Cellular expression of K-type pyruvate kinase in normal and neoplastic human tissues

The cellular expression of K-type pyruvate kinase was studied immunohistochemically in several normal and neoplastic tissues of human origin. The authors used the monoclonal antibody, designated as ES1, which was raised against human K-type pyruvate kinase. In contrast to the normal counterparts, a strong immunoreactivity was found in a rhabdomyosarcoma (n = 1), in a carcinoma of the pancreas (n = 1), and in neurofibromas (n = 2). Furthermore, the staining in leiomyosarcomas (n = 2) was shown to be more intense when compared with both normal smooth muscle cells and leiomyomas (n = 2). These findings show that knowledge about the cellular expression of the K-type pyruvate kinase identifies cell types for which its expression serves as oncodevelopmental marker. In addition, these immunohistochemical studies give information whether shifts toward K-type containing isozymes of pyruvate kinase, which are determined by electrophoresis in whole cytosolic extracts of various tumors, are due to an altered gene expression or due to proliferation of cells which normally express already the K-type pyruvate kinase. The first possibility probably occurs in rhabdomyosarcomas. The latter possibility seems to be valid for astrocytomas because astrocytes express the K-type pyruvate kinase in normal brain.