Simultaneously detected aberrant p53 tumor suppressor protein and HPV-DNA localize mostly in separate keratinocytes in anogenital and common warts

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Abstract
The E6 oncoprotein of human papillomavirus (HPV) is known to inactivate the control function on cell cycle exerted by p53 tumor suppressor protein in vitro by binding to p53 and thus facilitating the degradation of p53. We have applied a simultaneous in situ demonstration method for detecting p53 protein and HPV-DNA on formalin-fixed tissue sections, and investigated the in vivo interrelationship of p53 protein and HPV-DNA. Immunohistochemical staining for p53 protein with polyclonal and monoclonal antibodies, recognizing both wild-type (wt) and mutated p53 protein, was performed first and in situ DNA hybridization (ISH) for HPV types 6/11 or 16/18 with digoxigenin-labelled probes thereafter. 47% (25/53) of 48 histologically confirmed primary or recurrent condylomata acuminata (CA), 2 Bowenoid papulosis (BP) and 3 common wart (CW) biopsies, positive for HPV 6/11 or HPV 16/18 DNA, showed keratinocytes immunopositive for p53 protein. Of these, 11 lesions with abundant numbers of p53-positive cells were further analyzed with the double method. Signals for abnormal p53 protein and HPV-DNA were detected in separate cell nuclei in all biopsies and, additionally, in the same cell nuclei in 3 biopsies (1 BP, 1 CA, 1 CW). Usually the p53 positivity localized more basally in the epidermis than HPV-DNA, although p53- and HPV-positive keratinocytes were always located closely. The findings were similar for HPV-types 6/11 and 16/18. Our finding of both p53 and HPV-6/11 signals in the same cell nuclei may indicate complexing of p53 and low-risk HPV's without degradation of p53. Our results show abnormal p53 expression in HPV-infected skin lesions, and suggest that p53 protein is susceptible to aberrations even in the cells in the vicinity of productive HPV infection. However, it is not yet fully understood how HPV interferes with p53 protein in these cells.