Osteopontin facilitates ultraviolet B-induced squamous cell carcinoma development

Academic Article

Abstract

  • Background: Osteopontin (OPN) is a matricellular glycoprotein that is markedly expressed in cutaneous squamous cell carcinomas (cSCCs) and in actinic keratoses implicating its role in photocarcinogenesis. Objective: To determine whether OPN facilitates the development of cSCC and its function. Methods: cSCCs development was compared between wild-type (WT) and OPN-null mice subjected to UVB irradiation for 43 weeks. UVB-induced OPN expression was determined by Western blot, immunoprecipitation, ELISA, and semi-quantitative RT-PCR. Epidermal layer and TUNEL analyses assessed if OPN mediates UVB-induced epidermal hyperplasia or suppresses UVB-induced apoptosis of basal keratinocytes, respectively. In vitro experiments determined whether OPN enhances cell survival of UVB-induced apoptosis and its potential mechanisms. Immunohistochemical analyses of epidermis assessed the expression of CD44 and focal adhesion kinase (FAK), molecules that mediate OPN survival function. Results: Compared to female WT mice, OPN-null mice did not develop cSCCs. UVB irradiation stimulated OPN protein expression in the dorsal skin by 11. h and remains high at 24-48. h. OPN did not mediate UVB-induced epidermal hyperplasia; instead, it protected basal keratinocytes from undergoing apoptosis upon UVB exposure. Likewise, the addition of OPN suppressed UVB-induced OPN-null cSCC cell apoptosis, the activation of caspase-9 activity, and increased phosphorylation of FAK at Y397. Furthermore, the expression of CD44 and FAK in WT mice epidermis was greater than that of OPN-null mice prior to and during early acute UVB exposure. Conclusion: These data support the hypothesis that chronic UVB-induced OPN expression protects the survival of initiated basal keratinocytes and, consequently, facilitates cSCC develop. © 2014 Elsevier Ireland Ltd.
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    Digital Object Identifier (doi)

    Author List

  • Chang PL; Hsieh YH; Wang CC; Juliana MM; Tsuruta Y; Timares L; Elmets C; Ho KJ
  • Start Page

  • 121
  • End Page

  • 132
  • Volume

  • 75
  • Issue

  • 2