Effects of the combined arginase and canavanine treatment on leukemic cells in vitro and in vivo.

It was previously demonstrated in in vitro experiments that canavanine (Cav), a natural toxic arginine analogue of plant origin, is a promising candidate for augmenting the antineoplastic effects of arginine starvation. We demonstrated herein that recombinant human arginase, an arginine degrading enzyme, abrogated growth and significantly increased Cav cytotoxicity toward cultured L1210 murine leukemic cells. Cav co-treatment further reduced cells viability in a time-dependent manner and significantly promoted apoptosis induction. In the pilot study we also evaluated for the first time the potential toxicity of the combined arginine deprivation and Cav treatment in healthy mice. Administration of Cav alone or in combination with pegylated cobalt-containing human arginase (Co-hARG) did not evoke any apparent toxic effects in these animals, with no significant behavioural and survival changes after several weeks of the treatment. The therapeutic effects of the combination of Co-hARG and Cav were provisionally evaluated on the highly aggressive murine L1210 leukemia, which is semi-sensitive to arginine deprivation as a monotreatment. Combination of two drugs did not result in significant prolongation of the survival of leukemia-bearing mice. Thus, we have shown that the proposed combinational treatment is rather non-toxic for the animals. It has to be further evaluated in animal studies with alternative tumor models and/or drug doses and treatment modalities.

Multiple molecular forms of adaptor protein Ruk/CIN85 specifically associate with different subcellular compartments in human breast adenocarcinoma MCF-7 cells.

Ruk/CIN85 is a receptor-proximal 'signalling' adaptor that possesses three SH3 domains, Pro- and Ser-rich regions and C-terminal coiled-coil domain. It employs distinct domains and motifs to act as a transducer platform in intracellular signaling. Based on cDNA analysis, various isoforms of Ruk/CIN85 with different combination of protein-protein interaction domains as well as additional Ruk/CIN85 forms that are the products of post-translational modifications have been demonstrated. Nevertheless, there is no precise information regarding both the subcellular distribution and the role of Ruk/CIN85 multiple molecular forms in cellular responses. Using MCF-7 human breast adenocarcinoma cells and cell fractionation technique, specific association of Ruk/CIN85 molecular forms with different subcellular compartments was demonstrated. Induction of apoptosis of MCF-7 cells by doxorubicin treatment or by serum deprivation resulted in the system changes of Ruk/CIN85 molecular forms intracellular localization as well as their ratio. The data obtained provide a new insight into potential physiological significance of Ruk/CIN85 molecular forms in the regulation of various cellular functions.