Design, synthesis and biological evaluation of ezrin inhibitors targeting metastatic osteosarcoma.

Respiratory failure due to pulmonary metastasis is the major cause of death for patients with osteosarcoma. However, the molecular basis for metastasis of osteosarcoma is poorly understood. Recently, ezrin, a member of the ERM family of proteins, has been associated with osteosarcoma metastasis to the lungs. The small molecule NSC 668394 was identified to bind to ezrin, inhibit in vitro and in vivo cell migration, invasion, and metastatic colony survival. Reported herein are the design and synthesis of analogues of NSC 668394, and subsequent functional ezrin inhibition studies. The binding affinity was characterized by surface plasmon resonance technique. Cell migration and invasion activity was determined by electrical cell impedance methodology. Optimization of a series of heterocyclic-dione analogues led to the discovery of compounds 21k and 21m as potential novel antimetastatic agents.

Antiproliferative and apoptotic effects of two new Pd(II) methylsarcosinedithiocarbamate derivatives on human acute myeloid leukemia cells in vitro.

[Pd(MSDT)Cl]n palladium, chloro[methyl N-(dithiocarboxy-kS,kS')-N-methylglycinate], and [Pd(MSDT) Br]n palladium, bromo[methyl N-(dithiocarboxy-kS,kS')-N-methylglycinate], palladium (Pd)(II) derivatives are two newly synthesized Pd(II) derivatives of methylsarcosinedithiocarbamate (MSDT), containing a sulfur chelating ligand that is able to strongly bind the metal center, so preventing interactions with sulfur-containing enzymes. In fact, these reactions are believed to be responsible for the nephrotoxicity induced by platinum (II)-based drugs. Their activity has been evaluated in a panel of acute myeloid leukemia (AML) cell lines representing different French-American-British (FAB) subtypes and in the Philadelphia (Ph)-positive cell line K-562 and compared to cisplatin. Both compounds suppressed, in a dose-dependent manner, colony formation in methylcellulose with ID50 values comparable to those of the reference drug cisplatin, excluding the ML-3 cell line (ID50 10-fold lower than cisplatin). Exposure of HL-60, ML-3, NB-4, and THP-1 cell lines to a cytotoxic concentration of [Pd(MSDT)Br]n (5 microM) determined: downregulation of the antiapoptotic molecule Bcl-2, upregulation of the proapoptotic molecule Bax; apoptosis induction, as evaluated by APO2.7 and annexin V staining; mitochondrial membrane permeabilization; and DNA fragmentation. In ML-3 cells the Pd(II) complexes were more active than cisplatin in apoptosis induction. Finally, [Pd(MSDT)Br]n showed an inhibitory effect on clonogenic growth of hematopoietic progenitors (CFU-GM, CFU-GEMM, and BFU-E) with both ID50 and ID90 comparable to those of cisplatin. Remarkably, the Pd(II) complex was more potent in inhibiting the clonogenic growth of the less differentiated AML cell lines KG-1a, HL-60, NB-4, ML-3, and THP-1 (ID50 ranging from 0.02 +/- 0.001 to 0.52 +/- 0.04 microM), compared to normal hematopoietic progenitors (ID50 of 2.1 +/- 0.1, 3.8 +/- 0.4, and 2.5 +/- 0.2 microM) for CFU-GEMM, BFU-E, and CFU-GM, respectively). These data suggest that leukemic cells of myelomonoblast lineage might represent a preferential target for its cytotoxic activity compared to normal committed hemopoietic progenitor cells. Altogether, our results indicate that these new Pd(II) dithiocarbamate derivatives might represent novel potentially active drugs for the management of some selected myeloid leukemia strains, able to conjugate cytostatic and apoptotic activity with reduced toxicity.

Syntheses of alpha-dystroglycan derived glycosyl amino acids carrying a novel mannosyl serine/threonine linkage.

Alpha-dystroglycan (alpha-DG) is a membrane-associated, extracellular glycoprotein. It is anchored to the cell-membrane by binding to the transmembrane glycoprotein beta-dystroglycan (beta-DG) to form an alpha/beta-DG-complex. It was discovered that the bovine peripheral nerve alpha-DG possesses the Ser/Thr linked tetrasaccharide as the major constituent of the O-linked carbohydrates, which was proposed to contribute laminin binding activity of this glycoprotein. This structure has a striking feature in terms of the mode of linkage between oligosaccharide and the core protein. It has a mannose residue linked to the core protein through Ser/Thr residue. A similar structure was proposed to exist in brain derived HNK-1 immunoreactive O-glycans. Being interested in the structural novelty and potential biological significance of this type of glycan chains, the chemical synthesis of Ser/Thr linked mannose containing tetrasaccharide was investigated. Tetrasaccharide donor was constructed from monosaccharide blocks and coupled with Ser/Thr derivatives. Subsequent deprotection afforded target tetraosyl serine. Furthermore, synthetic routes to lower homologues, namely Gal-beta-(1,4)-GlcNAc-beta-(1,2)-Man-alpha-Ser and GlcNAc-beta-(1,2)-Man-alpha-Ser were also provided.