Osteopontin expression and its role in oral epithelial tumorigenesis

Osteopontin (OPN), a glycosylated phosphoprotein previously considered to play a significant role in mineralization and resorption of bone, has recently been described in the tumorigenesis of several malignant tumors.  Objectives: To study the expression of OPN in normal, benign and malignant tumors originated from 3 types of oral epithelium and the possible role of OPN in transformation of these epithelial cells.  Methods:  Standard indirect immunohistochemical technique using monoclonal antibody specific to human OPN was performed in formalin-fixed paraffin-embedded tissue sections containing normal, benign and malignant tumors of oral squamous epithelium, odontogenic epithelium and glandular epithelium. 

Results:

Types of    epithelium	Staining pattern
	Normal cells	Benign tumor	Malignant tumor
Squamous	+/-	+/-	++
Odontogenic	+/-	+	++
Glandular	+ ductal cells                                            + serous cells	+ ductal cells                              + myoepithelial cells	++

Conclusion:  In normal and benign tumors of all 3 types of epithelium, OPN is slightly and selectively expressed in the cytoplasm of the cells.  The expression of this protein increases to the higher level in malignant tumor cells.  The results suggest that increasing expression of OPN may play an important role in malignant transformation of these oral epithelial cells.