Genomic changes of the 55 kDa subunit of DNA polymerase epsilon in human breast cancer.

BACKGROUND: DNA polymerases (Pols) represent potential candidates for cancer genes because of their central functions in DNA metabolism. Defects of some DNA Pols have shown cancer associations, but data on DNA polymerase (Pol) epsilon is limited. MATERIALS AND METHODS: Twenty-four human breast cancer DNA samples and four control DNA samples were examined for possible mutation in the entire coding region of the 55 kDa small subunit of the human DNA Pol epsilon gene using polymerase chain reaction-single strand conformation polymorphism (PCR-SSCP) analysis of the DNA and sequence analysis. In addition, 20 control DNAs were studied with PCR-SSCP for the end of intron 18 and exon 19 region. RESULTS: An AATT deletion was found at one location in intron 18 in 2 out of the 24 breast cancer cases (8%), but in none of the control cases. In addition, a single base transition was found in the cancer DNAs in intron 14, but the same changes were also found in the control DNAs, suggesting polymorphism. CONCLUSION: Specific changes might occur in the 55 kDa small subunit DNA sequence of DNA Pol epsilon in breast cancer. The deletion at the region of intron-exon junction may not affect the protein code, but could potentially influence splicing efficiency and expression levels, possibly impairing the function of Pol epsilon DNA.