Abstract 207: Tumor suppressive role of NKX2-1 in advanced thyroid cancer progression

Abstract NKX2-1 is a homeodomain transcription factor, known as a master regulator of thyroid development. NKX2-1 is also crucial for lung epithelium differentiation, and the involvement of NKX2-1 in lung carcinogenesis and cancer progression has been intensely investigated. However, the role of NKX2-1 in thyroid cancer progression remains elusive. The Cancer Genome Atlas (TCGA) dataset analysis demonstrated that papillary thyroid cancer (PTC) patients with low NKX2-1 mRNA expression had significantly poorer prognosis than those with a combination of intermediate and high mRNA expression of NKX2-1. Lentivirus-transduced tetracycline (Tet) -inducible system was used to achieve NKX2-1 overexpression in advanced follicular thyroid cancer (FTC) cell lines, FTC-238 and WRO, and an anaplastic thyroid cancer (ATC) cell line 8305C, in which NKX2-1 expression is barely/not detected. All these thyroid cancer cell lines showed significant suppression of cell proliferation with NKX2-1 overexpression. In addition, NKX2-1 overexpression inhibited migration of FTC-238 cells. The levels of mRNA and protein expression of mesenchymal markers, matrix metalloproteinase-2 (MMP-2) and fibronectin, were decreased by NKX2-1 overexpression in FTC-238 cells, suggesting a possibility that NKX2-1 partially inhibits epithelial-mesenchymal transition (EMT). SNAIL and SLUG are essential EMT transcription factors involved in metastasis in cancer progression. NKX2-1 mRNA expression was significantly lower in high SNAI1 (encoding SNAIL) expressing PTC in TCGA database. Indeed, suppression of SNAIL protein expression was found upon overexpression of NKX2-1 in FTC-238 cells which naturally express high level of SNAIL. These findings suggest that NKX2-1 may inhibit the migration of advanced thyroid cancer cells through SNAIL-induced EMT. Similarly, suppression of SLUG protein expression by overexpression of NKX2-1 was observed in WRO and 8305C cells which express high level of SLUG protein. Whether NKX2-1 overexpression inhibits migration and invasion of WRO and 8305C cells through SLUG-induced EMT is currently under examination. The Tet-inducible NKX2-1 expressing thyroid cancer cells will be used for in vivo evaluation of their metastatic ability using an immunocompromised mouse model. The findings so far suggest that NKX2-1 exerts a tumor suppressive activity in advanced thyroid cancers through suppression of cell proliferation, and cell migration presumably via suppression of EMT transcription factors. Citation Format: Yo-Taro Shirai, Shioko Kimura. Tumor suppressive role of NKX2-1 in advanced thyroid cancer progression abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts) ; 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84 (6Suppl): Abstract nr 207.