FGF-2 is overexpressed in myoepithelial cells of carcinoma ex-pleomorphic adenoma in situ structures

Increasing emphasis has been placed on the role of myoepithelial cells, the contractile components of secretory glands, in the in situ to invasive carcinoma transition. These cells are placed at the interface between luminal epithelial cells and the stromal compartment, which favors their crosstalk with all other cell types comprising the tumor micro-environment. To obtain some clues about this cross-talk and also to better understand our previous immunoprofile study of myoepithelial cells in salivary gland carcinoma ex-pleomorphic adenoma (CXPA), we investigated FGF-2 expression in CXPA in situ structures as well as in cells cultured under conditions attempting to simulate the cellular interactions of this tumor stage. We have observed by immunohistochemistry that myoepithelial cells of CXPA in situ structures over-express FGF-2. In addition, our results supported by qPCR and Western blotting, demonstrated that the expression of FGF-2 in the benign myoepithelial cells was in fact increased by stimulation with the conditioned medium from malignant cells. Low molecular weight FGF-2, known to be primarily released from the cells to exert its biological activity through receptors, was the predominant FGF-2 form detected in the benign myoepithelial cells. Specific FGF-2 receptors were found in the malignant epithelial but not in the benign myoepithelial cells of CXPA, indicating a paracrine role for benign myoepithelial cell-derived FGF-2. Abnormal paracrine myoepithelial/epithelial cell interactions and also myoepithelial/stromal cell interactions could favor tumor growth, invasion and metastasis.