Tiam1, overexpressed in most malignancies, is a novel tumor biomarker.

T lymphoma invasion and metastasis 1 (Tiam1) is a guanine nucleotide exchange factor (GNEF) family member, and is considered to be involved in many important cellular processes and oncogenesis. In this study, we investigated Tiam1 expression differences between normal tissue and malignant tissue using tissue microarray (TMA), and further studied the Tiam1 mRNA and protein level in 9 hepatoma lines. Forty-nine tumor tissue and 47 normal tissue samples were detected via TMA by immunohistochemistry with polyclonal antibody. Tiam1 expression in 9 human hepatoma cell lines, namely Huh-7, HepG2, Hep3B, SMMC-7721, QGy-7701, QGy-7703, BEL-7402, BEL-7404 and BEL-7405, and 1 normal primary human hepatocyte, HL-7702, was compared by means of fluorescence quantitative PCR, immunocytochemistry assay and Western blotting. We found that Tiam1 was significantly expressed in various malignancies. Tiam1 mRNA and protein levels were significantly elevated in the 9 human hepatoma cell lines compared to the normal primary human hepatocyte. Our results suggest that Tiam1 overexpression in malignant neoplasms could be a novel effective supplementary biomarker for tumors, including hepatocellular carcinoma.