Clinical trials of bestatin for leukemia and solid tumors

Dissociated cells from 13- and 17-day-old embryonic rat mesencephali have grown in primary cultures in order to compare the early and late influences of different agents - insulin, dexamethasone and nerve growth factor (NGF) - on the expression of cholinergic maturation process. We have studied cholin acetyltransferase (ChAT) activity, which is regarded as a specific marker for cholinergic function of the brain, and a widely used differentiation marker, the acetyl-cholinesterase (AchE) enzyme. Biochemical maturation of increasing specific activity of ChAT in both younger and older cells was taken into consideration. During cultivation the AchE activity was slightly increased in younger cells, but a dramatic decrease could be noted in older ones. Insulin in concentration from 10 to 27 µg mL^–1 causes a significant inhibition in ChAT activity in comparison with the enzyme activity measured in control cultures (insulin ranging from 1 to 100 ng), independently of embryos age. This polypeptide hormone is able to enhance AchE activity in the cultured cells, especially in older ones. With continuous treatment of the culture with dexamethasone, a synthetic glucocorticoid, the ChAT activity in younger cells reaches a maximum curve by day 9 (nine). At this time the AchE activity shows a slighter, no significant increase than at any other time during cultivation. In cell cultures taken from 17-day-old embryos however dexamethasone treatment evoked a significant decrease in ChAT activity with a concomitant increase of AchE activity which was compared to insulin treatment. In spite of the fact that the NGF is able to enhance the ChAT activity, no significant alteration in AchE activity can be measured in younger cell cultures. These results suggest an uneven expression of the enzymes in embryonic rat mesencephali in the presence of above agents depending on the age of cells.