens (CD(33), CD(11b)) and expression of some oncogene (c-myc, c-fos, p53 and bcl-2) were analysed by flow cytometry. RESULTS: The growth of MR-2 and NB4 cells was inhibited after Tan IIA treatment, the inhibition rate were 73.5% and 67.7% respectively (P < 0.01, P < 0.01) without significant difference. After Tan IIA treatment, MR-2 and NB4 cells were induced to undergo morphological differentiation, which exhibited small cell bulk decreased nucleus/cytoplasm proportion, rough chromatin, disappearance of nucleolus and formation of azurophil granules and anomalous nucleus. MR-2 cells could be induced to metamyelocyte while NB4 could be induced to band form. NBT reduction of MR-2 and NB4 cells treated with Tan IIA showed that positive cells accounted for (95.30 +/- 0.76)% and (93.20 +/- 1.04)% respectively; but the positive rate of either group of the treated positive cells was significantly higher than that of untreated, being (3.50 +/- 1.32)% and (2.80 +/- 0.29)% respectively (P < 0.01). Flow cytometry showed that the expression of CD(33) was reduced, while that of CD(11b) was increased. The quantity of treated cells in G(0)/G(1) phase increased but that in S phase decreased. The proliferous index was also decreased. After treated with Tan IIA, the expressions of anti-oncogene p53 and c-fos were up-regulated while those of oncogene bcl-2 and c-myc were down-regulated (P < 0.01). CONCLUSIONS: 1.0 mg/L Tan IIA could inhibit proliferation of MR-2 cells and induce differentiation of MR-2 cells into mature granulocyte, the effectivity was the same as 0.5 mg/L Tan IIA treated NB4 cells. Its possible molecular mechanism might be related to modulation of oncogene expressions associated proliferation and differentiation as well as inhibition of DNA synthesis. Tan IIA probably can be applied to treat the patients with APL, particularly to the relapsed and drug resistant patients with broad prospect.
OBJECTIVE: To investigate retinoic acid-resistant acute promyelocytic leukemia (APL) cell differentiation induced by tanshinone IIA (Tan IIA) and its molecular mechanism. METHODS: NB4 cells treated with 0.5 mg/L Tan IIA was regarded as positive control. After in vitro incubation of MR-2 cells with Tan IIA at the concentration of 1.0 mg/L for 4 days, the cell differentiation was observed by growth status, cytomorphology, and nitroblue tetrazolium test. Cell cycle, membrane cluster differentiation (CD) antigens (CD(33), CD(11b)) and expression of some oncogene (c-myc, c-fos, p53 and bcl-2) were analysed by flow cytometry. RESULTS: The growth of MR-2 and NB4 cells was inhibited after Tan IIA treatment, the inhibition rate were 73.5% and 67.7% respectively (P < 0.01, P < 0.01) without significant difference. After Tan IIA treatment, MR-2 and NB4 cells were induced to undergo morphological differentiation, which exhibited small cell bulk decreased nucleus/cytoplasm proportion, rough chromatin, disappearance of nucleolus and formation of azurophil granules and anomalous nucleus. MR-2 cells could be induced to metamyelocyte while NB4 could be induced to band form. NBT reduction of MR-2 and NB4 cells treated with Tan IIA showed that positive cells accounted for (95.30 +/- 0.76)% and (93.20 +/- 1.04)% respectively; but the positive rate of either group of the treated positive cells was significantly higher than that of untreated, being (3.50 +/- 1.32)% and (2.80 +/- 0.29)% respectively (P < 0.01). Flow cytometry showed that the expression of CD(33) was reduced, while that of CD(11b) was increased. The quantity of treated cells in G(0)/G(1) phase increased but that in S phase decreased. The proliferous index was also decreased. After treated with Tan IIA, the expressions of anti-oncogene p53 and c-fos were up-regulated while those of oncogene bcl-2 and c-myc were down-regulated (P < 0.01). CONCLUSIONS: 1.0 mg/L Tan IIA could inhibit proliferation of MR-2 cells and induce differentiation of MR-2 cells into mature granulocyte, the effectivity was the same as 0.5 mg/L Tan IIA treated NB4 cells. Its possible molecular mechanism might be related to modulation of oncogene expressions associated proliferation and differentiation as well as inhibition of DNA synthesis. Tan IIA probably can be applied to treat the patients with APL, particularly to the relapsed and drug resistant patients with broad prospect.