The expression of ADAM12 (meltrin α) in human giant cell tumours of bone

Aims: To examine the expression of ADAM12 (meltrin α), a member of the disintegrin and metalloprotease (ADAM) family, in human giant cell tumours of the bone, skeletal muscle tissue from human embryos, and human adult skeletal muscle tissue. Methods: ADAM12 mRNA was detected by reverse transcription polymerase chain reaction and in situ hybridisation. Results: ADAM12 mRNA was detected in 14 of the 20 giant cell tumours of bone and in three of the six tumour cell cultures. The expression of ADAM12 in cells cultured from the tumour was linked to the presence of multinucleated giant cells. ADAM12 mRNA could not be detected in the five adult skeletal muscle tissue samples, although it was found in the two embryonic skeletal muscle tissue samples. ADAM12 mRNA was localised to the cytoplasm of multinucleated giant cells and some mononuclear stromal cells. Conclusions: These results indicate that multinucleated giant cells are formed by the cell fusion of mononuclear stromal cells in giant cell tumours of bone and that ADAM12 is involved in the cell fusion process.