Altered profiles in nuclear matrix proteins associated with DNA in situ during progression of breast cancer cells.

Nuclear matrix proteins (NMPs) show promise as informative biomarkers in following the pathogenesis of breast cancer. The nuclear matrix is a dynamic RNA-protein network involved in the organization and expression of chromatin. Cisplatin, which preferentially cross-links nuclear matrix proteins to DNA in situ, may be used to identify NMPs that organize and/or regulate the processing of DNA. In this study, we analyzed the nuclear matrix proteins from an estrogen receptor-positive breast cancer cell line panel consisting of MCF-7, MIII, LCC1, and LCC2 cell lines. This cell line panel reflects the stages of malignant progression in breast cancer. Proteins isolated from nuclear matrices and proteins cross-linked to nuclear DNA in situ with cisplatin were analyzed by two-dimensional gel electrophoresis. Specific changes in nuclear matrix proteins bound to nuclear DNA were identified. In concordance with estrogen independence and antiestrogen insensitivity, a loss in cisplatin cross-linking of specific NMPs to nuclear DNA was observed. Our results suggest that progression of breast cancer is accompanied by a reorganization of chromosomal domains, which may lead to alterations in gene expression.