Thyroid Hormone Receptor Beta Induces a Tumor-Suppressive Program in Anaplastic Thyroid Cancer

Abstract

The thyroid hormone receptor beta (TRb), a key regulator of cellular growth and differentiation, is frequently dysregulated in cancers. Diminished expression of TRb is noted in thyroid, breast, and other solid tumors and is correlated with more aggressive disease. Restoration of TRb levels decreased tumor growth supporting the concept that TRb could function as a tumor suppressor. Yet, the TRb tumor suppression transcriptome is not well delineated and the impact of TRb is unknown in aggressive anaplastic thyroid cancer (ATC). Here, we establish that restoration of TRb expression in the human ATC cell line SW1736 (SW-TRb) reduces the aggressive phenotype, decreases cancer stem cell populations and induces cell death in a T 3 -dependent manner. Transcriptomic analysis of SW-TRb cells via RNA sequencing revealed distinctive expression patterns induced by ligand-bound TRb and revealed novel molecular signaling pathways. Of note, liganded TRb repressed multiple nodes in the PI3K/AKT pathway, induced expression of thyroid differentiation markers, and promoted proapoptotic pathways. Our results further revealed the JAK1-STAT1 pathway as a novel, T 3 -mediated, antitumorigenic pathway that can be activated in additional ATC lines. These findings elucidate a TRb-driven tumor suppression transcriptomic signature, highlight unexplored therapeutic options for ATC, and support TRb activation as a promising therapeutic option in cancers.Implications: TRb-T 3 induced a less aggressive phenotype and tumor suppression program in anaplastic thyroid cancer cells revealing new potential therapeutic targets.

Thyroid hormone receptor beta inhibits the PI3K-Akt-mTOR signaling axis in anaplastic thyroid cancer via genomic mechanisms

“…PI3K signaling fuels cancer progression by stimulating cell survival, proliferation, and migration. We previously demonstrated that TRβ inhibits SW1736 proliferation in charcoal-stripped media, an observation that was dependent upon T 3 stimulation (15). To achieve phenotypic confirmation of our sequencing results, we challenged our engineered cells in full serum (10%) media with or without additional 10 nM T 3 to measure a functional consequence of PI3K inhibition.…”

“…Previously published RNA-seq data was used to determine expression levels of genes within the PI3K pathway (15). Construction of the PI3K signaling genes of interest for our study was based on the curated IPA pathway gene set.…”

“…Cells were cultured in RPMI 1640 growth media with L-glutamine (300 mg/L), sodium pyruvate and nonessential amino acids (1%) (Corning Inc, Corning, NY, USA), supplemented with 10% fetal bovine serum (Thermo Fisher Scientific, Waltham, MA, USA) and penicillin-streptomycin (200 IU/L) (Corning) at 37°C, 5% CO2, and 100% humidity. Lentivirally modified SW1736 cells were generated as described (15,22) with either an empty vector (SW-EV) or to overexpress TRβ (SW-TRβ). SW-EV and SW-TRβ were grown in the above conditions with the addition of 2 μg/ml puromycin (Gold Bio, St Louis, MO, USA Figure 4B was performed using ImageJ (NIH, Bethesda, MD, USA).…”

“…Since a long-term T3 treatment was needed for robust suppression of PI3K signaling in our cell line model, we hypothesized that TRβ may be regulating the expression of key components of this pathway. In order to better understand the extent to which TRβ suppresses PI3K signaling through genomic mechanisms, we leveraged our RNA-sequencing data performed on our EV and TRβ cell lines following 24 hours of T3 treatment (15). Numerous genes involved in the PI3K pathway were determined to be differentially expressed in the presence of both T3 and TRβ ( (27).…”

“…These factors include members of the nuclear hormone receptor family including estrogen, androgen, and thyroid hormone receptors (11)(12)(13). Our work has demonstrated that thyroid hormone receptor beta (TRβ) acts as a tumor suppressor in ATC through repression of several pathways important for tumor growth (14,15). However, the potential for TRβ to exhibit tumor suppression in ATC by suppressing PI3K is not fully understood.…”