Sueoka E, Goto Y, Sueoka N, Kai Y, Kozu T, Fujiki H
Saitama Cancer Center Research Institute, Japan.
Cancer Res. 1999 Apr 1;59(7):1404-7.
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 hnRNP B1 mRNA were separately studied, we found unique evidence that hnRNP B1 mRNA, which is a splicing variant of hnRNP A2 mRNA, was more significantly elevated in lung cancer tissues than hnRNP A2/B1 mRNA. Our hnRNP 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 hnRNP 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.
不均一核核糖核蛋白（hnRNP）A2/B1是一种RNA结合蛋白，是mRNA前体成熟所必需的。托克曼等人此前报道，分子量为31,000的hnRNP A2/B1在人类肺癌临床早期就过度表达（M.S.托克曼等人，《临床肿瘤学杂志》，6:1685 - 1693，1988）。然而，当分别研究hnRNP A2/B1 mRNA和hnRNP B1 mRNA时，我们发现了独特的证据，即作为hnRNP A2 mRNA剪接变体的hnRNP B1 mRNA在肺癌组织中比hnRNP A2/B1 mRNA升高得更显著。我们的hnRNP B1特异性多克隆抗体通过蛋白质印迹法特异性识别hnRNP B1蛋白为一种分子量37,000的核蛋白，但不识别hnRNP A2蛋白。用hnRNP B1抗体进行免疫组织化学染色显示，hnRNP B1蛋白在人类癌细胞的细胞核中特异性染色，尤其是在鳞状细胞癌中，但在相邻的正常肺上皮细胞中则不染色。我们认为，分子量为37,000的hnRNP B1蛋白而非hnRNP A2蛋白完全有资格作为检测人类肺癌的生物标志物。
