Summary. EB1089, a novel 1,25-dihydroxyvitamin D 3 analogue, has been known to have potent antiproliferative properties in a variety of malignant cells both in vitro and in vivo. In the present study, we analysed the effect of EB1089 on NCI-H929 human myeloma cells. EB1089 inhibited cell growth of NCI-H929 and efficiently induced the G 1 phase arrest of the cell cycle in a dose-dependent manner. We could also detect apoptosis in NCI-H929 cells exposed to EB1089 (1 Â 10 27 m for 72 h) using the sub-G 1 group of the cell cycle by FACS and annexin V binding assays. Induction of apoptosis by EB1089 was associated with down-regulation of the Bcl-2 protein without change of the Bax protein. Regarding caspase activity, which plays a crucial role in apoptosis, EB1089-treated NCI-H929 cells revealed an increased activity of caspase 3 protease accompanied by degradation of the PARP protein in a dose-and time-dependent manner. In addition, EB1089 caused the down-regulation of p44 extracellular signalrelated kinase (ERK) activity and up-regulation of the p38 kinase activity during apoptosis of NCI-H929 cells. These results suggest that EB1089 inhibits growth of NCI-H929 cells via G 1 cell cycle arrest as well as apoptosis by activating p38 kinase and suppressing ERK activity.

Abstract. This study investigated whether advanced glycation end products (AGE) and RAGE (receptor for AGE) are involved in the proliferation of leukemia cells. AGE strongly induced the proliferation of primary acute myeloid leukemia (AML) cells and cell lines. MAP kinase, PI3K and JAK/STAT pathways were involved in cellular proliferation of HEL cells by AGE. RAGE antisense S-ODN effectively inhibited cell growth, induced apoptosis and reversed AGE-induced expression of targeting molecules in HEL cells. The study demonstrated for the first time that AGE directly induced human AML cell proliferation via the MAPK, PI3K and JAK/STAT pathways.

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Summary. Monensin, a Na + ionophore, regulates many cellular functions, including apoptosis. We investigated the in vitro antiproliferative effect of monensin on nine human lymphoma cell lines. Monensin significantly inhibited the proliferation of all the lymphoma cell lines examined with a 50% inhibition concentration of about 0AE5 lmol/l, and induced a G 1 and/or a G 2 -M phase arrest in these cell lines. To address the antiproliferative mechanism of monensin, we examined the effect of this drug on cell-cycle-related proteins in CA46 cells (both G 1 and G 2 arrest) and Molt-4 cells (G 2 arrest). Treatment with monensin for 72 h decreased CDK4 and cyclin A levels in CA46 cells, and cdc2 levels in Molt-4 cells. In monensin-treated CA46 cells, increased p21-CDK2, p27-CDK2 and p27-CDK4 complex forms were observed. And, in monensin-treated Molt-4 cells, increased p21-cdc2 complex form was detected. Furthermore, the activities of CDK2-and CDK4-associated kinases were reduced in association with Rb hypophosphorylation in monensin-treated CA46 cells. The activity of cdc2-associated kinase was decreased in both cell lines, which was accompanied by induction of Wee1. Also, monensin induced apoptosis in these cell lines, as evidenced by annexin V binding assay and flow cytometric detection of sub-G 1 DNA content. This apoptotic process was associated with loss of mitochondria transmembrane potential (Dw m ). Taken together, these results demonstrated for the first time that monensin potently inhibits the proliferation of human lymphoma cell lines via cell cycle arrest and apoptosis.Keywords: lymphoma, monensin, cell cycle, apoptosis, CDKI.Monensin is classified as a typical carboxylic ionophore with a quasi-linear array of heterocyclic rings. When monensin is present in the plasma membrane, it readily forms the characteristic ring conformation, which plays a role in the exchange of Na + and H + (NA + /H + antiporter) (Pressman, 1976;Mollenhauer et al, 1990). At physiological intracellular pH (pH i ), this antiporter is electroneutral or electrically quiescent. When it becomes activated, an influx of Na + ions with a concomitant efflux of H + ions occurs, thereby resulting in a transient increase in the pH i (Nakazato & Hatano, 1991). Changes of pH i through the Na + /H + antiport participate in the regulation of many cellular functions such as cell proliferation and apoptosis (Grinstein et al, 1989;Rao et al, 1991;Bental & Deutsch, 1994;Zhu & Loh, 1995;Cobo et al, 1998). For example, monensin caused apoptosis as well as intracellular alkalinization in HL-60 cells (Zhu & Loh, 1995). However, the study on its role of pH i regulation in haematopoietic cells, including human lymphoma cells, has received little attention.The cell cycle in eukaryotes is regulated by cyclindependent kinases (CDKs). The cyclins, members of the cell cycle regulator family, bind to and activate CDKs. Sequential formation, activation and subsequent inactivation of cyclins and CDKs are critical for control of the cell cycle (Jeffrey et al, 1995;Morg...