Cartilage-derived morphogenic
protein (CDMP)-1 and -2 belong to the
bone morphogenetic protein (BMP) family in the
transforming growth factor (
TGF)-beta superfamily.
CDMP-1 and
CDMP-2 were reported to play essential roles in limb cartilage and limb-joint formation in developing mice. Although
pleomorphic adenoma of the salivary glands is an epithelial
tumor, it frequently shows ectopic cartilaginous formation. These findings suggested that
CDMP-1 and -2 may play essential roles in chondroid formation in salivary
pleomorphic adenoma. To evaluate this hypothesis, we examined the expression and localization of
CDMP-1 and -2 immunohistochemically in 20 normal human salivary glands and 35
pleomorphic adenomas.
CDMP-1 was immunolocalized in the striated ducts and the intercalated ducts in the normal salivary glands.
CDMP-1 was immunolocalized in the cuboidal neoplastic myoepithelial cells around the chondroid areas of the
pleomorphic adenomas, whereas these molecules were not localized in the spindle-shaped neoplastic myoepithelial cells of the myxoid
element or the lacuna cells of the chondroid
element in these
tumors.
CDMP-2 was expressed neither in normal salivary glands nor any of the elements of the
pleomorphic adenomas.
Type-II collagen and
aggrecan were immunolocalized throughout the matrix around the lacuna cells of the chondroid
element, whereas
type-X collagen was not immunolocalized in any epithelial or stromal elements, including the chondroid elements.
Aggrecan was deposited not only on the chondroid matrix, but also on the myxoid stroma and intercellular spaces of the tubulo-glandular structures, whereas chondromodulin-I was deposited on the chondroid matrix. These results indicated that the cuboidal neoplastic myoepithelial cells around the chondroid areas expressed
CDMP-1 and suggested that this molecule may play a role in the differentiation of neoplastic myoepithelial cells in
pleomorphic adenoma. The phenotype of the lacuna cells was similar to that of mature to upper hypertrophic chondrocytes of the authentic cartilage. In conclusion,
pleomorphic adenoma expressed
CDMP-1 but not
CDMP-2.