Table 2

A mixture of three anti-Her-2 F(ab′)₂ fragments induces similar growth inhibition and apoptosis as the mixture of three anti-Her-2 IgGs in vitro

Antibody	IC₅₀ × 10⁻⁸ (m)^a	% Annexin-V⁺ cells^b	% PI⁺ cells^b^,c	% Total dead cells
F(ab′)₂
Mixture	0.43 ± 0.32^d	28.0 ± 0.03	31.6 ± 14.5	59.6 ± 7.3
Herceptin	1.3 ± 0.0	15.9 ± 2.9	12.1 ± 3.1	28 ± 3.0
RFT5 (control)	582.5 ± 428.3	2.3 ± 1.6	1.8 ± 1.7	4.1 ± 1.7
IgG1
Mixture	0.1 ± 0.04	28.4 ± 0.7	38.2 ± 5.9	66.6 ± 3.3
Herceptin	0.3 ± 0.1	36.4 ± 2.2	10.0 ± 8.5	46.4 ± 4.3
RFT5 (control)	233.8 ± 167.8	0.7 ± 0.2	0.7 ± 0.3	1.4 ± 0.3
Other
None	NA	0.6 ± 0.2	0.64 ± 0.12	1.24 ± 0.2
NaN₃^e	0.004 ± 0.003	43.8 ± 9.0	49.2 ± 11.9	93 ± 5.3

^a Cells (2.5 × 10⁵ cells/ml) were incubated for 72 h at 37°C with different concentrations of anti-Her-2 monoclonal antibodies or F(ab′)₂s and then pulsed with [³H]thymidine for 6 h. IC₅₀ values represent the concentration of monoclonal antibodies required to kill 50% of cells. The difference between the IC₅₀in each treatment group versus untreated control is statistically significant, with Ps < 0.01.
^b Cells (2.5 × 10⁵ cells/ml) were incubated for 4 h at 37°C with 300 μg/ml anti-Her-2 monoclonal antibodies or F(ab′)₂s and then stained with annexin-V FITC plus propidium iodide (50 μg/ml) and analyzed by FACScan. The percentage of total dead cells is the sum of the percentage of annexin-V-FITC-positive plus propidium iodide-positive cells. The difference between the percentage of annexin-V-positive cells in each treatment group versus untreated control is statistically significant, with Pvalues < 0.04. The difference between the percentage of propidium iodide-positive cells in each treatment group versus untreated control is statistically significant, with Pvalues < 0.01.
^c PI, propidium iodide; NA, not applicable (because the untreated control values were taken as 100%).
^d SD are based on at least three experiments.
^e Positive control.