Table 1

Efficacy of rMETase and CDDP on human colon cancer in vitro

TreatmentGrowth rate as % of control
Observed (%)Expected (%)Observed/Expected
A. Efficacy of rMETase and CDDP on human colon cancer Colo 205 in vitro
CDDP (0.3 μg/ml)88.2 ± 6
rMETase (0.125 units/ml)72.4 ± 4
CDDP + rMETase44.8 ± 463.90.7
B. Efficacy of rMETase and CDDP on human colon cancer SW 620 in vitro
CDDP (0.3 μg/ml)83.4 ± 4
rMETase (0.125 units/ml)88.8 ± 5
CDDP + rMETase33 ± 3740.45
  • The in vitro growth inhibition efficacy of rMETase and CDDP was carried out as described in “Materials and Methods;” 3000 cells/well were seeded in 96-well plates, and 24 h later, CDDP (0.3 μg/ml) and rMETase (0.125 unit/ml) were added alone or in combination to the wells. After 72 h of exposure, the medium was discarded, and 200 μl of MTT solution (0.5 mg/ml) were added to each well. After incubation at 37°C for 3 h, the solution was discarded, and 200 μl/well of isopropanol were added. The resulting absorbance was read at 570 nm. The percentage of cell proliferation in the treated cultures was calculated by defining the MTT value of the untreated cells as 100%. All determinations were made three times. The combination results were evaluated by the method of Benz et al. (26) and Tan et al.(27) . The expected growth rate of the combination of drug A and drug B = growth rate of drug A × growth rate of drug B. The CI = observed growth rate/expected growth rate. CI of <0.8 was synergistic, 0.8–1.2 was additive, and >1.2 was antagonistic.