Meis1 Regulates Epidermal Stem Cells and Is Required for Skin Tumorigenesis

The study revealed that Meis1 had dual roles in the epidermis: it was essential for maintaining epidermal homeostasis in normal tissues and acted as a proto-oncogenic factor in neoplastic tissues. Meis1 was primarily expressed in the bulge region of hair follicles, where adult stem cells reside, and its deletion in mice led to a reduction in these stem cells. Mice lacking Meis1 in their epidermis developed significantly fewer DMBA/TPA-induced tumors compared to wild-type mice, indicating Meis1's involvement in tumor development and progression. Additionally, Meis1 expression increased as tumors advanced from benign to malignant stages, and its localization shifted from stem cells to more differentiated cells in tumor tissues, suggesting a functional switch during neoplastic transformation.