To confirm that calcitonin bioactivity was not lost after conjugation to mAb and to confirm the ability for mAb-sCT conjugate to trigger the calcitonin receptor, T47D human breast cancer cells (known to contain calcitonin receptors) were used, as previously described (22) . Briefly, T47D cells (ATCC, VA, USA) were cultured in triplicate in RPMI-1,640 culture medium containing 1% penicillinstreptomycin, 10% fetal bovine serum, and insulin (0.2 IU/ mL). Cells were seeded on 48-well plates at an initial density of 5×10 4 cells/well and incubated in 95% air and 5% CO 2 at 37°C for 2 days. Cells were then washed with HBSS and preincubated in RPMI-1640 culture medium devoid of FBS, insulin and antibiotics. Cells were dosed with the phosphodiesterase inhibitor, 3-isobutyl-1-methyl-xanthine (IBMX, 1 mM) and incubated at 37°C for 30 min. One hundred nM of mAb, mAb-sCT and sCT were then added to the wells except the control where T47D cells were treated with IBMX only. The plate was incubated for 20 min at 37°C.