The Prognostic Value of the Orphan Nuclear Receptor DAX-1 (NROB1) in Node-negative Breast Cancer

Background: DAX-1 inhibits oestrogen receptor (ER) activities and aromatase P450 expression. The prognostic effect of DAX-1 expression in breast cancer was investigated. Patients and Methods: DAX-1, apolipoprotein D (ApoD), mitotic activity index (MAI) and other prognosticators were evaluated, by quantitative immuno- histochemistry (IHC) and/or real-time reverse-transcription polymerase chain reaction (qRT-PCR) analysis, in 103 invasive node-negative breast carcinomas. Results: With median 122 months follow-up, 24 patients developed distant metastases, of whom, 21 (20%) died. Low DAX-1 expression both by qRT-PCR and IHC was associated with poor survival. Combined strong DAX-1 and Apo D expression identified a subgroup with excellent survival. The most favourable prognostic combination was MAI <3 or (MAI ≥3 combined with DAX-1 and ApoD high expression) versus MAI ≥3 with either low ApoD and/or low DAX-1 expression) (p<0.0001, HR=6.1). Conclusion: In operable node-negative breast cancer, strong DAX-1 expression is associated with excellent survival. Breast cancer is a leading cause of cancer mortality among women in the Western world, second only to lung cancer. Epidemiological features of human breast cancer are consistent with a positive aetiological role for oestrogens (1- 3), whose receptors are often overexpressed and function as