Y-box binding protein expression in thyroid neoplasms: its linkage with anaplastic transformation

Recent studies have demonstrated that Y-box binding protein (YB-1) regulates the transcription of genes linked to carcinoma progression. In this study, we investigated the expression of this protein in thyroid neoplasms to elucidate its significance. The expression of YB-1 was immunohistochemically investigated using the monoclonal antibody for various thyroid neoplasms. Normal follicles did not overexpress YB-1, and only moderate overexpression of YB-1 was observed in some follicular tumors and papillary carcinoma, especially those of a larger size. In contrast, 92.9% of anaplastic carcinoma strongly overexpressed YB-1. YB-1 immunoreactivity was seen in both cytoplasms and cell nuclei, but the former was more predominant. These findings suggest that YB-1 plays a role in regulating the transcription as well as translation of genes contributing to the anaplastic transformation of thyroid carcinoma.