[Ultrastructural immunocytochemical localization of diphosphate kinase/Nm23 in human cancer cells]

Nucleoside diphosphate (NDP) kinase/Nm23 is highly expressed in certain malignant tissues, as compared with the rate found in normal or hyperplastic tissues. The potential role of this overexpression in tumor progression and the mechanisms involved in it remain to be determined. We studied the ultrastructural localisation of the NDP kinase, and in particular looked for an association of this enzyme with the microtubules or cytoplasmic membrane. Using immunocytochemical methods with an antiserum raised against NDP kinase A, we analysed tissue sections of breast carcinomas and cells in culture derived from a cervical cancer. In malignant cells, a strong labeling of the cytoplasm, related to ribosomes, was observed. No labeling of microtubules, or other intracytoplasmic components was found. No labeling of the nucleus was noted. In contrast, a strong labeling of the cytoplasmic membrane of most malignant cells was observed. In the cytoplasm of non-malignant stromal cells, a slight labeling of ribosomes was observed. These results must be taken into account with regard to the different existing hypotheses relative to the role of the NDP kinase in tumor progression, and in particular relative to its activation function on the GTP-binding proteins involved in membrane signal transduction.