Table I.

Characteristics of anti-DR4 mAbsa

mAbIsotypeAffinityb Kd−1 (pM)Blockingc ActivityApoptosisd
+ None+ anti-Fc+ RC
4G7IgG2a20+++++
4H6IgG15++++/−++++/−
  • a Each mAb recognized receptors on 9D cells as determined by FACS (data not shown). These mAbs show very low cross-reactivity to DR5-IgG by capture ELISA (16 ).

  • b The mAb affinity for DR4-IgG was determined using KinExA.

  • c Blocking activity of mAbs was determined by their ability to inhibit Apo2L/TRAIL binding to DR4-IgG in a capture ELISA and to inhibit the apoptosis of 9D cells induced by Apo2L/TRAIL. +++, >90% blocking of Apo2L/TRAIL binding to DR4-IgG at 1 μg/ml of mAb.

  • d The apoptosis-inducing ability of these mAbs on various tumor cells was determined in the presence of goat anti-mouse IgG-Fc or RC. The apoptosis of 9D cells was determined by FACS analysis of FITC-annexin V binding, and those of SK-MES-1 and Colo 205 tumor cells were done by the crystal violet staining. Based upon the maximum apoptosis by Apo2L as 100%, the degree of apoptosis at 1 μg/ml of mAb was expressed as +/− (<30% killing), + (40–60% killing), ++ (60–80% killing), and +++ (>90% killing).