Backgrounds: Being a crucial hormone regulating growth, metabolism and various physiological processes, the status of thyroid hormone has long been implicated in cancer risks and tumor developments. In the present study, we aimed to look at the role of thyroid hormone, thyroxine (T4), in colorectal cancer cell proliferation and β-catenin activation, which is highly involved in both normal and oncogenic developments of the gut.

Materials and Methods: The effects of T4 in colorectal cancer cell lines HCT 116 (APC wild type) and HT-29 (APC mutant) as well as the primary cells derived from colorectal cancer patients were studied. Cell proliferation was evaluated according to cell counting, MTT assay and qRT-PCR. The activation of β-catenin was examined using Western blotting, qRT-PCR and immunoprecipitation.

Results: The results showed that T4 increased the cell number of both HCT 116 and HT-29 cells compared to the untreated cells. In both cell lines, T4 induced nuclear β-catenin accumulation and the protein levels of WNT/β-catenin targets Cyclin D1 and c-Myc. The mRNA expression of CTNNB1 was elevated by T4 in HCT 116 cells, but not in HT-29 cells. In APC wild type HCT 116 cells, T4 increased the WNT4 mRNA expression and decreased the association between β-catenin and the WNT-regulated β-catenin destruction complex. Moreover, the cell numbers of T4-treated primary cells were higher compared to the untreated cells while the mRNA expressions of proliferative genes PCNA, CCND1 and c-Myc were elevated by T4. In the primary cells, T4-induced nuclear β-catenin accumulation, protein levels of Cyclin D1 and c-Myc, and mRNA expressions of CTNNB1 and WNT4 were also observed.

Conclusions: T4 promoted cell proliferation and β-catenin activation in colorectal cancer. In the cells with different APC mutation status, the activation of β-catenin was regulated by different mechanisms.

Citation Format: Yee-Shin Lee, Meng-Ti Hsieh, Yu-Tang Chin, Aleck Hercbergs, Paul J. Davis, Han-Chung Wu, Hung-Yun Lin. Thyroid hormone, thyroxine, promotes cell proliferation and β-catenin activation in colorectal cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 3625. doi:10.1158/1538-7445.AM2017-3625