DNA repair is essential for the maintenance of genomic integrity and stability. Nucleotide excision repair (NER) is a major pathway responsible for remediation of damage caused by UV light, bulky adducts, and cross-linking agents. We now show that NER capacity is differentially expressed in human tissues. We established primary cultures of peripheral blood lymphocytes (PBLs: N = 33) and foreskin fibroblasts (FF: N = 6), as well as adult breast tissue (N = 22) using a unique culture system, and measured their NER capacity using the unscheduled DNA synthesis (UDS) functional assay. Relative to FF, primary cultures of breast cells exhibited only 24.6 +/- 2.1% of NER capacity and PBLs only 8.9 +/- 1.2%. Cells from the breast therefore have a unique and distinctive DNA repair capacity. The NER capacities of all three cell types had similar coefficients of variation in the range of 10%-15%, which should be taken into account when running controls for this contextual assay. Unlike previous studies and speculation in the field, we found that NER was not affected by cell morphology, donor age, or proliferation as measured by the S phase index. While the NER capacity of the transformed lymphoblastoid cell line TK6 was within the range of our PBL samples, the breast tumor-derived MDA MB-231 cell line was four-fold higher than normal breast tissue. These studies show that analysis of baseline DNA repair in normal human cell types is critical as a basis for evaluation of the effects of "mutator" genes as etiological factors in the development of cancer.

Our data suggest a pathogenic role for beta 2 GPI-induced aPL in the development of experimental models of APS in PL/J mice.

The molecular etiology of breast cancer has proven to be remarkably complex. Most individual oncogenes are disregulated in only approximately 30% of breast tumors, indicating that either very few molecular alterations are common to the majority of breast cancers, or that they have not yet been identified. In striking contrast, we now show that 19 of 19 stage I breast tumors tested with the functional unscheduled DNA synthesis assay exhibited a significant deficiency of DNA nucleotide excision repair (NER) capacity relative to normal epithelial tissue from disease-free controls (n = 23). Loss of DNA repair capacity, including the complex, damage-comprehensive NER pathway, results in genomic instability, a hallmark of carcinogenesis. By microarray analysis, mRNA expression levels for 20 canonical NER genes were reduced in representative tumor samples versus normal. Significant reductions were observed in 19 of these genes analyzed by the more sensitive method of RNase protection. These results were confirmed at the protein level for five NER gene products. Taken together, these data suggest that NER deficiency may play an important role in the etiology of sporadic breast cancer, and that early-stage breast cancer may be intrinsically susceptible to genotoxic chemotherapeutic agents, such as cis-platinum, whose damage is remediated by NER. In addition, reduced NER capacity, or reduced expression of NER genes, could provide a basis for the development of biomarkers for the identification of tumorigenic breast epithelium.human primary breast cell explant culture | human breast tumor explant culture | breast epithelial attached epispher | hypermutability