| It's well known that patients with MDS, especially with high-risk MDS, have poor prognosis, which may be related to decreased sensibility of MDS malignant clone to drugs. The aim of current therapy of MDS is to reduce, or even erase the malignant clone, reconstruct normal hematopoiesis partly or completely, and induce the abnormal cells differentiation into normal hematopoietic cells. In order to investigate the responses of MDS cells to drugs, a cell line MUTZ-1, derived from a patient with MDS-RAEB. has been introduced to our series, which has no response to traditional differentiation-inducing drugs. It's reported that aclacinomycin ( ACM ), the second-generation anthracyclines targeting at topoisomerase II, can be used to treat some MDS patients and acquire some response. Compared with other anti-tumor drugs, ACM doesn't tend to cause drug resistance in experimental study in vitro, but the mechanisms remain unknown. The aim of this paper is to investigate the effect of ACM on MUTZ-1 cell line derived from MDS-RAEB and its new mechanism, try to prove that ACM can induce MUTZ-1 cells afoptosis and (or) differentiation and maturation, so as to reduce the malignant clone of MDS, and try to clarify another new molecular mechanism of ACM on MDS cells. Thereby itwould help to find a new treatment target and develop new strategy to overcome the drug resistance of MDS cells to chemotherapeutic agents.Using MTT assay we investigated the effect of ACM on MUTZ-1 growth. The result showed that following treatment with ACM(0.05 μmol/L) for 48 h, the proliferation of MUTZ-1 cells was inhibited significantly, in comparison with the blank control group(P<0.05). IC50 was 0.46μ mol/L at 48h. To explore the possible mechanism of the inhibition of ACM on MUTZ-1 cells, further investigation was carried out from the two stratifications of inducing apoptosis and differentiation.Using Wright-Giemsa stain, the morphology of MUTZ-1 cells was observed with or without ACM treatment under a light microscope. The result displayed that a series of typical morphological features of apoptosis were observed following treatment with ACM(0.5μmol/L) for 48h, such as vacuolization of cell plasma, shrinkage of cell and nucleus, condensation of nuclear chromatin, marginated against the nuclear membranes, karyorrhexis and convolution ofnuclear, and membrane-bound apoptotic bodies(Figi.2).In order to exactly analyze the cell apoptosis quantitatively and qualitatively, in addition tosome classic and specific and sensitive methods, the flow cytometry was also used to evaluate the DNA content, percentage of hypodiploid and translocation of phosphatidyl serine( PS). It showed that following treatment with 0.25umol/L-0.5nmol/L ACM for 48h, a typical DNA ladder was observed. With TdT mediated-dUTP nick end labeling (TUNEL), it appeared that with the increasing concentration of ACM at a certain time-point, the TUNEL positive cells increased. Meanwhile, with the increasing treatment time at a certain concentration of ACM, the TUNEL positive cells increased. From biochemistry, it was proved that ACM could induce MUTZ-1 cells apoptosis with dose- and time- dependent manners in vitro.With the help of flow cytometry, the DNA content and hypodiploid changes of MUTZ-1 cells were observed with or without ACM treatment. The results showed that" the percentage of MUTZ-1 cells in the G2/M phase of the cell cycle increased, while in the G1/G0 phase decreasedfollowing treatment with 0.1μ mol/L 0.2μmoI/L ACM, indicating that MUTZ-1 cells were arrested in the Ga/M phase. At the same time, hypodiploid cells increased, and the sub-G| peak appeared (Fig1-7). This manifested that ACM at a certain concentration could arrest MUTZ-1 cells in the G2/M phase of cell cycle, and then induced the cells apoptosis. With the help of flow cytometry following annexinV-PI staining, exposure to 0.5nmol/L ACM for 36 h caused 21.83% early apoptotic cells, which was more than that of the untreated group (3.47%), while late apoptovic cells increased only sligh...
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