Absence of the DNA repair enzyme human 8-oxoguanine glycosylase is associated with an aggressive breast cancer phenotype.

<bold>Background: </bold>8-Oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) is the most abundant marker of DNA damage and it reflects oxidative stress. Human 8-oxoguanine glycosylase (hOGG1) is a DNA-repair enzyme that participates in 8-oxodG removal.<bold>Methods: </bold>hOGG1 protein expression was immunohistochemically studied in 96 patients with local or locally advanced breast cancer and in 20 lesions of non-malignant breast disease. 8-OxodG levels had been previously determined in all patients.<bold>Results: </bold>hOGG1 was overexpressed in invasive vs non-invasive lesions (P=0.006). 8-OxodG and hOGG1 had a significant inverse association (P=0.046). Lack of hOGG1 expression was associated with the most poor prognostic factors of breast cancer. In addition, all triple-negative breast carcinomas (TNBCs) were hOGG1 negative (P=0.027 vs non-TNBCs). Patients with a lack of both hOGG1- and 8-oxodG immunostaining showed extremely poor breast cancer-specific survival compared with those with either 8-oxodG- or hOGG1-positive tumours (P<0.000005).<bold>Conclusion: </bold>The current results imply that absence of hOGG1 expression is associated with features of aggressive breast cancer. Tumours lacking both 8-oxodG and hOGG1 seem to indicate especially poor prognosis. [ABSTRACT FROM AUTHOR]