Identification of tumorigenesis-related mRNAs associated with RNA-binding protein HuR in thyroid cancer cells

Abstract

RNA binding proteins (RBPs) play a central role in cell physiology and pathology. Among them, HuR is a nuclear RBP, which shuttles to the cytoplasm to allow its RNA targets processing. HuR over-expression and delocalization are often associated to cell transformation. Numerous cancers display increased HuR protein levels and its high cytoplasmic levels has been associated with a worse prognosis.In our study, we first evaluated HuR expression in normal and cancer thyroid tissues and then evaluated its function in thyroid cell lines. HuR is over-expressed in all thyroid tumor tissues; high cytoplasmic levels are detected in all thyroid carcinomas. HuR silencing decreased cell viability and determined apoptotic cell death, in a non-tumorigenic (Nthy-ori-3.1) and a tumorigenic (BCPAP) thyroid cell line. Global transcriptome analysis indicated that HuR silencing, though having similar biological effects, induces distinct gene expression modifications in the two cell lines. By using the RIP-seq approach, the HuR-bound RNA profiles of different thyroid cell lines were evaluated. We show that in distinct cell lines HuR-bound RNA profiles are different. A set of 114 HuR-bound RNAs distinguishing tumorigenic cell lines from the non-tumorigenic one was identified.Altogether, our data indicate that HuR plays a role in thyroid tumorigenesis. Moreover, our findings are a proof of concept that RBP targets differ between cells with the same origin but with distinct biological behavior.

Effects of HuR downregulation on anaplastic thyroid cancer cells

“…The Western Blot analysis displayed a significant HuR overexpression in both ATC cells (Fig. 1), confirming data obtained in vivo (8).…”

“…Moreover, various mRNA of tumorigenesis factors, oncogenes and anti-apoptotic factors have been identified as HuR targets (5). In a previous study, we demonstrated that HuR is overexpressed also in thyroid cancer (8).…”

miR18a and miR19a Recruit Specific Proteins for Splicing in Thyroid Cancer Cells

“…Binding of ELAVL1 probably alters RNA conformation enabling LET-7 binding and translational inhibition of c-MYC, which would also interfere with miR17-92 expression (30). The increase in ELAVL1/HuR levels has been previously observed in thyroid cancers, and also correlated with poor prognosis (31). Therefore, ELAVL1 might be an important regulatory factor of cancer pathogenesis, ultimately regulating miR17-92 expression.…”

Clinical Significance and Biological Role of HuR in Head and Neck Carcinomas

“…HuR expression has been investigated in 8 different thyroid cell lines: Nthy-ori-3.1, derived from normal thyroid follicular epithelial cells; BCPAP; K1; TPC1, derived from papillary thyroid carcinoma (PTC); FTC133; WRO, derived from follicular thyroid carcinoma (FTC); FRO; and SW1736, derived from anaplastic thyroid cancer (ATC) [ 97 ]. A significant overexpression of HuR protein was detected in all PTCs and in SW1736 cells, according to immunoblot analysis, whereas HuR positivity was higher in BCPAP compared to Nthy-ori-3.1 cells as shown by immunocytochemistry [ 97 ].…”

“…HuR expression has been noted in the majority of tissues from benign and malignant thyroid lesions, that is, hyperplastic nodules, Hashimoto thyroiditis, follicular adenomas, FTCs, PTCs, and ATCs, with a moderate to high immunoreactivity in almost half of those [ 97 , 98 ]. Normal thyroid tissue was negative for HuR immunostaining or showed lower expression compared to tumour lesions [ 97 , 98 ]. Cytoplasmic HuR immunostaining appears to clearly distinguish not only between normal and tumour tissue but also malignant and benign neoplasia.…”