Expression and function of the calcitonin receptor by myeloma cells in their osteoclast-like activity in vitro.

Malignant plasma cells exert osteoclast-like activity in vitro. We investigated the function of the calcitonin (CT) receptor (R) on myeloma cells from patients and in myeloma cell lines. Primary myeloma cells expressed high CTR levels whereas the cell lines uniformly exposed the CTR-2 variant expressed by osteoclasts. Treatment of myeloma cell lines with CT modified the intracellular Ca(2+) and cAMP levels, suggesting the activation of both PKC and PKA pathways, and abrogated their bone resorptive property as erosive pits on osteologic substrates. Thus, the expression, sensitivity and function of CTR-2 in myeloma cells emphasize their osteoclast-like behavior in vitro.