Liver X Receptor beta Related to Tumor Progression and Ribosome Gene Expression in Papillary Thyroid Cancer

Abstract

Backgrund: Intracellular lipid deposition has been reported in thyroid glands in obese animal and human. To understand the regulatory mechanism of lipid metabolism in thyroid cancer, we investigated the expression status of liver X receptor (LXR) and analyzed its clinicopathological characteristics and molecular biological features. Methods: Expression status of LXR and its transcriptional targets in human cancers were analyzed using The Cancer Genome Atlas (TCGA). The gene-sets related to high LXR beta expression was investigated by gene set enrichment analysis (GSEA) using Kyoto Encyclopedia of Genes and Genomes (KEGG) signaling pathways and gene ontology biologic process. Quantitative reverse transcription polymerise chain reaction was performed in thyroid cancer samples using our validation cohort. Results: In contrast to low expression of LXR alpha, LXR beta was highly expressed in thyroid cancer compared to the other types of human cancers. High LXR beta expression was correlated with the expression of LXR beta transcriptional targets genes, such as apolipoprotein C1 (APOC1), APOC2, apolipoprotein E (APOE), ATP binding cassette subfamily G member 8 (ABCG8), sterol regulatory elementbinding protein 1c (SREBP1c), and SPOT14. Furthermore, High LXR beta expression group indicated poor clinicopathological characteristics and aggressive molecular biological features independently from the drive mutation status. Mechanistically, high LXR beta expression was coordinately related to ribosome-related gene sets. Conclusion: The mechanistic link between LXR beta and ribosomal activity will be addressed to develop new diagnostic and therapeutic targets in thyroid cancers.