In a previous study, the authors have shown
cytokeratin 8 (CK8) and
epitope H ultrastructural localization in
breast cancer cell nuclei.
Epitope H contains an O-linked
N-acetylglucosamine (O-GlcNAc) residue in a specific conformation and/or environment recognized by
monoclonal antibody H. In this study, double immunogold labeling of CK8 and
epitope H combined with the
EDTA regressive staining method was applied in biopsy material from infiltrating ductal
breast carcinomas and
fibroadenomas, to localize both
antigens in correlation to RNPs distribution in the nuclear subcompartments of
cancer cells. CK8 and
epitope H were localized mostly over condensed
chromatin, whereas staining was weaker over interchromatin granule clusters and perichromatin fibers. These results revealed, the distribution of CK8 in the nucleus as MAR-
binding protein, contributing in the organization of the nuclear
DNA in the neoplastic cell, as well as the distribution of O-GlcNAc glycosylated
polypeptides bearing the
epitope H. The latter finding indicates that these
polypeptides might play a significant role in the neoplastic behavior of
breast cancer cells because they colocalize in the same nuclear subcompartments with
proteins modified by O-GlcNAc, such as hnRNPs G and A1,
RNA polymerase II, its
transcription factors, and the
oncogene product of c-myc. These
proteins are known to participate in coordinated transcription/RNA processing events, contributing in the neoplastic behavior of
breast cancer cells.