Double immunohistochemistry of Gli-1 and cytokeratin-17 in ameloblastomas

Abstract

<h3>Objective</h3> Our previous research showed relatively high RNA expression level of Gli1 present in ameloblastomas and frequently coexistent with <i>BRAF</i> mutation. Moreover, the mRNA expression level of Gli-1 seems to have positive correlation with acanthomatous change in the tumor nests morphologically. In order to investigate the relation- ship between Gli-1 and cytokeratin, double immunohistochemistry (IHC) of Gli-1 and cytokeratin -17 (CK17) was performed in ameloblastoma cases. <h3>Method</h3> Thirty formalin fixed paraffin embedded (FFPE) ameloblastoma tissue sections with known BRAFV600E status and Gli-1 mRNA expression level were included in the study. One syndrome associated odontogenic kerato- cyst was used as positive control and four radicular cysts and one calcifying odontogenic cyst as negative control. Double IHC of Gli-1 and CK17 was performed in these samples. Result: All of the 30 FFPE ameloblastoma cases revealed Gli-1 nuclear stain and CK17 cytoplasmic stain with various intensity and various amount of positive cells. Our results showed that Gli-1 expressed mainly in the peripheral ameloblast-like cells and the expression of CK17 was mainly in the central acanthomatous portion of the tumor nests. The expression of Gli-1 and CK17 was mainly not co-localized in the same tumor cells with few exceptional co-localized cells. In addition, the expression of CK17 was always present with Gli-1 positive cells at the periphery, and the Gli-1 negative tumor nests were not express CK17 in central. <h3>Conclusion</h3> Our results showed although Gli-1 mRNA expression was positively correlated with acanthomatous change in the tumor nests morphologically, Gli-1 and CK17 were not co-localized in majority of the cells, which indicated that Gli-1 may indirectly regulate the CK17 expression in ameloblastomas. The possible interpretation is that CK17 expression is a later event, which occurs after activation of SHH pathway.