Using an in vitro competitive binding assay, cAMP activity was determined in TD47 breast cancer cells known to contain the calcitonin receptor. The assay confirmed that sCT and the mAb-sCT conjugate were capable of stimulating cAMP production after binding the calcitonin receptor. The significantly lower absorbance values measured (due to the competitive nature of the assay) indicated the ability for sCT and/or mAb-sCT to generate intracellular cAMP in the presence of a phosphodiesterase inhibitor. Conversely, the mAb-treated and control wells exhibited negligible intracellular cAMP generation, and, accordingly, high absorbance values in the competitive binding assay were observed (Fig. 10) . Fig. 7 Tartrate-resistant acid phosphatase (TRAP) activity assay. mAb-sCT conjugate showed an inhibitory effect on TRAP activity, an important marker of osteoclasts. RAW: cells cultured in media with 0 ng/ml RANKL+0 ng/ml MCSF; OC: cells cultured in media with 50 ng/ml RANKL+25 ng/ml MCSF; mAb-sCT: cells cultured in media with 50 ng/ml RANKL+25 ng/ml MCSF+100 nM conjugate; mAb: cells cultured in media with 50 ng/ml RANKL+25 ng/ml MCSF+100 nM mAb; sCT: cells cultured in media with 50 ng/ml RANKL+25 ng/ml MCSF+100 nM sCT . * P<0.05 versus OC; ** P<0.05 versus sCT. No statistically significant difference was observed between naked antibody and the conjugate.