Background: Hyperplastic gingival tissues show the histopathological characteristics of thick parakeratinized squamous epithelia with acanthosis and rete pegs elongated into the lamina propria. However, the pathogenic factors that contribute to the epithelial morphogenesis of this disease are obscure and remain to be studied.
Methods: We immunohistochemically examined the expression of both c-Myc and bcl-2 oncoprotein, which can exert influence on the epithelial morphogenesis and homeostasis, in 12 hyperplastic gingival tissues induced by nifedipine and phenytoin as well as 5 control tissues using avidin-biotin-peroxidase complex methods.
Results: Four specimens out of 5 nifedipine-induced and 5 out of 7 phenytoin-induced hyperplastic gingival tissues revealed the expression of c-Myc oncoprotein, whereas no significant immunostaining of c-Myc oncoprotein was found in 5 control tissues. The c-Myc oncoprotein-positive cells were observed to be localized in the basal and suprabasal cell layers of the hyperplastic gingival epithelia. Although all of the 12 hyperplastic gingival epithelia showed the distribution of bcl-2 oncoprotein in the basal and suprabasal layer cells, in 5 control epithelia the bcl-2 oncoprotein expression was slight and confined to the basal layer cells.
Conclusions: The results of our present study indicate that the synergistic overexpression of c-Myc and bcl-2 oncoprotein may be related to the pathogenesis of gingival hyperplasia induced by nifedipine and phenytoin, especially to the morphogenesis of hyperplastic epithelia.