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Experimental and Clinical Therapeutics

Monday, October 17, 2005 3:00 PM-5:00 PM Exhibit Hall

(PP106) Hypoxia in human skin as measured by EF5 binding.

Evans, Sydney*,1, Schrlau, Amy1, Chalian, Ara2, Zhang, Paul3, Koch, Cameron1, 1 Radiation Oncology, Philadelphia, Pa., USA2 Otorhinolaryngology, Philadelphia, Pa., USA3 Pathology, Philadelphia, Pa., USA

ABSTRACT- Introduction and Objectives: The oxygen level in skin is of considerable interest to scientists and physicians in a diverse range of fields. Herein, we report on the oxygen levels in normal and irradiated human skin as measured by the hypoxia detection agent EF5. Methods: Written informed consent was obtained from all 21 patients entered on this study. 24 hours following completion of intravenous EF5, the patient was taken to surgery for tumor resection. Skin tissue, removed as part of the primary or reconstrution incision was collected. EF5 binding studies were performed as previously reported (Evans, Cancer Research, 2000). One patient did not receive EF5 (control). Results: EF5 binding did not occur in control tissues, confirming the absence of non-specific binding. To assess the presence and heterogeneity of reductases required to activate EF5, cubes (aproximately 3 x 3 mm) of skin tissue were incubated with EF5 under hypoxic conditions and stained. Analysis revealed that these tissues were capable of reducing and binding EF5; the epidermis, dermis and sebaceous glands demonstrated similar maximum binding levels. Analysis of in situ EF5 binding revealed that the epidermis always bound EF5, with an increasing gradient from the deep (stratum germinativim) to the superficial (stratum lucidum) epidermis. Blood vessels and proliferating cells were found in the dermis, adjacent to the deep epidermal layer, supporting the presence of an oxygen gradient. EF5 staining was found in all patients in some hair follicles and sebaceous glands. Minimal EF5 binding was found in the dermis. We will report pO2 levels for the various skin components in irradiated and non-irradiated tissues. Preliminary analyses support that the dermis is oxic and the most hypoxic regions of the skin are the basal cells of the hair follicles followed by the sebaceous glands. Regions of cellular proliferation were consistently located in oxic regions. Conclusions: These data are the first that we are aware of to measure hypoxia in human skin tissue. They are consistent with skin's known sensitivity to radiation. Grant Support: NIH RO1 CA75285; P50 AT00428

Key words: hypoxia, skin, EF5, radiation


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2005 RRS