EXPRESSION OF BONE MORPHOGENETIC PROTEINS IN SALIVARY PLEOMORPHIC ADENOMAS

Salivary pleomorphic adenomas are often associated with chondroid tiss ue formation. We investigated ed the relationship between chondroid ti ssue formation and the expression of bone morphogenetic proteins (BMPs ), which are strong inducers of ectopic bone and cartilage formation. Fifteen pleomorphic adenomas and seven normal salivary glands were exa mined genetically and immunohistochemically. Semiquantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis showed that BMP-1, BMP-2, BMP-3, BMP-4, and BMP-7 mRNAs were overexpressed in 10 ( 66.7%), 9 (60.0%), 1 (6.7%), 8 (53.3%), and 12 (80.0%), respectively, of the 15 pleomorphic adenomas. Overexpression of BMP-2 mRNA was obser ved in pleomorphic adenomas. Marked chondroid formation or expression of type II collagen was frequently observed in pleomorphic adenomas th at overexpressed BMP-2 mRNA. Immunohistochemically, BMP-2 was detected in modified myoepithelial cells aroud chondroid tissue and basement m embranes. These results suggest that BMPs, and especially BMP-2, have a role in chondroid formation in pleomorphic adenomas.