This table shows the concentrations (ED50) of vincristine, in the presence of different concentrations of GF109203X or Gö6976, needed to suppress the number of viable SK-N-BE(2) cells after three days in culture to 50% of the amount obtained in the absence of the drug. The data used for calculations are obtained from Figure 3. Values are geometric mean of three separate experiment with triplicate measurements. The ED50 values were calculated using the amount of viable cells in the absence of vincristine but in the presence of PKC inhibitor as 100% (values in A columns) or the amount of viable cells in the absence of vincristine and PKC inhibitor (values in B columns). Thus, values in column A reflect the potency of vincristine since the inherent growth-suppressing effect of the PKC inhibitors has been eliminated in the calculations, whereas values in column B reflect the combined growth-suppressing effect of PKC inhibitor and vincristine.NA – not available because culture in the presence of 500 nM Gö6976 reduced the number of cells to less than 50% of the number obtained in the absence of the compound.