Squamous cell carcinoma (SCC) and
basal cell carcinoma (BCC) are the most common forms of human
skin cancer. BCC is slow growing and mostly localized, whereas SCC metastasizes to the regional lymph nodes and subsequently to distal organs. In murine skin
carcinogenesis models for SCC, the incidence of
metastasis is very low. We report here that FVB/N transgenic mice, which overexpress (approximately 18-fold)
epitope-tagged
protein kinase C-epsilon (T7-PKCepsilon)
protein in the epidermis provide a unique murine model system for highly malignant/metastatic SCC. Skin
tumors were developed by the initiation-promotion protocol (initiation with 100 nmol 7,12-dimethyl-
benz[a]anthracene; promotion with 5 nmol 12-O-tetradecanoylphorbol-13-
acetate twice weekly). T7-PKCepsilon transgenic mice showed 92% suppression of
papilloma development compared with wild-type littermates after 23 weeks of
tumor promotion. However, within 15-20 weeks of 12-O-tetradecanoylphorbol-13-acetate promotion, 40% of T7-PKCepsilon mice developed at least one
carcinoma compared with 7% of the wild-type mice. All
carcinomas from T7-PKCepsilon mice appeared without prior
papilloma formation. Interestingly, 7,12-dimethyl-
benz[a]anthracene alone resulted in the development of
squamous cell carcinomas in 22% of T7-PKCepsilon mice, whereas wild-type littermates developed no
tumors. Histopathological analysis of
tumors from multiple T7-PKCepsilon mice revealed moderately differentiated SCC invading the dermal region with
neoplasia appearing to originate and invade from the hair follicle.
Carcinomas of T7-PKCepsilon mice rapidly metastasized to regional lymph nodes within 3 weeks of appearance. In wild-type mice, the grade of the invading
tumors, originating from interfollicular epidermis, was pathologically categorized as well-differentiated SCC and remained localized to the dermis. The T7-PKCepsilon transgenic mice may provide a rapid and unique in vivo model to investigate metastatic SCC.