Background: The activation of oncogenes is an important step in tumorigenesis, and recently, oncogene-induced senescence (OIS) was proposed as a critical barrier against malignant transformation in normal primary cells.
Objectives: The aim of this study was to examine the activation of fibroblast growth factor receptor 3 (FGFR3) as an oncogene product and OIS in human skin tumours.
Methods: We investigated the activation of FGFR3 and OIS by mutation and immunohistochemical analysis in skin tumours, including seborrhoeic keratosis, actinic keratosis (AK), Bowen's disease (BD), basal cell carcinoma (BCC) and squamous cell carcinoma (SCC).
Results: Activated point mutations of FGFR3 were identified in four of 22 cases (18%) of seborrhoeic keratosis, but no mutation was detected in the other skin tumours. Twenty-seven of 31 cases (87%) of seborrhoeic keratosis showed moderately to strongly positive expression of the FGFR3 protein, but almost all the other skin tumours were negative. On the other hand, almost all the seborrhoeic keratoses showed negative immunoreactivity for antiphoshohistone H2AX (gamma-H2AX) as a marker of OIS, but 17 of 22 cases (77%) of AK were moderately to strongly positive. Immunoreactivity for gamma-H2AX was significantly greater in AK than in seborrhoeic keratosis, BD, BCC and SCC.
Conclusions: The activation of FGFR3 might be a common feature in the tumorigenesis in seborrhoeic keratosis, although the activation does not induce a typical oncogenic signal in keratinocytes. In addition, OIS due to some oncogenic signals rather than activation of FGFR3 might be involved in the early skin carcinogenesis related to chronic ultraviolet radiation exposure.