Objective: To quantitatively examine changes in p53 tumor suppressor gene immunostaining after carbon dioxide (CO2) laser resurfacing of photodamaged skin to assess the potential value of this treatment in reducing the risk of progression to cutaneous carcinoma. Design: Serial in vivo immunohistochemical analyses after laser therapy. Setting: Academic referral center, Department of Dermatology, University of Michigan, Ann Arbor. Other Participants: Volunteer sample of 11 adults, 51 to 76 years old, with clinically evident photodamage of the forearms. Intervention: Focal CO2 laser resurfacing of photodamaged forearms and serial biopsies at baseline, 3 weeks, and 6 months after treatment. Main Outcome Measures: Because keratinocytes with mutations in p53 or altered p53 expression stain via immunohistochemical techniques, image analysis of immunohistochemically stained sections was used to quantify p53 expression. Results: Positive immunostaining for p53 in the interfollicular epidermis was noted in 8 of 11 subjects at baseline, with an average staining density of 250 cells/mm2. Average staining decreased to 3 cells/mm2 3 weeks after treatment. This decrease was sustained at 5 cells/mm2 6 months after resurfacing. Conclusions: There was a consistent decrease in p53 immunostaining in the interfollicular epidermis lasting for at least 6 moths after CO2 laser resurfacing of photodamaged skin. Since p53 mutation or overexpression is observed in a majority of cases of cutaneous carcinoma, the posttreatment repopulation of the epidermis with p53-negative keratinocytes should theoretically decrease the risk of malignant progression. Further study of laser resurfacing as a prophylactic procedure in patients at high risk for skin cancer development appears warranted.
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