NQO1 expression correlates inversely with NFjB activation in human breast cancer

NQO1 participates in cellular defense against oxidative stress and regulates apoptosis via p53- and NFjB-mediated pathways. We have previously found that homozygous missense variant NQO1*2 (rs1800566) predicts poor survival among breast cancer patients, particularly after anthracycline-based adjuvant chemotherapy. Here, we investigated NQO1 and NFjB protein expression and global gene expression profiles in breast tumors with correlation to tumor characteristics and survival after adjuvant chemotherapy. We used immunohistochemical analysis of tissue microarrays to study NQO1 and NFjB expression in two series of tumors: 1000 breast tumors unselected for treatment and 113 from a clinical trial comparing chemotherapy regimens after anthracycline treatment in advanced breast cancer. We used gene expression arrays to define genes co-expressed with NQO1 and NFjB. NQO1 and nuclear NFjB were expressed in 83% and 11% of breast tumors, and correlated inversely (P = 0.012). NQO1 protein expression was associated with estrogen receptor (ER) expression (P = 0.011), whereas 34.5% of NFjB-nuclear/activated tumors were ER negative (P = 0.001). NQO1 protein expression and NFjB activation showed only trends, but no statistical significance for patient survival or outcome after anthracycline treatment. Gene expression analysis highlighted 193 genes that significantly correlated with both NQO1 and NFjB in opposite directions, consistent with the expression patterns of the two proteins. Inverse correlation was found with genes related to oxidation/reduction, lipid biosynthesis and steroid metabolism, immune response, lymphocyte activation, Jak-STAT signaling and apoptosis. The inverse relationship between NQO1 protein expression and NFjB activation, underlined also by inverse patterns of association with ER and gene expression profiles of tumors, suggests that NQO1–NFjB interaction in breast cancer is different from several other tissue types, possibly due to estrogen receptor signaling in breast cancer. Neither NQO1 nor NFjB protein expression appear as significant prognostic or predictive markers in breast cancer.