Rabbit Anti-Human TTF1 monoclonal antibody for IHC-P, FC. Thyroid transcription factor-1 (TTF-1) , also known as NK2 homeobox 1 (NKX2-1) , is a member of the NKx2 family of homeodomain transcription factors. It binds and activates the promoter of thyroid specific genes such as thyroglobulin, thyroperoxidase, and thyrotropin receptor. TTF-1 is expressed in epithelial cells of the thyroid gland and the lung, and their derived tumors such as lung adenocarcinoma and small cell carcinomas and thyroid cancer. It is absent in mesotheliomas, breast cancer, and colon cancer.