BMI-1 is highly expressed in M0-subtype acute myeloid leukemia.

Recent studies have suggested that one of the polycomb group genes, BMI-1, has an important role in the maintenance of normal and leukemic stem cells by repressing the INK4a/ARF locus. Here, we quantitatively examined BMI-1 expression level in samples from patients with acute myeloid leukemia (AML) and other hematologic malignancies. Moderate to high BMI-1 expression was detected in AML patients, and the BMI-1 expression levels in AML samples were significantly higher than in normal bone marrow controls (P = .0011). Specimens of French-American-British classification subtype M0 showed higher relative expression of the BMI-1 transcript (median, 390.2 3 10(-3)) than the other subtypes (median, 139.0 3 10(-3)) (P < .0001). Leukemia other than AML showed low to moderate expression. INK4a-ARF transcript expression tended to be inverse proportion to that of BMI-1. In an M0 patient with a high BMI-1 transcript level, the INK4a-ARF transcript level fell promptly and maintained a low value after the patient achieved complete remission. These results indicated that a subgroup of M0 patients has a high expression level of polycomb group gene BMI-1, which may contribute to leukemogenesis.

Modulation of mdr1a and CYP3A gene expression in the intestine and liver as possible cause of changes in the cyclosporin A disposition kinetics by dexamethasone.

We investigated the effect of dexamethasone (DEX) on the disposition kinetics of cyclosporin A (CyA) and the mechanism of this drug interaction. Rats were treated with DEX (1 or 75mg/kg per day, i.p.) once a day for 1-7 days, and the blood concentration of CyA was measured after an i.v. or p.o. dose of CyA (10mg/kg) at 1.5hr after the last DEX treatment. In rats treated with a low dose of DEX (1mg/kg), the blood concentration of CyA after i.v. administration was unchanged compared with that of untreated rats, whereas the blood concentration after oral administration was significantly decreased, and this decrease was dependent on the duration of DEX administration. The total clearance (CL(tot)) of CyA was unchanged, but the bioavailability was significantly decreased to about one-third of that in DEX-untreated rats after 7 days of DEX treatment. At this time, the expression of mdr1a mRNA and P-gp in the liver and intestine was increased, whereas CYP3A2 was unaffected at both the mRNA and protein levels. In rats treated with a high dose of DEX (75mg/kg), the blood concentration of CyA was significantly decreased after both i.v. and p.o. administrations compared with those of untreated rats. The bioavailability of CyA was decreased, and the CL(tot) was significantly increased. The P-gp and CYP3A2 in the liver and intestine were increased at both the mRNA and protein levels. Our results indicate that the drug interaction between CyA and DEX is a consequence of modulation of P-gp and CYP3A2 gene expression by DEX, with differential dose-dependence.

Involvement of multidrug resistance-associated protein 2 in in vivo cisplatin resistance of rat hepatoma AH66 cells.

We previously showed that the rat ascites hepatoma cell line AH66 is cisplatin resistant in vivo, but not in vitro. We further found that the expression of multidrug resistance-associated protein 2 (MRP2) in AH66 cells harvested from tumor-bearing rats was markedly decreased after incubation for 48 hours in medium containing 5% fetal bovine serum (5% FBS DMEM), and that the expression recovered when the cells were re-inoculated into rats. To examine whether the in vivo cisplatin resistance of AH66 cells is related to modulation or the expression of MRP2, we used AH66 cells transfected with pBK-CMV expression vector containing MRP2 antisense DNA. The expression of MRP2 alone among the MRP transporter family was markedly decreased in the transfected cells. The uptake of cisplatin into these cells was significantly higher than that in AH66 parent cells or control vector-transfected AH66 cells. The uptake of cisplatin in AH66 parent cells and the vector control cells was increased by treatment with sodium azide or probenecid whereas the uptake in the MRP2 antisense transfectant cells was not affected. When AH66 parent cells and control transfectant cells were cultured with cisplatin in medium containing 5% ascites fluid (5% ASF DMEM) for 48 hours, the cisplatin sensitivity significantly decreased. In contrast, the cisplatin sensitivity of MRP2 antisense transfectant cells did not change after culture in 5% ASF DMEM. These results show that the cisplatin resistance of AH66 cells is dependent upon the enhanced expression of MRP2.

Costunolide induces differentiation of human leukemia HL-60 cells.

Costunolide has been reported to be a cytotoxic and chemopreventive agent. This work investigated the mechanism of the antiproliferative effect of costunolide and determined that it induced differentiation of the human leukemia cell line HL-60. Costunolide exhibited a potent antiproliferative activity against HL-60 cells. It was also found to be a potent inducer of differentiation in human leukemia derived HL-60 cells through the examination of differentiation markers, as assessed by the reduction of nitroblue-tetrazolium, the increase in esterase activities and phagocytic activity, morphology change and the expression of CD14 and CD66b surface antigens. These results, accompanied by a decline in the expression of c-myc protein, suggest that costunolide induces differentiation of human leukemia cells to granulocytes and monocytes/macrophages lineage.