We examined the expression of the human papiltomaviruses (HPV), p53, mutant type p53, Rb and p16 in oral dysplasia and oral squamous cell carcinoma (SCC). We used 10 samples each of irritation fibroma (IF), low grade dysplasia (LGD}, high grade dysplasia (HGD) and SCC obtalned from Osaka Dental University Hospital. We detected the DNA of HPV-16 and -18 by poNymerase chain reaction (PCR) and the mRNA of HPV by in situ hybridization (ISH). We also studied the immunohistochemical expression of

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... mutant type p53, Rb and p16. was detected in almost all cases of LGD and SCC, but in no cases of ISH. Ma ked expression of mutant type p53 and Rb was seen in HPV-16 pesitive LGD and SCC. HPV infections were detected by PCR in almost all cases of HGD and SCC. Specimens that showed over expression ot mutant type p53 and Rb were almost all positive for HPV-16. These results suggest that HPV-16 may play an important rote in the transformation of p53 and Rb.