BACKGROUND: Drug-induced gingival overgrowth (GO) is a frequent and adverse 
side-effect associated principally with the administration of the 
immunosuppressive drug cyclosporin A (CsA) and also certain anti-epileptic and 
anti-hypertensive drugs. It is characterized by a marked increase in the 
thickness of the epithelial layer and the accumulation of excessive amounts of 
connective tissue. Although the mechanism by which the drugs cause GO is not yet 
understood, keratinocyte growth factor (KGF), which is a potent epithelial cell 
mitogen, has been implicated in other hyperplastic conditions, including mammary 
and prostatic hyperplasia, and could also be involved in the molecular pathology 
of GO.
METHODS: Immunohistochemistry was used to examine the expression of KGF in 
normal gingiva (NG) and GO tissue sections. The relative level of KGF mRNA in GO 
tissue and cells was compared with that of NG tissue and fibroblast cells using 
the semi-quantitative reverse transcribed-polymerase chain reaction (RT-PCR) and 
DNA sequencing was carried out to confirm the identity of the PCR product.
RESULTS: KGF antigen and mRNA were readily detected in the GO tissue 
immunohistochemically and by RT-PCR, respectively, but were not expressed in the 
NG tissue. Moreover, KGF transcripts were found to be approximately 2 times 
higher in the GO than in the NG fibroblasts in vitro, although the difference 
was not statistically significant.
CONCLUSIONS: This study has shown, for the first time, that the level of KGF is 
elevated in GO and suggests that KGF may have an important role in the enhanced 
epithelial proliferation associated with GO.