Osteopontin Expression in Normal Skin and Nonmelanoma Skin Tumors

Pi-Ling Chang ^1*, Louie Harkins ¹, Yu-Hua Hsieh ¹, Patricia Hicks ¹, Kraisorn Sappayatosok ¹, Somchai Yodsanga ¹, Somporn Swasdison ¹, Ann F. Chambers ¹, Craig A. Elmets ¹ and Kang-Jey Ho ¹

¹ Department of Nutrition Sciences (P-LC,Y-HH,PH), Department of Pathology (LH,K-JH), and Department of Dermatology (CAE), University of Alabama at Birmingham, Birmingham, Alabama; Department of Oral Surgery and Oral Medicine, Srinakharinwirot University, Bangkok, Thailand (KS); Department of Oral Pathology, Chulalongkorn University, Bangkok, Thailand (SY,SS); and London Regional Cancer Centre, University of Western Ontario, London, Ontario, Canada (AFC)

^* To whom correspondence should be addressed. E-mail: plchang{at}uab.edu.

Submitted on July 19, 2007
Accepted on 10 September 2007

	Abstract

Osteopontin (OPN) is an adhesive, matricellular glycoprotein, whose expression is elevated in many types of cancer and shown to facilitate tumorigenesis in vivo. To understand the role of OPN in human skin cancer, the present study is designed to determine whether OPN is expressed in premalignant (solar/actinic keratosis, AK), and in malignant skin lesions such as squamous cell carcinomas (SCC) and basal cell carcinomas (BCC) as well as in normal skin exposed or not exposed to sunlight. Immunohistochemical analyses demonstrated that OPN is expressed in SCC (20/20 cases) and in AK (16/16 cases) which are precursors to SCC, but is absent or minimally expressed in solid BCC (17 cases). However, positive staining for OPN was observed in those BCC that manifest differentiation toward epidermal appendages such as keratotic BCC. In sunlight exposed normal skin, OPN is minimally expressed in the basal cell layer, but in contrast to those not exposed to sunlight, OPN is more prominent in the spinous cell layer with increasing intensity toward the granular cell layer. Additionally, OPN is expressed in the hair follicles, sebaceous glands and sweat glands of normal skin. In conclusion, these data suggest that OPN is associated with keratinocyte differentiation and that it is expressed in AK and SCC, which have metastatic potential, but minimally expressed in solid BCC.

Key Words: osteopontin, actinic keratosis, squamous cell carcinoma, basal cell carcinoma, differentiation, apoptosis, epidermis, calcitriol, ultraviolet light

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