Heterogeneous nuclear ribonucleoprotein B1 as a new marker of early detection for human lung cancers

Heterogeneous nuclear ribonucleoprotein (hnRNP) A2/B1 is an RNA binding protein that is required for maturation of mRNA precursor, Tockman et al, previously reported that hnRNP A2/B1 with a M-r of 31,000 is overexpressed from the early clinical stage of human lung cancer (M.S, Tockman et al,, J, Clin, Oncol,, 6: 1685-1693, 1988), However, when hnRNP A2/B1 mRNA and hr2RNP B1 mRNA were separately studied, we found unique evidence that hnRNP B1 mRNA, which is a splicing variant of hr2RNP A2 mRNA,was more significantly elevated in lung cancer tissues than hnRNF A2/B1 mRNA, Our hnRNF B1-specific polyclonal antibody specifically recognized hnRNP B1 protein as a M-r 37,000 nuclear protein by Western blotting but did not recognize hnRNP A2 protein, Immunohistochemical staining with the hnRNP B1 antibody revealed that hnRNF B1 protein was specifically stained in the nuclei of human cancer cells, and in squamous cell carcinomas in particular, but not in those of normal adjacent lung epithelial cells. We think that hnRNP B1 protein of M-r 37,000, not hnRNP A2, is well qualified as a biomarker for the detection of human lung cancer.