BioProject

T-cell intracellular antigen-1 (TIA1) is an RNA-binding protein modulating many regulatory aspects of target mRNA metabolism. More...

T-cell intracellular antigen-1 (TIA1) is an RNA-binding protein modulating many regulatory aspects of target mRNA metabolism. Despite several reports referring to the role of TIA1 in carcinogenesis, little is known about the significance of its expression and function in human cancers including esophageal squamous cell carcinoma (ESCC). In the present study, we found that ectopic localization of overexpressed TIA1 in the cytoplasm was observed in a cohort of 143 ESCC patients using immunohistochemistry, and the cytoplasmic TIA1 was an independent prognosticator for worse overall survival. Moreover, we revealed that TIA1 was overexpression in many ESCC cell lines, and silencing of TIA1 in those cells inhibited cell growth with an accumulation of cells in G0–G1 and sub-G1 phases. The human TIA1 gene generates two major protein isoforms, TIA1a and TIA1b. Expression of TIA1a isoform tended to be higher than that of TIA1b in ESCC cells, and TIA1a was expressed both in the nucleus and cytoplasm but TIA1b was expressed mainly in the nucleus. Further studies revealed that each isoform showed opposite effects on cell proliferation through ectopically introducing each gene: TIA1a promotes anchorage-dependent and independent cell proliferation, whereas TIA1b inhibits cell proliferation and/or induces cell death. The ribonucleoprotein immunoprecipitation followed by a microarray analysis or massive-parallel sequencing identified a set of TIA1-associating mRNAs including enriched cell cycle-associated genes. Among them, SKP2 and CCNA2 mRNA were shown to be interacted with TIA1 protein through their different regions, and SKP2 and CCNA2 protein levels were positively regulated by TIA1 through suppression of mRNA decay and translational induction, respectively. These findings provide new insights into the previously unknown role of TIA1 and its isoforms as tumor-promoting molecules regulating a set of downstream oncogenic proteins, and implicate their potential application as a useful marker of malignant potential and a therapeutic target in ESCC. Overall design: To investigate the target molecules regulated by TIA1 in esophageal squamous cell carcinoma cell line (KYSE180), the expression levels of mRNAs (total) and transcripts captured by RIP with TIA1 antibody (TIA1_RIP) were analyzed using microarray. Less...