Overexpression of Insulin-Like Growth Factor-1 Induces Hyperplasia, Dermal Abnormalities, and Spontaneous Tumor Formation in Transgenic Mice

The study investigated the effects of overexpressing insulin-like growth factor 1 (IGF-1) in transgenic mice, specifically targeting the interfollicular epidermis using a human keratin 1 promoter. The transgenic mice, identified by early ear unfolding and excessive skin growth, exhibited epidermal hyperplasia, hyperkeratosis, and thickened dermis and hypodermis. These changes were more pronounced in newborns and diminished with age. The adult transgenic mice developed spontaneous tumors and showed an increased proliferative response to the tumor promoter 12-O-tetradecanoylphorbol-13-acetate (TPA) compared to non-transgenic mice. The study concluded that IGF-1 plays a significant role in multistage carcinogenesis in mouse skin, as evidenced by the faster and more numerous development of papillomas in transgenic mice during initiation-promotion experiments.