Alternatively spliced variants of the regucalcin gene in various human normal and tumor tissues

Abstract

Regucalcin plays a pivotal role as a suppressor protein in signal transduction in various cell types. The regucalcin gene, which is localized on the X chromosome, consists of 7 exons and 6 introns. Decreased liver regucalcin gene expression has been suggested to play a suppressive role in the development of hepatocellular carcinogenesis in animal models. This study was undertaken to determine the changes in regucalcin gene expression in various human normal and tumor tissues, including liver, kidney, brain and lung tissues. The full-length and alternatively spliced variants of regucalcin mRNA were found to be expressed in various human tissues. This expression was suppressed in tumor tissues of hepatocellular carcinoma, kidney transitional cell carcinoma, brain malignant meningioma and lung non-small cell carcinoma. The full-length regucalcin protein was found to be highly expressed in normal human liver and kidney tissues; its expression was suppressed, however, in the liver and kidney tumor tissues. The spliced variant proteins were found to be expressed in the normal liver and kidney tissues, and decreased in the tumor tissues. Such alternative variants were not observed in the liver and kidneys of rats and mice. The alternatively spliced variants of the regucalcin gene were found to be expressed in various human normal and tumor tissues.