Unknown,Transcriptomics,Genomics,Proteomics

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Mutant thyroid hormone receptors (TRs) isolated from distinct cancer types display distinct target gene specificities: a unique regulatory repertoire associated with renal clear cell carcinomas.

ABSTRACT: Thyroid hormone receptors (TRs) are hormone-regulated transcription factors that regulate a diverse array of biological activities, including metabolism, homeostasis, and development. TRs also serve as tumor suppressors, and aberrant TR function (via mutation, deletion, or altered expression) is associated with a spectrum of both neoplastic and endocrine diseases. A particularly high frequency of TR mutations has been reported in renal clear cell carcinoma (RCCC) and in hepatocellular carcinoma (HCC). We have shown that HCC-TR mutants regulate only a fraction of the genes targeted by wild-type TRs, but have gained the ability to regulate other, unique, targets. We have suggested that this altered gene recognition may contribute to the neoplastic phenotype. Here, to determine the generality of this phenomenon, we examined a distinct set of TR mutants associated with RCCCs. We report that two different TR mutants, isolated from independent RCCC tumors, possess greatly expanded target gene specificities that extensively overlap one another, but only minimally overlap that of the WT-TRs, or those of two HCC-TR mutants. Many of the genes targeted by either or both RCCC-TR mutants have been previously implicated in RCCC, and include a series of metallothioneins, solute carriers, and genes involved in glycolysis and energy metabolism. We propose that TR mutations from RCCC and HCC are likely to play tissue-specific roles in carcinogenesis, and that the divergent target gene recognition patterns of TR mutants isolated from the two different types of tumors arises from different selective pressures during development of RCCC versus HCC. Gene expression was analyzed in HepG2 transformants expressing ectopic wildtype THRA, wildtype THRB, HCC-TR mutants ?? and ?N, and RCCC-TR mutants 6? and 15? using Affymetrix Human Gene 1.0 ST arrays in the presence or absence of T3. Each HepG2 transformant was assayed in triplicate.

ORGANISM(S): Homo sapiens

SUBMITTER: Scott Ochsner

PROVIDER: E-GEOD-29159 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Hepatocellular carcinoma (HCC) is a frequent cancer with poor prognosis and with limited possibilities for anti-cancer treatment. Evidence has recently accumulated suggesting that multiple signaling pathways are activated in human cancer. It has been recently shown by exosome sequencing of HCC that 161 putative driver genes are associated with 11 recurrently altered pathways, suggesting that we need to inhibit these multiple pathways for HCC therapy. THOC5, a member of transcription/export (TREX) complex, that plays a role in less than 1% of mRNA processing in normal cells such as fibroblasts or macrophages, is not required for maintenance of mature hepatocytes. In this study, we have examined the role of THOC5 in human HCC. Enhanced THOC5 expression was not observed in differentiation grading 1 (G1) human HCC, but 78% of G2 and G3 exhibited increased levels of THOC5. Furthermore, the 50% depletion of THOC5 in hepatocellular carcinoma cell lines, Huh7 and HepG2 causes lipid accumulation and apoptosis. Transcriptome analysis using THOC5 depleted Huh7 and HepG2 cells revealed that 1049 and 837 genes were downregulated upon depletion of THOC5 in Huh7 and HepG2 cells, respectively. Among these genes, 396 were commonly downregulated in both cell lines. Some of these, such as tissue inhibitor of metalloproteinase 3 (TIMP3), tripartite motif containing 24 (TRIM24), ribosomal protein S6 kinase polypeptide 3 (RPS6KA3) and transmembrane emp24-like trafficking protein 10 (TMED10) are known to be fine tuners for several signal transduction pathways. The expression of these proteins was correlated with the THOC5 expression level in HCC. To inhibit multiple signaling pathways we are currently examining the effects of a combination of siRNAs against THOC5 target genes in HCC cell lines. Our data suggest that THOC5, which controls a set of genes that are involved in HCC malignancy can be a potential biomarker for HCC. In addition, THOC5 target gene, TMED10 may also be a novel biomarker of HCC. Furthermore, the suppression of the THOC5 gene per se or multiple THOC5 target genes may represent a novel strategy for cancer therapy. Huh7 and HepG2 cells were infected with lentiviral THOC5 and control shRNAs. Five days after infection, total RNAs were isolated and subjected to microarray analysis.

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Mutant thyroid hormone receptors (TRs) isolated from distinct cancer types display distinct target gene specificities: a unique regulatory repertoire associated with renal clear cell carcinomas.

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