Expression of hnRNP B1 in four major histological types of lung cancers

Heterogeneous nuclear ribonucleoprotein B1 is one of the nuclear pre-mRNA binding proteins involved in RNA metabolism. Recently, over-expression of B1 has been reported to be useful in the early detection of squamous cell carcinomas of the lung. To elucidate its significance in other histological types of lung cancers, we carried out a comparative study, four major types of lung cancers and normal lung tissues. 37 surgical specimens were examined using a B1-specific monoclonal antibody (2B2). Immunohistochemically, 2B2 demonstrated B1 protein in the nuclei not only of squamous cell carcinoma (10/10) but also of adenocarcinoma (17/18), small cell carcinoma (5/5) and large cell carcinoma (3/4). A lesser amount of B1 protein was also detected in normal cells. Quantitative immunoblotting revealed that B1 expression was markedly higher in cancer tissues than normal tissues and it varied among the four histological types. To establish the usefulness of B1, a threshold should be set for over-expression.