Characterization of pyruvate kinase from human rhabdomyosarcoma in relation to immunohistochemical and morphological criteria

Comparison of pyruvate kinase variants from breast tumor and normal breast

BACKGROUND

Pyruvate kinase isozymes in human breast tumor tissue were compared in this study with normal human breast tissue. Two forms of pyruvate kinase present in normal and tumor human breast were purified by ammonium sulfate precipitation, dialysis, gel filtration, ion exchange, and affinity chromatography. Molecular weight of the native enzyme was determined.

METHODS

Presence of pyruvate kinase activity was examined in normal and tumor breast tissues. Pyruvate kinase was purified with Sephadex DEAE-50, Sepharyl S-200, and Blue Sepharose CL-6B chromatography. Spectrophotometric methods were used to determine activities of pyruvate kinase.

RESULTS

Molecular weights of fractions I and II as determined by gel filtration on Sepharyl S-200 were 135,000 Da, 260,000 Da in normal breast tissue, and 72,000 Da, 250,000 Da in tumor breast tissue, respectively. Fractions I and II of pyruvate kinase may be purified approximately 1,591-fold, 636.4-fold in normal breast tissue and 219-fold, 318-fold in tumor breast tissue, respectively. Pyruvate kinase activity in tumor tissue was found higher than in normal tissue. Only tumor fraction II showed tumor-specific sensitivity to L-cysteine. L-phenylalanine inhibited both fractions I and II of normal breast and fraction I of tumor breast, but not fraction II of pyruvate from tumor. ATP inhibited normal and tumor fraction I of pyruvate kinase. The influence of ATP on enzyme activity from normal and tumor fraction II depended upon its concentration.

CONCLUSIONS

It was thought that isozymes of pyruvate kinase from human breast tissue might be M1 and M2 isozymes when compared with those of other tissue pyruvate kinase isoenzymes. Fraction II from breast tumor represented different sensitivity to L-cysteine, L-phenylalanine, and specific activity in comparison with fraction II from normal breast. Different kinetic behavior of fractions in the human breast tumors may support the concept of an isozyme shift.

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.

Pyruvate kinase activity and isozyme composition in normal fibrous tissue and fibroblastic proliferations

Pyruvate kinase (PK) was studied in 57 fibroblastic and fibrohistiocytic proliferations and normal fibrous tissue (n = 10). The specific activity was significantly increased in malignant tumors (1.67 +/- 0.25) compared with normal tissue (0.26 +/- 0.04; P less than 0.001) and benign proliferations (0.52 +/- 0.05; P less than 0.005). Although an overlap exists between aggressive fibromatosis and the benign group, high values of PK activity are indicative of Grade 2 and 3 malignancy. Significant shifts in isozyme pattern, favoring the expression of K-type subunits were found in tumors with a metastasizing potential and aggressive fibromatosis. These changes in the isozyme pattern of PK in aggressive fibromatosis may act as another argument to place them in the category of malignant fibroblastic tumors.

Phosphofructokinase and pyruvate kinase in mouse embryonal carcinoma P19 cells in relation to growth and differentiation

Two key enzymes of glycolysis, phosphofructokinase and pyruvate kinase, were studied in embryonal carcinoma cells (P19 EC cells) and three differentiated derivatives in relation to growth rate and differentiation state. The growth rates of P19 EC cells and its differentiated derivatives are positively correlated with both the specific activity of phosphofructokinase and the expression of the L-subunit of this enzyme. The specific activity of pyruvate kinase and its isozyme composition is not correlated with growth rate but seems to be correlated with the differentiation state of these cells. The decrease in specific activity of pyruvate kinase during differentiation of P19 EC cells induced by retinoic acid or dimethylsulfoxide preceded the shift from K- to M-type pyruvate kinase. In contrast to aggregates that were treated with dimethylsulfoxide, the specific activity of pyruvate kinase was reduced after aggregation in the presence of retinoic acid. Only after plating dimethylsulfoxide-treated aggregates again in the presence of dimethylsulfoxide, was a decrease in specific activity obtained. Both retinoic acid and dimethylsulfoxide are able to induce a K- to -M shift of pyruvate kinase.