Human papillomavirus type 16 in an oral squamous carcinoma and its metastasis

DNA was extracted from fresh frozen tissues of eight patients with primary oral squamous carcinoma. Samples of normal oral mucosa were available in seven cases and metastatic tumor in two cases. The samples were probed for human papillomavirus types 16 and 18 by Southern hybridization. In one case of squamous carcinoma of the floor of the mouth, human papillomavirus type 16 was identified in the primary tumor and a lymph node metastasis, but it was not detectable in normal oral mucosa from this patient. Human papillomavirus DNA was not detected in any other sample of primary tumor, metastasis, or normal oral mucosa. Restriction enzyme digests of the human papillomavirus positive primary tumor and its metastasis revealed that the viral DNA was identical to the prototype human papillomavirus type 16 and present at 50 to 100 copies per cell in an episomal state with no evidence of integration into the host DNA. Compared to the human papillomavirus DNA in the primary tumor, the viral DNA in the metastasis was of the same type, in the same physical state, and at the approximately the same copy number. The consistent maintenance of human papillomavirus DNA in metastases from human papillomavirus positive primary tumors supports the hypothesis that human papillomaviruses are cofactors in the pathogenesis of some carcinomas.